It looks significant on a graph but look at the time scale. Sound travels around 30cm in 1 millisecond, around 0.03cm per microsecond. Just moving your head or sitting in a slightly different position must surely swamp the effect that any delay in the opamp causes.
Mooly , maybe you are confusing two situations that are quite different.
If all the information of one channel is delayed relative to each other then it is not a big problem: just replace the listener to find the "right time " in which the two channels arrive simultaneously.
You note that in this case the two signals of right and left channels remain independent . In this case a phase splitter affected by the problem of the delay, which I mentioned , is acceptable.
A different case is when the phase splitter drive the push-pull output stage of of the same channel .
In this case the push-pull stage performs an algebraic sum of the two signals provided by the phase shifter stage into a single signal which represents the output signal supplied to the loudspeaker. When there is interaction between the two signals provided by phase splitter, for a faithful reconstruction is necessary that there is the same time reference .
So if Gav were using your circuit to drive regardless of the two channels separately , not there would be too many problems , but since he uses the two channels connected in bridge mode (in monaural), the two signals would be added in one only output signal, with two different times respect to the origin of the input signal and this can create problems that I mentioned in my previous post .
Sincerely .
Last edited:
Thanks... I was
mental block, to much going on I've no excuse How so
---------------------------------------------------------------------------------
I looked at this "issue" for curiosity and its not just a case of adding another opamp to equalise the delays. And as expected, opamp type will play a part too as well as the layout.
However.... I came up with this where the impulse response can be equalised between inverting and non inverting channels by manipulating the "noise gain" and compensation of both opamps. The circuit is very tweakable but it must be done on an individual basis by real test measurements.
Attachments
Very interesting Mooly !
I drive my 5 channel HT amp with 2 channels "Out of phase" to avoid Buspumping , because it's class D and I did notice some strange effects in the placements of instruments and female voices and the shifting over the stereo field , when I used the amp in stereo mode .
Normally in my amp , the FL and FR and SL and SR amps are phase shifted ,with a TL072 , because they take up most of the power .and are likely to cause the most buspumping .
I experimented with the carrier frequency of the amps , because I was not fully happy with the stereo performance of the 5 channel amp . I was able to match the carrier of the FR and FL to within a couple of Hz ,
The stereo sound was better , but the placement was not perfect , it was shifting within the song .
When I swapped channels on the power amp and used 2 non inverted channels for my FL and FR the placement was much better and stable!
Don't have the software to simulate this for a simple phase splitter , but my ears don't lie
Cheers ,
Rens
Last edited:
Thanks
That would work well in practice. The impulse response might be a little different between inv/noninv but again, its complexity vs simplicity.
Very interesting Mooly !
I drive my 5 channel HT amp with 2 channels "Out of phase" to avoid Buspumping , because it's class D and I did notice some strange effects in the placements of instruments and female voices and the shifting over the stereo field , when I used the amp in stereo mode .
Normally in my amp , the FL and FR and SL and SR amps are phase shifted ,with a TL072 , because they take up most of the power .and are likely to cause the most buspumping .
I experimented with the carrier frequency of the amps , because I was not fully happy with the stereo performance of the 5 channel amp . I was able to match the carrier of the FR and FL to within a couple of Hz ,
The stereo sound was better , but the placement was not perfect , it was shifting within the song .
When I swapped channels on the power amp and used 2 non inverted channels for my FL and FR the placement was much better and stable!
Don't have the software to simulate this for a simple phase splitter , but my ears don't lie
Cheers ,
Rens
The software is LTspice and its free,
Linear Technology - Design Simulation and Device Models
If you wanted to download it I could post the sim file and it would run straight off. Then you could experiment.
Have to admit I've done nothing with Class D power amps at all but your observations are interesting.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.