Question on Dunlop Uni Vibe

[glebert]

I've got this Uni Vibe UV-1 that I am fixing up and I got the basic effects functional, but notice that there is a noticeable loss of treble (and maybe some distortion) in chorus mode and what seems like a boost in treble in tremolo mode. I don't know if this is "normal" or something to be addressed when I open it back up to replace the pots.

This schematic has been accurate for my use so far. https://www.freestompboxes.org/membe...0%282-3%29.pdf

[TomCarlos]

Glebert..... I just happen to have a Uni-Vibe in the house. But it is not something I am familiar with.

In any event, when I listen to the dry signal and then compare it to the chorus, I do not hear any difference in the treble level. The same when I compare dry to vibrato. I also checked with the switch for the Vintage setting. I did not attach the controller pedal for this test.

Hmmmm....

[J M Fahey]

It´s an OLD circuit, and I bet input and output impedances are "wrong" by modern standards, there´s a reason old pedals needed True bypass ... or else.

I guess it´s affecting how your pickups sound, big time, and much worse, in an inconsistent way, as different pickups will react in a different way.

[glebert]

It´s an OLD circuit, and I bet input and output impedances are "wrong" by modern standards, there´s a reason old pedals needed True bypass ... or else.

I guess it´s affecting how your pickups sound, big time, and much worse, in an inconsistent way, as different pickups will react in a different way.

I'm pretty sure the input and output buffering is the same for both tremolo and chorus mode, so I don't think it would be that.

[Helmholtz]

I'm pretty sure the input and output buffering is the same for both tremolo and chorus mode, so I don't think it would be that.

That's what I thought at first.

But if you look carefully, the input buffer is bypassed by the switching Opto-Fet (U9) in effect mode.

You might try to use a stand-alone buffer or buffered pedal before the Univibe.

[glebert]

That's what I thought at first.

But if you look carefully, the input buffer is bypassed by the switching Opto-Fet (U9) in effect mode.

You might try to use a stand-alone buffer or buffered pedal before the Univibe.

I do have a buffered pedal before the Univibe. I could see that bypassing might cause a difference between bypass and effects mode, but don't know how it would cause a difference between chorus mode and tremolo mode. I could live with the bump in treble in tremolo mode but the chorus mode sounds quite muffled.

[Aj6stringsting]

I have an original Univibe, one thing, when you activate it with the expression pedal , you lose some volume .

[glebert]

AJ, that is really cool looking. I put my Univibe on the shelf after my last post in this thread, but was thinking recently I need to dig into that and figure it out. This is going to the be the "Summer of Finishing Projects, and Not Acquiring Any More."

[The Dude]

......This is going to the be the "Summer of Finishing Projects, and Not Acquiring Any More."

Ha! I wish I could count the number of times I've thought that. It never works out that way.