Volume issue with octave on Foxx Tone Machine.

[hairyandy]

I've done some searching but I didn't find anything directly related to this problem that had a solution.  I made a FTM from Toney's latest vero layout (with the Q3 & Q4 caps correctly oriented:  base of tranny to +) and wired the octave up to a 3PDT switch.  Everything works fine and sounds great except the octave volume is about half of the non-octave volume.  The volume kind of scoops down which leads me to believe that it's a cap charging issue somewhere, although I'm not sure about that.  I know that the diodes may suck a little volume out of it but not this much.  The other weird thing is that it's gotten worse.  At first there was barely any difference between octave on/off and now it's like half after using it a few times.  Could I have a crappy electro in there somewhere that's dying?  I'm not quite sure where to start with this one and I don't want to start unsoldering my vero unless I have a good idea where to start with this.

Has anyone else had any experiences like this?  Or does anyone have an educated guess as to what I can start replacing?  I have swapped out the trannys and it didn't make any difference.  (I used the NTE equivalent of 2N3565s.)

Thanks guys,

[Bernardduur]

Hmmmm, that's not good. The octave volume should be the same as the non octave one.

I never had an experience like this...... but I can say that I like the circuit more with some low gain trannies (I use four BC140's wich really improve the sound)

[Mark Hammer]

I will also corroborate that the several I've made (not 2N3565 but close cousins, like 5088 or MPSA18) have no change in volume with octave selected.

Just out of curiosity, is it a robust octave sound? (i.e., an obvious octave)

[hairyandy]

I will also corroborate that the several I've made (not 2N3565 but close cousins, like 5088 or MPSA18) have no change in volume with octave selected.

Just out of curiosity, is it a robust octave sound? (i.e., an obvious octave)

The octave sounds great.  In fact, it sounds just like a FTM is supposed to sound--I worked at a vintage shop here in Columbus (Cowtown Guitars) and I've played a lot of them.  I have a theory that I have the two 10uf caps off the bases of Q3 & Q4 in backwards which may be causing the problem.  If you notice, the schematics on GGG and on Fuzzcentral disagree on their orientation.  I used Toney's vero layout for mine which he based off of the Fuzzcentral schematic.  Toney then updated it to the GGG schematic so I'm thinking that therin lies the issue.  One of them is right.  I'm going to swap them today and I'll report back.

Thanks a lot for the replies guys!

[Bernardduur]

Hmm, I used the GGG layout and it works.

[hairyandy]

Well I figured out what was going on.  I had the 3PDT switch for the octave wired wrong so that the LED was in the circuit!     That explains why it was still working but had the drop in volume.  I looked at it for a minute, thought "I wonder..." and disconnected the LED and voila!  Instant, nice loud octave.  That's what I get for working in the wee hours.

BTW, I flipped those 10uf caps on Q3 & Q4 and it works either way.  It sounds way better to me though when it is + to the base of the trannys as in the GGG schematic.  Just in case inquiring minds would want to know...

Thanks,

[Toney]

Excellent.

I test built it from my first layout and it sounded great.

I think it was Johan who pointed pointed out the schem conflict.

The current one is up to date.

Glad you got it firing. 

[hairyandy]

Funny enough I was correct in my initial wiring of the 3PDT for the octave switch.  What was happening was that I didn't have enough resistance in line with the two LEDs and when I'd kick on the octave it was drawing too much current from the 9v.  I finally realized it when I plugged it into my 1-spot and the volume came back up.  DUH!

To save an extra step I bought some 3mm LEDs from a guy on Ebay that was selling them pre-wired with a resistor and 6" leads.  The resistor was heat shrinked (or is that heat shrunk?) so I couldn't tell what the value was.  The LEDs were pretty bright but I didn't really mind too much.  Now I've got to add in the extra resistance to make it right again.  So much for saving a step.  Lesson learned:  don't cut corners!