Effects loop issue

[lowell]

My custom amp has a series fx loop. I just tried wiring in 2 taps off the driver's cathode.

1 is C14 and bypasses the loop.
2 is C37 which goees to the loop.

I did this mod because I was not getting the amount of drive I wanted. The series loop by itself, with the 100k/1k voltage divider on the driver cathode, is dropping too much signal to get the power amp distortion that I'm after. The recovery stage just doesn't provide enough gain of <78. I need a gain of 100 if I'm to get the same ratio of driver division and recovery gain. I've thought to just increase the send level, which I may do, however I fear 5v p-p is too much for a line out signal.

Back to why I'm posting. My delay I'm using in the fx loop inverts the signal. This causes my bypassed signal to be out of phase w/ the loop signal. My main question is, do all effects invert phase or is it a crap shoot?

[Redhat]

For temporal based effects (delay, chorus etc...) one (usually) wants the loop to be totally serial to avoid phase issues like you mention. With dynamic based effects (Fuzz, Wha, compression...) one can use a parallel path since sometimes the phase effects sound cool. Of course everything's subjective in this game. We are after all "artists".

Is your effect set to serial mode (if it has one) and is the Kill Dry switch on? It should be so that you have no parallel path. Your delay should sound OK then.

[d95err]

For temporal based effects (delay, chorus etc...) one (usually) wants the loop to be totally serial to avoid phase issues like you mention. With dynamic based effects (Fuzz, Wha, compression...) one can use a parallel path since sometimes the phase effects sound cool. Of course everything's subjective in this game. We are after all "artists".

Is your effect set to serial mode (if it has one) and is the Kill Dry switch on? It should be so that you have no parallel path. Your delay should sound OK then.

I would say almost the opposite

For time based effects like delay or reverb, phase does not matter much on the delayed/reverbed signal. However, this applies only as long as the effect is set to 100% wet. I.e. the effect should only produce the delayed/reverbed signal, and none of the original signal.

If your delay pedal does not allow you to set it to 100% wet, then it may be useless in a parallell loop. Get one where you can turn the dry signal off completely.

[d95err]

My main question is, do all effects invert phase or is it a crap shoot?

Some invert, some don't. It's probably 50/50.

[Redhat]

Oops, you are indeed correct. I typo-ed. Actually for some effects, its good to have a mix of the two modes: serial and parallel.

My very cool TC Electronics G Major 2 has a routing setup where you can mix, say, the reverb and delay in parallel and the end of a serial effect chain. This sometimes sounds cleaner than having the standard reverb following delay routing, especially if there are other effects being used.

[KevinOConnor]

Hi Guys

Ambient effects have an inherently random-phase wet output so there is no issue of mixing the 100% wet sound with the internal dry sound through the effects loop.

The only units that will sound strange in a loop with mixed phase are ones that just boost or EQ the signal.

As far as the signal level goes, 5Vpp through a real line-level processor is no problem. Most such units operate from normal opamp rails of +/-12V to +/-20V, and thus have a large signal window. It is only the 9V pedals that impose signal amplitude restrictions. So, change the 100k / 1k divider to provide more output and to match the return gain.

The circuit sounds like an SLO or a clone, where the loop precedes the MV. Personally I don't like that order. But since it is what you have the thing to do is to measure real signals at the CF output and at the send jack with an effect connected. This high attenuation is optimised for pedals most likely as it is impossible to get players to buy line-level devices. You pay a noise penalty with the high-gain afterwards, and the whole thing represents a headroom bottleneck and noise compromise.

Have fun