ST35 Rev E!

for the DIY ST35, the Dynakit and every other PP EL84

ST35 Rev E!

Postby Shannon Parks » Wed Jul 17, 2013 6:05 pm

Here's a pic of the new Rev E. This is also the 10th Anniversary Edition.

Shannon
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Re: ST35 Rev E!

Postby highflyin9 » Wed Jul 17, 2013 11:01 pm

Congrats Shannon! Looking forward to hearing what sorts of changes you made.
My DIY Electronics Blog: DIYAudioBlog.com
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Re: ST35 Rev E!

Postby Shannon Parks » Thu Jul 18, 2013 5:43 am

Generally cleaned things up a bit. I've added screen and grid stoppers on the EL84s to make conversion to Dave Gillespie's EFB circuit much easier. But I also addressed some of the EFB features in a KISS-type of way, so the traditional bias circuit is still there but one can also use individually bypassed zeners, too. This means heavier current in Class AB won't raise the cathode bias due to the much lower series resistance of zener versus a 400 to 500 ohm resistor network, i.e. pseudo fixed bias. I also adjusted the power supply so that the 2nd and 3rd HV cap are combined for 240uF on the B+ supply, so it will be much more stout. Also will have cut & jumper mods for 6.3V phase splitters (6GU7/6FQ7/6CG7) and 6.3V voltage gain tubes like the 6N2P.

The layout and mounting holes remain the same so upgrading an old DIY ST35 (Rev C & D) is easy, and the Triode Electronics chassis is still supported. I probably will do an FPE top plate, too. Working on an updated manual, too.

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Re: ST35 Rev E!

Postby Marshman » Thu Jul 18, 2013 6:37 am

Looks great!!

Count me in for one!!

mm
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Re: ST35 Rev E!

Postby TomMcNally » Fri Jul 19, 2013 8:19 am

Sweet looking board as usual Shannon!

The Triode chassis and the ST-35 board make a very nice commercial quality amp at a reasonable price. Highly recommended for those guys who aren't into doing their own metalwork. I've built about 4 of them so far, in fact the picture on Triode's site is one of mine, maybe even the first one built.

Looking forward to putting one together.

My ST-35 revision B plays daily in my office!

... tom
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Re: ST35 Rev E!

Postby justinsweber » Sun Jul 21, 2013 10:05 am

I agree... The steel chassis and your board is is much nicer than most comerial units currently.
Havig the FPE board will be a nice option
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Re: ST35 Rev E!

Postby nyazzip » Tue Jul 30, 2013 7:58 pm

this is good news!
....i have a trace or 2 lifting on my Rev D, and i'd like to replace the whole board
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Re: ST35 Rev E!

Postby Kyle K » Fri Aug 30, 2013 12:59 pm

Shannon,

Are the Rev. E boards being supplied to Triode Electronics already? I thought I saw that version listed on their site.

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Re: ST35 Rev E!

Postby Shannon Parks » Sat Aug 31, 2013 8:55 am

Kyle K wrote:Shannon,

Are the Rev. E boards being supplied to Triode Electronics already? I thought I saw that version listed on their site.

Kyle


Yep - Triode Electronics now has the Rev E in stock. Looks like their name has shortened to Triode USA.

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Re: ST35 Rev E!

Postby TomMcNally » Mon Sep 09, 2013 6:56 pm

separks wrote: so the traditional bias circuit is still there but one can also use individually bypassed zeners, too. This means heavier current in Class AB won't raise the cathode bias due to the much lower series resistance of zener versus a 400 to 500 ohm resistor network, i.e. pseudo fixed bias.
Shannon


Hey Shannon ...

I just finished up my first "E" ... sounding good off the line. How should I adjust the bias with the Zener mod ?

... tom
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Re: ST35 Rev E!

Postby LMAN » Tue Sep 10, 2013 9:21 pm

I just started putting together the board and noticed some discrepancies between the BOM and the manual.
The 4.75k, 475K and 150K resistors are rated at 1/4 watt in the BOM but are listed at 1/2 watt in the manual. Similarly, the 10 ohm and 1K resistors are 1/8 watt in the BOM but are listed at 1/4 watt in the manual.

Which is correct?

Lou
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Re: ST35 Rev E!

Postby TomMcNally » Wed Sep 11, 2013 8:10 pm

Hi Lou -

Shannon replied to this question a week or so ago, but I can't find it.
He basically said the 1/8 watt and 1/4 watt resistors you have will work fine,
they are mil spec and well within the ratings.

I noticed that when I built mine, and it hasn't smoked yet!

Post some pix when you finish it up. I'll post some soon, although it will look pretty
much like the one on Triode's site, and will be taken in the same spot on my deck
as that one was. (y)

... tom
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Re: ST35 Rev E!

Postby Shannon Parks » Thu Sep 12, 2013 8:41 am

TomMcNally wrote:Hey Shannon ...

I just finished up my first "E" ... sounding good off the line. How should I adjust the bias with the Zener mod ?

... tom


Cool, Tom! OK, adjust the 100 ohm pot just like the old adjustable method. I would shoot for 33 to 35mA across the 10 ohm resistor. Let me know if you have plenty of adjustment range and what brand EL84s you are using. With these 2% Zeners, it should be fairly predictable, though some EL84s (like JJs) might be harder to get in range.

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Re: ST35 Rev E!

Postby Shannon Parks » Thu Sep 12, 2013 8:44 am

Tom is correct, Lou. Those resistors have different ratings for <70C and are derated for miltary specifications. All is good. I'll try and edit the manual in the future to clear that up.

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Re: ST35 Rev E!

Postby LMAN » Thu Sep 12, 2013 10:05 am

Thanks for the replies. I was pretty certain the lower rated parts would work but I wanted to be sure. When I'm finished I'll try to post some pictures - I'm using Shannon's FPE top plate for this build.

Lou
Last edited by LMAN on Mon Sep 16, 2013 10:56 am, edited 1 time in total.
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