Preamp Phase Inversion?

[Oldschoolfanatic]

This question immediately pertains to the new Conrad Johnson pre and power amps... but my confusion is more general than that. I read where CJ's preamps do, and are designed to, invert the phase of the audio signal before it's passed to the rest of the audio chain.

1) Why
2) for what purpose
3) is that something that would need to be compensated for downstream

Any comments or advice is appreciated, my real audio knowledge is many years out of date, and I'm trying to catch up!

 

[Steve Williams]

Many preamps are inverting including my Lamm LL1 Signature . You either need to reverse the polarity of the interconnects from the preamp to the amp OR attach the interconnect properly from the preamp to the amp BUT reverse the polarity of the speaker cable from the amp to the speaker

 

[DonH50]

Single-ended gain stages, which are most tube preamp gain stages and many SS gain stages, are usually inverting. That means that, if you have an odd number of them in the signal path, the polarity of the signal will be reversed coming out of the preamp. Rather than add another stage just to correct the polarity, you get less noise and distortion (and heat, and cost, etc.) by just passing an inverted signal on down the chain.

Some argue polarity reversal matters though many studies (AES, Toole, etc.) say otherwise. In any event, the solution is as Steve said -- just swap connections someplace to fix it. Swapping the speaker cables at one end (amp or speaker end, not both) is often the easiest fix.

HTH - Don

 

[Steve Williams]

Single-ended gain stages, which are most tube preamp gain stages and many SS gain stages, are usually inverting. That means that, if you have an odd number of them in the signal path, the polarity of the signal will be reversed coming out of the preamp. Rather than add another stage just to correct the polarity, you get less noise and distortion (and heat, and cost, etc.) by just passing an inverted signal on down the chain.

Some argue polarity reversal matters though many studies (AES, Toole, etc.) say otherwise. In any event, the solution is as Steve said -- just swap connections someplace to fix it. Swapping the speaker cables at one end (amp or speaker end, not both) is often the easiest fix.

HTH - Don

I swap my speaker cable’s polarity as they come out of the amp

 

[DonH50]

I swap my speaker cable’s polarity as they come out of the amp

I do as well, mainly because a year from now I won't remember if red is + or - at the speaker when I have to move the speaker for whatever reason. I always keep red to + and black to - at the speaker and swap at the amp if need be. At least it's consistent. Over the years I have been more likely to unplug the speaker (or speaker cable) to move it out of the way or get behind it than the amp. E.g. dusting, or need to get behind the console, or moving the speakers out of the way to vacuum or for HVAC service.