Boss SD-1 output buffer

[Silvio55]

I just replaced the input buffer on my SD-1 clone with an "always on" TL071 buffer since I dont have any buffers on my pedal board, I removed the SD-1 original buffer and put the new one inside the pedal, always online.
But how about the output buffer? Being a true bypass pedal I don't think it's needed, what effect can this buffer have if I remove it also?

[iainpunk]

the Jfet switches are pretty imperfect, so having an output buffer after those is good practice.
also the output impedance of this pedal is quite high, it has 22k resistors after the switches.

cheers

[Silvio55]

the Jfet switches are pretty imperfect, so having an output buffer after those is good practice.
also the output impedance of this pedal is quite high, it has 22k resistors after the switches.

cheers

Mine is a clone, it's true bypass and doesn't have the Jfet switches, if I remove the output buffer the output would be the wiper of the 10K volume pot.

[iainpunk]

in that case, you don't need that buffer

cheers

[Mark Hammer]

The biggest difference between the more "legendary" TS-808, and the TS-9, is the output buffer.  In the 808, the resistors equivalent to R16 and R17 in the SD-1 were 100R and 10K, respectively, later changed to 470R and 100k, respectively, in the TS-9.  I suspect that provided less loading of the signal, yielding better preservation of the highs, when the effect was bypassed.

One wonders if the desirability of the 808 partly stems from a "warming" effect of the output buffer by loading down the output a little.  Naturally, this would really only pertain if the signal was going directly from the 808 into a long cable to the amp, where the loading would interact with cable capacitance to tame some of the harshness when in effect mode.

That may not represent your own context.  But if it does, consider tinkering with the R16/17 values to more closely approximate those of the TS-808.  It might be that the output buffer, while not absolutely essential in its stock form, and especially with true bypass switching, can be helpful to your tonal goals when in effect mode.

[antonis]

Just to add on what very well said by Mark..

Q6 role on "character" isn't only limited to tonal depiction but also to distortion..

Single BJT buffer, as it's biased, is significantly asymmetrical both from unequal swinging margins and from current sourcing/sinking point of view..

That said, identical circuits with different output buffers exhibit different "overal" audio behavior..

[nooneknows]

still a sd1, even with ts808 key values for cap and Res (yes, I did it once, replaced them almost all, with simmetrical clipping too), sounds different, not better or worse, just different, I suspect it might be something with the buffer part