Direct Coupled 76/5687 linestage

athos56 · 3rd August 2010, 03:30 AM

Here is a schematic for a linestage I want to make. I made a 76 tube resistance coupled amplifier with a voltage gain of about 9, and a 5687 tube buffer. I loved them both. Now I want to put the two together into a single unit. I didn't use any solid state in either but I want to in this one. I would use both halves of the 5687 for one channel, one for the regular out and one for a Sub out. I would set the 76 tube to 2.5ma and the 5687 tube to 20ma. The input transformer would be to correct the phase.
Please check out my work. I'm not sure about the direct coupling.

Athos

athos56 · 4th August 2010, 12:15 AM

I understand there is a ton of these questions, but I'll ask one more time. Input welcome.

Athos

Sheldon · 4th August 2010, 01:41 AM

I didn't calculate voltages, so won't comment on operating points, but the basic design looks fine. I'd add a safety diode from grid to cathode on your followers.

Sheldon

athos56 · 02:08 AM

Quote:

Originally Posted by Sheldon

I didn't calculate voltages, so won't comment on operating points, but the basic design looks fine. I'd add a safety diode from grid to cathode on your followers.

Sheldon

Thanks for the look, I go back and forth on those, I think though, since the part is cheap I might as well

.

Athos

athos56 · 5th August 2010, 06:13 PM

I got some feedback on Audiokarma that the DC coupling wouldn't work. Here is a Cap coupled version.

Athos

jerluwoo · 5th August 2010, 07:28 PM

I see no reason for the dc coupled version to not work. For what reason did they say it wouldn't?

athos56 · 5th August 2010, 10:02 PM

Quote:

Originally Posted by jerluwoo

I see no reason for the dc coupled version to not work. For what reason did they say it wouldn't?

Hmm, not much of one really, I think there was a language barrier. However, I'm still nailing down the final schematic so I thought I'd show one with the coupling cap and gridleak. I really would like to couple it directly. I got my chassis and parts coming from Mouser and AES.

Athos

analog_sa · 5th August 2010, 10:23 PM

Nice idea. If i were to use a transformer i would expect it to do more that just invert phase. And the dc coupling is certainly doable, don't let language barriers spoil your sound

Btw, no need for a diode in the cap coupled version.

athos56 · 5th August 2010, 11:15 PM

Another vote for the DC version, I'm glad to hear that my original idea was sound! I have a bunch of builds under my belt, but I get nervous when I cook stuff up myself

.

athos56 · 6th August 2010, 12:18 AM

Here is the semifinal version, I added the PSU and whatnot. Thanks for the comments!

Athos

4th August 2010, 12:15 AM	#2
athos56 diyAudio Member Join Date: May 2006 Location: Yakima, Washington	One more try! I understand there is a ton of these questions, but I'll ask one more time. Input welcome. Athos

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4th August 2010, 01:41 AM	#3
Sheldon diyAudio Member Join Date: Dec 2003 Location: San Diego	I didn't calculate voltages, so won't comment on operating points, but the basic design looks fine. I'd add a safety diode from grid to cathode on your followers. Sheldon

5th August 2010, 07:28 PM	#6
jerluwoo diyAudio Member Join Date: Feb 2006 Location: Ashland,Ky U.S	I see no reason for the dc coupled version to not work. For what reason did they say it wouldn't?

5th August 2010, 10:23 PM	#8
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	Nice idea. If i were to use a transformer i would expect it to do more that just invert phase. And the dc coupling is certainly doable, don't let language barriers spoil your sound Btw, no need for a diode in the cap coupled version.

5th August 2010, 11:15 PM	#9
athos56 diyAudio Member Join Date: May 2006 Location: Yakima, Washington	Another vote for the DC version, I'm glad to hear that my original idea was sound! I have a bunch of builds under my belt, but I get nervous when I cook stuff up myself .

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