First Build Complete - Red Fuzz - But I have 1 Question

[mavrick10_2000]

And All working well.   It was easier than I thought it would be, Painting the enclosure however was a bit of a PITA.   I spent about 1 hour total on the components and PCB, and test wiring the pots and jacks to do a test which went well.   The enclosure drilling I planned out fairly well, I would do some things differently next time but it worked out well.    The painting I just kept screwing up, It would look good, then when preparing for another coat, I'd bump it against something and chip it, or overspray the next coat - It was windy outside so it wasn't the best 2 days to try to paint.

I built the red fuzz using only the Red LED's for clipping.   I bought the Si Diodes and and SPDT switch to do the mod listed here ----->http://www.generalguitargadgets.com/diagrams/redfzzmd.gif

But I couldn't get my head wrapped around how to wire in the switch and add the diodes to the circuit.   Can anyone explain it to me?

I first thought I could solder the two led's together, and the two diodes together and place them in the drilled holes in the PCB, but then I couldn't figure how the switch was going to be able to select them. So I just went with the LED's for now -  figuring I would get clipping from both with the above approach.

Bob

[petemoore]

  BTB LED/s and Si's diodes, each pair of type looks like
  --l<--*
  -->l--*
  this is TS feedback loop type clipping, signal from OA output to btb clipping diodes to the negative input.
  If you connected all four diodes, a BTB LED pair and a back to back Si pair, the Si's low threshold would cause them to do all the clipping, connecting the LED does nothing.
  With all four connected, lifting the Si's will allow the LED's to do the clipping[providing the threshold voltage is met/gain set high enough].
  But the way they have it is that the clipping elements all have one end connected to the OA output, then a switch selects between Si or Led pairs, each pairs is connected.
  It could be wired either way, I like just wire 'em all and 'lift the LED's' [at either end] because it requires only a SPST, and in a WCS the Led's are still solder connected.
 

[Cardboard Tube Samurai]

Have a look here --->http://www.generalguitargadgets.com/pdf/ggg_its8_mods.pdf. It's a link to the mods for a TS808. In the second diagram/blurb, it tells you how to wire a switch in that would serve exactly the same purpose as you are looking for. Simply make another little board off the main board and mount both the LEDs and the Si's in it and use a switch to toggle between them.

[mavrick10_2000]

Thanks Guys!    Between Peter's description and the diagram on GGG I think I've got it. 

[mac]

All 4 diodes soldered to one side of the feedback loop, say pin2. The center lug of the 2dpt to the other side of the loop, say pin6. Then one lug to the leds and the last lug to the silicons.

That's exactly what I did with my red fuzz clone. Keep in mind that the silicons will reduce the volume unless you use two in series.

The only mod I have to do to it is to replace the 100k tone pot with a 50k since all the interesting things happens in the first 25k. Or maybe reducing the 3.3n cap. But this is my personal taste.

mac

[Bronsonrock]

I am really new to this and am just about finished with the pedal (my first).  I'd like to do this mod as well and had the same problem as the original poster.  I have to confess that I don't really understand the answers given.  I don't know what "lifting the LEDs" means nor do I know what pins (I'm assuming from the OpAmp?) Mac is referring to.  Can someone put this at "pedal building for total idiots" level?  Maybe draw it out?

I'm trying to learn how/why things are done and not just put components on a prebuilt board so I'd like to know what's going on with this mod.  I appreciate any answers and your patience .

[mac]

Yes. I mean the opamp pins. See datasheet at www.alldatasheet.com

There is another way of connecting the diode switch that involves just a spst switch, ie, lift the LEDs I presume

                  I------>I---->I-----I      /  SPST
                  I------I<----I<-----I----o/  o----------I
                  I            silicons                   I
pin 2     --------I                                       I------- pin 6
                  I----------->I---------I----------------I
                  I-----------I<---------I
                               LEDs


The trick here is that when you connect the switch, ie the silicons, they override the LEDs since silicons have lower voltage drop than LEDs.
To be precise, only a very small fraction of signal will pass through the LEDs.
I draw 2 Si diodes in series to avoid too much volume drop between the LEDs and Si.

BTW, I never used the Si.

mac

[Bronsonrock]

Thank you very much.  The part that was getting me makes sense now that I understand that silicons will override the LEDs.  I was trying to see how they formed a discreet circuit (i.e., the LEDs completely out) but it's not necessary to remove them, just override them.

You didn't like the Si tone?

Thanks again...

[mac]

I like the Si but I use it at low gain settings to push the preamp, so Si and Leds are almost identical. I never used it as a distortion.

mac

[Bronsonrock]

The mod on the GGG site says to use either 1N914 diodes or 2N4148s.  I'm pretty new to this but it doesn't look to me to like 2N4148s are diodes.  I think they meant to say 1N4148 which is a diode but I can't get them to confirm that.  Does 2N4148 makes sense?  Not that I can even source those (I can't find them in any of my normal spots like Mouser or Allied Electronics) but I'd like to know.  I have 1N4148s that I can put in the project now otherwise I'd have to order 1N914s as the alternative.

Thanks in advance...

[Talon5051]

I think they meant to say 1N4148 which is a diode but I can't get them to confirm that.

From what I can see I think you are correct with the 1N4148.  I also don't think that it specifically needs to be a 1N4148 either.  Many diodes will work and produce slightly different sounds.  Search diode clipping in this forum and you will get a lot of info.  Experiment with different diodes to find what you like.

[mac]

Yes. They meant 1n4148.

The diodes you will usually see round here are silicon 1n4148, 1n914, 1n4001/7 and ge 1n34, 1n270.
There are also a lot of threads about using transistors and fets as diodes.

mac