• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Review and Measurements of Purifi 1ET400A Amplifier

Thomas savage

Grand Contributor
The Watchman
Forum Donor
Joined
Feb 24, 2016
Messages
10,260
Likes
16,298
Location
uk, taunton
Does adding the 2nd power supply improve the measured results? You should send an amp to Amir with 2 supply’s, along with the harness to connect a single supply. So we can all see if adding the 2nd supply is worth the additional money.
Ah Mike ... Again ?! Really ...
 

rodtor

Member
Forum Donor
Joined
Aug 21, 2019
Messages
97
Likes
180
Location
Toronto
FYI I'm about to order an Audiophonics HPA-S400ET with OPA1612 instead of OP275. They said no problem, easy to work with and quick follow-up.
This is interesting, @TomJ. I am also interested in this amp. What are the advantages of the OP1612 over the OP275, and what is the additional cost?
 

mocenigo

Major Contributor
Joined
Dec 8, 2018
Messages
1,274
Likes
1,034
This is interesting, @TomJ. I am also interested in this amp. What are the advantages of the OP1612 over the OP275, and what is the additional cost?

Advantage: better measurements.

Disadvantage: the OPA 1612 has some phase rotations that could cause oscillations when feedback is used. The LME49720 is better from this point of view. In fact, I would say that it is better because of this. So you can use more feedback on the LME49720 and keep better linearity, lower noise THD and IMD in the final circuit considered as a whole and at the same time be sure it is more stable as well.

Roberto
 

TomJ

Active Member
Joined
Sep 16, 2019
Messages
129
Likes
177
Location
Palo Alto CA
Advantage: better measurements.

Disadvantage: the OPA 1612 has some phase rotations that could cause oscillations when feedback is used. The LME49720 is better from this point of view. In fact, I would say that it is better because of this. So you can use more feedback on the LME49720 and keep better linearity, lower noise THD and IMD in the final circuit considered as a whole and at the same time be sure it is more stable as well.

Thank you Roberto, very helpful. FYI Audiophonics changed their standard build spec yesterday from OP275 to LM4562. Any thoughts? What would be your top op amp choice(s) for a Purifi buffer?
 

mocenigo

Major Contributor
Joined
Dec 8, 2018
Messages
1,274
Likes
1,034
Thank you Roberto, very helpful. FYI Audiophonics changed their standard build spec yesterday from OP275 to LM4562. Any thoughts? What would be your top op amp choice(s) for a Purifi buffer?

I would be tempted to follow NwAvGuy and say that all proper opamps when used properly are all equally good and sonically indistinguishable. But there are caveats.

Opa1612 and LM4562/LME49720 are both good. If you want discrete, then Sonic Imagery 994 or the Weiss op amps. The sparkos opamps are very good as well but are IMO sonically warmer than the Sonic Imagery. I ended up not linking that at all. Never heard a Weiss.

hence, once you have a LM4562/LME49720 or a OPA1612 I would not worry, the circuit around is what makes a bigger difference.

Roberto
 

TomJ

Active Member
Joined
Sep 16, 2019
Messages
129
Likes
177
Location
Palo Alto CA
This is interesting, @TomJ. I am also interested in this amp. What are the advantages of the OP1612 over the OP275, and what is the additional cost?
Since my post they replaced the OP275 with the LM4562 in their build spec and I've ordered that. To your question, the price would have been the same with the OPA1612.
 

Vincentponcet

Active Member
Forum Donor
Joined
Mar 13, 2020
Messages
248
Likes
106
How to compare different brands of purifi amps sound quality wise ?
It is all about the buffer as they use the same amp board and the same power supply.
Looks like the current bargains are audiophonics and Nord
Any reviews of the audiophonics buffer ?
 

SIY

Grand Contributor
Technical Expert
Joined
Apr 6, 2018
Messages
10,386
Likes
24,752
Location
Alfred, NY
How to compare different brands of purifi amps sound quality wise ?

Unless someone really screwed something up, they'll sound alike as long as you match levels and don't peek.
 

Billy Budapest

Major Contributor
Forum Donor
Joined
Oct 11, 2019
Messages
1,812
Likes
2,689
How to compare different brands of purifi amps sound quality wise ?
It is all about the buffer as they use the same amp board and the same power supply.
Looks like the current bargains are audiophonics and Nord
Any reviews of the audiophonics buffer ?
Both of those use boutique discrete op amps which although have negligible (or zero) impact on sound quality, would adversely affect the measurements. I’d look at March Audio for an implementation with standard opamps.
 

mocenigo

Major Contributor
Joined
Dec 8, 2018
Messages
1,274
Likes
1,034
Both of those use boutique discrete op amps which although have negligible (or zero) impact on sound quality, would adversely affect the measurements. I’d look at March Audio for an implementation with standard opamps.

Audiophonics is using a LM4562 opamp and Nord has a "bargain" option with OPA1612 opamps. They are not boutique, they are solid, well established IC opamps. Please double check your facts and avoid spreading false information.
 

TomJ

Active Member
Joined
Sep 16, 2019
Messages
129
Likes
177
Location
Palo Alto CA
Any reviews of the audiophonics buffer ?
It gets complicated... If you find a review, it could be for an OP275 buffer (they changed the build spec to LM4562 just 2 days ago). Or some other op amp, because their IC socket supports op amp rolling and you can order it with a different op amp if you prefer. Another variable might be the buffer gain which you can reset with jumpers.
 
Last edited:

Vincentponcet

Active Member
Forum Donor
Joined
Mar 13, 2020
Messages
248
Likes
106
It gets complicated... If you find a review, it could be for an OP275 buffer (they changed the build spec to LM4562 just 2 days ago). Or some other op amp, because their IC socket supports op amp rolling and you can order it with a different op amp if you prefer. Another variable might be the buffer gain which you can reset with jumpers.

The op amp used is one thing, but the buffer board itself is also a thing to consider. It has voltage regulators, and caps. The schema and the components could be good or bad.
Btw audiophonics is using a single stage lm317 / 337 voltage regulator. Does not sound that much high end. Any information on Nord revC buffer board ?
https://www.audiophonics.fr/en/prea...odule-buffer-stereo-aop-op275-v22-p-4227.html
 

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
The best "boutique" op amps perform about the same as the quality op amps from the likes of Texas Instruments. However certainly not better and cost significantly more, 10 or 20x. Some of these boutique parts perform significantly worse.

There is just no technical logic to implement them, but they do appeal to audiophiles and they can be charged more for the privilege.

Now, the op amp is one thing but there is a lot more to the final performance of the buffer. Board layout has an impact. Different caps and resistors have different distortion characteristics. Regulators need to be suitable for rejecting the smps high frequency noise. Standard regs are poor in this respect.

So just because a board contains "op amp X" does not mean it has good technical performance or sounds better.
 
Last edited:

TomJ

Active Member
Joined
Sep 16, 2019
Messages
129
Likes
177
Location
Palo Alto CA

Attachments

  • Audiophonics voltage regulators.png
    Audiophonics voltage regulators.png
    59.2 KB · Views: 288
Last edited:

Billy Budapest

Major Contributor
Forum Donor
Joined
Oct 11, 2019
Messages
1,812
Likes
2,689
Audiophonics is using a LM4562 opamp and Nord has a "bargain" option with OPA1612 opamps. They are not boutique, they are solid, well established IC opamps. Please double check your facts and avoid spreading false information.

Chill out, dude! I’ve looked at the configurations on their websites and have seen the boutique discrete opamps. It is certainly not “false information” and I am not “spreading” anything. For sure regarding the Nord. As for the Audiophonics, I had remembered seeing an implementation where they used discrete opamps. Maybe their design has changed since then. In any event, I find the entire discrete opamp industry rather silly.
 
Last edited:

Vincentponcet

Active Member
Forum Donor
Joined
Mar 13, 2020
Messages
248
Likes
106
Chill out, dude! I’ve looked at the configurations on their websites and have seen the boutique discrete opamps. It is certainly not “false information” and I am not “spreading” anything. For sure regarding the Nord. As for the Audiophonics, I had remembered seeing an implementation where they used discrete opamps. Maybe their design has changed since then. In any event, I find the entire discrete opamp industry rather silly.
I was talking of the cheapest purifi amps, around 1500 euros for stereo amp. Those are not using boutique opamp.
Nord uses opa1612a with their RevC buffer board
https://www.nordacoustics.co.uk/product-page/nord-three-1et400a-stereo-amplifier-1
Audiophonics uses lm4562
https://www.audiophonics.fr/fr/ampl...ereo-class-d-purifi-2x400w-4-ohm-p-14393.html
 

mocenigo

Major Contributor
Joined
Dec 8, 2018
Messages
1,274
Likes
1,034
Chill out, dude! I’ve looked at the configurations on their websites and have seen the boutique discrete opamps. It is certainly not “false information” and I am not “spreading” anything. For sure regarding the Nord. As for the Audiophonics, I had remembered seeing an implementation where they used discrete opamps. Maybe their design has changed since then. In any event, I find the entire discrete opamp industry rather silly.

Yes, audiophonics explicitly states you can use your own discrete op amps (but they sell you only the IC ones) and Nord has models with discrete ones for sale — but you were referring to the bargains. And the “budget” model from nord has the version C of their boards with a socketed IC opamp.

the nord models with boutique discrete opamps are no bargains wrt the other offerings by competition (Apollon, Rouge, etc)
 

Billy Budapest

Major Contributor
Forum Donor
Joined
Oct 11, 2019
Messages
1,812
Likes
2,689
Yes, audiophonics explicitly states you can use your own discrete op amps (but they sell you only the IC ones) and Nord has models with discrete ones for sale — but you were referring to the bargains. And the “budget” model from nord has the version C of their boards with a socketed IC opamp.

the nord models with boutique discrete opamps are no bargains wrt the other offerings by competition (Apollon, Rouge, etc)
“But you were referring to the bargains.” That’s an incorrect assumption.
 
Top Bottom