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Class D Switching Power Amplifiers and Power D/A conversion

TPA3250 somebody is listening?
TPA3250 somebody is listening?
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Old 7th February 2018, 04:13 PM   #111
judderod is offline judderod  United Kingdom
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Quote:
Originally Posted by doctormord View Post
Might be some capacitive coupled voltage, does the power supply offers "real" earth connection? May you try a different power supply?
The PSU isn't connected to earth as it only has a 2 pin power lead. I don't think I have a spare 24v supply. I guess I could try a 12v and see if it comes on. It doesn't seem to affect the sound output.

When tested with the multimeter, whatever power I felt on the case seemed to discharge quickly through the multimeter to earth, with the reading going from about 5-7VAC down to zero quickly.
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Old 7th February 2018, 08:30 PM   #112
Yatsushiro is offline Yatsushiro  United Kingdom
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Originally Posted by judderod View Post
The PSU isn't connected to earth as it only has a 2 pin power lead. I don't think I have a spare 24v supply. I guess I could try a 12v
I think 18v is the minimum?
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Old 9th February 2018, 01:00 PM   #113
jigglebones is offline jigglebones  United States
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I have the FX502SPRO, replaced the NE5532 with LME49720 like I said before...it sounds very good, I may even consider getting the metal can version but its a bit more expensive. Are there any other mods that are worth doing on this amp that are cheap and worthwhile? Those inductors, maybe replace with some denon or coilcraft if they fit? maybe the caps? Will there be any improvement there?
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Old 9th February 2018, 01:04 PM   #114
doctormord is offline doctormord  Germany
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No.
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Old 12th February 2018, 09:48 AM   #115
jigglebones is offline jigglebones  United States
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Originally Posted by doctormord View Post
No.
Thanks, good to hear For anyone who does have this and wants to get the most out of it: -Better opamps (LME49720) - Worth it IMO -Good power supply esp. Linear - Worth it IMO -Open lid off enclosure for better cooling - Probably a good idea -Cryo-treatment - what? Other than that, this looks like as good as it gets. I'm guessing there will be more stock once chinese new year is over.
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Old 12th February 2018, 10:29 AM   #116
abraxalito is online now abraxalito  United Kingdom
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Quote:
Originally Posted by jigglebones View Post
Are there any other mods that are worth doing on this amp that are cheap and worthwhile? Those inductors, maybe replace with some denon or coilcraft if they fit? maybe the caps? Will there be any improvement there?
I've just started modding a TPA3255 board (from Taobao) - the chip looks very similar to the 3250 except for the maximum voltage rating.

The mods I've found making a difference so far as PSU-related. Looks like the FX502 has a buck regulator (the 5pin device) which will generate plenty of noise. Hence filtering out its noise pays dividends in SQ. I also just found out that more decoupling on the TPA's analog regulator output (pin14) improves dynamics and transparency. I started off with 470uF (put in parallel with the 1uF the application shows) and I've since moved up to 1800uF.

I've yet to try upgrading the opamps (TL072 on mine) but I may try that at some stage, along with biassing the outputs into classA with a current source.

I'm documenting the mods here : TPA3255 - all about DIY, Discussion, Design etc.
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Old 13th February 2018, 07:50 PM   #117
strongbow60 is offline strongbow60  Sweden
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TPA3250 somebody is listening?
Got my FX502SPRO amp today and immediately unpacked it and connected it to a small system in my study. Hardware wise it looks and works really well, but the power cord was quickly replaced. It uses some kind of horrible adapter from US to EU pins, not at all safe for children (or even adults).
I use a Chromecast audio as input and a pair of XTZ 95.21 speakers with 89 dB efficiency. This is my third class-D amp and a smaller sibling to my TPA3255EVM.
After connecting everything and power on it was dead quiet from the speakers. Even when turning the volume way up I had to put my ear very close to the speaker to hear any noise, and it could very well come from the Chromecast.
The output level of the Chromecast is very high, I had to dampen the output from it and only turn up the volume on the amp two clicks from zero to play at a level suitable for background music.
Playing some music I can quickly relate the sound to the 3255, same type of dynamic and easy flowing sound that don't stand out in any way - a bit boring in fact.
Quality wise, the amp needs a few days playing before it can give its best, but I don't suspect it will stand up to the EVM board.
Later I will probably see what can be gained by changing out the op-amp.
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Old 14th February 2018, 07:24 PM   #118
chermann is online now chermann  Austria
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...FX502SPRO...ordered...... in approx 15days delivery...
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Old 14th February 2018, 11:28 PM   #119
forestsgump is offline forestsgump
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FX502SPRO uses NE5532, which op-amp are you considering to replace it?
By the way ditto on Chromecast audio... on a pair of 86dB wharfedales 10.2

Last edited by forestsgump; 14th February 2018 at 11:31 PM.
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Old 15th February 2018, 05:55 AM   #120
chermann is online now chermann  Austria
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Originally Posted by forestsgump View Post
FX502SPRO uses NE5532, which op-amp are you considering to replace it?
By the way ditto on Chromecast audio... on a pair of 86dB wharfedales 10.2

maybe some ideas for mod ....... there...?
Drop in replacement for NE5532?


DIY Audio Projects Forum • NE5532 vs. OPA2134

Last edited by chermann; 15th February 2018 at 05:57 AM.
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