Beavis Audio Screamer Questions

[arawn]

I used the design here to bread board a simplified Tube Screamer. It sounds great better than the one I used to own, I just have one problem it won't play nice with any of my pedals except my digitech rp80 (all digital multi effects) I presume that this is due to the lack of input and out put buffers. I simply can't figure out a good way to add those, and could really use some help. I tried reading Jack Ormans article on input and output impedance but i just couldn't make the leap from there.

[Ben N]

As for an input buffer, if you use a jfet input opamp, like the ubiquitous TL072, you should have a plenty high input impedance without a separate buffer. As for the output, just graft on the buffer from a tubescreamer--look at RG's Anatomy article, here http://www.geofex.com/Article_Folders/TStech/tsxtech.htm, and scroll down to "Output Buffer Stage". I'm not sure if you need the coupling cap, though.

[petemoore]

  *Any commercial pedal has input and output buffers.
  [Any as in any with buffers].
  If laying around with PS and cables, when in bypass mode, they buffer the signal path, they can be used to test buffage and how it influences sound. Many installed wah buffers were found to be useful before the installation in this way, wahs have low input impedance, FF's don't necessarily 'push' a wah input.
I presume that this is due to the lack of input and out put buffers
  I think you can figure this out before re-working the circuit you like the sound of, also just where to splice in the buffer is a good topic for pre-fix contemplation, perhaps it will change the sound of 'that' circuits output less than it will the screamers input...add in variables such as: which one is on whenx, what exactly will the signal path see whenx, etc.
  Or just take the Boss's approach and put buffers before and after everything !

[ayayay!]

Is your RP80 the only other pedal you have with a buffer?  If so, there you go:  You need a buffer on your TS.  If if sounds better with the RP80 in front, put a buffer in front of the TS.  If after, try it on the backside.  Overthinking buffers can be a huge time killer. 

I would personally just add the simple AMZ buffer that uses 5 parts on the input and call it a day.     (Ignore the "blocks w/ dots?" comment.)  Make it on perf to be extra tiny. 

[petemoore]

Overthinking buffers can be a huge time killer.     

[arawn]

It already has been,
so could i use 1/2 of a tlo82 for my input buffer and the other half for my output buffer?

[slacker]

It shouldn't need buffers, it already has a high input impedance and low output impedance so adding buffers isn't really going to do very much.
In what way doesn't it play nice with other pedals?

[ayayay!]

It already has been,  so could i use 1/2 of a tlo82 for my input buffer and the other half for my output buffer? 

Mmmm, well I guess you could try.  I dunno, seems like an awful lot of wiring.  But like I said I would just try it with the input buffer. 

I feel your pain arawn, but this is the good stuff that makes you (and I) a better pedal builder.  You'll find the solution you like, I'm sure.  (By the way, that's a TL071 in the drawing I posted.)

[arawn]

well it works fine with commercial pedals  - I did some more testing, but not with any of my builds not the whisker biscuit or the professor tweed etc.

[ayayay!]

well it works fine with commercial pedals

OK so my theory is still making sense.  Is the "commercial" pedal before or after your TS?   

As a side note, I only play my Trotsky Drive with buffered pedals.  By itself is sounds like arse.  I keep telling myself to put that buffer in there but I've go so much other stuff going on that it's not that important right now. 

[dano12]

Hey! Glad you built it.

I've built lots of non-buffered pedals and found there are a lot of variances in connected them to other buffered/non-buffered pedals.

Probably the best way to cure this is to tack a simple output buffer on the end, as others have suggested.

Take a look at the tube screamer schematic here: http://www.geofex.com/Article_Folders/TStech/tsxtech.gif

and R.G.'s accompanying article. You should be able to easily implement the output buffer from the TS9.

[suprleed]

BJT and Jfet buffers are pretty simple, just look at the MFP102 section of a Ruby, its just a buffer before the power amp.

[arawn]

Okay still on breadboard and my task this afternoon is to try and find room to add a buffer to this but in the mean time I am also trying to get my perf layout settled and want to make sure that this looks correct or will work anyway