Out of phase issue with blender

lukedlb

Mosquite blender with 3 pedals in the loop (univibe, tremolo, Reverb) have different phase settings requiring me to switch the phase depending on the pedal. Is there a clever fix? the vibe is wired 18v centre positive; could that be part of the problem?

lukedlb

Answer: ‘it’s a crap shoot’.
http://www.ovnilab.com/articles/blending.shtml

ICBM

lukedlb said:

Is there a clever fix? the vibe is wired 18v centre positive; could that be part of the problem?

No, and no.

Some pedals reverse phase when on. The only fix is to fit an inverting buffer (or audio transformer, if you prefer) inside the pedal to correct it.

lukedlb

ICBM said:

lukedlb said:

Is there a clever fix? the vibe is wired 18v centre positive; could that be part of the problem?

No, and no.

Some pedals reverse phase when on. The only fix is to fit an inverting buffer (or audio transformer, if you prefer) inside the pedal to correct it.

Where could I get one of these for an internal pedal solution?

ICBM

lukedlb said:

Where could I get one of these for an internal pedal solution?

Something like this should work - https://uk.rs-online.com/web/p/audio-transformers/1237207/

Glue it to the inside of the casing somewhere and connect it between the output of the effect circuit and the switch, if the switch is separate - if it isn't then it becomes more difficult since you'll need to find where to break the circuit.

An inverting buffer is pretty easy to build on stripboard using either an IC or a single transistor.

Sporky

Geofex has a schematic for a switchable buffer - one pole switch makes it invert or not.

ecc83

You need a '600 Ohm' 1 to 1 output transformer. OEP electronics have the 1200 . The specc looks ghastly for 'hi fi' but is fine for the frequency range of guitar and the neg ten'ish levels.

Actually have a couple somewhere, shout and I will Jiffy.

Dave.

lukedlb

ecc83 said:

You need a '600 Ohm' 1 to 1 output transformer. OEP electronics have the 1200 . The specc looks ghastly for 'hi fi' but is fine for the frequency range of guitar and the neg ten'ish levels.

Actually have a couple somewhere, shout and I will Jiffy.

Dave.

Dave, thank you. Once I get the pedal order fixed, I will contact you.
Strangely, I discovered that although the tremolo and reverb pedals require separate phase settings, they work together. So the phase issue does not effect successive pedals, only the first in the queue (all turned on of course).

ICBM

lukedlb said:

Strangely, I discovered that although the tremolo and reverb pedals require separate phase settings, they work together. So the phase issue does not effect successive pedals, only the first in the queue (all turned on of course).

No, that's because two phase reversals is the same as no phase reversal. A phase reversal is a phase reversal, it always affects what follows it as well.