dynaco st 70 c3

dcb50 · 1st October 2008, 02:01 AM

hi, complete newbie here any body have a pic. of the component layout for the board on this kit?? I have one but is so faded cant clearly see much. this is the original board, any help at all .. thanks

DigitalJunkie · 1st October 2008, 02:20 AM

http://www.curcioaudio.com/st7_mnl.pdf

kmaier · 1st October 2008, 02:37 AM

The ST-70-C3 was a modification by Audio Research Corp. Not a Dynaco at all actually, but an ARC design scaled into the Dyna chassis and using only the iron. Some details and pics can be found here:

http://www.arcdb.ws/ST70C3/ST70C3.html

I built a few of these way back... added DC balance to the output stage and a few other bits. Overall a very nice amplifier.

Regards, KM

kenpeter · 1st October 2008, 03:52 AM

Awesome Schade strapping of the output tubes.
Triode emulation with full screen voltage! And
the OPT is wrapped into the local loop... There
are actually several more clever things going on
within this schematic.

Definitely one worthy of further study.

kmaier · 1st October 2008, 04:32 AM

Actually, it was based on the ARC D-76 power amplifier but scaled back due to both physical space limitations and available power for filaments, etc. from the original components. Here's info for the D-76:

http://www.arcdb.ws/D76/D76.html

Regards, KM

dcb50 · 1st October 2008, 05:11 AM

your absolutely right its not a dynaco!! but audio research calls it a st-70-c3 super modification kit for dynaco 70 .. that off the manual.. my question was if anyone had a clear picture of the layout of the component on the board?? THANKS..

Rjones5296 · 22nd October 2008, 03:32 AM

Hello
I built the amplifier on this page, or at least the amp showing in the botton view.
If you look closely, you will notice a regulator chip there for the first tube fillaments and a small bias trandformer next to the power transformer.
The original Dyna transformer ran the tubes at 450v B+
I changed the transformer for a lower voltage tranny, but 400ma versus 300ma for the original.
I had to add the bias transformer because the new transformer did not have a bias tap.
bob

http://www.arcdb.ws/ST70C3/ST70C3.html

lawbadman · 22nd October 2008, 04:38 AM

Anyone know the impedance of the output trafo on the ARC_D76A and where I can get a PCB?

Thanks

Lawrence

mikebarney · 8th December 2008, 09:42 PM

The diagram you seek is on page 14 of the St-70-C3 Modification Manual, a PDF copy is in the link toward the bottom of my webpage dedicated to this amp:
http://mpbarneyamps.googlepages.com/...70-c3amplifier
Best regards,
Mike

SY · 8th December 2008, 09:58 PM

Lawrence, 4k3, but 6k6 might work slightly better.

1st October 2008, 02:01 AM	#1
dcb50 diyAudio Member Join Date: Sep 2008	dynaco st 70 c3 hi, complete newbie here any body have a pic. of the component layout for the board on this kit?? I have one but is so faded cant clearly see much. this is the original board, any help at all .. thanks

1st October 2008, 05:11 AM	#6
dcb50 diyAudio Member Join Date: Sep 2008	ST-70-C3 [DYNACO ST-70] your absolutely right its not a dynaco!! but audio research calls it a st-70-c3 super modification kit for dynaco 70 .. that off the manual.. my question was if anyone had a clear picture of the layout of the component on the board?? THANKS..

22nd October 2008, 03:32 AM	#7
Rjones5296 diyAudio Member Join Date: Mar 2002 Location: Dayton Ohio	ARC ST-70C3 kit Hello I built the amplifier on this page, or at least the amp showing in the botton view. If you look closely, you will notice a regulator chip there for the first tube fillaments and a small bias trandformer next to the power transformer. The original Dyna transformer ran the tubes at 450v B+ I changed the transformer for a lower voltage tranny, but 400ma versus 300ma for the original. I had to add the bias transformer because the new transformer did not have a bias tap. bob http://www.arcdb.ws/ST70C3/ST70C3.html

22nd October 2008, 04:38 AM	#8
lawbadman diyAudio Member Join Date: Mar 2003 Location: St. Catherine, Jamaica	Anyone know the impedance of the output trafo on the ARC_D76A and where I can get a PCB? Thanks Lawrence __________________ <a href="http://www.danasoft.com"><img src="http://www.danasoft.com/sig/lawbadman.jpg" border="0"></a><div style="font-family:arial,sans-serif;font-size:11px;"><p>Sign by Danasoft - <a href="http://www.danasoft.com">For Backgrounds and Layouts</a></p></div>

8th December 2008, 09:42 PM	#9
mikebarney diyAudio Member Join Date: Nov 2003 Location: Connecticut	ARC ST-70-C3 PCB layout The diagram you seek is on page 14 of the St-70-C3 Modification Manual, a PDF copy is in the link toward the bottom of my webpage dedicated to this amp: http://mpbarneyamps.googlepages.com/...70-c3amplifier Best regards, Mike

1st October 2008, 02:20 AM	#2
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	http://www.curcioaudio.com/st7_mnl.pdf

1st October 2008, 02:37 AM	#3
kmaier diyAudio Member Join Date: Jul 2007	The ST-70-C3 was a modification by Audio Research Corp. Not a Dynaco at all actually, but an ARC design scaled into the Dyna chassis and using only the iron. Some details and pics can be found here: http://www.arcdb.ws/ST70C3/ST70C3.html I built a few of these way back... added DC balance to the output stage and a few other bits. Overall a very nice amplifier. Regards, KM

1st October 2008, 03:52 AM	#4
kenpeter diyAudio Member Join Date: Nov 2007 Location: Dallas	Awesome Schade strapping of the output tubes. Triode emulation with full screen voltage! And the OPT is wrapped into the local loop... There are actually several more clever things going on within this schematic. Definitely one worthy of further study.

1st October 2008, 04:32 AM	#5
kmaier diyAudio Member Join Date: Jul 2007	Actually, it was based on the ARC D-76 power amplifier but scaled back due to both physical space limitations and available power for filaments, etc. from the original components. Here's info for the D-76: http://www.arcdb.ws/D76/D76.html Regards, KM

8th December 2008, 09:58 PM	#10
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Lawrence, 4k3, but 6k6 might work slightly better. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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