Stacked Tube Screamers

[erick4x4]

I have a question, and I have tried to faithfully read up before hand, and need some help.

I really like my tube screamer as both a distortion and as a boost. I really like using boosts in front of my distortions for solos, etc.

I have noticed that unlike most distortions I have, when I boost in front of the tubescreamer it tends to get louder rather than more saturated.

I have also noticed that when a tube screamer boosts a tube screamer it does get a louder but this does a better job of increasing saturation at the same time.

So I am led to believe that maybe the input buffer is what causes the screamer to boost rather than saturate on stacks. And that maybe the output/input combo of 2 tube screamers is why together I can kind of achieve the effect?

SO ...
1) Is it true that if I dump the input buffer on my screamer that I use as a distortion will I be able to boost it for a saturation increase for solos. Both with another screamer, and with typical boosts like mini-boosts, comps, rangemasters, etc.
2) If so, I already have a PCB from GGG, can I just plug the input wire after the input buffer, and remove the buffer, or are other mods needed?

Thanks!

[R.G.]

So I am led to believe that maybe the input buffer is what causes the screamer to boost rather than saturate on stacks. And that maybe the output/input combo of 2 tube screamers is why together I can kind of achieve the effect?

No, it's the gain structure. The gain of the distortion opamp is 1+Rf/Ri. The "1+" part of that gives the output a replica of the input that grows with the input. The feedback/clipping portion is limited to +/- a diode drop no matter how hard it's driven. The input buffer has little or nothing to do with it.

[caress]

the saturation you're hearing is likely just adding a slightly distorted boost to an already distorted sound... probably why a clean boost before sounds less "saturated".

[vondran]

I have noticed that unlike most distortions I have, when I boost in front of the tubescreamer it tends to get louder rather than more saturated.

I have also noticed that when a tube screamer boosts a tube screamer it does get a louder but this does a better job of increasing saturation at the same time.

What you're noticing may be a result that a tube screamer clipping stage amplifies and clips frequencies differently.  Specifically as RG stated it uses a non-inverting op-amp structure to add gain (1+Rf/Ri) to the signal.  (Rf being the resistance or impedence in the feedback path which includes the clipping diodes, and Ri is the resitance/impendence from the "-" input to ground).  But, Ri is actually an R-C circuit with a 0.047uf cap.  (BTW, a common mod is to change this to a 0.1uf to increase bass response.)  Bottom line is below certain frequences Ri gets very large, making the gain go to one, independent on the clipping diodes in the op-amp feedback since as Ri gets very large and Rf has less of an effect on the gain and clipping.

My guess is your non-tubescreamer boost pedal may be boosting many freqences in the lower range, which don't experience as much gain in the Tubescreamer and thus aren't clipped.  Instead, a Tubescreamer used as a boost in front of a another tube screamer will boost the same mid-range and up frequences which the second tubescreamer has a higher gain response and thus clips more so you'll hear more saturation in this setup.

[erick4x4]

Thank you so much, this really clarifies how the screamer is working for me!

[snap]

more "Technology of the Tubescreamer" on "Geofex":
http://www.geofex.com/Article_Folders/TStech/tsxtech.htm

[vondran]

more "Technology of the Tubescreamer" on "Geofex":
http://www.geofex.com/Article_Folders/TStech/tsxtech.htm

Good link.  A gain stage section provides the clue
"With the stock 4.7K resistor and 0.047uF capacitor, this frequency is 720Hz. Only notes and harmonics above this point get the full gain of the distortion stage, and everything below it gets pregressively less gain - and distortion. This fact probably accounts for the lack of "muddiness" of the distortion in the TS series as bass notes are clipped least"