What pedal is this circuit from?

[cd]

SSIA.  Can't find any info on it.  

http://www.diystompboxes.com/pedals/schems/bscr1.gif

[Paul Marossy]

If you look at the text in the lower right hand corner, it says the circuit is based on the Ibanez TS-9 (Tube Screamer) circuit.

I thought it looked very similar to a Tube Screamer... :wink:

[cd]

Yeah but is it taken from any particular pedal (other than 808 - every maker and their brother makes an 808 variant, the text also says copied from PCB top photos, so I assume yes?)

[Marcos - Munky]

I think this is a simple Tube Screamer with some mods, based in all TS series.

[Paul Marossy]

The TS-9 and TS808 are very similar, as are almost all of the Tube Screamer circuits, according to "The Technology of the Tube Screamer" at geofex.com

The circuit linked above is just a simplified TS circuit, without the flip-flop channel switching and all that stuff.

[PeopleHateMe7666]

NICE SITE PAUL!! VERY HELPFUL!!!! :-D :-D :-D!!!

[cd]

All the replies so far have been stating the obvious, the schem itself SAYS it's a simplified TS circuit.  I want to know WHAT PEDAL IT WAS TRACED FROM.  Anyone have any idea?  What TS like pedal out there has gain, tone, presence, and level controls with true bypass?

[Alex C]

It doesn't necessarily have to be a production pedal or even a pedal that exists.  Just a thought here - the file is called  "bscr1.gif" - perhaps Boscorelli (Stompbox Cookbook)?

[Paul Marossy]

PeopleHateMe7666-

"NICE SITE PAUL!! VERY HELPFUL!!!!"
I'm glad that you could get something out my site.  

cd-

"All the replies so far have been stating the obvious, the schem itself SAYS it's a simplified TS circuit. I want to know WHAT PEDAL IT WAS TRACED FROM. Anyone have any idea? What TS like pedal out there has gain, tone, presence, and level controls with true bypass?"

What does it matter which one it was traced from if they are all very similar? According to the schematic, I would assume it was traced from an Ibanez TS-9 Tube Screamer. I don't think any commercial pedals out there offer the same things as the circuit in question - it is a modified TS-9 circuit, if you ask me. It just has an added "presence" control. This appears to be someone's design, not something directly traced from a commerical pedal.

Just my take on it.  

[Mark Hammer]

Here's the deal.  The gain of the first stage depends on the value of two resistances: the one in the feedback loop of the op-amp (R4+RV1), and the one from the inverting pin to ground (R3+RV4).  As the feedback resistance gets bigger, relative to the resistance to ground, the gain (and clipping) increases.

HOWEVER...there are caps in the feedback path (C3) and the path to ground (C4) which set the high-end (C3) and low-end (C4) rolloffs, and these also depend on the resistances described above to determine the rolloff points.

In particular, the low-end rolloff is determined by the joint product of C4 and its series resistances.  With RV4 set to max resistance (5k + 470R),  C4 sets the low-end rolloff at 132hz.  With RV4 set to min resistance (resistance = R3 = 470R), the rolloff point now shifts to just over 1.5khz.  You can do the math yourself using the standard formula: Frolloff[/b] = 1 / (2*pi*R*C).

I mentioned that Gain depends on that resistance but also the feedback resistance.  As feedback resistance increases, the high-end rolloff also shifts.  With RV3 resistance maxed, the high-end is rolled off at 2*pi*.512Meg*.000056uf = 5550hz.  With RV3 at min, the treble rolloff moves to  236khz, or essentially no high-freq limitations at all.

What you can see from this is that it is possible to achieve the
identical gain in the circuit with different sports of rolloffs at the high and low ends, by adjusting both RV3 and RV4.  What this circuit labels as "presence" is essentially a gain control whose side effect involves shifting the low-end rolloff around - in other words cutting bass, rather than boosting treble.

As an aside, I might point out that this is often one of the choice-points designers face when designing op-amp-based clippers: should you make the distortion amount control the *feedback* pot/resistance or the resistance to ground?  If you make it the feedback resistance, higher gain settings are also associated with reduced treble, which isn't such a bad thing in high gain situations.  If you make the gain pot the resistance to ground, higher gain settings can involve more shriek-ey strident tone, which may be exactly what you're looking for in a fuzz anyways.

You will note that the MXR Distortion+ and DOD 250/308 use a pot to ground, where the TS-9/SD-1/et al use a feedback resistance pot.  The first two fuzzes are thought of as more ragged sounding, while the second category are thought of as sounding "smoother".  A lot of that comes from the impact that the gain-control location in the circuit has on bandwidth changes at one end or the other.  This particular circuit under discussion here allows for choices in that regard.

Incidentally, if you want a simpler means of achieving "the best of both worlds", you can use a single pot whose wiper is tied to the "-" input of the opamp, with one leg of the pot subbing for RV3 and the other subbing for RV4 (naturally you flip R3 to the other side of the pot to do this, which has no bearing on the tone whatsoever).  Some designs I've seen use a dual-ganged pot for this with the second pot attached to the output of the op-amp, so as to reduce the clipper's output and retain relatively constant  levels across various gain settings.

[cd]

Mark -

Thanks for the insights but that still doesn't answer my question  I only ask out of curiosity's sake.  Everyone's being very helpful, but one thing my 2nd grade teacher taught me that still resonates is that it's OK to say "I don't know"  

Anyway, I think I found the answer: it's a Menatone Blue Collar.  See this pic:

http://www.bostonguitar.com/Merchant2/graphics/00000001/menatone-blue-collar.jpg

It fits the description as an 808 clone, with Volume, Tone, Presence, and Gain controls.  I'm guessing the "b" in "bscr" is for blue collar, and "scr" for screamer.

[cd]

Also found the original thread reference, it's in the archives:

http://diystompboxes.com/sboxforum/viewtopic.php?t=6945

Dates match up (Dec. 2002)

[Paul Marossy]

Good detective work, bro.  

It would have helped if the name of the pedal was included on the schematic. So now I know that there is a commercially manufactured version of that circuit with a presence control...
Ya' learn somethin' new evry day.  :wink: