ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

No Vibrato

:

6/22/2000 6:39 PM
PTJohn	No Vibrato On my hotbox/vibrobox clone, I seem to be getting no vibrato. I was going to post to Steve Ahola, but this is by all means open to anyone who can help me. I used the "blue" schematics, and was going to post this question to Steve A., but for some reason, only the mirror sites work--not the "ampage.org" site. Does anyone have any ideas? Any at all? PTJohn

6/22/2000 11:51 PM

SPOKE TOO SOON! IT WORKS! EUREKA! PRELIMINARY REVIEW ENCLOSED!

The alligator clip I used to activate my relay wasn't long enough to hit the inside contact on the RCA jack; add to that I had a 2.2 instead of a 22 uF cap off the cathode of the vibrato oscillator triode.

The vibrato sounds pretty darn good; I may want to play with either the slope of it or not, I'm not sure yet; I need to put in the proper 12ax7's to tune it.

FYI, the hotbox/vibrobox schematics labeled 1 of 2 and 2 of 2 running off 1 power supply are the correct ones; the oscillator circuit is wrong on the other one (Steve A., take note).

As far as the tone goes, after playing it a bit, I think right off the bat, the 220k plate resistors do need to be changed out for 150k or 100k. The hotbox puts out MONDO distortion. If you want endless fuzz, the stock circuit's the way to go, but otherwise, if you're looking for dynamics, as I am, I think switching the plate resistors out will help big time. I used RS reed relays for the switching, and FWIW, they are virtually silent when switching in and out. Lessee... what else...
Oh yeah-- the tone stack on the hotbox section; I think it could benefit with a bit of midrange girth, so I'm gonna try swapping in a 22k or 27k resistor at the bottom of the tone stack in place of the 10k and see what happens.

Any other opinions?

PTJohn.

6/23/2000 4:38 PM
Stephen Conner	Hey PT, Is that the two-box preamp you were talking about when you asked about ground loop issues etc? Did the thing with the diodes work all right? Steve C.

6/23/2000 4:45 PM

Yes it did, Steve, and thanks so much for all your help. I really appreciate it. One thing I did add to it was to reference the signal to chassis through the back-to-backs as well. I noticed that the signal ground had quite a bit of float, and I wanted it to stay close to ground so the heater-to-cathode voltage wouldn't go negative. If it creates a ground loop, I may have to lift the shields on the patch cables on one end, but since the whole effects unit will be in one box, that shouldn't be a big deal.

Thanks again,
PTJohn.

6/24/2000 11:02 PM

quote:
"Yes it did"

quote:
"One thing I did add to it was to reference the signal to chassis through the back-to-backs as well"

Yup- that's the way it should be. You can't leave the signal ground completely floating, for safety reasons.

Steve C.

6/23/2000 4:48 PM
PTJohn	ONE MORE THING The pix are under the "if anyone is on right now, how do you post a JPEG" thread down the page a few entries.

6/23/2000 12:33 AM
PTJohn	MINUTE BY MINUTE UPDATE: 100k plate resistors. Oh, yeah! this is what the hotbox circuits needed! I paralleled 2 more 220k resistors, since I didn't have any 100k handy, and it is much meatier and less fizzy. It is now approaching overdriven Marshall territory. Which makes me wonder why they didn't use this value to begin with. Sounding great!

Page 1 of 2