Univibe output problem

[ronh]

Hi there. I built a Univibe using Viva Analogue"s board. My problem is that it sounds like its coming out of a telephone. Here is what I have done and found. I injected a 300mV AC signal in and with a scope traced the signal path thru the vibe. The problem appears at the output mixer before the chorus/vib switch. Both the wet and dry signal level is a little bit above 300mV. After the 100k resistors, at their junction the signal level is 30mV. At the other output, after the 47k resistor the signal is 175mV. The signal level at the 100k and 47k junction is about 300mV. Where is and what has happen to my signal level? The resistors read correct ohm wise, I checked for shorts on the board and found none.. So, for some reason these resistors are dropping the signal level.
Resistors read 97K, 101k and 46k. The 220k reads 224k.
Anyone please have an idea to solve this. This effect is useless like this. Thanks

[R.G.]

I'll take a swing at it. I know the univibe circuit backwards and forwards. Literally hundreds of people have made successful clones of the univibe with the board I laid out and licensed to General Guitar Gadgets for sale.

Hi there. I built a Univibe using Viva Analogue"s board.

The "I'll take a swing" goes with the caveat that I have not checked the "viva analogue"(?) board, and do not know if it's correct or not. We'll assume it is, and go from there.

My problem is that it sounds like its coming out of a telephone.

By that, do you mean the bass and treble are missing?

Here is what I have done and found. I injected a 300mV AC signal in and

Did you have the LFO sweeping the signal and lots of depth when you did this?
What frequency did you use?

with a scope traced the signal path thru the vibe. The problem appears at the output mixer before the chorus/vib switch. Both the wet and dry signal level is a little bit above 300mV. After the 100k resistors, at their junction the signal level is 30mV. At the other output, after the 47k resistor the signal is 175mV. The signal level at the 100k and 47k junction is about 300mV. Where is and what has happen to my signal level? The resistors read correct ohm wise, I checked for shorts on the board and found none.. So, for some reason these resistors are dropping the signal level.

If you happened to use the wrong frequency signal and were not sweeping the LFO, you might have accidentally hit a notch in the phasing. That's why I asked if you were running the LFO with a lot of depth pot. You might be describing a perfectly normal situation.

If you have some experience with effects you know that 90+ percent of bugs with new made effects are soldering issues and wiring. Is it possible that your soldering on the mix point is bad in a high resistance way? I would just reflux and remelt that joint and check the wiring again. I might also remove the wire to the output jack to see if my external wiring was pulling the signal level down.

Do you have a dual trace scope so you could see the phase of the signal before the mixing point change?

[ronh]

Well, silly me. I did my scoping again and I guess I was looking at a notch.
Changed the freq a little and signal level went up. I guess I am looking for a problem when there isn't one. Thanks for your help R.G.