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    VTA PH15 Build thread PH14

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    TMadden

    Posts : 99
    Join date : 2011-12-22

    Re: VTA PH15 Build thread PH14

    Post by TMadden on Fri Apr 20, 2012 9:39 pm

    You might want to get a pair of the PC boards for small transformers shown on this page:
    http://www.kandkaudio.com/accessories.html if you haven't already. Makes it much easier to work with the Lundahls.

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Fri Apr 20, 2012 9:45 pm

    Yeah I got those boards too

    TMadden

    Posts : 99
    Join date : 2011-12-22

    Re: VTA PH15 Build thread PH14

    Post by TMadden on Fri Apr 20, 2012 10:04 pm

    I have settled on Jan Philips 6922's and RCA clear top 12AU7 in my PH14. You can pick up the Jan Philips pretty reasonable if you want to try them. Sounds very good to my ears!

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Thu Apr 26, 2012 5:18 pm

    Lundhal LL9226's arrived and I will install tonight. the hope is these mate with my cartridge better than the Jensen 34Ks I am using. I do get some "edge" on high level signals off vinyl and I am hoping this will fix that. they were $100 each. The next step up is the LL1931 which are about $250 each and above that is the LL1931Ag which is silver wire wound and I am told those are $800 each! backing up a bit, I was told (by a knowledgeable party) that the 9226 is not "embarrassed" by the 1931, it just sound a bit better. and a bit better more is the silver wound one. can't wait to hear what this sounds like.

    Tube Nube

    Posts : 643
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: VTA PH15 Build thread PH14

    Post by Tube Nube on Thu Apr 26, 2012 8:02 pm

    I've been using the K & K step up transformer kit with the LL1931 in it. I have nothing else to compare it with, but I'm sure pleased with the sound of my analog system. Assembling the thing was quite fun as well. It's a good little kit, straight forward to build.

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Fri Apr 27, 2012 1:26 am

    You're looking at a $2000 phono stage kids. Roy's PH15 with all the goodies.












    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Fri Apr 27, 2012 12:47 pm

    I was watching a used pair of Amperex white lettering pinched waist 6922, apparently the holy grail in 6922's. they sold for about $540US for the pair. INSANE! I will live with my lowly Amperex JAN 6922's :/

    http://www.ebay.ca/itm/251044599175?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

    From what I am read in order from best to worst:

    - Amperex 6922 pinched waist white lettering
    - Amperex 6922 PQ white lettering
    - Amperex 6922 PQ orange lettering
    - Amperex 6922 PQ all others
    - Amperex JAN 6922 white lettering
    - Amperex JAN 6922 all others
    - All other 6922's

    This doesn't include the 7308's which are a mil spec version and also shuffle into that list where basically the 7308 version is better than the 6922 version.

    I might splurge on the PQ white lettering one day. they are around $100 a tube from what I have seen.

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Thu May 10, 2012 2:51 pm

    Update. Had 3 custom enclosures made by Keith Kirby with Bolivian Rosewood side panels. They arrived monday and as of today I have the chassis parts installed. The internal wiring+work needs to be completed which I hope to have done today. The enclosures are just amazing - very high quality workmanship from Keith and the materials are top notch. I used an optical centre punch and cobalt unibit for the round holes and a nibble for the IEC hole which was a lot of work because of the thick gauge aluminum Keith uses. I also EMI shielded the wood panels on the inside with copper tape.

    Here is the over-all "look" of the system. The top case is the PH15 power supply, the middle is a passive line stage and the bottom is the PH15. They PSU and PH15 connect with a 4 conductor umbilical shown in the other picture.

    Some interesting features of this design: note the 3 large holes on the top edge of the PSU and PH15 - this allows the power connector to be moved so you can run the umbilical however you want, the open holes will provide some extra ventilation. Also, Keith's cases assume that the cover plate will be the bottom - there are more screws and they are not counter sunk like they are on the top. typically you'd use the cases to make a tube amp and have the tubes sticking out the top so the removable panel makes sense on the bottom. in my design, all the electronics are in the enclosure and I want the cover to the top to gain easy access to the tubes etc. what I did was make the cover the bottom for the PSU (the board will be mounted on the bottom plate) and for the PH15 the cover is the top. the reason for this is, that when stacked with the PSU on the top, it looks better from the top. When stacked it doesn't matter what the PH15 looks like and its better to have the cover be the top for tube access. if you have them side by side, then ok, the top of the PH15 wont look as nice, but i think typically they would be stacked and the PH15 be on the bottom. hence the decision to do it this way.

    Tonight I will finish this up and report back with some nice pics.

    Oh and I did end up getting a pair of Amperex USA white lable PQ 6922's and they do sound smoother and more extended. i did some measurments of them compared to the green label and the EH's and i can see why.




    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Sat May 12, 2012 1:40 am

    I've got the PH15 operating. its amazing. anyway before i get into details, a question: i am getting about 50C/125F ambient temp inside the enclosures. would this be ok for solid state devices in the PSU and the 6922/12AU7 in the phono? It will be a real issue to create ventilation holes in the enclosures so i am hoping to get by without them.

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: VTA PH15 Build thread PH14

    Post by tubes4hifi on Sat May 12, 2012 4:10 pm

    those temps sound just about right, all the SS devices are rated at 100C, or 212F
    of course the tubes themselves usually run about 250-350F, so don't touch!!

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Fri May 18, 2012 12:19 pm

    I haven't posted any final shots of the build because I am still evaluating etc. I will post some pics soon. needless to say the project turned out really well. better than I expected. the PH15 sounds really great and is a major step up from what I was using for a phono stage, and that was a pretty high end solid state phono stage. I still get some hum but its bearable however the hum output is considerably lower than the install in the temporary case - i think the PSU was sending EMI to the phono stage, right side, that it was closest too. that hum is gone but there is now an equal amount of hum at a lower level coming through. i *think* its coming in from the turntable but i am not sure.

    I also am having some serious microphonics. but that's the tubes. i have some dampers on order so hopefully that will help.

    like the guy in the SP14 post mentioned, i too have been staying up late listening to LPs especially during the final stages of the build. and since the PH15, i have basically not been listening to anything but LPs!

    Nice to see a big renaissance in vinyl too! lots of really nice pressings out there.

    heyraz

    Posts : 58
    Join date : 2011-10-26

    Re: VTA PH15 Build thread PH14

    Post by heyraz on Fri May 18, 2012 1:24 pm

    Try some NOS military tube types, preferably with triple mica and added support rods to reduce microphonics. That made all the difference in the world for me.
    Rich

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Fri May 18, 2012 1:56 pm

    @heyraz can you tell me specifically what tubes you are using? initially i got a pair of Amperex JAN 6922 green printing and then I read that the Amperex PQ with white printing sounded 2nd best to the coveted "pinched waist" version. I saw a pair of "pinched waist" tubes go on ebay for $550! im not spending that kind of money on these tubes. but the PQs sound good, better than the "green printing" Amperex's - I also did a spectral analysis of the PQ tube and it has a smoother response and is flatter on the high end so this accounts for the sound difference. but, they are quite microphonic.

    Good sounding 6922's seem to get quite expensive. well, $500-600 for 2 of the apparently "best sounding" 6922's around (the pinch waist). there was even a "pinched waist" that the seller said had sonic issues in his amp (noise, clicking) but it still sold for around $150. yikes.

    Anyway, let me know what you are using and I'll see if I can find any.

    In the meantime I ordered some dampers and hope that will help. if not the company offers a money back guarantee.

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: VTA PH15 Build thread PH14

    Post by tubes4hifi on Fri May 18, 2012 2:08 pm

    TubeDepot.com has a good selection of 6922 types (including several different Amperex) and they can be pre-tested
    for low-noise and low-microphonics, which is very important for this tube type.

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Fri May 18, 2012 2:23 pm

    Hi Roy. I know, I also got a pair of EH 6922's from tubedepot.com, low noise/microphonics. they sound ok but the Amperex PQ's sound much better, smoother, clearer. I find tubedepot's vintage tube prices quite high however, generally speaking, compared to ebay or classified. but then again its a crap shoot for microphonics.

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: VTA PH15 Build thread PH14

    Post by tubes4hifi on Fri May 18, 2012 4:21 pm

    another good supplier for new and used is Brent Jesse, AudioTubes.com
    some nice Telefunken's for $175 a pair

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Fri May 18, 2012 5:18 pm

    wow those are insane prices. i don't have first hand experience with anything but the 6922's i have which are: new EH, vintage JAN green printing USA, vintage PQ white printing USA. The green print were $100 for the pair and the PQ's were $150 for the pair. from what i have read the PQ's are second best sounding to the pinched waist tubes which are $500-600/pr. but this is just what I have read. pretty much everyone who has tried the pinch waist and the PQ says the same thing: #1 pinch waist, #2 PQ, after that they are less distinct in terms of sound quality. so outside of spending $500 on 2 used tubes (NOT!) i got the PQ's. i will try dampers for the microphonics but really i can live with the microphonics because they only occur at loud volume levels. but granted microphonic tubes could cause sonic issues even at lower sound levels. i'll try and the dampers and take it from there...

    maybe one day i'll get a pair of pinch waist and try them. i understand from reviews that the telefunken and mullard 6922's are "meh". but in the 12AU7 world Telefunkens are some of the best sounding.

    heyraz

    Posts : 58
    Join date : 2011-10-26

    Re: VTA PH15 Build thread PH14

    Post by heyraz on Fri May 18, 2012 6:35 pm

    My situation is a little different as my preamp uses 12ax7's. In my situation I use a Sylvania Gold Brand 5751. The 5751 has a lower gain than typical 12ax7, but it's the military build that really makes the difference. I try to use a vintage military tube whenever I can and like pretty much anything made by RCA and Sylvania. I get them from ebay and have been lucky so far. I don't mind collecting a few extra tubes here and there because sometimes you need a tube that you don't care about if you're testing a component you're not sure about. Having a few extra tubes around also lets me "voice" the component. Kind of like changing the strings on a guitar.
    Rich

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Wed May 23, 2012 12:58 pm

    I am listening to a vinyl transcription I made using the PH15. As you may know from my previous posts I do have a bit of hum when listening to the PH15. I have installed parallel output jacks on the PH15 so I can go into my Dynaco MK3's and into my tube preamp/ADC -> computer. So the output of the PH15 drives both simultaneously.

    What is startling to me is that the transcription has NO hum on it! so the hum I am getting is not coming out of the PH15. The other output of the PH15 goes into my passive attenuator box, through a rotary switch and then through the passive attenuator. When listening to the PH15 through the amps, the hum level is affected by the attenuator, so I assumed that the hum was originating out of the PH15.

    This appears to not be the case, as the recording has no hum, recorded simultaneously as listening through the other outputs. Any ideas how I can trace this hum down?

    EDIT: I assume its a ground loop issue. all the components are plugged into the same grounded power bar. i guess its a matter of ground loop tracking down - unplug, try cheaters, etc. good news though that its not the PH15. in that sense the PH15 is dead quiet.

    I am going to make some recordings of just the PH15 output with no audio. I also want to test out the dampers I get to see if they help with the microphonic tubes - again I will make digital recordings of with and without to compare. I will post the results here.

    ruffian

    Posts : 43
    Join date : 2010-02-26

    Re: VTA PH15 Build thread PH14

    Post by ruffian on Sat Jun 02, 2012 2:02 pm

    Very nice. I'm about to start on my own PH14. I'm going to boprrow some ideas from you and Pigface and do some things different myself. I'm probably going to cut the board. Single chassis, I have the 16" widebody one. I'm giving serious consideration to a paired set of inputs to allow the use of RCA mounted load plugs.

    I studied your upgrades, you didn't use the Vishays for R4 and R13, can I assume cost being a factor and it being hard to arrive at the correct values without using several?
    Can I ask you what the board trace surgery and jumpers are for in the area of R13?

    Thanks.

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA PH15 Build thread PH14

    Post by plexus on Sat Jun 02, 2012 2:12 pm

    Hi. It was not possible to get the RIAA values using the values available in Vishay nude bulk film resistors. the cost would have been a factor as well, since each resistor is about $15-20 and you need 2 for those values. it gets expensive. but since the values were not available anyway...

    The surgery there is because the stock traces are for two resistors in series to arrive at the target value. instead, i used two different values in parallel so i had to convert that series arrangement to parallel.

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