Super Reverb Tonestack Lift Noise

[ModMan]

Thanks again guys will be trying some of your suggestions today.
Here is the link I read to make the plate resistor a load splitter:

http://www.blueguitar.org/new/articl...s/bp010629.pdf

[ModMan]

Oh and here is the article that confused me with grid leak/stoppers the drawing shows both?

http://www.diystompboxes.com/pedals/tubedummy.html

[pdf64]

Yes I can see your point. My understanding is a little different to the author of the tubedummy page (though it's very well written and presented).
An actual grid leak resistor would normally be fitted to the input side of the grid stopper, rather than the grid side.
A grid stopper, when truly used as a grid stopper, isn't generally used to attenuate gain (over the audio bandwidth).

[ModMan]

O.k so they are not the same thing then.

Just finished moving input resistors to sockets, 22k grid stopper on v1b, 100k fixed mid on bright switch changed feed back cap from mallory to orange drop and eq caps to malorys with 51k slope resister and it's bloody 2 in the morning.

Oh well pluged it in and it powers up ok and all works it is also dead quiet and from what I can tell without playing it's not doing weird stuff with the 100k on the tonestack instead of the full lift.

I will let you all now how it really sounds tomorrow! It's not quite over yet I didn't have some of the resistor/cap values a actually wanted to try.

Thanks again everyone.

[ModMan]

Any suggestions of tonestack values to get a plexi type eq curve from what I can make out maybe
.1 bass
.022 mid
500pf treb
33k slope
500pf bright
.022 coupling
Any suggestions?

[ModMan]

O.k all sounds good I now have a diffrerent tone on the normal channel actually sounds nothing like a fender perfect!

Please don't misunderstand that I love Fender and the vibrato channell, P.I and power section are still pure blackface with a baldwin 12au7 that stood out from assorted mullards and rca tubes that were tried.

Only problem the 22k grid stopper on the input of V1b did fix the noise problem with the tonestack lifted but seemed to remove the awesome gain I was getting completely.

Going to try it again tommorow with the 100k on the tonestack again witch was removed first before I discovered it was the 22k causing the loss.

If that doen't work the only thing I can think of is splitting the plate resistor V1b to 10/91k so the 10 is then in series with the coupling cap?

Also check out this guy on the ultimate american/british super reverbs he has modded with his tech.
MetroAmp.com Forum • View topic - Super Reverb mods

[überfuzz]

Oh dear! Why did you get a Super Reverb in the first place if you were looking for something else than a clean sound? I find it hard to follow your modification. Care to post a schematic over it?

[J M Fahey]

This is going to sound extreme but I would say put the amp back as stock as you can. You don't like this amp, it doesn't do what you want an amp to do. Sell it and use the money to get another amp.

+1

Another alternative would be to put the amp back as stock as you can and use a pedal for distortion. Then you can control the volume of the distorted tones below the amps full output. But if it must be cranked tube amp distortion you need a different amp. Spending too much time trying to make a square peg fit into a round hole isn't advancing your musical experience one bit.

+1
Not counting:
1) Now you want to "Plexize" it.
Well, it won't work as expected: the tone stack is in a different point in the gain structure, *won't* be driven by a cathode follower, which will radically alter its response, ... do I need to go on?
2) You lost your tone stack just to get a little more gain. You are trying all kinds of add-ons and mods to avoid instability, all of which kill gain at different frequencies; in the long run you will end with a muddy, only_slightly_gainier no-longer-Super-Reverb.
3) If you want to keep it, yet want a grittier sound, pull the Super Reverb board and build a Plexi Bassman there.
With care you may even build a very heavy JCM800 preamp, driving a Bassman power amp.
You will still need to be careful with lead dress, shielding, etc. , but you will be working on a project which is already 90% of what you want.
Just My Two Cents

[pdf64]

'Only problem the 22k grid stopper on the input of V1b did fix the noise problem with the tonestack lifted but seemed to remove the awesome gain I was getting completely'
That shouldn't happen. Can you confirm that you connected it in series with the wire to the grid, not grounded in any way.

[pdf64]

J M Farey, I agree on the tone stack cathode follower issue. However, a 22k grid stopper, with a 12AX7 effective 150pF miller capacitence, should have a -3dB of about 50kHz. Even though that's still -1dB at 5kHz and several may be required with the cascaded gain stages, I don't think that they'll result in a 'muddy' tone. Pete.

[J M Fahey]

Hi Pete/PDF.
I fully agree with your grid stopper calculations.
What I'm adressing here goes beyond that, I fear our friend ModMan started with an amp which is quite opposite of what he seems to be wanting to achieve.
When talking about "muddying" I rather referred to the removal of the tonestack.
Typical Fender ones have the broad dip around 250 Hz, an "ugly" frequency.
This it is a big step towards the classic Fender tone; removing the tonestack "increases gain" (removes attenuation) precisely there.
In contrast, adding an extra gain stage basically increases gain at all frequencies , much more than the "passive" solution, and you still can shape that gain increase anyway you wish.
That's why I suggest our friend ModMan to save time and go straight into a new project instead of patching the Super here and there, which personally I find "halfway" solutions..
Of course, it's his amp, his money, his time, and I respect his decision.
Peace.
PS: I still think that adding *external* gain is the practical way to go.
That Super on 10 and driven with a clean boost will have a killer tone, best of both worlds.

[pdf64]

Ah, yes, the tone stack 'lift'. I concede your point, that would muddy to tone for my taste also, though ModMan seems to like to effect.
And yes also to an external boost, that would be my preferred way of adding a gain stage - I'm having fun working on a AC128 based boost circuit currently. Pete.