3e Audio A7 [TPA3255 PFFB Stereo] Finished Amplifier - User Impressions | Owner's Thread

[r-36m2]

It’s clear to me that you exemplify the Dunning-Kruger effect and that you don’t appreciate when others try to aid you.

You’re on my “ignore” list.

I reread the dialogue. I was talking about the op amp's dual power supply and the interstage capacitors (electrolytics), which are currently installed in the amplifier's audio path, before and after the op amp, to isolate the DC component of the signal due to the op amp's single power supply. Google Translate isn't very good with technical terms and just calls things whatever comes to mind. This is likely why we had a misunderstanding.
Regardless of what you think of me, I apologize for being abrupt because I thought you were giving advice without understanding the subject.

 

[Guddu]

Yes

It could definitely be useful to supply +/- 12v to the opamps used in A7 and may be it is the case, @3eaudio could chime in here to provide some details that you might be looking for.
Regardless, look at the Steller performance. Its already amongst the BEST.

 

[r-36m2]

It could definitely be useful to supply +/- 12v to the opamps used in A7 and may be it is the case, @3eaudio could chime in here to provide some details that you might be looking for.
Regardless, look at the Steller performance. Its already amongst the BEST.

I wrote about this back in 2022, when I modified a 3eaudio amplifier based on the TPA3250 chip. I wanted to implement a PFFB and a bipolar power supply, but abandoned the idea because the ADAU chip is the amplifier's bottleneck and the improvements wouldn't be noticeable.
Now I'm asking this question again because a bipolar power supply is useful and easy to implement. Why it's not used is a mystery. But perhaps it would be possible to add a converter to the circuit and power the op amps with a bipolar voltage. To do this, it's advisable to look at the schematic and the component layout on the board.
Thanks for the recommendation!

 

[TurtlePaul]

The opamps are driven by +/- 18V but there is a switch to reduce this to +/- 15V if you want to use 30V opamps.

The coupling caps are ELNA Silmic II which are sufficiently good measuring but are indeed electrolytic.

 

[r-36m2]

The opamps are driven by +/- 18V but there is a switch to reduce this to +/- 15V if you want to use 30V opamps.

The coupling caps are ELNA Silmic II which are sufficiently good measuring but are indeed electrolytic.

A more universal solution would be +12 and -12 volts, because for some op amps that's the maximum. You can go with +15 and -15. I wouldn't go higher.
Yes, I know Elna capacitors are good. But it's better to do without them. It's not that difficult.

 

[Guddu]

The opamps are driven by +/- 18V but there is a switch to reduce this to +/- 15V if you want to use 30V opamps.

The coupling caps are ELNA Silmic II which are sufficiently good measuring but are indeed electrolytic.

Thanks, I hope you have mentioned in regards to A7.

I wrote about this back in 2022, when I modified a 3eaudio amplifier based on the TPA3250 chip. I wanted to implement a PFFB and a bipolar power supply, but abandoned the idea because the ADAU chip is the amplifier's bottleneck and the improvements wouldn't be noticeable.
Now I'm asking this question again because a bipolar power supply is useful and easy to implement. Why it's not used is a mystery. But perhaps it would be possible to add a converter to the circuit and power the op amps with a bipolar voltage. To do this, it's advisable to look at the schematic and the component layout on the board.
Thanks for the recommendation!

I just had a look at their user manual, and I see this under OPAMP replacement procedure: "Op-amp working voltage should meet 36V(+/-18V) maximum,34V Minimum."
This makes me say that the opamps are already supplied with the power they need to perform optimally.

 

[r-36m2]

I just had a look at their user manual, and I see this under OPAMP replacement procedure: "Op-amp working voltage should meet 36V(+/-18V) maximum,34V Minimum."
This makes me say that the opamps are already supplied with the power they need to perform optimally.

If the op amp is bipolar according to the datasheet, it will perform better with a bipolar power supply than with a single supply. However, it will certainly work with a single supply as well.
Furthermore, a bipolar power supply allows us to remove 2-3 electrolytic capacitors from each channel of the audio path.

 

[Guddu]

If the op amp is bipolar according to the datasheet, it will perform better with a bipolar power supply than with a single supply. However, it will certainly work with a single supply as well.
Furthermore, a bipolar power supply allows us to remove 2-3 electrolytic capacitors from each channel of the audio path.

I do hope @3eaudio jump in with the information and engineering choices you are chasing.

 

[harkpabst]

If the op amp is bipolar according to the datasheet, it will perform better with a bipolar power supply than with a single supply. However, it will certainly work with a single supply as well.
Furthermore, a bipolar power supply allows us to remove 2-3 electrolytic capacitors from each channel of the audio path.

Do you assume that a single rail supply voltage (which the A7, A7 Mono, A7se, A5 and A5se do not use) was the only reason to use input coupling capacitors? I don't think so.

 

[TurtlePaul]

Do you assume that a single rail supply voltage (which the A7, A7 Mono, A7se, A5 and A5se do not use) was the only reason to use input coupling capacitors? I don't think so.

I agree. The coupling caps are there to ensure that any slight DC offset from the source, which then has gain through the opamps, doesn’t push the TPA3255 into DC protection.

 

[John.D]

Auto off is 15 minutes.

3e confirmed 20min?

 

[TurtlePaul]

3e confirmed 20min?

guess it is 20 minutes then.

 

[r-36m2]

Do you assume that a single rail supply voltage (which the A7, A7 Mono, A7se, A5 and A5se do not use) was the only reason to use input coupling capacitors? I don't think so.

That's a good question, colleague. Indeed, TPA32XX chips are single-supply and, according to the datasheet, have 10 µF DC-cut capacitors at the input.
It's possible to build 10 µF capacitors with polypropylene, but it's difficult. A more practical option would probably be to bypass the 10 µF electrolytic capacitors with 1 µF polypropylene.
However, I would do without the capacitors at the op amp inputs, using a dual-supply supply.
And there are at least four capacitors before the op amp.
I've now returned to studying the options for connecting preamplifier stages before the TPA32XX. I looked at them three years ago, but I've forgotten about them. I'll do some reading, look at the schematics, and let you know what I think. Thanks for the conversation.

 

[r-36m2]

I agree. The coupling caps are there to ensure that any slight DC offset from the source, which then has gain through the opamps, doesn’t push the TPA3255 into DC protection.

A normal audio source shouldn't have any DC current in the audio path. The TPA inputs contain capacitors specified in the datasheet, and we can't get rid of them. They cut off DC current in both directions.

 

[MaxwellsEq]

A normal audio source shouldn't have any DC current in the audio path

You are aware that some music releases have DC and close-to-DC offsets I assume?

 

[r-36m2]

You are aware that some music releases have DC and close-to-DC offsets I assume?

Do you think that the DC component present in the recording is converted into DC at the output of the sound source?

 

[KL....]

You are aware that some music releases have DC and close-to-DC offsets I assume?

Thank you, @MaxwellsEq, Yes but do you mind clarifying what these mean?

 

[MaxwellsEq]

Do you think that the DC component present in the recording is converted into DC at the output of the sound source?

It is, the DAC is DC-coupled or has a HPF with a knee close to 1 Hz.

 

[MaxwellsEq]

Thank you, @MaxwellsEq, Yes but do you mind clarifying what these mean?

There is nothing in music sample theory that says a DC signal is illegal (obviously one can discuss infinitely long samples).

So, it's easy to create a CD or digital file that, when played through a DC-coupled DAC deliberately (or accidentally) damages speakers or amplifiers. Some professional gear such as RME protects against this as a default setting.

Over the years a number of such destructive music content (probably accidentally) has been published.

 

[r-36m2]

There is nothing in music sample theory that says a DC signal is illegal (obviously one can discuss infinitely long samples).

So, it's easy to create a CD or digital file that, when played through a DC-coupled DAC deliberately (or accidentally) damages speakers or amplifiers. Some professional gear such as RME protects against this as a default setting.

Over the years a number of such destructive music content (probably accidentally) has been published.

I won't argue about this fantastical phenomenon; we know that the TPA32xx input contains capacitors through which DC current cannot flow.

In any case, the question wasn't whether the respected audio engineers present on this forum consider the presence of electrolytic capacitors in the audio path beneficial or detrimental to sound, but rather how to implement a bipolar power supply for the op amps in this amplifier to eliminate these capacitors.
And that's the second question.

But the first question is: will it be possible to HEAR the difference between the A5 and A5ce amplifiers on 8-ohm speakers, assuming the same op amps are used in the preamp stage?