octavia build problems

[jrem]

hey to all . . .    I'm breadboarding a Tychobrahe Octavia, I have the JDSleep schematic (neg ground) and the J Philpott schem (pos ground) and can't seem to get the signal past the third transistor (tried both builds).

I can get the signal to read off of the emitter of the second transistor (with the third tranny out of the circuit) but once I drop in the third transistor the signal gets pulled down, i.e., nothing coming out of the second transistor's emitter.  I don't have the exact values, I substituted on the voltage dividor (for the input signal reference) and I used a 1k instead of the 1.2k on the third thanny collector.

Any ideas?

Thanks, John.

[jrem]

okay, so I fiddled with the emitter resistor and capacitor on the third transistor, and got some signal to come through, but  I can't seem to get any gain from the given values . . .   anyone actually build this?

[Pedal love]

Which values did you use on the voltage divider?pl

[jrem]

what an excellent question.  680 instead of 680k, for starters (duh).  Maybe I'll go and get the right values and try again.   

(edit)  that was a first mistake . . .   then I used 200k (2x100k) for the 180, 940k (2x470k) for the 820k, and 470k for the 680k.  Same results, hardly any gain past the first two transistors.

[petemoore]

'680 instead of 680k'
  680,000 ohms
  compared to 680...that's a 1000x difference, will matter.
 

[jrem]

yes, I understand.  found a host of other problems, like the second emitter resistor hot (instead of grounded, duh), etc, now I have sound coming from the output (yeah) too bad it sounds like ass (boo).

time to tweak.

[bwanasonic]

anyone actually build this?

Do you mean the GGG layout? I think it's fair to say a LOT of people have built that circuit. I made my own layout, but used the neg ground schemo from GGG with no major variations. Troubleshooting someone's breadboard layout is tough, at least if your breadboard builds look like mine . I often trace problems to crossed part leads, and other annoying minor problems.

Kerry M

[jrem]

okay, I replaced all the non-accurate resistors with pots dialed to the right value, and it still sounds like ass.

How important are the values for the electrolytics?  i.e., I don't have 33uf and 220ufs . . .   I'm substituting 22's, 47's, 330's, etc. 

ideas?  time for another mouser order just to make this work?

[jrem]

Sorry for not letting go on this . . .   but if I short one of the 1n34A's it sounds a whole lot better, but loses that "octave" thing.

So my question . . .   is there a difference in 1N34A's by manufacturer?  or are they all identical, sound wise?

[petemoore]

  Measuring the threshold voltage for any diode is the 'complete' test, the voltage drop is what differentiates one from the next...but If the diode is good, I don't that part tolerance there would be a 'problem'.
  Whn you say sounds like ass do you mean Pffffffft or Braaaaappp?
  The Tycho's a wierd effect, amaybe it fits the 'ass' description [ie: is 'working'] ?

[jrem]

hmm, well, I downloaded a clip from the roger maher (sp?) site, so I'm sure I'm not there.

Straight through, single coil, into studio monitors (c-c-c-clean) and it's more like phzzztttt . . .    short one diode and with a fuzz face in front of it it doesn't sound too bad . . .     not sure if the "octave" thing is all there, though.

Sure would be nice to see a scope trace of the output with a 1k sine wave input  . . .     do folks around here ever share that kind of thing?