"wouldn't the Sheldon Stokes board best the old selenium set up?"

Posted by 1973shovel (A) on October 13, 2024 at 07:54:35

In Reply to: RE: Unfortunately the SDS board... posted by mark.korda@myfairpoint.net on October 12, 2024 at 20:06:09:

Yes, if for nothing else, a decreased voltage drop and more importantly, to potentially avoid the rancid fumes produced by the selenium rectifier when they 'go'.

I wasn't suggesting that you keep the selenium rectifier, but I would suggest using caps much greater in capacitance than the Stokes board's 1,800 uF. You have posted that you have a Last PAS, but if you still have the selenium rectifier, stock value caps in the heater supply, and are using the 12X4 rectifier tube instead of regulated B+, then you really don't have a 'Vorhis' Last PAS, in my opinion.

The improvement in adding significant capacitance to the heater supply is easy to hear. Using your current set-up, get yourself two 25 V or greater electrolytic caps of substantially higher capacitance than what is already in your heater supply, along with some alligator clip leads. With the preamp off, attach the caps in parallel to those already in place, being sure to observe proper polarity.

Turn the preamp on, and listen for a while. Then, without the need to power the preamp down, carefully disconnect the clip leads from the stock supply, and listen again. As long as you're careful not to discharge the external caps, you can reconnect and disconnect them at will. I think you'll like what you hear with the added capacitance.

All this already is detailed in The Last PAS article by Dave Vorhis. Email me through the Asylum if you don't have a copy.

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Follow Ups Full Thread

Topic - Dynaco ST 70 Carpenter Mod - mark.korda@myfairpoint.net 19:02:31 10/04/24 (23)

Another modded Dynaco ST-70 - mlsstl 13:26:57 10/07/24 (1)

Very nice work! - Story 13:42:11 10/07/24 (0)

RE: Dynaco ST 70 Carpenter Mod - altecboy 08:56:27 10/07/24 (8)

RE: Dynaco ST 70 Carpenter Mod - mark.korda@myfairpoint.net 11:02:40 10/07/24 (7)

The Last PAS article by David Vorhis - 1973shovel 14:40:00 10/09/24 (5)

RE: The Last PAS article by David Vorhis - mark.korda@myfairpoint.net 03:42:34 10/10/24 (4)

Unfortunately the SDS board... - 1973shovel 05:07:35 10/10/24 (3)

RE: Unfortunately the SDS board... - mark.korda@myfairpoint.net 07:36:50 10/13/24 (0)

RE: Unfortunately the SDS board... - mark.korda@myfairpoint.net 20:06:09 10/12/24 (1)

"wouldn't the Sheldon Stokes board best the old selenium set up?" - 1973shovel 07:54:35 10/13/24 (0)

RE: Dynaco ST 70 Carpenter Mod - mark.korda@myfairpoint.net 11:07:00 10/07/24 (0)

RE: Dynaco ST 70 Carpenter Mod - Tre' 07:57:46 10/05/24 (0)

Glad that you were able to remedy your transformer hum - 1973shovel 06:45:28 10/05/24 (10)

HiFi is not contraband per se - farfetched 07:49:08 10/05/24 (9)

Everybody in the whole cell block... - 1973shovel 08:22:12 10/05/24 (8)

Around here the music always wins (nt) - farfetched 08:55:05 10/06/24 (4)

RE: Around here the music always wins (nt) - mark.korda@myfairpoint.net 13:02:50 10/06/24 (3)

Another mod comparison was covered in issues 33 and 39 of The Sensible Sound. - alaskahiatt 18:52:21 10/08/24 (0)

RE: Around here the music always wins (nt) - altecboy 06:27:00 10/07/24 (1)

"I remember the article" - 1973shovel 08:40:56 10/07/24 (0)

RE: Everybody in the whole cell block... - mark.korda@myfairpoint.net 10:11:34 10/05/24 (2)

RE: Everybody in the whole cell block... - mark.korda@myfairpoint.net 10:17:20 10/05/24 (1)

RE: Everybody in the whole cell block... - mark.korda@myfairpoint.net 17:22:49 10/05/24 (0)

Follow Ups

"wouldn't the Sheldon Stokes board best the old selenium set up?" - 1973shovel 07:54:35 10/13/24 (0)

"wouldn't the Sheldon Stokes board best the old selenium set up?"

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