There's another post on the Hagerman Circle about the Bugle being non-polarity inverting...and it got me thinking.
A phase (or polarity) inversion is the introduction of a phase difference of 180° into a waveform.
For example, in a push-pull power amplifier using vacuum tubes, the signal is most often split by a phase splitter stage which produces two signals, one in phase, and the other out of phase, that is, phase inverted. These two signals then drive the two halves of the first push-pull stage, which may be either the output stage (in which case the phase splitter will be in between the driver stage if there is one and the output stage) or the driver stage. The other common arrangements for driving a push-pull stage are by using an isolation transformer to produce the split signals, or by using the in-phase half of the first push-pull stage to drive the other half. A common circuit using this last technique is the long-tailed pair, often seen in television sets and oscilloscopes.
In solid state electronics all of these techniques can be used, and phase inversion can also be produced by the use of NPN/PNP complementary circuitry, which has no corresponding technique in vacuum tube designs.
Phase inversion may occur with a random or periodic, symmetrical or non-symmetrical waveform, although it is usually produced by the inversion of a symmetrical periodic signal, resulting in a change in sign. A symmetrical periodic signal represented by f (t ) = A ejωt, after phase inversion, becomes f 1(t ) = Aej(ωt +π), where t is time, A is the magnitude of the vector, ω is angular frequency (ω = 2πf ), where f is the frequency and π ≈3.1416 and e ≈ 2.7183. The algebraic sum of f (t ) and f 1(t ) will always be zero.
So, I poured thru my manual for my Dynaco PAS-4 the night before last...
Phono - non-phase inverting. The only test I have for it is my Stan Ricker engineered test disc....and it always was clearly phase correct....in vinyl playback.
Line - son-of-a-gun if my line stage is indeed phase inverting
So, I reversed speaker leads (black where red traditionally goes, and vice versa on both speakers) and, viola! All that dead space in the middle of my 'soundstage' (when a CD is played
) that I thought was just a problem with CD playback or my speakers or amps were insufficient at creating center fill....was now fully filled in.
There is now a better perception of depth in layered/orchestral recordings and, somehow, and non-descript
rightness to the music now.
For 3 friggin' years I have been listening to CD playback out-of-phase with this (otherwise remarkable value) tube preamp.
Now, unfortunately, I have to re-reverse the leads when I switch from CD to vinyl....but the results are quite worthwhile.
So, folks, check your preamp manuals or ask your manufacturers about phase or polarity inversion......it could be a goodly difference in the way you enjoy music. Or, reverse the leads and try it yourself (something I never thought to do before 2 nights ago).
I hope this free 'tweek' makes someone's day out there.
TCD (TheChairDolt )
