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CJ tube preamp experts

RS Steve

RS Steve

Tube Junkie
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I purchased a Conrad Johnson PV-8 a few years back that I really like, but never tried reversing phase of the speakers like the manual says. I'm a bit confused with the reverse phase thing that they state about the preamp and why they wouldn't design it with regular phase. Below is what is stated in the manual, just curious how many have experimented with this. Never reversed phase with my JBL 4435's.

THE PV8 IS PHASE INVERTING. If your system has an odd number of inversions, then you must add one phase inversion. This will be the case if the PV8 is the only unit in the chain that inverts phase. THIS IS CONVENIENTLY DONE BY REVERSING THE POSITIVE AND NEGATIVE CONNECTIONS TO YOUR SPEAKERS (be sure to reverse both channels). If you are not sure about the phase of every piece in your system, you can establish correct absolute phase by careful listening. When the system is in correct phase, transients will be noticeably cleaner and more sharply defined. The effect is especially apparent on plucked string sounds. A final warning-not all recordings are phase correct (including some "audiophile" recordings), so listen to several before concluding your investigation of absolute phase.
 
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My understanding is that for some designs, inverting phase results in the simplest designs and inverting phase again to normal (non-inverting) phase would result in another preamp stage which some designers feel is not necessary since the issue can easily be addressed by reversing polarity at both speakers.

I’ve played around with this and though the difference is not night and day obvious, I believe I can hear the difference. You should try it yourself - I think it’s worth the effort to see if you can hear the difference too.
 
CJ tube gear of that era was minimalist in design. They used the minimum number of stages to achieve the gain needed with the tubes types chosen. In the case of the PV8 that meant phase inverted outputs.

It would easily be possible to create a preamp with phase correct outputs but it either adds a stage or adds complexity or puts transistors in the signal path.

I had a PV12 for many years. It was dead simple in the line stage--one common cathode gain stage direct coupled to an output stage buffer (with no loop or global feedback), which created phase inverted outputs, and I expect the PV8 had a similar line stage topology.
 
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I doubt my White Oak Phase Linear amp, and SL-1100A turntable is playing in phase through the PV-8 then, looks like I have some experimenting to do.:idea:
 
captouch said:
My understanding is that for some designs, inverting phase results in the simplest designs and inverting phase again to normal (non-inverting) phase would result in another preamp stage which some designers feel is not necessary since the issue can easily be addressed by reversing polarity at both speakers.

I’ve played around with this and though the difference is not night and day obvious, I believe I can hear the difference. You should try it yourself - I think it’s worth the effort to see if you can hear the difference too.
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Usually, phase reversal (on both channels) is subtle but audible. Problem is, which is correct? No way of knowing. After listening to a Stereophile demo record with a trumpet piece, I recalled my high school band days and concluded that phase reversal sounded like playing a different brand of trumpet. Which brand did the artist actually play? Who knows?
 
Most C-J preamps have inverted phase since way back. Like others have stated it is to have a single stage of gain. When I bought my Classic 2SE , I emailed cj with a question and to my surprise I received a reply from Lew Johnson ... in addition to helping me he went on to say the Classic was probably one of their most bang for the buck pieces, and t was it's simplicity that makes it sound great.

I swap my speaker polarity and flip the phase on the sub to 180.
 
Strictly speaking, they mean polarity inverting, but it amounts to the same thing in this case. Polarity is absolute, either the entire chain will produce an acoustic output identical to the polarity of the acoustic signal at the mic, or it will be inverted. Two inversions anywhere in the chsin by any means will give a corrected result. Inverted absolute polarity sounds "wrong" to some listeners (me included), dull and lifeless. Imaging and bass response may not however be noticably affected.

Phase inversion however can be relative, one channel to another with one being polar correct and the other inverted. That always sounds "wrong" to most listeners with reduced LF response and wonky stereo imaging.
 
Pio1980 said:
Strictly speaking, they mean polarity inverting, but it amounts to the same thing in this case. Polarity is absolute, either the entire chain will produce an acoustic output identical to the polarity of the acoustic signal at the mic, or it will be inverted. Two inversions anywhere in the chain by any means will give a corrected result.
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That nicely sums up the issue. While there is only one absolute polarity at the speakers, there is no way to tell if the recording was made in absolute polarity and there is no way to tell how many times that absolute polarity was inverted along the signal chain from recording microphone to your speakers. As the health insurance salesman told me, "It's a crap shoot."
 
Palustris said:
That nicely sums up the issue. While there is only one absolute polarity at the speakers, there is no way to tell if the recording was made in absolute polarity and there is no way to tell how many times that absolute polarity was inverted along the signal chain from recording microphone to your speakers. As the health insurance salesman told me, "It's a crap shoot."
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I can usually tell on hearing, but my system doesn't have a convenient way to flip polarity, yet.
 
Pio1980 said:
Strictly speaking, they mean polarity inverting, but it amounts to the same thing in this case.
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Yes, indeed. It's often referred to as absolute phase and there's some dispute as to its audibility. Here's an article about the topic from Stereophile for anyone who is interested:
https://www.stereophile.com/content/absolute-phase-fact-or-fallacy

And here you can listen to recordings to test your ability to detect a difference:
https://www.audiocheck.net/blindtests_abspolarity.php
 
rothwellaudio said:
Yes, indeed. It's often referred to as absolute phase and there's some dispute as to its audibility. Here's an article about the topic from Stereophile for anyone who is interested:
https://www.stereophile.com/content/absolute-phase-fact-or-fallacy

And here you can listen to recordings to test your ability to detect a difference:
https://www.audiocheck.net/blindtests_abspolarity.php
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Audibility seems to be by individual perception, some like myself readily hear it, some do not including one of Stereophile's resident golden eared principals.
Stereophile's own test disc includes a test cut for it that sounds distinctly differentiated to me.
 
Sound is the phenomenon of compressions and rarefactions of air between a transducer and our ears. Proper polarity retains the initial nature of the material. Polarity reversal would result in the initial attack of an instrument moving the speaker cone backward thereby creating a rarefaction where a compression should be. I know some people that prefer this orientation as they feel it is smoother or less jarring when transients occur.
 
UncleBingo said:
Sound is the phenomenon of compressions and rarefactions of air between a transducer and our ears. Proper polarity retains the initial nature of the material. Polarity reversal would result in the initial attack of an instrument moving the speaker cone backward thereby creating a rarefaction where a compression should be. I know some people that prefer this orientation as they feel it is smoother or less jarring when transients occur.
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I would describe it as dynamically lackluster and lifeless.
 
Pio1980 said:
Audibility seems to be by individual perception, some like myself readily hear it, some do not including one of Stereophile's resident golden eared principals.
Stereophile's own test disc includes a test cut for it that sounds distinctly differentiated to me.
Click to expand...

My Audible Illusions Modulus 3 inverts absolute phase on the line input but not the phono input.

So I spent an afternoon trying to detect absolute phase differences and the results were...inconclusive. Well, no, actually I concluded it’s a non-issue for me.
 
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rothwellaudio said:
Yes, indeed. It's often referred to as absolute phase and there's some dispute as to its audibility. Here's an article about the topic from Stereophile for anyone who is interested:
https://www.stereophile.com/content/absolute-phase-fact-or-fallacy

And here you can listen to recordings to test your ability to detect a difference:
https://www.audiocheck.net/blindtests_abspolarity.php
Click to expand...
After listening to the blind test, I seem to hear the biggest difference in the fingers sliding across the guitar strings. Inverted seems to have less detail or high frequency squeak to my ears, very subtle though.
 
I find the inversion most audible with male voices, brass, and percussion insteuments. Sounds with a basic even sine wave character would in theory be least affected.
Best practice is always to attempt to ensure that the inversion factor in a system is established and comp'ed. Source material or sources themselves that produce a polarity inverted signal are another matter, something that shouldn't occur if good standard practice is observed. A system with a single inverted source can be comp'ed for that quite easily as can a system with a common essential chain component, an inverting source component amongst others noninverting is another matter.
 
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