List of power supply boards/options for ST-70?

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List of power supply boards/options for ST-70?

Postby Aljaheejus » Thu Feb 02, 2012 10:38 pm

Is there a thread or list of the currently available power supply boards/options for the ST-70? My ST-70 project will include the DIYtube driver, cloth-lead A470 OPTs, a new toroidal power tranny. Though I have a quad cap that is untested by me, I want to consider one of the modern cap boards depending on the response and recommendations from this forum. The chassis I am using had a quad cap meltdown, so I'm going to clean that up and rebuild. I have rebuilt an ST-70 before that I kept in the stock configuration with stock driver, so this one will include a variety of inexpensive upgrades.

I would like to ask here for the pros and cons of the power supply options, given the above parts I have, or have on the way.

Here's what I've found for capboards:

I was reminded of and I'm adding here the Curcio offering which can be either above or below chassis:
Blank Board w/ Parts (KIT-S7U-B) = $65

Classicvalves has one at http://www.classicvalve.ca/dynaco.html#ST70P but it is *out of stock* $19.50 plus parts $40 more or less I would guess. Geek, any lead time info?

There's the triodestore.com offering - an updated SDS Labs design...ST70capupgrade board alone $38.95 or with parts at $76.95

the original or classic SDS Labs board which would be a homemade (my first) PCB based on the design and instructions PDF download from http://www.quadesl.com/pdf/st70_capboard.pdf plus approx $38 - $49 in parts, it appears depending on cap values - regular or high.

Stock configuration options appear more affordable, but additionally require the PS parts (a couple of caps, resistors on the terminal strip as I recall) under the chassis :
Capacitor - Electrolytic, 30/20/20/20 µF @ 525 VDC from tubesandmore for $33.95 (This looks like the one I inherited with the project.)

Tubes4hi-fi: original type UPGRADED quad cap (80+40+30+20uF@525v) $40

Thanks in advance for your opinions and advice. I am not an electrical engineer, but love the hobby. I will save the bias options (maybe they are in the question above with some of the solutions) and rectification options questions for another evening/thread.
Last edited by Aljaheejus on Fri Feb 03, 2012 9:58 am, edited 1 time in total.
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Postby Geek » Fri Feb 03, 2012 12:02 am

I actually found two in a cleanup and put 'em on Facebook.... easier than updating the site for two boards.

They're still here if you want one.

Cheers!
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Postby Aljaheejus » Fri Feb 03, 2012 9:53 am

Thanks, Gregg! That is good to know, and I am very interested in your board. I have downloaded your instructions and they are only slightly over my head. I would appreciate it if you could elaborate a little bit on a comparison between yours and the SDS options?

Probably because I am not knowledgeable enough on the technology side, I am still unclear about the features and their sonic and user implications. For example, do both of these options (SDS labs and ClassicValves) take the place of the bias pots? Or optionally so? How do they affect the use of tube rectification / offer SS rectification? And, among those of you more tech-savvy and audio oriented do any of these power supply options _significantly_ affect the audio quality?

In particular, with the DIYtube driver I understand increasing capacitor values is not always better for sound quality. Because I notice that many increase values of the power supply capacitors - I would like assurance that I am choosing a PS configuration that is MOST compatible with the DIY tube driver and the rest of the build.

Thanks again, David.
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Postby DeathRex » Fri Feb 03, 2012 11:33 am

Just wondering, if you put in a CL-80 or without, can you use 500V electrolytic capacitors in a ST-70?
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Postby Geek » Fri Feb 03, 2012 3:08 pm

Aljaheejus wrote:I would appreciate it if you could elaborate a little bit on a comparison between yours and the SDS options?


Never heard a SDS in the ST-70, so maybe someone else could?

For example, do both of these options (SDS labs and ClassicValves) take the place of the bias pots?


Only mine has the bias replacements, but there's at least one copycat out there at the moment ;)

Or optionally so? How do they affect the use of tube rectification / offer SS rectification?


They are different. No one is better.


And, among those of you more tech-savvy and audio oriented do any of these power supply options _significantly_ affect the audio quality?


The only opinion that matters in this regard in yours - it's your ears. Any answer we're likely to give you is just opinion that may or may not jibe with your ears.

My answer is get both and try them.

Cheers!
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Postby Aljaheejus » Sat Feb 04, 2012 10:13 pm

DeathRex wrote:Just wondering, if you put in a CL-80 or without, can you use 500V electrolytic capacitors in a ST-70?

I appreciate your interest and question, but with my limited knowledge and familiarity with the circuitry I can only take a wild guess that you might be talking about this "CL-80" that I found via scroogle on Mouser at:
http://www.mouser.com/Search/Refine.aspx?Keyword=527-CL80

with a data sheet at: http://www.ge-mcs.com/download/temperature/920_325a.pdf

So, "no" I'm not putting one in though I'd like to find out more if this is something I should consider, and I would need a schematic showing it's placement.

I think I better just follow the DIYtube installation instructions in context of a stock circuit with the introduction of a cap board in the power supply, and a diode in lieu of the selenium rectifier.
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Postby Aljaheejus » Sat Feb 04, 2012 10:25 pm

.......

The only opinion that matters in this regard in yours - it's your ears. Any answer we're likely to give you is just opinion that may or may not jibe with your ears.

My answer is get both and try them.

Cheers!


Thanks for addressing all my questions! I appreciate it. and want to hear it all. I may just use the old Quad Cap solution to start with to isolate any improvements in sound attributable to the two upgrades/alternate components that I have to use - DIYtube driver board and the toroidal power tranny. I'll send you a p-mail, Geek, if I decide to find out more about your bias/cap boards. Sounds interesting and it would save me getting the two pots.
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pentode - triode switching???

Postby Aljaheejus » Sat Feb 04, 2012 10:27 pm

Is the pentode / triode switching possible / compatible with the DIYtube driver installation?

Thanks again in advance, David
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Postby DeathRex » Sun Feb 05, 2012 8:51 am

Aljaheejus wrote:
DeathRex wrote:Just wondering, if you put in a CL-80 or without, can you use 500V electrolytic capacitors in a ST-70?

I appreciate your interest and question, but with my limited knowledge and familiarity with the circuitry I can only take a wild guess that you might be talking about this "CL-80" that I found via scroogle on Mouser at:
http://www.mouser.com/Search/Refine.aspx?Keyword=527-CL80

with a data sheet at: http://www.ge-mcs.com/download/temperature/920_325a.pdf

So, "no" I'm not putting one in though I'd like to find out more if this is something I should consider, and I would need a schematic showing it's placement.

I think I better just follow the DIYtube installation instructions in context of a stock circuit with the introduction of a cap board in the power supply, and a diode in lieu of the selenium rectifier.


Nope, sorry you won't need it because you have a GZ34. The GE CL-80/90 is a surge limiter, particularly helpful to keep the voltage down on the filter caps when using silicon rectification. It also keep curge currents down and helps the transformer.

The ST-70's power transformer is a 360-0-360 that would make a peak of 504 volts, running at about 420-430, which would be fine for 500 volt caps. You can use a can cap, but with more capacitance. CE's 80/40/30/20 µF @ 525 VDC would be good.

Put the 40uf section first, the 80uf section would shorten the life of the GZ34.
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Postby Aljaheejus » Sun Feb 05, 2012 11:19 pm

Here are the images of what I am starting with.
http://home.bway.net/bogle/ST-70_before/st-70-before.html

You can see where the Quad Cap leaked corrosive stuff both inside and outside the chassis.

Can anyone assess if anything that remains might be fried from the Quad Cap meltdown?

Thanks, deathrex for more clarification on your question. I'll see if I can figure the ordering of the quad cap if I get that one. I'm still thinking of either using the 30/20/20/20 uF that came with this project chassis for starters, then installing one of the cap-board solutions.

Looks like both Curcio Audio's and ClassicValve's deal with bias and don't require the bias potentiometers, but I have not studied their schematics to confirm that.
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Postby burnedfingers » Fri Mar 02, 2012 7:07 pm

Quote:
Put the 40uf section first, the 80uf section would shorten the life of the GZ34.


Actually the Quicksilver mono block 8417's and KT88's have a first cap of 320 mfd/450vdc. Now there are a pair of 5Ar4's on the quicksilvers chassis. Without a diode mod they will eat a pair of 5AR4's in 6 months or less. With diode mods well I have 10 years on the rectifiers in my modified 8417 quicksilvers and their still running.
Have done 80mfd 1st cap with my diode mod and never had a problem.
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Postby Ty_Bower » Fri Mar 02, 2012 8:55 pm

I have a set of SDS boards in my Mark III. They work well, but lack features such as 2 oz cladding and through hole plating. The construction quality is OK, but not up to the same level as the boards that Shannon sells. I understand that SDS has recently improved their boards, so maybe they are heavier duty now.

I saw a CChong board in a Stereo 70, and it looked like a very nice board indeed. If I had known about CChong before I purchased the cap boards for my Mark III, I probably would have gone with his version instead. I can't say for certain whether or not they are still currently available. He used to sell exclusively through eBay.

CChong board for ST70:
Image
"It's a different experience; the noise occlusion, crisp, clear sound, and defined powerful bass. Strong bass does not corrupt the higher frequencies, giving a very different overall feel of the sound, one that is, in my opinion, quite unique."
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Postby jgf » Fri Apr 06, 2012 10:45 am

I got 2 of the SDS boards for Mark II / III a few months ago, they're good and solid. Project is on hold now, because the 2 power transformers I have are early/late and about as different in output voltage as possible. Anyone have any for trade?

One thing I don't get with some of these '70 boards now, why stack two 250v caps? 500v caps are easily available.
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Re: List of power supply boards/options for ST-70?

Postby pmarcin » Sat Apr 20, 2013 1:41 pm

Just thought I'd add my two cents worth. I've used the SDS, Curcio and CChong boards in the ST70. I was most impressed with the CChong board, so I bought his versions for the ST35 and Mark III. I was very pleased with all of them and had no problems. He uses some upgrade like a hexfred in the bias and a power up timer in the ST35. His boards arrive assembled,wave soldered so the pricing is very competitive.

Another characteristic that I'd noticed was Chart's layout was so well thought out that it was easier for me to dress the wires very neatly. (You should see some of Chart's buiods.)

Alas, Chart is no longer onllne. I was able to track him down last year and purchase two Mark III boards, but he's waiting for the economy to pick up. :(
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Re: List of power supply boards/options for ST-70?

Postby pmarcin » Sat Apr 20, 2013 1:41 pm

Just thought I'd add my two cents worth. I've used the SDS, Curcio and CChong boards in the ST70. I was most impressed with the CChong board, so I bought his versions for the ST35 and Mark III. I was very pleased with all of them and had no problems. He uses some upgrade like a hexfred in the bias and a power up timer in the ST35. His boards arrive assembled,wave soldered so the pricing is very competitive.

Another characteristic that I'd noticed was Chart's layout was so well thought out that it was easier for me to dress the wires very neatly. (You should see some of Chart's buiods.)

Alas, Chart is no longer onllne. I was able to track him down last year and purchase two Mark III boards, but he's waiting for the economy to pick up. :(
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