6SN7 Driver in Paramount 1.0 (Original with 12AT7)

[Paul Birkeland]

Yeah, cap-coupled with the 300B, you'll be OK.

Your drawing is correct, except that the jumper to "K" should be on the solder pad on the edge of the PC board (which you'd undoubtedly do once the board had the 431 in it).

-PB

[galyons]

Yeah, cap-coupled with the 300B, you'll be OK.

Your drawing is correct, except that the jumper to "K" should be on the solder pad on the edge of the PC board (which you'd undoubtedly do once the board had the 431 in it).
-PB

Glad you mentioned that!  I was already looking for a sharp 1/2" drill bit to enlarge the solder hole!!    

Here is a corrected drawing. I  noted and changed the original, as well.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FOFeU0Ke.jpg&hash=97088df9e7fc35622e5b79c5ee3aed7579a74b6d)

Thanks for all of the help!

Cheers,
Geary

[galyons]

From Stereomour thread:

There is a pattern. The guys with high sensitivity speakers are hearing the hiss. Owners of lower sensitivity speakers don't seem to be noticing it. Noise issues are not all or none, it's more a matter of degree. So what we can say is that we will do what we can to find a chip with a consistently lower noise level. But if you have really sensitive speakers and you hear noise that bothers you, you may have to use the alternative approach we have offered here anyway. That is the one of trade offs - along with reduced bandwidth - that you have to deal with when you go to very sensitive speakers.

I am not going to panic!!!  I have 102dB/1w/1M horn speakers.  I ordered the  LM413's from Digikey. They will be here tomorrow.  They are Fairchild LM431ACZ, so if I read the thread in Stereomour correctly, http://bottlehead.com/smf/index.php/topic,5828.0.html , I should be OK?

...So I called last week and Eileen sent me three new 431s to try. I tried all three in the channel with the hiss, and it still remained. Also, I even tried one of these new 431s in the silent channel and guess what: hiss was introduced where it wasn't before. I took a closer look at the markings on each and found that the original two that came in my kit were different: fKB31 LM431 ACZ (silent channel) and WS TL431A 12427 (hiss channel). Also, the three that were sent as the replacements were all the WS TL431A 12427 as well. My conclusion: I agree with your previous assumption that these different 431s are the hiss problem possibly due to manufacturing.

My next step will be to bypass the 431s with resistors as instructed in your previous reply, but what tolerance, voltage, etc. of 680 ohm resistors should I get? What specs on those very resistors should I stick to to have a successful outcome?...

I have one monoblock up and running.    The other will be up by the weekend.  Looking to do the driver board mods to go to 6CG7, then 6SN7 shortly thereafter.

Cheers,
Geary

[johnsonad]

The white noise or hiss will drive you a little nutty at first. After a few weeks you'll realize that the music is sublime and forget about it. . I too would like a dead quiet circuit but the quality of sound is worth the added noise, at least for me.

I need to add that I moved from 100 dB sensitive to 95 dB and it still bothers me from time to time. That is, until I hit play

[Paul Joppa]

I don't think the markings are a reliable indicator of performance. We'll know more in a few weeks after we've tested a variety of sources.

[galyons]

Thanks Paul.  I should have everything to do the board mods by this weekend.  It will be interesting to see if the Digikey/Fairchild LM431's are hissy.  Is so, I hope there will be a resistor alternative.

Cheers,
Geary

[galyons]

The white noise or hiss will drive you a little nutty at first. After a few weeks you'll realize that the music is sublime and forget about it. . I too would like a dead quiet circuit but the quality of sound is worth the added noise, at least for me.

I need to add that I moved from 100 dB sensitive to 95 dB and it still bothers me from time to time. That is, until I hit play

Aaron,
I agree.  My system is not dead quiet, too many tubes!  My listening position is about 12' from the speakers.  Nearly dead quiet from there.  Up close to the equipment & speakers there is low level tube rush.

Cheers,
Geary

[galyons]

Working on driver board #1.  Everything in.  9 pin socket rewired for 6CG7.  Just a point of clarification.   I will need to pull the current lead from "A" side K from B8 and replace it with the new lead from "B" side K via "+" to B8, yes?

Thanks,
Geary

[Paul Birkeland]

Yeah, this is where support will get a little lean.

The power supply regulator has the 431 with fixed resistors.  The "K" pad from this portion of the PCB, and the "O" pad that feeds the "+" linked to that 431 (should be "OA") need to hit the same half of the 6CG7 (1,2,3 or 6,7,8).

The driver stage will take the lower current "O" pad (OB most likely) and the K from the adjustable half of the board.

[galyons]

Yeah, this is where support will get a little lean.

I understand.  So the current fact is I now have 3 LM431’s in possible play.

LM431 -(1), is on the 9 pin socket, going from the center post, (ground) to B3 cathode.

LM431 -(2), was already on the driver board “A” side and is, before any changes, going to B8 cathode.

LM431 -(3), I added to the driver board “B” side along with the 2.49K @ R3 and 3.5K @ the outboard end of R4 &  the inboard larger +  pad.   The new lead goes from the smaller, outboard + pad.

The power supply regulator has the 431 with fixed resistors.  The "K" pad from this portion of the PCB, and the "O" pad that feeds the "+" linked to that 431 (should be "OA") need to hit the same half of the 6CG7 (1,2,3 or 6,7,8).

 If I understand correctly, this is LM431 (2). Then this circuit remains unchanged and the wire from KA remains on the cathode B8.

The driver stage will take the lower current "O" pad (OB most likely) and the K from the adjustable half of the board.

So here is where we need to check my understanding. The added LM431 (3), 2.49K & 3.5K resistors are to change the driver cathode bias from 2.5v to 6.0v.  If that is correct, then the new lead from "B" side K via "+"  would go to B3. 

Do I then need to remove the currently installed LM431 (1), (from the center post to B3)? Then wire the new lead from the new circuit with LM431 (3) to B3 to provide the 6.0v bias?

Or?  Leave LM431 (1) in place, as is and add the new circuit lead to B3 and the combined old and new LM431 (1+3) will give me the desired 6.0v cathode bias?

OR? Just grab the closest bottle of Scotch and enjoy the Paramour 45's and try thinking  again tomorrow!? 

Thanks for hanging in with me on this!

Cheers,
Geary

[Paul Birkeland]

The 431 on the socket needs to be removed - it is superseded by the 431 that you're adding to the PC board.

-PB

[galyons]

Perfect.  So once I do this all of the test voltages will remain the same, excepting:

B3 will now be 6.0v instead of 2.5V and
B9 will be 0 instead of 3.1V.

I am still waiting for parts to finish the second board.  Maybe tomorrow?  Will report when I am up and running.

Thank you for all of the support and guidance.  Gotta go find that Scotch!!

Cheers,
Geary

[Paul Birkeland]

Yeah, no doubt you may run into other oddities, just be sure to take your time and let us know if something isn't quite right.

-PB

[galyons]

Thanks PB.  I am stalled until Monday or Tuesday. Still missing a couple of parts.
I'll have to tough it out with the Paramour 45's until then!!

Cheers,
Geary

[johnsonad]

Geary, I'm looking forward to your comparison of the 6CG7 and the 6SN7.  I have a stash of the former but am quite happy with the later at the moment.  Good luck with your project!