Zero-loss FX loop and a Vox TB35C1

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Zero-loss FX loop and a Vox TB35C1

Post by lance_fowler » Thu May 02, 2019 1:24 am

Hi all,

1st-time post here - I'm wondering if anyone can help resolve a zero-loss FX loop installation problem.

The amplifier is a Vox TB35C1, part of the 'Tony Bruno' series.

The schematic can be found here on page 3:

As you can see, less like a Vox and more like a Fender!

The outcome I'm going for is to insert the FX loop 'post gain' - that is, after the pre-amp overdrive has occurred.

But this amp has a PPIMV - which changes the volume by bringing one side of the phase inverter's output into/out of phase with the other side - so I reckon the PI might be playing an active role in creating pre-amp overdrive.

At this stage I'm thinking it might not be possible to achieve the outcome I'm after - but I'm open to your suggestions / feedback!

Q1) can I get the outcome i'm after?
Q2) where should I interrupt the audio signal path for send/return?
Q3) what circuit mods will be necessary to ensure the zero loss circuit performs as intended?

Cheers all,


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