My own take on a tube screamer... Buffer help please?

[pott]

Like a lot of people I've been messing with the TS/SD1 circuitry for a while and I figured I should do some more messing about to find EXACTLY what I need, maybe a couple of pedals, then house them and do a real custom thing for myself. I'll call it the Hot Baguette since I'm French. Anyway the plan is to have the same 3 controls as a TS, with maybe two wee switches to control two different gain resistors and possible a symmetric/assymetric clipping switch. Either way the pedal will get a flatter EQ, smoother gain and more open sound. The diodes will be 1N4002 and the opamp a TL072. I'll first mod a SD1 or two (thank you Boss!) and then finalize the design in a box with extra switches here and there.

This is not to sell to people: I have very limited knowledge of electronics and this would be my take on a TS circuit by changing components everywhere and checking out what differences it makes.

I'd like to use a DPDT stompswitch as I'd want the pedal to be buffered and have an indicator LED. So I'd switch it in right before the output and the other side of the DPDT will control the LED.

I hope it's ok to link this geofex image..?

The main question is... what buffer should I use, that'd guarantee me no tone sucking, if at all possible..? On the AMZ buffer page there is one that's noted as being used on TS style pedals. I guess that'd be a good choice?

Also for the output buffer... could I just use the SD1's?

Mostly I'm concerned with no tone sucking, the capacity to drive long cables, high input impedance and using parts and trannies easy to find.

I really want to avoid true bypass. Basically I'd like this pedal to perform as a buffer and a clean boost or OD.

Thanks a lot if you can help!

Pierre

[GibsonGM]

Personally, I'd go with a 3PDT true-bypass setup, and use the buffers from the original TS series pedals with your gain stages.   You could always just hot-wire a buffer in there that is always on, if that is a concern/desire of yours....you could place it BEFORE the bypass switch for the TS style circuit....

[pott]

So you mean true bypass, but with the buffer between input of pedal and switch as opposed to right after switch?


I can't see any reasons why it wouldn't work... why don't people do it? Thanks for the idea though, it seems pretty obvious. Doh.

Wait... I'd have to switch the out just before the output buffer too right?

[km-r]

id say omit the buffers, use your dpdt, use millenium bypass led indicator, use one of the switch for the input and the other for the output... thats as much as "non-tonesucking" that you can get...

[pott]

I really want to avoid any possible noises or over complications...
Would the geofex diagram posted incur much tonesucking or wouldn't drive long cables well then?

[km-r]

well, IMO it could pass up you sound after lengths of cable but if you are going to connect your guitar before this effect, it may load your pickups resulting to a different sound [good or bad]...

a simple FET buffer [source follower] with a >1M input impedance can be connected between the effect and the input.

i would not really call the millenium bypass complicated...
i even envy you for having DPDT stompswitches [never existed in my area]

[pott]

The millenium bypass doesn't pop at all? I'd also like to use that OD for higher gain levels.

So basically there is no best of both worlds of having LED with buffered input as on my diagram..?

[km-r]

why should it pop? its just a bypass indicator...
*reviews circuit*
honestly think it wouldnt pop...

So basically there is no best of both worlds of having LED with buffered input as on my diagram..?
* if you dont have a very long cable and/or you have high output pickups, you'll do good.

[pott]

Mhmm ok...Well I could just do the bypass bleed mod on the SD1 I already have and keep it first in the chain and stop worrying so damn much about it all haha ...   Right now my first in chain pedal is a Bad Monkey. It used to be a Route 66 I was confident in but money problems had me sell it not a month ago
Alright then it'll be true bypass... *sigh* less hassle in a way. I may try the Millenium for giggles at some point to see how it performs
This should be a fun project hopefully... I'm thinking of doing a vero or perf layout and socketing all gain resistors, opamp, tone caps...and just messing around
Thanks guys!

[pott]

Ahhh nevermind. I'll juse us a 3PDT anyway, but build a buffer before the circuit's input and the switching. I'll have the buffer, no tone sucking and the LED. I'll find a way to get 3PDTs somehow.

[d95err]

why should it pop? its just a bypass indicator...
*reviews circuit*
honestly think it wouldnt pop...

LED indicators can sometimes cause pops, because of the sudden current rush when the LED lights up. Usually not a big problem, but there is some info on how to prevent that here:
http://www.muzique.com/lab/led.htm

[GibsonGM]

Check out the GeofX page (link at top of main page) and look up Technology of the Tube Screamer....the Son of Screamer has no buffers (I think), but still functions very well.  With true bypass, you won't get ANY tone sucking when the effect is bypassed, only what is caused by the length of your cables.   The buffer will just function to "prepare" the signal for the TS.....it'll provide a high impedance input. And also buffer any other effects that may follow.  The final transistor stage on the TS is a typical 'recovery stage' to boost the output after the tone stack.     

With a 3PDT, and the link from d95 there, you should have minimal switch popping.  Good luck!  ) 

[pott]

Yeah... I'll put the buffer before the switch but use a 3PDT anyway so that'll take care of everything I need. I can't get hold of these too easily but I'll figure something else.


If I do so, will the bypassed signal still have a low enough output impedance? I.e does an input buffer have an output impedance...? I.e will I be ok with just an input buffer in the bypassed path?   


I'll be using the TS buffer from the geofex site and then the son of a screamer circuit I believe. It'll keep things nice and tidy. Only problem remainign is of a low enough output impedance when the effects is bypassed...