Versatile 6L6 w/1 tube reverb

[UncleRuckus]

Hi folks,
Looking for some advice before I try to build this one.
It's admittedly non-traditional...

Also - I did my highlighter homework. Layout matches the SCH I believe...
Sincerely,
J

[EL34]

Posted in wrong board............ moving

[UncleRuckus]

Sorry!!!

[UncleRuckus]

Hi folks,
Looking for some advice before I try to build this one.
It's admittedly non-traditional...

Also - I did my highlighter homework. Layout matches the SCH I believe...
Sincerely,
J

Updated the power supply resistors to properly reflect the current they are managing.
Updated the FWB to Choke predicted voltage out.
Updated the 'Variclipper' pot for gain channel (swapped hi/lo).
J

[Merlin]

Couple of comments:
Do you really want the 18k resistor between the cathode follower and the tone stack?
I don't know why you have specified 1% tolerance resistors on the cathode follower.
You appear to have a 220k resistor in series with the reverb tank input coil, surely that's not right?

[UncleRuckus]

Merlin,
Thank you for the interest and advice!
I've not yet taught myself how to properly calculate the output at each stage, so I put in these voltage dividers - in the past I've used small pots to adjust then replaced them with the measured results (these are pure guesses at this stage). 

The gain channel is similar to the SLO on Robinette's site, so needs to 'dump' some gain after each stage as I understand it.  I'm experimenting with a pot to adjust the cold clipper - what do you think? I chose a log and used a 220k across the 50k to have a spread of roughly 39k (Claude.ai totally drew an interactive graph for it!).

The CF has the estimated gain of 86 set for softer clipping with the 47k's -  If you have a good way to track gain over stages (I promise I read both of your books!) I could use a checklist of sorts - fodder for your next book.  (The Checklist Manifesto is a good 100 page read)

Then there's the 'how much power can a reverb tank handle' piece. I'm still struggling a bit with the differences between voltage vs resistance coupling and what that means for power. But I also may never get that sophisticated...

The 6DX8 has a plate dissipation max of 4 watts - so I'm not sure how much can go into the reverb tank without cooking the output coil. But then I believe the 12AT7 in Fenders would be putting out about 5 watts - so maybe I don't need this limiter?  How does the cap output instead of transformer affect the power into the tank? : )

Any assistance will be much appreciated,
J

[Merlin]

in the past I've used small pots to adjust then replaced them with the measured results (these are pure guesses at this stage). 

Fair enough, that's the right way to do it. You can't calculate the perfect values for a guitar amp, so starting with pots and replacing with fixed resistors later is the only true solution.

I'm experimenting with a pot to adjust the cold clipper - what do you think?

Looks like overkill, a 50k pot (variable resistor) by itself is all you need, no?

If you have a good way to track gain over stages I could use a checklist of sorts

I'm not sure what you mean.

Then there's the 'how much power can a reverb tank handle' piece.
The 6DX8 has a plate dissipation max of 4 watts - so I'm not sure how much can go into the reverb tank without cooking the output coil. B

Tanks are driven by current rather than power. For a cap output driver like yours, you want the idle current in the driver tube to be around 10mA, then use a 1k series resistor to the tank (instead of the 220k you have). Easy!

[UncleRuckus]

I'm experimenting with a pot to adjust the cold clipper - what do you think?

Looks like overkill, a 50k pot (variable resistor) by itself is all you need, no?
A little overkill, it brings it right to the range of 39k. : )  Do you think there is a big difference in the tone between ~20k and 39k? I suppose I'll find out, but I figured the log style would be helpful.

If you have a good way to track gain over stages I could use a checklist of sorts

I'm not sure what you mean.
Yep. I see people saying Peak to Peak at stage 'x', but I'm not sure how to know what that 'should' be. The tubes have max voltages, and then there's the maximum throw in the voltage based on the plate voltage - would you divide the plate voltage by the expected gain to know the maximum input peak to peak (and thereby when it starts clipping)?  Or is this another put a pot in and find out deal?

Then there's the 'how much power can a reverb tank handle' piece.
The 6DX8 has a plate dissipation max of 4 watts - so I'm not sure how much can go into the reverb tank without cooking the output coil. B

Tanks are driven by current rather than power. For a cap output driver like yours, you want the idle current in the driver tube to be around 10mA, then use a 1k series resistor to the tank (instead of the 220k you have). Easy!
[/quote]
Ah - the 1K is used in addition to the impedance of the coil to know the watts being pushed? 10ma and 1k ohms would be 10 watts? but add the impedance?
Thanks so much!