New Clipper problems

[Paul Marossy]

Have you checked all of your solder joints? Once or twice I had a blob of solder just barely touching an adjacent blob of solder, and it screwed up my circuit so that it didn't work properly. In your case, maybe you have something in your signal path that is partially grounded and causing a low output. Maybe you could check out your circuit with a continuity checker and see if anything is connected to ground that shouldn't be.

If that's not the problem, then maybe you could just start over. I've had to do that with a couple of circuits. The first time I built the circuit it didn't work properly and I couldn't find any reason why it shouldn't work. So I just resolved to rebuild it and it worked great the second time!
Go figure?!?

[Gary]

Black Mariah,

Send me a PM with your address and I'll mail you my prototype.  I'll send you the circuit board and all you'll need to do is add the jacks, pot, knob and enclosure.

It is built just like the schematic on RoG.  I assure you there are no tweaks and it functions perfectly.  In fact, it's the one I used for my clips.

Mark,

The opamp clips on it's own, as well as adding clipping from the diodes.  I thought the opamp clipping was good enough to make a nice OD pedal, without the diodes.  The diodes send it over the top.  The schem is based heavily upon the Blue Clipper schems that floated around a long time ago.  In the write up, we discovered the old schem couldn't have been correct, due to mis-bias.  BTW, I used a TL071 opamp.

The schem will work as drawn.

Thanks,

[black mariah]

Paul: I've reflowed all the connections twice, and checked the layout umpteen dozen times (not that it helped me with that freaking ground pin). I'll take your advice and rebuild it. I think I'll go off of the PCB layout this time. It's a bit clearer to me.

Gary: You have PM.

[Mark Hammer]

The opamp clips on it's own, as well as adding clipping from the diodes.  I thought the opamp clipping was good enough to make a nice OD pedal, without the diodes.  The diodes send it over the top.  The schem is based heavily upon the Blue Clipper schems that floated around a long time ago.  In the write up, we discovered the old schem couldn't have been correct, due to mis-bias.  BTW, I used a TL071 opamp.
The schem will work as drawn.

Gary,

First, thanks for the circuit.  Second, thanks for your patience.  Third, thanks for your response.

Yeah, I'll bet that sucker DOES clip without diodes!  This is also a part of what happens with the Dist+ too, as many of us have experienced, and with several other circuits that park a pair of diodes near the end of an otherwise "too-high-gain" circuit.  For instance, the Bosstone, the JSH fuzz, and probably even the Univox Square Wave all yield an obvious not-at-all-subtle distortion, and the diodes simply secure the "raggedness" for more of the note's duration.

Do you suspect at all that the tonal outcome of the biasing scheme needs a BiFet op-amp to work well, or do you see this as being more device-independent?  I should probably just build the damn thing and experiment myself, but assorted recent household and family emergencies have pushed all hobby activity behind the back burner.

[Paul Marossy]

I'm not totally positive, but I think that I used a BiFet opamp in mine. I should pull it out tonight and verify what I used just for the record.

[Gary]

Black Mariah,
Check your PM.  Look for the box in a few days!


Mark,
I always enjoy a conversation with you, even if by electronic means.

The noise level is not so bad, really.  It's comparable to or less than the Jordan or Univox units.  It may be noisier with the old 741, but not an intolerable amount.  As I recall, the opamp alone clipping was along the lines of the TS effects.  The 741 sounded a little fizzier and less attractive to my ears.

I've seen Blue Clippers that used 4558 dual amps with the second section left dead.  I know a 741 will work also, so I'd say it isn't device specific at all.  There are marked differences in sound, but not due to the biasing.  I have to admit, there is usually atleast a resistor from the vref divider to the + input, but this setup works fine and sounds interesting.  It is subtly different from a MXR, but not drastically so.  You'd never notice in the heat of battle, if all the filtering was identical to the MXR unit.  The clipper does have the impression of more gain, for whatever that may be worth.

The "secret" seems to be in getting the vref divider to sit at the right point, but you knew that already.  It's interesting to hear how the bias voltage changes affect the sound.  One can get an interesting, splatty fuzz effect if the bias is set just so.  In the article on RoG, we mention using a pot for the divider so one can play with the bias.  The only downside is extreme mis-biases either cut off the sound (no shocker) or greatly reduce the output power to the point the circuit is well below unity gain.  There is a good bit of ground between extremes, though.

I think you may have some fun breadboarding this circuit.  For the minimal parts count, it does offer a great sound.

BTW, have you tried the Princeton emulation yet?  I'm really interested in your views.

Sorry to hear about your emergencies.  I hope all is well now.

Regards,

[Mark Hammer]

Actually your description of the behaviour resulting from misbiasing sounds suspiciously close to what was originally described as the problem by the person starting the thread.

I'm looking forward to making a "multi-model" board with the various valve-to-FET emulators you guys have dreamt up lately at the first available opportunity.  If you saw my bench and home office, though, you'd know why this hasn't happened yet. :oops:  I'll certainly be eager to try the Princeton emulator and provide a "real world" comparison as soon as I can, though.

The next emulator I'd like to see is the white Tolex Bandmaster.  I think the model is the 6G-2 or something like that.  The 6G6 Bassman (http://www.ampwares.com/ffg/schem/bassman_6g6_schem.gif) is the same thing, I think.  This one is rather unique among Fender amps in that it splits the tonestack.  The bass control is first in line, and the treble control actually *follows* the volume control several gain stages down the line.  It comes about as close to a pre-plus-post-clip EQ as Fender has ever gotten.  The capacity to push subsequent gain stages with differing amounts of bass drive, and then roll off harmonic content after that is an attractive one and something that one doesn't often see.  I've never heard one in action, but my sense is that it has the capacity to be as smooth and fat as double cream in your coffee.  Tack on a master volume at the end and I'll bet that's a nice-sounding emulator.

[Gary]

I'll certainly be eager to try the Princeton emulator and provide a "real world" comparison as soon as I can, though.

I'm looking forward to it.  No pressure, though!

The next emulator I'd like to see is the white Tolex Bandmaster.  I think the model is the 6G-2 or something like that.

I'll look into it.  Sounds very interesting.  The jfet circuits tend to sound very thick, so this may add up to quite a bit of corpulence!  Sounds interesting.

The bass control is first in line, and the treble control actually *follows* the volume control several gain stages down the line.

I've seen a recent SS Marshall that uses a split tone stack.  I think it was the bass control afterward, though.  After your explanation of the Fender, it makes me wonder why they would put the bass last...  Must have something to do with Nu Metal

I'll let you know how the Bandmaster turns out.  We have one more circuit ready for release, but it won't be until Brian gets back from his vacation.  This latest circuit has an interesting tone stack, too.

[petemoore]

Built one a long time ago [two actually].
 Built another yesterday, very nice ! ! ! I used a TL082, then a TL072 [well half], and tied the unused inputs to ground. Very nice Fuzz Box, with 3PDT. Sounds really great.
 I decided since it's box already has an 'extra' pot hole drilled, to put a notch filter after, partly as an excuse for filling the voidhole, also thinking of using an old 1/2 good stompswitch to a/b capacitences of the cap I socketted...pulling it 'pulls' the notch up, 'adding' mids...actually sounds QAB Better than I'd remembered My old N.C.'s did.
 Such an easy, great sounding circuit, begging for mods, [I left it 'stock']...but used the 100k pot trick for biasing the OA. Works great, needs the 10k trim on the Volume pot tho...Not a problem really just would probably taper better and not shut off completely before fully CCW.
 Nice thick, tight and bright 'internal' sounding distortion.