Clean Booster

[Leevi]

I built the following clean booster for 6SN7 or 6SL7.The idea is to keep the sound as clean as possible. There is not that much gain but the signal looks very nice and clean.I'm asking some comments and possible improvements?
/Leevi

[HotBluePlates]

What is the voltage at "A"?
What voltages do you have that the cathodes?
Why have a plate load for the 2nd stage, but also a large cathode resistor?

[Leevi]

What is the voltage at "A"?

A = 312V Plate (triode 1)  299V Plate (triode 2) 232V Cathode (triode 1) 2.5V Cathode (triode 2) 5V

Why have a late load for the 2nd stage?

No idea, it's probably not needed?

..but also a large cathode resistor?

what is an optimal value of the cathode resistor without load resistor?
/Leevi

[PRR]

> A = 312V
> Plate (triode 1)  299V
> Plate (triode 2) 232V
> Cathode (triode 1) 2.5V
> Cathode (triode 2) 5V
????

These as not making sense, so much that I fear I am mis-reading your compact data.

> possible improvements?

What do you want it to do better? Play clean? Distort badly? Make coffee?

[Leevi]

These as not making sense, so much that I fear I am mis-reading your compact data.

I made a new check and unfortunately the triode numbering was wrong in my previous post. Sorry for that.You are right PRR.
Corrected values:

> A = 312V
> Plate (triode 1)  232V
> Plate (triode 2) 299V
> Cathode (triode 1) 2.5V
> Cathode (triode 2) 5V

What do you want it to do better? Play clean? Distort badly? Make coffee?

Play clean with max gain without distortion
Situation on max. volume,  input: blue, output: yellow
Note! the signal is inverted in the scope.

The tube is 6SL7

/Leevi

[PRR]

> Play clean with max gain without distortion

Eventually *something* in the system will distort. Or if "gain" is to bring-up soft playing, something will hiss.

The easy path to more gain is a 6SL7 and a 22uFd cap on the first capacitor {edit: Cathode}.

That gain/volume control connection is unusual.

I checked that your readings add-up; they do (close enough). As was said, the plate resistor on the cathode follower is not needed and maybe not wanted.

[Leevi]

Thanks for the analysis PRR

The easy path to more gain is a 6SL7 and a 22uFd cap on the first capacitor.

You probably mean the first cathode?

That gain/volume control connection is unusual.

Yes, it is. The first triode works as a volume driver. And this kind of connection of the pot does not change the sound (no serial resistor)

As was said, the plate resistor on the cathode follower is not needed and maybe not wanted.

I already removed it


I'm planning to increase the cathode resistor to 56K which probably adds gain a bit.

[PRR]

...I'm planning to increase the cathode resistor to 56K which probably adds gain a bit.

It's a cathode follower! Gain is something less than unity, and not much affected by circuit values. Pencil "0.9", though it can be 0.98, not much difference.

It is a "ground biased" cathode follower. So it can only take a volt or three of down-swing before clipping. Bias it up and then it can swing big down-swings. But already it can clobber almost any guitar amp input. Which comes back to What Do You Want?? Actual gain, so you can use a rose pedal pick to play loud? Or "dirt", the usual side-effect of excess gain?

[uki]

I like the idea !   Is it a pedal or stage on amp ? 

[Leevi]

I like the idea !   Is it a pedal or stage on amp ?

The idea is to use it as a  pedal and the first version is more like a proto.


/Leevi

[uki]

Could it work as amp stage as well ?

[Leevi]

Could it work as amp stage as well ?

Yes, definitely
/Leevi