I decided to make a new thread on the measurements I did on this amp, since the 3255 thread is long and covers a lot of different amps: https://www.diyaudio.com/forums/class-d/287470-tpa3255-diy-discussion-design-etc.html
First some pics of the board, which is the later 'cost efficient' green board, not the earlier black PCB.
First some pics of the board, which is the later 'cost efficient' green board, not the earlier black PCB.
Attachments
Measurements
All measurements using a 19,5V HP laptop brick rated 7,5A with pretty clean supply voltage. No extra cap on supply. Both channels loaded with 8ohm resistors, but only one channel measured. Measured using a Focusrite Scarlett solo using balanced input.
Output voltage was adjusted with single sine at 50Hz and DVM. No adjustment done when switching to other signals.
All measurements using a 19,5V HP laptop brick rated 7,5A with pretty clean supply voltage. No extra cap on supply. Both channels loaded with 8ohm resistors, but only one channel measured. Measured using a Focusrite Scarlett solo using balanced input.
Output voltage was adjusted with single sine at 50Hz and DVM. No adjustment done when switching to other signals.
Attachments
The 10V output gets a bit ugly, maybe because of mild saturation of the output inductors, or possibly it could need some extra cap on the supply?
The 6+7kHz test is something I started doing recently, and it seems pretty revealing of IMD. I have only measured one 'homebrew' AB amp in this way, and it gave similar results. Does not look too nice in my eyes, but as I said, I have very little reference.
I'm listening to the amp now, in the same configuration as measured. It is probably sounds better than any other class D I have heard, but none of them have been top end class D.
I'm a bit disappointed about the bass 'drive', I was expecting more control and extension somehow. Maybe an extra cap on the supply could do something to improve it.
It also seems to get a bit 'unclear' with 'busy' music. Mostly mid and treble. Treble seems a bit bright and like there is hiss added to it. And a hint of headache is beginning after some hours of listening now.
I'm thinking I should try the extra cap on the supply, and I would like to bypass the op-amps and measure it again. I'm also a bit keen to try PFFB as in Ti 'application report', but that would probably mean messing around with the SMD resistors and caps on the board, and I'm not keen on that..
The 6+7kHz test is something I started doing recently, and it seems pretty revealing of IMD. I have only measured one 'homebrew' AB amp in this way, and it gave similar results. Does not look too nice in my eyes, but as I said, I have very little reference.
I'm listening to the amp now, in the same configuration as measured. It is probably sounds better than any other class D I have heard, but none of them have been top end class D.
I'm a bit disappointed about the bass 'drive', I was expecting more control and extension somehow. Maybe an extra cap on the supply could do something to improve it.
It also seems to get a bit 'unclear' with 'busy' music. Mostly mid and treble. Treble seems a bit bright and like there is hiss added to it. And a hint of headache is beginning after some hours of listening now.
I'm thinking I should try the extra cap on the supply, and I would like to bypass the op-amps and measure it again. I'm also a bit keen to try PFFB as in Ti 'application report', but that would probably mean messing around with the SMD resistors and caps on the board, and I'm not keen on that..
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Nice measurements! Keep them coming!
I´ve got 3 of these A04´s.
One of them was going into protection at about three o´clock. (even without load)
The latter seems to be a general problem with these amps. (have seen it on a second amp too but can´t reproduce)
Still haven´t figured out what´s the root cause. (anyways, got on extra amp for free)
I use it on my woofer only at the moment. Tried with 24V&32V.
I do like the sound although I have yet to make some A/B-comparisons and use another A04 on the mid/treble-section.
Changed the NE5532 or whatever is in there with an LM4562 which seemed more precise sounding to me. Others have reported some distortion with a OPA2604 in place. Probably no an ideal layout.
All in all still quite a bargain IMHO.
I´ve got 3 of these A04´s.
One of them was going into protection at about three o´clock. (even without load)
The latter seems to be a general problem with these amps. (have seen it on a second amp too but can´t reproduce)
Still haven´t figured out what´s the root cause. (anyways, got on extra amp for free)
I use it on my woofer only at the moment. Tried with 24V&32V.
I do like the sound although I have yet to make some A/B-comparisons and use another A04 on the mid/treble-section.
Changed the NE5532 or whatever is in there with an LM4562 which seemed more precise sounding to me. Others have reported some distortion with a OPA2604 in place. Probably no an ideal layout.
All in all still quite a bargain IMHO.
Ok, thank you for the tip!
I listened to it fed from the linear supply yesterday. Could not notice much difference anywhere. Again I started to get a headache when listening, I get this with some amps.
After some more listening, my impression of the sound would be bright, but still not that detailed (as I would expect from an amplifier sounding bright), and missing some depth in the soundstage.
I listened to it fed from the linear supply yesterday. Could not notice much difference anywhere. Again I started to get a headache when listening, I get this with some amps.
After some more listening, my impression of the sound would be bright, but still not that detailed (as I would expect from an amplifier sounding bright), and missing some depth in the soundstage.
Interesting. Haven´t tried with linear supply so far.
I wasn´t suggesting brainlessly putting in some fancy opamps BTW.
Was simply afraid of having fakes and not unleashing the full potential of the amp. A genuine NE5532 should be plenty fine.
It´s more down to the layout anyway; with class-D especially so.
The amp is a little different from the TI-evaluation-board:
The input opamp is setup with additional gain for a total of ~29dB.
Attachments
This music
Put Your Records On - Bossa Nova Hits 2015 - Fullsong - YouTube
pass easily on any linear amp, but too difficult with class D.
This is in wave streaming that I have it on CD.
Shazam
Put Your Records On - Bossa Nova Hits 2015 - Fullsong - YouTube
pass easily on any linear amp, but too difficult with class D.
This is in wave streaming that I have it on CD.
Shazam
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I own the original Aiyima with great caps.(Elna)
I updated the OP amps >OPA1656 and also the Inductances > TI MA5173-AE
I compared it to my DrMordor top end TPA3251 with PFFB Enabled and high end caps and genuine OPA1642 OP amps :
Both amps are impressive, DrMordor one is a bit more "holographic" with a fantastic sound stage. OPA1642 bring a "tube like" veil.
A friend of mine came to listen both amps. This friend is making some 3000$ to 10 000$ speakers for "la maison du haut parleur" in France / Lyon which is a famous Audiophile shop here.
Here what he said, word for word (I translate) : "These amplifiers clearly bear the name of audiophile amplifiers. They are incredible value for money. The soundstage is impressive and the tones are captivating, I am absolutely convinced now. "
Two days after listening, the person bought me DrMordor's TPA3251 to integrate it into his DIY speaker project.
He concluded the purchase with this sentence: "even if we have nothing to measure this amplifier, I can assure you that my ears remain the best instrument to confirm its quality in every way."
I updated the OP amps >OPA1656 and also the Inductances > TI MA5173-AE
I compared it to my DrMordor top end TPA3251 with PFFB Enabled and high end caps and genuine OPA1642 OP amps :
Both amps are impressive, DrMordor one is a bit more "holographic" with a fantastic sound stage. OPA1642 bring a "tube like" veil.
A friend of mine came to listen both amps. This friend is making some 3000$ to 10 000$ speakers for "la maison du haut parleur" in France / Lyon which is a famous Audiophile shop here.
Here what he said, word for word (I translate) : "These amplifiers clearly bear the name of audiophile amplifiers. They are incredible value for money. The soundstage is impressive and the tones are captivating, I am absolutely convinced now. "
Two days after listening, the person bought me DrMordor's TPA3251 to integrate it into his DIY speaker project.
He concluded the purchase with this sentence: "even if we have nothing to measure this amplifier, I can assure you that my ears remain the best instrument to confirm its quality in every way."
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As I said earlier, applying a high-speed opamp like the OPA1656 in an unknown/untested PCB is not necessarily an upgrade. Chances are it´s a major downgrade if the layout is subpar.
Well, I doubt that. It´s nice if you can trust them but more often than not they might not prefer high fidelity but some musical interpretation with certain distortion characteristics.
Other than that, it´s really nice if you´re happy with your amplifier but it might not be on-topic if you feature/advertise it here.
You can doubt sure... but those words were not mine amigo ) I just share what has been felt by someone.
OPA1656 has not been tested / measured but you can read in the forum that some users are really happy with it. And everybody knows that a Fake 5532 will never sound like a genuine OPA1656 or any genuine OP amps.
I also own some Hypex Ncore NC250 + 500MP (double mono) and everybody knows about their performance and measures so I really have something to compare by telling you that a good well implemented TPA3151 sounds extremely good )
OPA1656 has not been tested / measured but you can read in the forum that some users are really happy with it. And everybody knows that a Fake 5532 will never sound like a genuine OPA1656 or any genuine OP amps.
I also own some Hypex Ncore NC250 + 500MP (double mono) and everybody knows about their performance and measures so I really have something to compare by telling you that a good well implemented TPA3151 sounds extremely good )
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I don´t doubt that but to repeat myself:
you have to be careful with bad layouts.
In a bad layout an old 741 might sound better than low-distortion high-speed-opamp that oscillates due to improper decoupling or similar.
I think so too. And the power coming out of these tiny things is just crazy.
Ears are the WORST instrument for evaluating audio equipment, except to pick out the most extreme of faults. Listening is about the most subjective thing out there, because you have to listen to music and that will have an influence on your perception. Finally, talk is cheap as the expression goes (in English). Words are empty, hollow. That's why anytime I hear someone say that something sounds really good, but has no measurements to back it up, I do not take the comment as valid. Also, everyone's hearing is different and with the subjectivity mixed in there is no way you can make sense out of evaluations done in this way.
At the same time, I am glad it pleases you. I am not saying your opinion is not valid, only that to share information in an objective way you need objective metrics.
AGREE but a a fine human ear can perceive the difference between a good and a bad amp.
There is also a part of subjectivity in all our choices .... Millions of Audiophiles will tell you that class D amps are bad (compared to Class A or Tube amps), bad dynamic, too analytical etc .... While a Hypex NC400 or Purifi show exceptional measurements on ASR ....
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