Re: 3rd party testing
In any case, I've always had good results using the system one together with the AUX0025 (which is not an AES17 filter, but a passive LPF with 2 corners).
Didn't know they sold AES17 filters for the system one. Is the filter before the autoranging circuit? Or is it simply a brick-wall plug-in after the notch filter? In the latter case, even a small amount of switching ripple is enough to make the AP1 mis-read tremendously.Sheriff said:
In any case, I've always had good results using the system one together with the AUX0025 (which is not an AES17 filter, but a passive LPF with 2 corners).
Re: More coffee req'd
Inasmuch as both parties aren't more interested in going on holidays (includes me). Just before you came in we more or less decided to put the whole affair to rest. So, if you want to do these measurements it's OK but I in that prefer to see it as a personal endeavour from your side, not so much a continuation of this "battle".
Sheriff said:
Inasmuch as both parties aren't more interested in going on holidays (includes me). Just before you came in we more or less decided to put the whole affair to rest. So, if you want to do these measurements it's OK but I in that prefer to see it as a personal endeavour from your side, not so much a continuation of this "battle".
It would be very kind of you both, Jan-Peter and Lars, to send Sherif one of your standard modules, at least. Otherwise I would have to rely on my own non-calibrated and not very nice looking soundcard-measurements, if I don't trust the salesmen. 
Thank you very much in advance, the test is not only interesting because of the shootout, far from it! It provides a far deeper insight into the true performance of your classD amplifier modules.
Regards, Timo
Thank you very much in advance, the test is not only interesting because of the shootout, far from it! It provides a far deeper insight into the true performance of your classD amplifier modules.
Regards, Timo
peranders: As promised the system noise floor for the two tone measurement:
I found out why the 'two tone IMD curves' look so different. The freq scale i have used first was log, while Jan-Peter's is linear (like the one shown above).
http://www.hypex.nl/classd/imd zap ucd 10w 2w.pdf
Now they look more alike
All the best from
Lars
An externally hosted image should be here but it was not working when we last tested it.
I found out why the 'two tone IMD curves' look so different. The freq scale i have used first was log, while Jan-Peter's is linear (like the one shown above).
http://www.hypex.nl/classd/imd zap ucd 10w 2w.pdf
Now they look more alike
All the best from
Lars
Somehow I trust Audio Precision more than a sound card but it's hard to draw any accurate conclusions. The thing is also that class D amps have so much "garbage" compared to conventional amps. I'll guess it's really important to have full control over the measurement setup and also _how_ the instruments really measure, how the software works etc. Compare true rms measurements with high crest factors.
I'm not very technical and am a math n00b but...
I'm reading here that class-d's usually have 180° phase shift at the output.
Does that mean, when combining class D with regular amps (for example, 2 ucd's driving L & R, one class AB running center) that the UcD's output will be out of phase? (speakercone moves backward at time that class ab controlled cone moves out?)
Don't laugh, correct me if i'm wrong
I'm reading here that class-d's usually have 180° phase shift at the output.
Does that mean, when combining class D with regular amps (for example, 2 ucd's driving L & R, one class AB running center) that the UcD's output will be out of phase? (speakercone moves backward at time that class ab controlled cone moves out?)
Don't laugh, correct me if i'm wrong
Capacitor suppliers
Dear All,
I see that someone has mentioned the Vishay SAL 123 RPM capacitor series. Is there anywhere that these can be purchased for small quantities?
I was thinking about using them as coupling caps instead of the Black Gates in an amplifier or two I am building.
Regards,
George.
Dear All,
I see that someone has mentioned the Vishay SAL 123 RPM capacitor series. Is there anywhere that these can be purchased for small quantities?
I was thinking about using them as coupling caps instead of the Black Gates in an amplifier or two I am building.
Regards,
George.
Hi
I think nowadays, they are called SAL 128 RPM.
Part number 2222 128 ..... (value)
See here: http://www.vishay.com/product?docid=28354&query=2222 128
I think nowadays, they are called SAL 128 RPM.
Part number 2222 128 ..... (value)
See here: http://www.vishay.com/product?docid=28354&query=2222 128
UCD Phase shift
Yves,
That is only true at the frequency at which the amplifier (LC output Filter) osscilates (around 400kHz). Further down the frequecy spectrum and as it nears the audible range the phase shift tends towards zero.
Different amplifiers can be used together with the UCD as long as they have the same gain of 26dB and have enough power to drive the speaker unit. So you can use a lower power amplifier to drive the tweeter for instance.
Yves Smolders said:I'm not very technical and am a math n00b but...
I'm reading here that class-d's usually have 180° phase shift at the output.
Does that mean, when combining class D with regular amps (for example, 2 ucd's driving L & R, one class AB running center) that the UcD's output will be out of phase? (speakercone moves backward at time that class ab controlled cone moves out?)
Don't laugh, correct me if i'm wrong
Yves,
That is only true at the frequency at which the amplifier (LC output Filter) osscilates (around 400kHz). Further down the frequecy spectrum and as it nears the audible range the phase shift tends towards zero.
Different amplifiers can be used together with the UCD as long as they have the same gain of 26dB and have enough power to drive the speaker unit. So you can use a lower power amplifier to drive the tweeter for instance.
Yves Smolders said:
Phase shift at the high audio frequencies can of course happen with any amplifier depending on how it drops off at high frequencies. The nice part of UcD amps is that the LC filter is in the feedback loop and that the frequency response (and thus phase response) is very well controlled and behaved and independent on what speaker you use. Some other class d amps may have more or less phase shift at high frequencies depending on the speaker load.
Those class d bashers, had they actually heard a class d amp? Or was there judgment based on something else?
Best regards
Gertjan
Phase Shift
I agree with Gertjan.
Unfortunately I have not come across the exact phase behaviour response diagrams of the UcD amplifiers, but if there is the possiblity of a slight phase shift at high audio frequencies it would probably be better to use identical amplifiers in an active system so that all the drivers remain in phase (in step) at all frequencies. There should also be no audible difference as long as the phase shift remains linear across the audible frequecy envelope (spectrum)
It is useful to remember that filter theory dictates that a waveform will remain undistorted if the phase shift of the waveform does not change at all or only changes in a linear fasion. But remember that if you have, say, a 2 way active system, then for both channels and both amplifiers and the active crossover must all have the exact same phase response! This is especially critical in the crossover reqion where both drivers can be heard.
I agree with Gertjan.
Unfortunately I have not come across the exact phase behaviour response diagrams of the UcD amplifiers, but if there is the possiblity of a slight phase shift at high audio frequencies it would probably be better to use identical amplifiers in an active system so that all the drivers remain in phase (in step) at all frequencies. There should also be no audible difference as long as the phase shift remains linear across the audible frequecy envelope (spectrum)
It is useful to remember that filter theory dictates that a waveform will remain undistorted if the phase shift of the waveform does not change at all or only changes in a linear fasion. But remember that if you have, say, a 2 way active system, then for both channels and both amplifiers and the active crossover must all have the exact same phase response! This is especially critical in the crossover reqion where both drivers can be heard.
ewildgoose said:
That's true Ed,
As long as the phase shift causes a delay of less than 3.2ms @ 500Hz and 1ms @ 2kHz. If you delay the Bass any more than this (relative to the high frequencies) it will become audible at some point. See:
http://www.trueaudio.com/post_010.htm
Cheers
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