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Class D Switching Power Amplifiers and Power D/A conversion

what D amp give best sound.
what D amp give best sound.
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Old 22nd February 2018, 03:12 PM   #211
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by Grizlek View Post
This is related to the latest schematics ?
This one, double feedback, voltage, the current is not yet very stable, but if quite faster regulation. Fase shifts are the big problem there, also with voltage the low pass poles do shift making things more complicated, it can be done, but needs more electronics.

I get however on 60 Khz a harmonic who I think is from the simulation itself, maybe in the parts models things are cause.

regards
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Old 22nd February 2018, 03:52 PM   #212
kees52 is offline kees52  Netherlands
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As you see I get very low distortions, the square test is unsuccesfull when I use post feedback as the dominant one, with the tuning of both feedback we can get a nice square test.

See some more pictures, after tune the feedback lines I see that the prefeedback do make a nice square, including the lowpass making it worse, after put in a little network with resistor and 12 PpF capacitor the peaks are gone, but do slow down the speed of the amp, the fastest speed is when use only prefeedback, so I do try that with a air coil and oil capacitor, both high quality, size is not important with a high end class d, and see what happens.

Current feedback I did try looks like work better when a 0.01 ohm resistor is between amp and null of the supply, amplify that give a nice triangle who can included in the feebback loop, not tryed that yet,

regards
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File Type: jpg ScreenHunter_859 Feb. 22 17.56.jpg (133.1 KB, 512 views)
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File Type: jpg ScreenHunter_861 Feb. 22 17.59.jpg (189.1 KB, 508 views)

Last edited by kees52; 22nd February 2018 at 04:06 PM.
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Old 22nd February 2018, 04:29 PM   #213
kees52 is offline kees52  Netherlands
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Here I see only uneven harmonics, and no even. strange for a single bridge.

but is low, on 8 amp output current.

Question, what is the best way for dead time, see picture.
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Old 23rd February 2018, 05:07 AM   #214
Grizlek is offline Grizlek
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Quote:
Originally Posted by kees52 View Post
This one, double feedback, voltage, the current is not yet very stable, but if quite faster regulation. Fase shifts are the big problem there, also with voltage the low pass poles do shift making things more complicated, it can be done, but needs more electronics.

I get however on 60 Khz a harmonic who I think is from the simulation itself, maybe in the parts models things are cause.

regards
I am missing model, it seems you are using OPA134 ? It is slow audio op amp, try faster op amp?

Why about adding transistor network to shut down poles if when signal is too strong, to prevent unstability?

Last edited by Grizlek; 23rd February 2018 at 05:09 AM.
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Old 23rd February 2018, 11:54 AM   #215
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by Grizlek View Post
I am missing model, it seems you are using OPA134 ? It is slow audio op amp, try faster op amp?

Why about adding transistor network to shut down poles if when signal is too strong, to prevent unstability?
You can use LT1722 also for sim, the opa627 also is fast enough for input opamp.

LT1722 is in your ltspice.

a AGC is possible yes, but two diodes antiparalell and good setup feedback will do, use a series resistor for soft clipping, this is enough, just make enough power output so you never reach diode clipping exept with small accidents?.

OPA134 is 8 Mhz, 20 V/us opamp, so quite fast and very good sounding ones also, the OPA627 is best, but expensive.
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Old 23rd February 2018, 08:09 PM   #216
phase is offline phase  United States
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Has anyone tested the newer GaN output devices for linearity vs the older parts?
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Old 26th February 2018, 08:10 PM   #217
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by phase View Post
Has anyone tested the newer GaN output devices for linearity vs the older parts?
I did not, but these are interesting, like low nC. It has ball solder so very low ringing.

I have play with a BD modulator UCD, self osc.

I get quite shoot through's so I do something wrong, maybe I need some more info about these, it is quite a nice idea, even usable with buck converter like output, act as a class ab, small pulses injection I have seen, making it a bi version bd.

someone here can advice me why I get such shoot through, I do see both negative and positive are in line, making it short circuit, in paper I see both a shifted 180 degrees so it do not make trouble.

regards/
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Old 27th February 2018, 09:11 AM   #218
JonesySA is offline JonesySA  Australia
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Quote:
Originally Posted by amix View Post
I can not really help you, since I do not have the experience required. But in German DIY audio forums there is a guy, Saarmichel, (he is also a member here, though, not very active), who has built a lot of Class-D amps (he built tube-amps before). He has put together a list of his subjective findings. You can find it over here. The only thing, that changed is, that he now has a new #1, which is being referenced here. Since you are from Holland I guess, that your German may be better than my Netherlandish ;-) I would especially recommend the last thread, I have mentioned. I take the freedom to quote and translate his list of Class-D amplifiers, he built:Now, there is a single change to the list: The Hypex UcD2K has been replaced by the Sure AA-AB32512. However, there is one caveat. People are uncertain as of it is really the AB32512. While this has been the module people ordered, it seems, that Sure is delivering the AA-AB32313 instead. The model-number on the mainboard implies this. He also mentioned, that in order to achieve the best sound, he had to use either his self-made PSU or the Meanwell HLG-320-36A. When he used a Meanwell HRP-600-48 the sound wasn't to his satisfaction. So, (his) dream-combo seems to be the Sure AA-AB32313 + Meanwell HLG-320-36A atm. That's the one I am going to use for an IA, I just need to settle on a pre-stage before that.

I am aware, that this list is not giving you the technical information, you asked for, but it may give some limited direction.
Has Saarmichel updated this list since first posed?
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Old 27th February 2018, 01:06 PM   #219
kees52 is offline kees52  Netherlands
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Full bridge double feedback UCD class D. low HD, I'ts time to build something.
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Old 1st March 2018, 02:48 PM   #220
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by kees52 View Post
I did not, but these are interesting, like low nC. It has ball solder so very low ringing.

I have play with a BD modulator UCD, self osc.

I get quite shoot through's so I do something wrong, maybe I need some more info about these, it is quite a nice idea, even usable with buck converter like output, act as a class ab, small pulses injection I have seen, making it a bi version bd.

someone here can advice me why I get such shoot through, I do see both negative and positive are in line, making it short circuit, in paper I see both a shifted 180 degrees so it do not make trouble.

regards/
Someone? I try this and get not what I want, like the BD modulation scheme as in pic two and lot shoot through. Need the 1 Khz modulation input a offset? like minus for the lower comparator and plus for the above one.

I thought this is not complicated, it is not but sim not oke. Some help welcome.'I read some papers about this and the buck converter system looks nice.

regards
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