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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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Seamus
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    new amp style - vote your opinion !

    tubes4hifi
    tubes4hifi
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    Post by tubes4hifi Wed Dec 15, 2021 3:00 pm

    Hello all,
    this is a followup to my opinion poll about 3 months ago.
    I had a couple samples made, so here are some photos.
    The top is identical on both, as per the survey, staggered tubes.  ALL parts mount on the top plate.
    NO parts mount on the chassis itself.   This makes assembly SUPER EZ !
    Top photo is on black steel chassis, bottom photo on stainless steel chassis.
    I may eliminate the quad cap and put caps under the top, not sure yet.   Also for this octal version will use longer spacers
    so the tubes don't stick out the top so much.
    Let me know what everyone thinks!   The chassis is 14 x 11", and will also be used for ALL amps, ST70, ST120, M125s, plus a few new ones!

    new amp style - vote your opinion ! New-amp-BS


    new amp style - vote your opinion ! New-amp-SS

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    ttocs
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    Post by ttocs Wed Dec 15, 2021 5:29 pm

    Very nice! I like the Stainless Steel version.

    I'm also very interested in seeing how this chassis would look for the M-125!!
    solderblob
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    Post by solderblob Wed Dec 15, 2021 5:33 pm

    Roy, I'm sure it might be too difficult to do, but my wish would be to have a voltmeter and selector switch to measure bias of the output tubes.

    BTW, I like it!

    dave

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    ttocs
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    Post by ttocs Wed Dec 15, 2021 5:39 pm

    +1 ^^^^
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    ltusler


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    Post by ltusler Wed Dec 15, 2021 6:14 pm

    And balanced inputs?
    tubes4hifi
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    Post by tubes4hifi Wed Dec 15, 2021 6:18 pm

    good ideas, all.
    I see 40 people looked at this but only 2 or 3 posts so far.

    Here's some possibilities for M125s below, maybe even room for a meter and switch

    new amp style - vote your opinion ! M140


    new amp style - vote your opinion ! M140b
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    ericoto


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    Post by ericoto Wed Dec 15, 2021 7:59 pm

    Like the M125 layout with everything on the top, would look great in stainless. Keeping switch and AC away from output would also be helpful. What about adding a ground loop beaker? Yes to eliminating quad cap too expensive

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    corndog71
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    Post by corndog71 Thu Dec 16, 2021 12:05 am

    I’ve drawn up a similar design but without the quad cap.
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    DavidT1


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    Post by DavidT1 Thu Dec 16, 2021 2:51 pm

    Hello Roy,

    Looks good! Almost like ours. We reversed the output tube stagger, however, so that the tubes make a continuous "smile" shape.

    David

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    buchela


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    Post by buchela Thu Dec 16, 2021 9:23 pm

    I am not a fan of the quad cap on top of the chassis, it's like looking through a window, with a light pole right in front of it. Yes, placing it on top solves many unnecessary complications, but......
    Trying to relocate the quad under the chassis is impossible.(M-125) unless a bigger chassis is made.
    I like the second photograph.
    On the two proposed layouts, there are too many things on top, old school style, if that is the look you are shooting for, you are spot on.
    I wonder if it is possible to move the rectifier and quad cap, behind the transformers, ( M-125 ) for a cleaner look. corndog made a very interesting layout for his M125, and it looks great, although the chassis is larger than the original.
    My 1/8 of a cent

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    Post by corndog71 Fri Dec 17, 2021 1:31 am

    buchela wrote:I am not a fan of the quad cap on top of the chassis, it's like looking through a window, with a light pole right in front of it. Yes, placing it on top solves many unnecessary complications, but......
    Trying to relocate the quad under the chassis is impossible.(M-125) unless a bigger chassis is made.
    I like the second photograph.
    On the two proposed layouts, there are too many things on top, old school style, if that is the look you are shooting for, you are spot on.
    I wonder if it is possible to move the rectifier and quad cap, behind the transformers, ( M-125 ) for a cleaner look. corndog made a very interesting layout for his M125, and it looks great, although the chassis is larger than the original.
    My 1/8 of a cent

    I appreciate the compliment. I’ve considered rebuilding them with a tighter layout but I spent a lot of money on those chassis plates and ultimately I’m still happy with them.

    I did make a few changes underneath in the last year or so. I added a ground loop breaker and 3 amp diodes to the rectifier socket. I recently swapped the electrolytic cap on the voltage amp section of the driver circuit to a 45uF Clarity Cap TC film cap. This made a noticeable step up in dynamics. Those Clarity TC caps are really big but they easily sound better than electrolytic caps. When directly compared the latter add a slight haze to the sound. Bias has been very stable over the last couple years. And they are virtually dead quiet with my 97dB sensitive speakers.

    I have most of the parts to make a VTA-70 with octal drivers. I just need a chassis and a way to secure the big Clarity caps. I have a design ready but unfortunately it’s been put on hold until I take care of some other responsibilities.

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    vtshopdog
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    Post by vtshopdog Fri Dec 17, 2021 12:55 pm

    Plus 1 for replacing the quad cap with modern electrolytics housed inside the chassis but for functional rather than cosmetic reasons. This would enable reworking and modernizing the grounding scheme as quad cap elements would no longer be tied to the chassis.

    My thinking here is if you’re going to make layout revisions why not update the functionality as well?

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    kaner
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    Post by kaner Fri Dec 17, 2021 6:56 pm

    100% love the stainless. I also like the quad cap on top, for what it's worth.
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    Post by yel17 Sat Dec 18, 2021 7:40 am

    DavidT1 wrote:Hello Roy,

    Looks good! Almost like ours. We reversed the output tube stagger, however, so that the tubes make a continuous "smile" shape.

    David

    Reversing the output tube stagger to a smile shape moves the right rear tube a little further away from the quad cap. That is desirable because heat reduces the usable life of electrolytic capacitors. KT88s and KT120s generate substantial amounts of heat.
    I would seriously consider buying one with this output tube configuration.
    I like stainless steel.
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    Post by corndog71 Sun Dec 19, 2021 12:40 am

    One thing I would suggest for Roy is to move the bias test points to the outer side of the power tubes. Having them on the inner side right in between a bunch of hot tubes reminds me of that old game Operation.

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    Post by Hops Sun Dec 19, 2021 7:16 pm

    Not particularly in the market for an amp -- I have an Dynakit Parts ST-35 and an ST-120, both of which sound great. If I was in the market for an amp. I would like: grounded three prong plug, switch on the power cord, multiple input power taps so I didn't need to use a variac, two rectifiers to reduce the load on the tube rectifiers ( ST-120 periodically eats rectifiers) and something other than pushing VOM leads into a socket to read bias -- at least a better way of connecting to ground than scratching up the front of my amp with a VOM lead. I liked the earlier poster's idea of a voltage display and selector switch for setting bias. Maybe include the parts for the yellow sheet mod and make them part of the standard instructions.

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    Post by jimmeq Mon Dec 20, 2021 6:29 pm

    I assembled an ST-120 in 2016, and am in the cue for a pair of M-125's; I choose the stainless steel version. For the 125, the top drawing.
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    Post by Sfguitarworks Mon Dec 27, 2021 1:04 pm

    Having just installed a Triode Power board in mine, it seems caps on a board are the way to go. I like the black. Are the black buttons near the power tubes bias access points? If not, that would be a real handy place, with a ground receptacle for your neg probe. I hate trying to wedge the negative probe here and there.

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    Post by Dale Stevens Tue Dec 28, 2021 3:45 pm

    Stainless.
    X2 for a ground receptacle for the neg meter probe. Also, a point to read the incoming ac from a variac. I'm the one who drilled a small hole in the ac fuse cap, but that's in the rear (ST-120) Dale
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    Post by BryceJ Wed Dec 29, 2021 2:17 pm

    I really like the stainless steel chassis for the M125. I am not quite sure what all of the holes are for on the top. Are the two holes without mounting holes for capacitors? One suggestion I would make is that the two octal driver tubes be spaced far enough apart that the larger "coke bottle" shaped tubes will fit comfortably. I think cleaning up the front of the M125 chassis is a huge improvement.
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    Post by Seamus Wed Dec 29, 2021 2:28 pm

    tubes4hifi wrote:Also for this octal version will use longer spacers so the tubes don't stick out the top so much.

    Tubes like the KT88 will not benefit from spacers as the base is much larger than the socket. Use of top mount sockets would solve the KT88 et al. problem as would using counter sunk screws for the sub chassis socket.
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    Post by ttownscott Wed Dec 29, 2021 5:09 pm

    I also agree on removing the quad cap. My vta amp I used the triode cap board and my Curcio amp I used his cap board. I kept my quad caps just for cosmetics so I did not have a hole. However the flexibility of under chassis cap board with a hopefully cleaner top is a good idea.
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    Post by New2Tubez Thu Dec 30, 2021 5:43 pm

    I like the stainless chassis, not a fan of the brushed aluminum top- hard to clean and un-scratch. Don't mind the quad cap up top. Like bias points accessible, all I/O on the back panel including fused IEC. Ample cooling for an included inrush current limiter. NO meters, LEDs. Does the rectifier need to be really close the the xformer? Maybe a little more airspace unless it interferes with the sound. Maybe room for an attenuator? A little more height than the ST120 (breathing room). Nice work Roy!

    Torx instead of slot screws (again- fewer scratches)- I did this on my ST120 and they don't look out of place.
    new amp style - vote your opinion ! Img_7815
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    new amp style - vote your opinion ! Img_7814
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    Post by Corona Thu Jan 06, 2022 3:39 pm

    I've currently got m125s and a sp14 so I'm not really in the market currently, but I do like the look of it. I like the quad cap on top because it gives that legit vintage vibe. As for future products, I could see myself wanting to build a tube headphone amp kit or a single ended triode amp.
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    Post by tubes4hifi Fri Jan 07, 2022 1:25 am

    OK, finally, real life photos of the new amp style for either ST70 or ST120
    this chassis is 14" wide x 10.5" deep instead of the usual 13" wide x 9.5" deep
    same price - no quad cap, all the caps are under the hood, and the PCB is not exposed

    www.tubes4hifi.com/amps.htm

    new amp style - vote your opinion ! VTA80-front2

    new amp style - vote your opinion ! VTA80-rear2

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