Guitar Overdrive distorting signal when not engaged

Question

I have a Hampstead Subspace, and recently when is engaged I noticed that if the settings are set very high there is a very slight distorting to the signal, meaning that even when not engaged the signal is no longer clean. It can be reduced by turning everything down, eg gain, active bass and treble controls and the level (as well as input multiplier). It's very odd. Hampstead tested it themselves and could not replicate it.

What could cause this kind of behaviour? Essentially its as if the circuit still has signal going through it and a tiny bit is feeding back into the dry signal. Hampstead say it has never happened before, and since they cannot replicate it, it makes me think that perhaps its something to do with my set up, be it a power supply (1spot cs7) or amplifier issue (Orange tremlord 30).

Any thoughts welcomed!

Thanks,

Blair

Answer 1

It would be useful to know whether this pedal is true bypass or not. Can't see it from the manual. I suspect it's not, which is in principle ok – provided the circuit is developed carefully. Which guitar tech all too often is not...

At any rate, apparently the overdrive circuitry is still active even when the pedal is in bypass. That means in particular that sharp clipping-transients are produced. Transients have a lot of high-frequency content which can easily interfere with other circuitry, and human ears are very good at detecting such artifacts.

One likely way this comes about is that the transients first feed into the power rails, and from there either into the buffer that has the bypass signal passing through it, or a decoupling capacitor, or perhaps even a different FX pedal you have on the same power supply. If this is what's going on then it should be possible to fix it on the power supply side. The CS7 with its switching design should already be as good as it gets though, but perhaps you're using a long DC cable from it to the Subspace? Do try with a different supply and/or cable, at any rate. It could also make sense to address the problem with a bigger capacitor in the overdrive between ground and power rail, or perhaps actually a smaller capacitor (lower resistance and inductance) in parallel to the standard electrolytic one.

If nothing helps, you can always operate the Subspace in permanently-engages, and switch it with an ABY pedal instead, but that's of course a bit unsatisfying.

Answer 2

Is the problem simply that you're overdriving it? Overdrive is simulating what happens when you set the preamplifier gain too high, and the signal distorts. If you turn all the knobs to 11, then you're going to overdrive it, even without using the "overdrive" control.