DIY Purifi Amp builds

[Hasse B]

It would be a shame to give such a clean, transparent and accurate amp "character".

So you mean that the OPA that sits on Purifi's buffer is the one to use?

 

[Hasse B]

And what do you think of Neurochrome's buffer?

 

[Julf]

So you mean that the OPA that sits on Purifi's buffer is the one to use?

Yes.

 

[Julf]

And what do you think of Neurochrome's buffer?

Seems competently designed, and the jumper-selectable gain can be handy, but otherwise I don't see the benefit.

 

[antcollinet]

And what do you think of Neurochrome's buffer?

You are unlikely to get an answer here to questions like that.


The purify amps are at the top of all amps measured here for transparency and performance. That means that if you make any change that alters the sound you have probably made it perform worse. Further, it is most likely that (if the Neurochrome is competently designed) you won't hear any difference anyway. So unless there is a measurement of the thing you are asking about that we can discuss, no-one (who values measurements) will advise you to change.

EDIT (Unless there are features you value as mentioned by @Julf )

 

[Sokel]

You are unlikely to get an answer here to questions like that.


The purify amps are at the top of all amps measured here for transparency and performance. That means that if you make any change that alters the sound you have probably made it perform worse. Further, it is most likely that (if the Neurochrome is competently designed) you won't hear any difference anyway. So unless there is a measurement of the thing you are asking about that we can discuss, no-one (who values measurements) will advise you to change.

EDIT (Unless there are features you value as mentioned by @Julf )

Totally agreed.
And statements by Bruno Putzeys like this:

you can replace the existing OPA in Purifi's buffer table with the OPA1656 to get a different sound character

certainly don't help.

 

[antcollinet]

Totally agreed.
And statements by Bruno Putzeys like this:

certainly don't help.

Did he really say this? It doesn't sound like him.

 

[Sokel]

Did he really say this? It doesn't sound like him.

It's not the first time I read it and there are other similar stuff he claims (he has to make a living too I suppose).

 

[Julf]

It's not the first time I read it and there are other similar stuff he claims (he has to make a living too I suppose).

And he does not claim the OPA1656 is better, just that you "get a different sound character".

 

[Sokel]

Did he really say this? It doesn't sound like him.

From 27.00 and forth:

Of course he's saying that measurements after changing are paramount to find the balance one wants,it's not only about sound but good working order.

 

[boXem]

You guys love to hear what you want to hear.
He says that the OPA1656 is better than the OPA1612 for using in an input buffer not because it sounds better but because it's technical characteristics are more appropiate, in particular the input bias current.

 

[Sokel]

You guys love to hear what you want to hear.
He says that the OPA1656 is better than the OPA1612 for using in an input buffer not because it sounds better but because it's technical characteristics are more appropiate, in particular the input bias current.

That's exactly what I wrote if you are referring to me:

it's not only about sound but good working order

But you admit that he has made some "audiophile" statements from time to time.
(not that I blame him,it's business after all)

 

[DonVinc3nzo]

You could make the change to 4V input range, but I wouldn't go more since the MRX540/740 curves show that its best performance is between 2-4 V, not higher. Really, you could just as well keep the stock EVAL1 values (2V input range) and have essentially optimum performance. Performance of the MRX540/740 is better at 2V out than at 5V.

Thank you for your opinion.

it's strange, I have a friend who also has the MRX540, and who buys a Purifi Audiophonics (https://www.audiosciencereview.com/...ics-hpa-s400et-review-stereo-amplifier.32014/ )
But ...

@ 4.2vrms audio volume sound is low but amazing sound details/clarity/quality. (Up the volume)

@ 2vrms audio volume sound is to high but not amazing, is flat ... no details/clarity/quality. (No necerary up to volume)

- How do you explain that?
- so for me, if I'm at 5vrms, I'd be at the best of what the PreOut RCA of my MRX540 / MRX740 can provide. (as a reminder, my cable is an RCA->XLR) to connect to the Purifi.

Vincenzo.

 

[JimB]

Thank you for your opinion.

it's strange, I have a friend who also has the MRX540, and who buys a Purifi Audiophonics (https://www.audiosciencereview.com/forum/index.php?threads/audiophonics-hpa-s400et-review-stereo -amplifier.32014/)
But ...

@ 4.2vrms audio volume sound is low but amazing sound details/clarity/quality. (Up the volume)

@ 2vrms audio volume sound is to high but not amazing, is flat ... no details/clarity/quality. (No necerary up to volume)

- How do you explain that?
- so for me, if I'm at 5vrms, I'd be at the best of what the PreOut RCA of my MRX540 / MRX740 can provide. (as a reminder, my cable is an RCA->XLR) to connect to the Purifi.

Vincenzo.

I'm not really sure what you and your friend are comparing. You CANNOT make ANY judgements about sound quality unless the volume levels in both cases are well matched - precisely. Of course, you will need the volume setting on your source to be higher to get the same output from a lower gain system (4.2V versus 2.0V). What matters is the sound at the volume you want to hear, not the setting on the knob source device. Now, if anyone is LISTENING to music at 2.0 vs 4.2V RMS, then you are choosing to hear insane distortion. Finally, you can choose any input sensitivity you want, but the data you provided show that your source will perform worse at 5+V output than at 2. The green (2.0) operating point is equivalent to blue (4.0), which are both clearly better than red (5.2). About 3.2V is "best", but hardly worth the effort, really.

 

[Julf]

@ 4.2vrms audio volume sound is low but amazing sound details/clarity/quality. (Up the volume)

@ 2vrms audio volume sound is to high but not amazing, is flat ... no details/clarity/quality. (No necerary up to volume)

Thanks for illustrating how human hearing works. The louder sounds "better" - less flat, clearer, with more details. Indeed.

 

[DonVinc3nzo]

I'm not really sure what you and your friend are comparing. You CANNOT make ANY judgements about sound quality unless the volume levels in both cases are well matched - precisely. Of course, you will need the volume setting on your source to be higher to get the same output from a lower gain system (4.2V versus 2.0V). What matters is the sound at the volume you want to hear, not the setting on the knob source device. Now, if anyone is LISTENING to music at 2.0 vs 4.2V RMS, then you are choosing to hear insane distortion. Finally, you can choose any input sensitivity you want, but the data you provided show that your source will perform worse at 5+V output than at 2. The green (2.0) operating point is equivalent to blue (4.0), which are both clearly better than red (5.2). About 3.2V is "best", but hardly worth the effort, really.
View attachment 260137

Ah! Yes! All right! I understand better what you are trying to explain to me now thanks to the graph! (I didn't know how to read/interpret the graph before.) (I'm an amateur as a reminder)

Actually 3.2vrms I couldn't compare with 4.2vrms or 2vrms but I think the feeling/listening will be closer to 4.2vrms than what I appreciate less in listening at 2vrms.

So what would be the value to replace of resistance R17 on EVAL1 or R22 on EVAL2 to get 3.2Vrms?

Thanks again!
Vincenzo.

 

[Julf]

Actually 3.2vrms I couldn't compare with 4.2vrms or 2vrms but I think the feeling/listening will be closer to 4.2vrms than what I appreciate less in listening at 2vrms.

Do you mostly listen at full volume? How inefficient are your speakers?

Just as a reminder, the difference between 2V and 4.2V is only 6.4 dB.

 

[mocenigo]

Thanks for illustrating how human hearing works. The louder sounds "better" - less flat, clearer, with more details. Indeed.

Actually he observed the opposite :-D

 

[Julf]

Actually he observed the opposite :-D

What he wrote is actually rather confusing:

@ 4.2vrms audio volume sound is low but amazing sound details/clarity/quality. (Up the volume)

@ 2vrms audio volume sound is to high but not amazing, is flat ... no details/clarity/quality. (No necerary up to volume)

So 4.2 V (the higher signal level / gain) "had amazing sound details/clarity/quality", while 2 V (lower signal level) had "no details/clarity/quality". That is what I was referring to. Then on the other hand the 4.2 V signal was "low" and required "upping the volume", and 2 V "No necerary up to volume" (sic). So rather conflicting.

 

[DonVinc3nzo]

What he wrote is actually rather confusing:


So 4.2 V (the higher signal level / gain) "had amazing sound details/clarity/quality", while 2 V (lower signal level) had "no details/clarity/quality". That is what I was referring to. Then on the other hand the 4.2 V signal was "low" and required "upping the volume", and 2 V "No necerary up to volume" (sic). So rather conflicting.

Yes exactly !