Dynaco ST 70 Carpenter Mod

Hi, I have this great amp a friend wired up for me in 1990.I traded him 2 Dyna PAS's with 1 coming back modified by him and one for me to keep.Also in the deal was he modified my Dyna ST 70 into a Purist Audio Mod by jim Aud in Texas.It uses 12AX7"s instead of the 7199 original tubes and bias's at .75 volts instead of !.56 like the original ST-70.I've never changed an output tube because they don't get hot,warm but can be touched.The mod was a winner in a 5 amp ST 70 shootout in one of my old stereo mags.I noticed one day a small hum coming from the amp.When I looked closer and the output and power transformers had missing screw rods and nuts where holes were drilled in the bell housings.If you look at a lot of pictures of the Stereo 70 these holes are vacant.While looking for new ones on the net I did a little experiment.I put a shiv,a little wedge of wood carpenters use for hanging doors ect, under the power transformer.The noise reduction was like night and day! I saw this clip on McIntosh amps where they poor tar into the transformer bell submersing the primary and secondary in black gunk.My idea is the iron plates in the Dyna transformers must corrode because of their age and pressure from the securing screws is important to keep out corrosion.Less screws hense....the Poor Man's McIntosh.Just my observations,I could be dead wrong.The amp still plays beautifully....Mark Korda

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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)

Dynaco ST 70 Carpenter Mod

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