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    Recomended voltage ratings for PAS 3 resistors and caps

    Midwestside
    Midwestside

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    Recomended voltage ratings for PAS 3 resistors and caps Empty Recomended voltage ratings for PAS 3 resistors and caps

    Post by Midwestside on Fri May 22, 2020 6:02 pm

    Shopping on Mouser to find some resistors and caps for a rebuild of the line stage and phono boards.
    For resistors i seem to see voltage values such as 350, 500 and 700v values to choose from.
    I would like to know what Voltage rating i can get away with.
    Also having trouble over there finding 68, 33pf caps in polypropylene.

    So i also went over to Sonic Craft looking and found most of what i need.
    saved a shopping cart over with 1% takman resistors and sonicap capacitors.
    Still looking for the 68,33pf caps. im guessing they are disc caps.
    I still need to buy the pcbs! and tube sockets.
    This is really adding up!

    I wonder if its not more cost effective to just buy some dropin boards from Erhard audio,
    if there wont be a huge trade off in sound quality..

    looking for suggestions and experiences.
    PeterCapo
    PeterCapo

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    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by PeterCapo on Fri May 22, 2020 7:43 pm

    350 VDC for the resistors should be fine, as the highest B+ to either board is 200 VDC.  Please note that most resistors in the PAS were originally 1/2-watt carbon composition, but there were some 1-watt precision resistors on PC6.  Most of the capacitors have their voltage rating marked right on them.

    A 33pf is available in a Wima polypropylene from Mouser - try looking up Mouser #: 505-FKP2O100331D00JN.  You'll have to drill a small hole in the PC board to install it.  In other words, one lead will be soldered to one of the original solder pads but the other will go through the small hole you'd drill in the board, and then you'll have to run a wire from that lead to the other solder pad.  Worth the trouble, because this 33pf capacitor is in the line stage feedback loop, and I'd much rather have polypropylene here than ceramic or even mica.

    I wouldn't be too anxious to replace the original 68pf and other original precision parts on PC6.  I'd give it careful thought.  I'm not sure if you can get better parts to replace them with.  For the PCBs, I assume you are considering new production copies of PC5 and PC6.  If that is correct, have a look here: https://www.ebay.com/itm/Dynaco-Dyna-PAS-Preamp-NEW-BASIC-BARE-BOARD-SET-PC-5A-PC-6A-Made-In-USA/372987766390?hash=item56d7cda676:g:VYkAAOxySE9Q9LXA

    With regard to your musings over aftermarket drop-in replacement circuits, I am sure you'd find enthusiastic responses from satisfied customers.  But, I would expect that the sonic character of the PAS would very likely be changed.  I'd think this is especially so, since some aftermarket circuits incorporate solid-state devices that I expect would shift the sonic character significantly closer to a solid-state sound.  I've run into this with some of my gear that uses tubes as well as solid-state devices.  It's really a question of what kind of sound you prefer.  A PAS rebuilt [with all new parts] to the original Dynaco circuit design can have a clean, all tube sound, with a holographic sound-stage and other high-end sonic goodies that can compete with anything else in its price range and even beyond that.  The final arbiter is personal sonic taste.  That's the subjective parts of this.

    On the objective side, the original Dynacos like the PAS have long since published their specs and have long since been vetted by independent labs where they were found to have solid performance all the way around.  If you have not seen them, have a look at the Audio Regenesis lab analysis of the original PAS, found along the left-hand side of the following webpage: http://www.audioregenesis.com/
    Midwestside
    Midwestside

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    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by Midwestside on Fri May 22, 2020 8:03 pm

    PeterCapo wrote:350 VDC for the resistors should be fine, as the highest B+ to either board is 200 VDC.  Please note that most resistors in the PAS were originally 1/2-watt carbon composition, but there were some 1-watt precision resistors on PC6.  Most of the capacitors have their voltage rating marked right on them.

    A 33pf is available in a Wima polypropylene from Mouser - try looking up Mouser #: 505-FKP2O100331D00JN.  You'll have to drill a small hole in the PC board to install it.  In other words, one lead will be soldered to one of the original solder pads but the other will go through the small hole you'd drill in the board, and then you'll have to run a wire from that lead to the other solder pad.  Worth the trouble, because this 33pf capacitor is in the line stage feedback loop, and I'd much rather have polypropylene here than ceramic or even mica.

    I wouldn't be too anxious to replace the original 68pf and other original precision parts on PC 6.  I'd give it careful thought.  I'm not sure if you can get better parts to replace them with.  For the PCBs, I assume you are considering new production copies of PC5 and PC6.  If that is correct, have a look here: https://www.ebay.com/itm/Dynaco-Dyna-PAS-Preamp-NEW-BASIC-BARE-BOARD-SET-PC-5A-PC-6A-Made-In-USA/372987766390?hash=item56d7cda676:g:VYkAAOxySE9Q9LXA

    With regard to your musings over aftermarket drop-in replacement circuits, I am sure you'd find enthusiastic responses from satisfied customers.  But, I would expect that the sonic character of the PAS would very likely be changed.  I'd think this is especially so, since some aftermarket circuits incorporate solid-state devices that I expect would shift the sonic character significantly closer to a solid-state sound.  I've run into this with some of my gear that uses tubes as well as solid-state devices.  It's really a question of what kind of sound you prefer.  A PAS rebuilt to the original Dynaco circuit design can have a clean, all tube sound, with a holographic sound-stage and other high-end sonic goodies that can compete with anything else in its price range and even beyond that.  The final arbiter is personal sonic taste.  That's the subjective parts of this.

    On the objective side, the original Dynacos like the PAS have long since been vetted by independent labs and have been found to have solid performance all the way around.  If you have not seen them, have a look at the Audio Regenesis lab analysis of the original PAS, found along the left-hand side of the following webpage: http://www.audioregenesis.com/


    Good to know.  I am using Tubes4hifi's parts list on this thread:

    https://dynacotubeaudio.forumotion.com/t215-board-layouts-for-the-pc-5-line-stage-and-pc-6-phono-board-on-the-pas-preamps-photos

    I have everything crossed off my list over there except for a  1.2M, 4.7M resistors, and 33pf and .02uf (which i can build out of 2x .01uf)
    guess i will keep the 68pf and get the rest of the non Sonic Craft items at Mouser.

    Oh... besides the the 68pf , which other components would you not touch on pc 6? Maybe just replace the black cats and resistors or what ?

    I do have those basic Ebay PCBs that you have listed on my watch list, so that is good to know.  Now just tube sockets and im done.
    (any recommends on tube sockets?)
    While im at it. what gauge wire should i keep on hand? Maybe some 20awg teflon 600v?

    I also have not decided what to do about the power supply,  I do have 2x 2200uf Nichicon caps and some 1N4007 diodes handy for doing it that way.
    I am talking to someone over on AK that recommended that as opposed to a drop in powersupply with a fuse and the cap can integrated on to it.
    I was still waiting to see how the guy on the other tread came along with his SDS install.
    I'm not opposed to it.
    PeterCapo
    PeterCapo

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    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by PeterCapo on Fri May 22, 2020 9:04 pm

    I took a quick look through that thread.  Sounds like the recommendations changed some parts values?  Do you have an original PAS you are rebuilding, or are you cobbling one together by gathering parts?  I'd also cross-check part values, ratings and physical placement against the original Dynaco PC boards, the original Dynaco schematic, the original pictorial wiring diagrams and the photos in the original manual.  Do you have a copy of the PAS-3X manual WITH the pictorial wiring diagrams?  If not, PM me and I'll work on getting a copy to you.

    For a 0.02µF have a look at Mouser #: 667-ECW-F6203HL

    I'd have to look at an original PC6, but it has 1% capacitors, and I believe the one-watt resistors (brownish/reddish color) are something like 2%, they were sealed and are probably fine.  I'd just replace the six big, black tubular capacitors and the carbon composition resistors only.  Take care working on PC6, because there are wires going up to the selector switch, and that selector switch isn't very tolerant of being pushed and pulled.  IOW, the selector switch has open contacts that can lose good contact without a lot of provocation.

    For tube sockets, I like the Japanese Azuma nine-pin ceramic sockets with either gold or silver contacts - but only their nine-pin sockets.  I am not crazy about their octal sockets.

    20 gauge with Teflon insulation sounds fine.

    For the power supply... cap boards have the potential to outperform the quad section capacitor.  But cap boards are also more difficult to implement.  I've read a number of reports of hum problems with cap boards.  I don't believe it's a problem with the cap boards.  Rather, I think it's a problem with integrating them into the PAS grounding scheme.  So, it can be challenging if you were to have hum problems.

    I’ve given it some thought recently, because I’ve been working with someone rebuilding his PAS.  I’ve suggested getting a new quad section capacitor and putting a 0.1µF polypropylene bypass capacitor in parallel with each of the four sections.  Also, put a 10µF polypropylene between E16 and ground on both PC boards.  I have not tried this, but it retains the original Dynaco power supply topology and could close the gap with a cap board.  Anyway, something to mull over.

    For the filament supply, consider upping the electrolytics to something closer to 10,000µF apiece and using UF4008 ultra-fast diodes.
    Midwestside
    Midwestside

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    Post by Midwestside on Fri May 22, 2020 9:23 pm

    PeterCapo wrote:I took a quick look through that thread.  Sounds like the recommendations changed some parts values?  Do you have an original PAS you are rebuilding, or are you cobbling one together by gathering parts?  I'd also cross-check part values, ratings and physical placement against the original Dynaco PC boards, the original Dynaco schematic, the original pictorial wiring diagrams and the photos in the original manual.  Do you have a copy of the PAS-3X manual WITH the pictorial wiring diagrams?  If not, PM me and I'll work on getting a copy to you.

    For a 0.02µF have a look at Mouser #: 667-ECW-F6203HL

    I'd have to look at an original PC6, but it has 1% capacitors, and I believe the one-watt resistors (brownish/reddish color) are something like 2%, they were sealed and are probably fine.  I'd just replace the six big, black tubular capacitors and the carbon composition resistors only.  Take care working on PC6, because there are wires going up to the selector switch, and that selector switch isn't very tolerant of being pushed and pulled.  IOW, the selector switch has open contacts that can lose good contact without a lot of provocation.

    For tube sockets, I like the Japanese Azuma nine-pin ceramic sockets with either gold or silver contacts - but only their nine-pin sockets.  I am not crazy about their octal sockets.

    20 gauge with Teflon insulation sounds fine.

    For the power supply... cap boards have the potential to outperform the quad section capacitor.  But cap boards are also more difficult to implement.  I've read a number of reports of hum problems with cap boards.  I don't believe it's a problem with the cap boards.  Rather, I think it's a problem with integrating them into the PAS grounding scheme.  So, it can be challenging if you were to have hum problems.

    I’ve given it some thought recently, because I’ve been working with someone rebuilding his PAS.  I’ve suggested getting a new quad section capacitor and putting a 0.1µF polypropylene bypass capacitor in parallel with each of the four sections.  Also, put a 10µF polypropylene between E16 and ground on both PC boards.  I have not tried this, but it retains the original Dynaco power supply topology and could close the gap with a cap board.  Anyway, something to mull over.

    For the filament supply, consider upping the electrolytics to something closer to 10,000µF apiece and using UF4008 ultra-fast diodes.

    I have a stock PAS 3. I do have a manual.  I can follow wiring diagrams, look at cap values, (parrot instructions and visuals) But dont really have the knowledge to formulate within circuits or analyze well. (Yet)

    Yeah, i can get the last bits on mouser, which is fine. How many volts on the 10000uf caps? perhaps this:

    https://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/109TTA035M?qs=3tP%252BN51vMXfjgh3C1XxVZQ%3D%3D

    Where have you been sourcing the quad cap? I've read people saying the ones at dynakit are taller and its not the same capacitance as the original.

    Also , i have kind of marked a few components that i think you are telling me to keep.
    I have numbered them so you can tell me by number which ones to keep or which ones can go.

    thanks for the help so far.


    Recomended voltage ratings for PAS 3 resistors and caps Pas_in10
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    rjpjnk

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    Post by rjpjnk on Fri May 22, 2020 11:08 pm

    What is the goal here? Are you building new boards or upgrading existing boards? Is there something wrong with the ones in the picture?

    If just upgrading existing boards, I don't see the point in replacing any of the caps other than the electrolytics unless they test out of spec. I measured many of those Black Cats in mine and found them more accurate than most modern replacements, and they look way cooler to boot. They are not the troublesome paper and wax type that fail so frequently.

    The carbon resistors, on the other hand, are way more likely to have drifted high and may be worth replacing.

    The can almost certainly has failed, but you can leave it in place and just buy 3 separate electrolytics if you like for much less $$.

    I know others may differ, but I feel vintage gear is most enjoyable with vintage parts where possible.
    PeterCapo
    PeterCapo

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    Post by PeterCapo on Fri May 22, 2020 11:23 pm

    Midwestside wrote:I have a stock PAS 3. I do have a manual.  I can follow wiring diagrams, look at cap values, (parrot instructions and visuals) But dont really have the knowledge to formulate within circuits or analyze well. (Yet) ...

    That's all Dynaco was counting on when they wrote the assembly manuals.  All you need to do is gather parts and let the manual do the rest.

    Midwestside wrote: ... Yeah, i can get the last bits on mouser, which is fine. How many volts on the 10000uf caps? perhaps this:

    https://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/109TTA035M?qs=3tP%252BN51vMXfjgh3C1XxVZQ%3D%3D ...

    One correction on my part.  I was thinking of around 10000µF total for the two, and, yes, 35VDC rating is good.  Perhaps this: https://www.mouser.com/ProductDetail/CDE-Illinois-Capacitor/688TTA035M?qs=3tP%252BN51vMXf4FCUT4G4xtA%3D%3D

    Midwestside wrote: ... Where have you been sourcing the quad cap? I've read people saying the ones at dynakit are taller and its not the same capacitance as the original. ...

    So far I've managed to use discrete electrolytics in my projects.  But Antique Electronic Supply has a wide selection of multi-section electrolytics https://www.tubesandmore.com/products/capacitors?filters=Brand%3DCE%20Manufacturing%2CType%3DMulti-Section%20/%20Can%20Type  Please check me on this, but I think the original quad cap in the PAS is 2" tall, is that correct?  Would I correctly remember that there is another 1/2" inch of headroom to accommodate a 2-1/2 inch high quad cap?  Please have a look and let me know.

    Midwestside wrote: ... Also , i have kind of marked a few components that i think you are telling me to keep.
    I have numbered them so you can tell me by number which ones to keep or which ones can go. ...

    1 and 2 are 1% and 2% parts, respectively.  I'd leave those alone (and avoid pushing them from side-to-side), unless you can find exact value and tolerance, or closer tolerance, in polypropylene or polystyrene.  Remember, however, that polystyrene is more vulnerable to soldering heat.

    3 and 4 are 1500pf and part of the audio high filter circuit.  If you want to retain the filter circuit, you could look for a replacement in polypropylene or polystyrene.  Remember, however, that polystyrene is more vulnerable to soldering heat.  If you don't want to retain the high filter circuit, we can talk about how to bypass it.

    5 and 6 are 1% and 2% parts, respectively.  I'd leave those alone (and avoid pushing them from side-to-side), unless you can find exact value and tolerance, or closer tolerance, in polypropylene or polystyrene.

    7 and 8 are the 33pf capacitors, 10% tolerance. This can be replaced with the Wima 33pf polypropylene we talked about.

    What kind of tubes are you running in it?  Are those 5751?

    Now that I see you have a very nice original, factory assembled PAS-3, I'd like to float an idea by you.  But it's kind of past my bedtime, so maybe we can pick this up over the weekend.


    Last edited by PeterCapo on Fri May 22, 2020 11:32 pm; edited 3 times in total (Reason for editing : correct formatting, redundancy and spelling)
    PeterCapo
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    Post by PeterCapo on Fri May 22, 2020 11:24 pm

    rjpjnk wrote:What is the goal here? Are you building new boards or upgrading existing boards? Is there something wrong with the ones in the picture?

    If just upgrading existing boards, I don't see the point in replacing any of the caps other than the electrolytics unless they test out of spec. I measured many of those Black Cats in mine and found them more accurate than most modern replacements, and they look way cooler to boot. They are not the troublesome paper and wax type that fail so frequently.

    The carbon resistors, on the other hand, are way more likely to have drifted high and may be worth replacing.

    The can almost certainly has failed, but you can leave it in place and just buy 3 separate electrolytics if you like for much less $$.

    I know others may differ, but I feel vintage gear is most enjoyable with vintage parts where possible.


    I agree with you. In fact, this is what I hope to discuss more, over the weekend.
    Midwestside
    Midwestside

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    Post by Midwestside on Fri May 22, 2020 11:37 pm

    Now that I see you have a very nice original, factory assembled PAS-3, I'd like to float an ideas by you. But it's kind of past my bedtime, so maybe we can pick this up over the weekend. wrote:

    Yes, my bed time too. I read what you wrote, I will start with the filament supply and then wait for the rest. Its in nice shape, i just want to do this thing justice and hear what it was designed to do sonically. obviously other have the expertise for that. Any suggestions welcome.
    peterh
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    Post by peterh on Sat May 23, 2020 4:47 am

    Midwestside wrote:

    Yes, my bed time too.  I read what you wrote,  I will start with the filament supply and then wait for the rest. Its in nice shape, i just want to do this thing justice and hear what it was designed to do sonically. obviously other have the expertise for that. Any suggestions welcome.
    One suggestion is to get a power supply board from, lets say erhard audio
    See https://www.erhard-audio.com/Power_Supply_Kits.html , the topmost board ( $42 )
    replaces the filament caps and Se rectifier and also replaces the can cap, all this as
    the price of teh can-cap.

    Grounding is no pain, just follow the instructions that comes with the board. The result
    will be an amp that can be serviced in the future using standard components ( board mounted
    electrolytes, standards Si diodes etc)
    PeterCapo
    PeterCapo

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    Post by PeterCapo on Sat May 23, 2020 8:40 am

    Midwestside wrote:

    Yes, my bed time too.  I read what you wrote,  I will start with the filament supply and then wait for the rest. Its in nice shape, i just want to do this thing justice and hear what it was designed to do sonically. obviously other have the expertise for that. Any suggestions welcome.

    It might not be necessary to change all of its parts to arrive at a satisfying sound.  Maybe work in stages.  For instance, start with a refresh of the filament and B+ supplies and see how you like it.  Then you could try changing the volume control pot, which has often been reported as an improvement.  You could then non-destructively bypass the tone controls, meaning you'd perform the bypass procedure in such a way that it could be reversed.  By following the tone control bypass procedure, you'd also eliminate the DC offset at the main preamp outputs.  Finally, check the voltages at the test nodes given on the right-hand side of page 11 of the manual and correct any problems you might find.  These things alone can result in a significant cleanup of the sound that you may find satisfactory without changing all of the parts.
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    rjpjnk

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    Post by rjpjnk on Sat May 23, 2020 11:55 am

    PeterCapo wrote:
    Midwestside wrote:

    Yes, my bed time too.  I read what you wrote,  I will start with the filament supply and then wait for the rest. Its in nice shape, i just want to do this thing justice and hear what it was designed to do sonically. obviously other have the expertise for that. Any suggestions welcome.

    It might not be necessary to change all of its parts to arrive at a satisfying sound.  Maybe work in stages.  For instance, start with a refresh of the filament and B+ supplies and see how you like it.  Then you could try changing the volume control pot, which has often been reported as an improvement.  You could then non-destructively bypass the tone controls, meaning you'd perform the bypass procedure in such a way that it could be reversed.  By following the tone control bypass procedure, you'd also eliminate the DC offset at the main preamp outputs.  Finally, check the voltages at the test nodes given on the right-hand side of page 11 of the manual and correct any problems you might find.  These things alone can result in a significant cleanup of the sound that you may find satisfactory without changing all of the parts.

    I agree with this. The readily available replacement boards for the power supply that provide both B+ and filament voltage are a real win/win in my opinion. You can take out the original selenium rectifier and big caps in one piece and put it in a box to save for later so you have all original parts for the next generation when these become even more of a collector's item, and you don't have to remove the can at all.

    I have one of these boards and it works great except for one thing. The filament voltage is too high, but this is simple to remedy with a resistor. The Dynaco original design runs the filaments a little low for a reason.

    https://www.ebay.com/itm/Dynaco-PAS-Z-PSU-Power-Supply-Upgrade-Kit-6/122728355713?hash=item1c932e1781:g:XowAAOSwstJZRtGi
    Midwestside
    Midwestside

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    Post by Midwestside on Sat May 23, 2020 1:01 pm

    peterh wrote:
    Midwestside wrote:

    Yes, my bed time too.  I read what you wrote,  I will start with the filament supply and then wait for the rest. Its in nice shape, i just want to do this thing justice and hear what it was designed to do sonically. obviously other have the expertise for that. Any suggestions welcome.
    One suggestion is to get a power supply board from, lets say erhard audio
    See https://www.erhard-audio.com/Power_Supply_Kits.html  , the topmost board ( $42 )
    replaces the filament caps and Se rectifier and also replaces the can cap, all this as
    the price of teh can-cap.

    Grounding is no pain, just follow the instructions that comes with the board. The result
    will be an amp that can be serviced in the future using standard components ( board mounted
    electrolytes, standards Si diodes etc)

    I went ahead and ordered one. The one rjpjnk recommended. I just read the SDS ones were kind of confusing so i wrote off the idea entirely.
    I also have volume , balance and tone control kit coming from dynaco designs as well as an LED light replacement.

    So that will be phase one i suppose.

    I want that original refreshed sound. I know i have a ground loop or some other hum for the phono, and maybe a rewire and a new selector switch would help.
    The turntable grounds to the chassis and gets quieter, but there is still faint buzzing in both speakers that you can 'sense' more than hear, but you can hear it.

    I know im in the right place for help, so i can take it slow , just need to get the critical pieces refreshed first.

    would an rca back panel upgrade be night and day with better contacts?

    Someone asked about the tubes i think it came with 2x chinese 12ax7 and 2x 12ax7 sovtek (which are in the phono section)
    peterh
    peterh

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    Post by peterh on Sat May 23, 2020 1:34 pm

    Midwestside wrote:
    peterh wrote:
    Midwestside wrote:

    Yes, my bed time too.  I read what you wrote,  I will start with the filament supply and then wait for the rest. Its in nice shape, i just want to do this thing justice and hear what it was designed to do sonically. obviously other have the expertise for that. Any suggestions welcome.
    One suggestion is to get a power supply board from, lets say erhard audio
    See https://www.erhard-audio.com/Power_Supply_Kits.html  , the topmost board ( $42 )
    replaces the filament caps and Se rectifier and also replaces the can cap, all this as
    the price of teh can-cap.

    Grounding is no pain, just follow the instructions that comes with the board. The result
    will be an amp that can be serviced in the future using standard components ( board mounted
    electrolytes, standards Si diodes etc)

    I went ahead and ordered one. The one rjpjnk recommended.  I just read the SDS ones were kind of confusing so i wrote off the idea entirely.
    I also have volume , balance and tone control kit coming from dynaco designs as well as an LED light replacement.

    So that will be phase one i suppose.

    I want that original refreshed sound. I know i have a ground loop or some other hum  for the phono, and maybe a rewire and a new selector switch would help.
    The turntable grounds to the chassis and gets quieter, but there is still faint buzzing in both speakers that you can 'sense' more than hear, but you can hear it.

    I know im in the right place for help, so i can take it slow , just need to get the critical pieces refreshed first.

    would an rca back panel upgrade be night and day with better contacts?

    Someone asked about the tubes  i think it came with 2x chinese 12ax7 and 2x 12ax7 sovtek (which are in the phono section)
    changing selector won't cure hum problems, in fact is must be a last resort to be done
    if the selector breaks down.
    The dynaco selector has a big feature - it shorts unused inputs to prevent them from
    blleding over. As an example: a tuner might be on all the time, if one listens to
    phono ( or CD ) then you don't want radio ads or anything else bleed over to the
    phono music. Dynaco selector prevents this, the other i have seen does not.

    For debugging phono hum :
    get a pair of shorting plugs. Install them in the phono inputs, select phono and
    turn up volume. The expected AC signal  at the pre output should be 2-3 mV . If
    you measure this the amp is fine, the hum problem is to be fixed elsewhere.
    A ground connector between PAS and record player, make sure this is electrically
    connected to the tonearm outside.
    Connect the record player to the phono inputs, connect power amps and speakers.
    Move the cables between record player and PAS while listening at the speakers. Often
    cheap cables will pick up electromagnetic disturbances in the room, changes in
    volume while moving cables will confirm this. Bad contact a tthe backplace rca  connectors will
    be hearabe if rotating the contacts , a cleaning with a glassfiber brush usually fixes this.
    There is new backplanes to bye, but this are big jobs with lots off opportunities
    of problems. Like selector, avoid these if possible.


    Does any of the above actions work out ?


    Last edited by peterh on Sat May 23, 2020 1:37 pm; edited 1 time in total (Reason for editing : spelling)
    Midwestside
    Midwestside

    Posts : 44
    Join date : 2019-03-20

    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by Midwestside on Sat May 23, 2020 2:06 pm

    peterh wrote:
    Midwestside wrote:
    peterh wrote:
    Midwestside wrote:

    Yes, my bed time too.  I read what you wrote,  I will start with the filament supply and then wait for the rest. Its in nice shape, i just want to do this thing justice and hear what it was designed to do sonically. obviously other have the expertise for that. Any suggestions welcome.
    One suggestion is to get a power supply board from, lets say erhard audio
    See https://www.erhard-audio.com/Power_Supply_Kits.html  , the topmost board ( $42 )
    replaces the filament caps and Se rectifier and also replaces the can cap, all this as
    the price of teh can-cap.

    Grounding is no pain, just follow the instructions that comes with the board. The result
    will be an amp that can be serviced in the future using standard components ( board mounted
    electrolytes, standards Si diodes etc)

    I went ahead and ordered one. The one rjpjnk recommended.  I just read the SDS ones were kind of confusing so i wrote off the idea entirely.
    I also have volume , balance and tone control kit coming from dynaco designs as well as an LED light replacement.

    So that will be phase one i suppose.

    I want that original refreshed sound. I know i have a ground loop or some other hum  for the phono, and maybe a rewire and a new selector switch would help.
    The turntable grounds to the chassis and gets quieter, but there is still faint buzzing in both speakers that you can 'sense' more than hear, but you can hear it.

    I know im in the right place for help, so i can take it slow , just need to get the critical pieces refreshed first.

    would an rca back panel upgrade be night and day with better contacts?

    Someone asked about the tubes  i think it came with 2x chinese 12ax7 and 2x 12ax7 sovtek (which are in the phono section)
    changing selector won't cure hum problems, in fact is must be a last resort to be done
    if the selector breaks down.
    The dynaco selector has a big feature - it shorts unused inputs to prevent them from
    blleding over. As an example: a tuner might be on all the time, if one listens to
    phono ( or CD ) then you don't want radio ads or anything else bleed over to the
    phono music. Dynaco selector prevents this, the other i have seen does not.

    For debugging phono hum :
    get a pair of shorting plugs. Install them in the phono inputs, select phono and
    turn up volume. The expected AC signal  at the pre output should be 2-3 mV . If
    you measure this the amp is fine, the hum problem is to be fixed elsewhere.
    A ground connector between PAS and record player, make sure this is electrically
    connected to the tonearm outside.
    Connect the record player to the phono inputs, connect power amps and speakers.
    Move the cables between record player and PAS while listening at the speakers. Often
    cheap cables will pick up electromagnetic disturbances in the room, changes in
    volume while moving cables will confirm this. Bad contact a tthe backplace rca  connectors will
    be hearabe if rotating the contacts , a cleaning with a glassfiber brush usually fixes this.
    There is new backplanes to bye, but this are big jobs with lots off opportunities
    of problems. Like selector, avoid these if possible.


    Does any of the above actions work out ?


    Put in shorting plugs, phono selected, volume up got a reading of about .002v AC which i assume is Mv.
    There is no 'noise' twisting around the rca inputs. So i will try hooking a wire directly to the tone arm and moving around to the amp and the pas.
    Perhaps a new volume knob will help, i have to turn it to around 12 oclock to get good listenable sound for phono. with a cd player it can be around 10 oclock.
    I can turn the volume on phono to around 9 oclock and the buzz is amost non existent, but it is too low for listening.

    using another pre and a phono stage with the turntable grounded to the phono stage, i get no hum. so it must be a ground loop i suppose.
    PeterCapo
    PeterCapo

    Posts : 794
    Join date : 2008-12-05

    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by PeterCapo on Sat May 23, 2020 2:16 pm

    Midwestside wrote: ... I also have volume , balance and tone control kit coming from dynaco designs as well as an LED light replacement. ... I want that original refreshed sound. ...

    Don't shoot the messenger, but last time I looked it appeared to me as if the DD tone control kit is not an exact replacement for the original tone control circuit; looked to me like it is something different from the original.
    Midwestside
    Midwestside

    Posts : 44
    Join date : 2019-03-20

    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by Midwestside on Sat May 23, 2020 2:38 pm

    PeterCapo wrote:
    Midwestside wrote: ... I also have volume , balance and tone control kit coming from dynaco designs as well as an LED light replacement. ... I want that original refreshed sound. ...

    Don't shoot the messenger, but last time I looked it appeared to me as if the DD tone control kit is not an exact replacement for the original tone control circuit; looked to me like it is something different from the original.

    Its slightly different, I went for this based on ease of purchase. I did not set out to keep it  super all original, thought i might like to.
    I just didn't know 'correct' choices as such. I've never heard a pristine working PAS 3 so i may not even notice,
    I still have time to cancel the order, do you recommend a different route Peter Capo?
    My current volume knob and some of the tone controls fell 'jiggly' inside their housing. All controls are firmly mounted to face plate,
    but there is the slop in some of them.
    peterh
    peterh

    Posts : 1317
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by peterh on Sat May 23, 2020 2:45 pm

    Midwestside wrote:
    peterh wrote:
    Midwestside wrote:
    peterh wrote:
    Midwestside wrote:

    Yes, my bed time too.  I read what you wrote,  I will start with the filament supply and then wait for the rest. Its in nice shape, i just want to do this thing justice and hear what it was designed to do sonically. obviously other have the expertise for that. Any suggestions welcome.
    One suggestion is to get a power supply board from, lets say erhard audio
    See https://www.erhard-audio.com/Power_Supply_Kits.html  , the topmost board ( $42 )
    replaces the filament caps and Se rectifier and also replaces the can cap, all this as
    the price of teh can-cap.

    Grounding is no pain, just follow the instructions that comes with the board. The result
    will be an amp that can be serviced in the future using standard components ( board mounted
    electrolytes, standards Si diodes etc)

    I went ahead and ordered one. The one rjpjnk recommended.  I just read the SDS ones were kind of confusing so i wrote off the idea entirely.
    I also have volume , balance and tone control kit coming from dynaco designs as well as an LED light replacement.

    So that will be phase one i suppose.

    I want that original refreshed sound. I know i have a ground loop or some other hum  for the phono, and maybe a rewire and a new selector switch would help.
    The turntable grounds to the chassis and gets quieter, but there is still faint buzzing in both speakers that you can 'sense' more than hear, but you can hear it.

    I know im in the right place for help, so i can take it slow , just need to get the critical pieces refreshed first.

    would an rca back panel upgrade be night and day with better contacts?

    Someone asked about the tubes  i think it came with 2x chinese 12ax7 and 2x 12ax7 sovtek (which are in the phono section)
    changing selector won't cure hum problems, in fact is must be a last resort to be done
    if the selector breaks down.
    The dynaco selector has a big feature - it shorts unused inputs to prevent them from
    blleding over. As an example: a tuner might be on all the time, if one listens to
    phono ( or CD ) then you don't want radio ads or anything else bleed over to the
    phono music. Dynaco selector prevents this, the other i have seen does not.

    For debugging phono hum :
    get a pair of shorting plugs. Install them in the phono inputs, select phono and
    turn up volume. The expected AC signal  at the pre output should be 2-3 mV . If
    you measure this the amp is fine, the hum problem is to be fixed elsewhere.
    A ground connector between PAS and record player, make sure this is electrically
    connected to the tonearm outside.
    Connect the record player to the phono inputs, connect power amps and speakers.
    Move the cables between record player and PAS while listening at the speakers. Often
    cheap cables will pick up electromagnetic disturbances in the room, changes in
    volume while moving cables will confirm this. Bad contact a tthe backplace rca  connectors will
    be hearabe if rotating the contacts , a cleaning with a glassfiber brush usually fixes this.
    There is new backplanes to bye, but this are big jobs with lots off opportunities
    of problems. Like selector, avoid these if possible.


    Does any of the above actions work out ?


    Put in shorting plugs, phono selected, volume up  got a reading of about .002v AC  which i assume is Mv.
    There is no 'noise' twisting around the rca inputs.  So i will try hooking a wire directly to the tone arm and moving around to the amp and the pas.
    Perhaps a new volume knob will help, i have to turn it to around 12 oclock to get good listenable sound for phono.  with a cd player it can be around 10 oclock.
    I can turn the volume on phono to around 9 oclock and the buzz is amost non existent, but it is too low for listening.

    using another pre and a phono stage with the turntable grounded to the phono stage, i get no hum. so it must be a ground loop i suppose.
    Your PAS seems to have no internal generated hum, it's externally you find the source of hum.
    A new volume pot ( not knob) won't change anything here. It will help if tracking is bad.
    Now back to hum:
    Ground loop is unlikely as the PAS has no ground connection with it's 2 prong cable.
    Connecting the PAS case to ground might change things. The proper way is to install
    a 3 prong mains cable , but before that a ground cable connected to any of the backside screws
    will do. Reversing the power cord might also make a difference.
    Mine PAS is grounded with a copper cable to my outlet ground, as are the rest of
    my equipment.
    The volume differences of various sources comes by the sources, there is no standard
    (or rather many conflicting standards) for "line level" sources. Some preamps has
    adjusting pots for each input, PAS lacks this.

    peterh
    peterh

    Posts : 1317
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by peterh on Sat May 23, 2020 2:53 pm

    Best not lack focus, do one thing at a time ; hum is one set of actions , then if
    any of the pots needs changing do that. But don't dig everywhere at once !
    Volume pot is available ( you need a 250k w/loudness
    which is available at ebay). The tonecontrol pots differs for PAS3 and PAS3X. The PAS3X is special
    and has as far as i know no source other then used from scrapped amps.
    PAS bass pot is 750k, the treble pot 400k both rather unusual but not impossible to find.
    Midwestside
    Midwestside

    Posts : 44
    Join date : 2019-03-20

    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by Midwestside on Sat May 23, 2020 3:14 pm

    Your PAS seems to have no internal generated hum, it's externally you find the source of hum. A new volume pot ( not knob) won't change anything here. It will help if tracking is bad. Now back to hum: Ground loop is unlikely as the PAS has no ground connection with it's 2 prong cable. Connecting the PAS case to ground might change things. The proper way is to install a 3 prong mains cable , but before that a ground cable connected to any of the backside screws will do. Reversing the power cord might also make a difference. Mine PAS is grounded with a copper cable to my outlet ground, as are the rest of my equipment. The volume differences of various sources comes by the sources, there is no standard (or rather many conflicting standards) for "line level" sources. Some preamps has adjusting pots for each input, PAS lacks this. wrote:


    I basically had my turntables ground wire connected to to the PAS testing it via aligator clip to PAS chassis screw. It never occurred to me that the PAS wasn't grounded. I may install a 3 prong or atleast switching it around for now.

    Best not lack focus, do one thing at a time ; hum is one set of actions , then if any of the pots needs changing do that. But don't dig everywhere at once ! Volume pot is available ( you need a 250k w/loudness which is available at ebay). The tonecontrol pots differs for PAS3 and PAS3X. The PAS3X is special and has as far as i know no source other then used from scrapped amps. PAS bass pot is 750k, the treble pot 400k both rather unusual but not impossible to find. wrote:

    Ok, i may cancel the order for the pot kits. I just thought certain pots were causing weirdness. when i turn one of the sloppy tone pots, i hear a 'crack / pop' in the channel.

    Like i said, i wasn't sure where i could make the biggest impovement, i figured it was in the controls / tone circuit. Maybe i should slow down.
    PeterCapo
    PeterCapo

    Posts : 794
    Join date : 2008-12-05

    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by PeterCapo on Sat May 23, 2020 4:05 pm

    Yes, slowing down could be helpful to achieving your desired goal.

    All of my comments are, of course, my opinion and will be in reference to you goal as I understand it.  At the following link, you'll see a close-up image of the DD kit to which you refer, taken from the DD website: https://dynacodesigns.files.wordpress.com/2017/05/p4d.jpg?w=1107&h=&zoom=2  Can't get a good look at the value of the balance pot, but the value of the volume pot and tone controls are different from the original PAS.  When you introduce changes, the sound can change and there could be other issues, for instance Audio Regenesis discussed some of the technical effects from changing the original 250KΩ volume pot to a 100KΩ.  I see this kind of kit as more appropriate for someone whose original tone pots are damaged, non-functioning or missing and who is not particular about retaining originality.  There isn't much more information on the website about how the DD tone control circuit may function differently from the original and how the DD kit is integrated into the circuit - would be helpful to see a schematic.  Another consideration is that, AFAIK, there are no published specs for the preamp with this kit installed, and neither are there, AFAIK, any results from a disinterested lab analysis.

    I've read a number of posts where folks have reported a significant improvement in sound quality by replacing the volume pot with a "better" pot or stepped attenuator.  My own PAS improved when I went to a better volume pot.  The nice thing about this is that you get an improvement in the sound quality while keeping the circuit design original.  Lacking more details about the pots in the DD kit, IMO they do not look like anything of standout quality.  Audiophile-preferred upgrades to the original volume pot include Blue Alps, or a stepped attentuator, or something like the Noble brand pots (if you can still find them).

    Sounds like one or more of your original tone control pots aren't working quite right.  If you want to keep to the originality of the PAS, then you'd need to find exact replacements if they are even available (I kind of doubt it).  If not, then the only option is to bypass them, which will clean up the sound (the bypass procedure also has the benefit of eliminating the DC offset at the main preamp outputs).  Or, go with the DD kit in spite of any open questions about it.  I don't know where to get replacements for the original tone pots.  Maybe @peterh can suggest where to look?
    peterh
    peterh

    Posts : 1317
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by peterh on Sat May 23, 2020 5:06 pm

    Midwestside
    Midwestside

    Posts : 44
    Join date : 2019-03-20

    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by Midwestside on Sat May 23, 2020 5:41 pm

    peterh wrote:
    Midwestside wrote:
    peterh wrote:
    Midwestside wrote:
    peterh wrote:
    Midwestside wrote:

    Yes, my bed time too.  I read what you wrote,  I will start with the filament supply and then wait for the rest. Its in nice shape, i just want to do this thing justice and hear what it was designed to do sonically. obviously other have the expertise for that. Any suggestions welcome.
    One suggestion is to get a power supply board from, lets say erhard audio
    See https://www.erhard-audio.com/Power_Supply_Kits.html  , the topmost board ( $42 )
    replaces the filament caps and Se rectifier and also replaces the can cap, all this as
    the price of teh can-cap.

    Grounding is no pain, just follow the instructions that comes with the board. The result
    will be an amp that can be serviced in the future using standard components ( board mounted
    electrolytes, standards Si diodes etc)

    I went ahead and ordered one. The one rjpjnk recommended.  I just read the SDS ones were kind of confusing so i wrote off the idea entirely.
    I also have volume , balance and tone control kit coming from dynaco designs as well as an LED light replacement.

    So that will be phase one i suppose.

    I want that original refreshed sound. I know i have a ground loop or some other hum  for the phono, and maybe a rewire and a new selector switch would help.
    The turntable grounds to the chassis and gets quieter, but there is still faint buzzing in both speakers that you can 'sense' more than hear, but you can hear it.

    I know im in the right place for help, so i can take it slow , just need to get the critical pieces refreshed first.

    would an rca back panel upgrade be night and day with better contacts?

    Someone asked about the tubes  i think it came with 2x chinese 12ax7 and 2x 12ax7 sovtek (which are in the phono section)
    changing selector won't cure hum problems, in fact is must be a last resort to be done
    if the selector breaks down.
    The dynaco selector has a big feature - it shorts unused inputs to prevent them from
    blleding over. As an example: a tuner might be on all the time, if one listens to
    phono ( or CD ) then you don't want radio ads or anything else bleed over to the
    phono music. Dynaco selector prevents this, the other i have seen does not.

    For debugging phono hum :
    get a pair of shorting plugs. Install them in the phono inputs, select phono and
    turn up volume. The expected AC signal  at the pre output should be 2-3 mV . If
    you measure this the amp is fine, the hum problem is to be fixed elsewhere.
    A ground connector between PAS and record player, make sure this is electrically
    connected to the tonearm outside.
    Connect the record player to the phono inputs, connect power amps and speakers.
    Move the cables between record player and PAS while listening at the speakers. Often
    cheap cables will pick up electromagnetic disturbances in the room, changes in
    volume while moving cables will confirm this. Bad contact a tthe backplace rca  connectors will
    be hearabe if rotating the contacts , a cleaning with a glassfiber brush usually fixes this.
    There is new backplanes to bye, but this are big jobs with lots off opportunities
    of problems. Like selector, avoid these if possible.


    Does any of the above actions work out ?


    Put in shorting plugs, phono selected, volume up  got a reading of about .002v AC  which i assume is Mv.
    There is no 'noise' twisting around the rca inputs.  So i will try hooking a wire directly to the tone arm and moving around to the amp and the pas.
    Perhaps a new volume knob will help, i have to turn it to around 12 oclock to get good listenable sound for phono.  with a cd player it can be around 10 oclock.
    I can turn the volume on phono to around 9 oclock and the buzz is amost non existent, but it is too low for listening.

    using another pre and a phono stage with the turntable grounded to the phono stage, i get no hum. so it must be a ground loop i suppose.
    Your PAS seems to have no internal generated hum, it's externally  you find the source of hum.
    A new volume pot ( not knob) won't change anything here. It will help if tracking is bad.
    Now back to hum:
    Ground loop is unlikely as the PAS has no ground connection with it's 2 prong cable.
    Connecting the PAS case to ground might change things. The proper way is to install
    a 3 prong mains cable , but before that a ground cable connected to any of the backside screws
    will do. Reversing the power cord might also make a difference.
    Mine PAS is grounded with a copper cable to my outlet ground, as are the rest of
    my equipment.
    The volume differences of various sources comes by the sources, there is no standard
    (or rather many conflicting standards) for "line level" sources. Some preamps has
    adjusting pots for each input, PAS lacks this.


    I just changed it to a 3 prong cable soldered in. Buzz is gone!
    However, on the phono section the volume controller is good for listening about 9 oclock.
    For spare, with a cd player hooked in, i have to crank it to 12'oclock.
    Thats why i thought something could be wrong with the vol controller, tone circuit or something else.
    Midwestside
    Midwestside

    Posts : 44
    Join date : 2019-03-20

    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by Midwestside on Sat May 23, 2020 5:43 pm

    I've read a number of posts where folks have reported a significant improvement in sound quality by replacing the volume pot with a "better" pot or stepped attenuator. My own PAS improved when I went to a better volume pot. The nice thing about this is that you get an improvement in the sound quality while keeping the circuit design original. Lacking more details about the pots in the DD kit, IMO they do not look like anything of standout quality. Audiophile-preferred upgrades to the original volume pot include Blue Alps, or a stepped attentuator, or something like the Noble brand pots (if you can still find them). wrote:


    I have a 250k and 150k alps pot from parts express. However it has no loudness tap.
    PeterCapo
    PeterCapo

    Posts : 794
    Join date : 2008-12-05

    Recomended voltage ratings for PAS 3 resistors and caps Empty Re: Recomended voltage ratings for PAS 3 resistors and caps

    Post by PeterCapo on Sat May 23, 2020 5:58 pm

    Without loudness taps, there have been reports of too much gain with too little rotation of the volume pot. There have also been some reports contradicting this. Not sure what to make of it. Having one with loudness taps should avoid any difficulty.

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