Univox guitar circuit schematic

[booj]

I know this is really a longshot, but does anybody have a schematic for this circuit? It uses one 2Sk49 FET, (labeled K49), and one 1458 op amp. The fuzz and phase switches work, but the tremolo and whatever they mean by echo does not.

[dobrota]

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I know this is really a longshot, but does anybody have a schematic for this circuit? It uses one 2Sk49 FET, (labeled K49), and one 1458 op amp. The fuzz and phase switches work, but the tremolo and whatever they mean by echo does not.

It isn't possible to build echo using only FET and op amp.

[booj]

That's not a schematic, but thanks for replying!

[dobrota]

That's not a schematic, but thanks for replying!

I'm sorry, but it isn't in my schematics archive

[Enzo]

If you mean a reverb, then you are right, you can't make one with those two parts. However, if they make a variation on the trem circuit where instead of a smooth variation in volume, it becomes just off and on, you get a sort of "repeat" effect. I suspect that might be what the echo does. I think AMpeg or Gibson did that on a couple models.

[teemuk]

...if they make a variation on the trem circuit where instead of a smooth variation in volume, it becomes just off and on, you get a sort of "repeat" effect. I suspect that might be what the echo does. I think AMpeg or Gibson did that on a couple models.

Never heard of that. I think the actual idea (at least how Ampeg did it) was to modulate the wet signal of a spring reverb's output with the tremolo effect. Then they mixed that signal with the dry signal and the result sounded like a crude slapback echo. They patented that idea and called it tape echo simulation.

Naturally, you can't do that without a spring reverb tank or some kind of device providing reverberated output.

[52 Bill]

I think what Enzo is referring to may be the Repeat Percussion thing that Vox had back in the 60's, basically a choppy tremolo effect.

As for the original question, have you tried the Univox Board? Someone here I think posted a link a while ago.

[teemuk]

And if it uses just one FET and one dual OpAmp it shouldn't bee too tough to crack. If you can provide enough of detailed photos of the circuit to work with I can sketch a schematic for you just out of plain curiosity.

[Enzo]

Yeah, but I was speaking generically. Yes, the old Ampeg was modulating the reverb off and on, but they called it an echo. SO by extension, perhaps this Univox is gating something off and on and calling it an echo. But that is merely an opinion.

[Mark Hammer]

That's my take on it too. It's a simple switch between the triangle LFO waveform for tremolo to the square LFO output for "echo".

[booj]

Thanks for your replys everyone. The deed is done. The guitar works. The echo was an LFO square wave pulsed output. (quieter-louder-quieter-louder) The tremolo was just that. The fuzz was a germanium diode clipper.
I changed all the electrolytics (5), the 2SK49 with a 2N5485, which I installed in reverse to the original part because of the pin layout, and the 1458 IC.
The culprit I think was the 2SK49. I think it had a fractured internal lead.