Review and Measurements of Purifi 1ET400A Amplifier

[ctbarker32]

I would very much like to build this amp. I am having trouble tracking down all the pieces to assemble. I see on the Purifi web site that I can order the EVAL Kit with cables. It appears I can purchase a Hypex PSU that would be suitable? I do not know where to buy a case to put this all into? I sent an email to Ghent audio who I have used when building IcePower Amps but they did not respond. All the DIY discussions don't provide a simple build BOM to put this together. I have contacted VTV amps but they are out of stock now? So, I am a bit stuck. Any suggestions?

 

[JimB]

I would very much like to build this amp. I am having trouble tracking down all the pieces to assemble. I see on the Purifi web site that I can order the EVAL Kit with cables. It appears I can purchase a Hypex PSU that would be suitable? I do not know where to buy a case to put this all into? I sent an email to Ghent audio who I have used when building IcePower Amps but they did not respond. All the DIY discussions don't provide a simple build BOM to put this together. I have contacted VTV amps but they are out of stock now? So, I am a bit stuck. Any suggestions?

Hi. Are you following the DIY topic here on ASR? Note the most recent update about a Ghent case.
https://www.audiosciencereview.com/...y-purifi-amp-builds.10478/page-77#post-510323

While that topic has gotten quite long, it has a lot of what is needed, especially pages 7-26 or so. It does NOT have a specific BOM, because it is DIY in the sense that people will do their own thing. The most basic can be: a Purifi EVAL1; a Hypex SMPS1200A400; cables between the two (addressed in extreme detail, with options and part numbers in that ASR DIY topic); and a case. Watch out for the required (and not supplied) mains jumper on the SMPS if you have 110-120VAC.

 

[Matias]

@ctbarker32
There is the GX288 case from Modushop that I posted earlier too.

 

[JimB]

@ctbarker32
There is the GX288 case from Modushop that I posted earlier too.

Right. And at least one other option I think.

 

[JimB]

Has anyone else ever fantasized about walking one of these Purifi amps into a Mac clinic in the early 70's?

 

[Bruce Morgen]

Has anyone else ever fantasized about walking one of these into a Mac clinic in the early 70's?

I have now!

Dave O'Brien and the McIntosh Clinics

 

[JimB]

I have now!

Dave O'Brien and the McIntosh Clinics

That's the one. Thanks, Bruce!

 

[Bruce Morgen]

That's the one. Thanks, Bruce!

You're welcome, Jim. I brought my old KM-8002 to Dave, and it met specs with flying colors. Those were the days!

 

[amirm]

I have now!

Dave O'Brien and the McIntosh Clinics

And here I complain about lugging my Audio Precision to local audiophile group to test their gear:

It is arduous work to test things while people wait. I have done it a few times but am reluctant to do more.

 

[Jack B]

And here I complain about lugging my Audio Precision to local audiophile group to test their gear:

View attachment 92713

It is arduous work to test things while people wait. I have done it a few times but am reluctant to do more.

I'm old enough to remember lugging my Dynaco Mark 3s into the hi-fi store for the McIntosh man to test. He was invariably polite, despite his heavy (pun intended) workload and a long line of ignoramuses like me to deal with. Nice guy.

 

[nerdoldnerdith]

You said in your review for the Benchmark AHB2 that you gained 3dB of SINAD by using Speakon connectors instead of the binding posts. This review unit only has the binding posts. Do you think there would be the same added benefit from using speakons in a Purifi build, and could this possibly be the source of the higher than expected noise level you measured with your unit?

 

[ZestClub]

You said in your review for the Benchmark AHB2 that you gained 3dB of SINAD by using Speakon connectors instead of the binding posts. This review unit only has the binding posts. Do you think there would be the same added benefit from using speakons in a Purifi build, and could this possibly be the source of the higher than expected noise level you measured with your unit?

Bruno said something to the effect that SpeakOns were the best for noise.
Ever tried wiring the damn things though with even reasonably thick cables... not easy.

 

[Julf]

Bruno said something to the effect that SpeakOns were the best for noise.

I would love to see where he said that, and what he based it on. I do know he thinks they are the most sensible choice pure from a practival (not sound quality) point of view, and I agree.

Ever tried wiring the damn things though with even reasonably thick cables... not easy.

At least the ones I use are OK with pretty thick cables. I would not use them for welding cables, but...

 

[mocenigo]

Bruno said something to the effect that SpeakOns were the best for noise.
Ever tried wiring the damn things though with even reasonably thick cables... not easy.

IIRC the main reason is that many binging post connectors have a ferromagnetic metal ring of some sort (it may be a washer, or the external cover of the connector itself, or in the connect itself) that increase distortion and noise. The speakons do not have those parts. So if you have a pure copper binding post that has plastic cover, bolts, and washers, affixed to an aluminium case, the noise and distortion profile should be similar. And then of course the quality of the connection itself is important. Never use curved spring bananas, they suck. I only use Z-plugs, they have a large and stable contact surface.

 

[Julf]

IIRC the main reason is that many binging post connectors have a ferromagnetic metal ring of some sort (it may be a washer, or the external cover of the connector itself, or in the connect itself) that increase distortion and noise.

Do you have any pointers to measurements or studies showing those effects? Where would the noise be coming from?

 

[JimB]

Do you have any pointers to measurements or studies showing those effects? Where would the noise be coming from?

Benchmark has said this about ultimate performance with the AHB2, and @amirm has confirmed that the type of connection made a difference in his measured results. Contact quality and materials are the potential causes. Benchmark advice was to use speakONs as first choice, followed by locking banana plugs. This argues for contact quality as an important factor. I believe spades and bare wire can be good, but a bit more care is required to ensure that. After all, screw-tightened bare wire is the connection inside the speakONs. In last place were spring-contact banana plugs. However, inadequacy of such banana plugs has been disputed by several members, including @restorer-john (who is looking surprisingly feminine these days ). YMMV.

 

[mocenigo]

Benchmark has said this about ultimate performance with the AHB2, and @amirm has confirmed that the type of connection made a difference in his measured results. Contact quality and materials are the potential causes. Benchmark advice was to use speakONs as first choice, followed by locking banana plugs. This argues for contact quality as an important factor. I believe spades and bare wire can be good, but a bit more care is required to ensure that. After all, screw-tightened bare wire is the connection inside the speakONs. In last place were spring-contact banana plugs. However, inadequacy of such banana plugs has been disputed by several members, including @restorer-john (who is looking surprisingly feminine these days ). YMMV.

locking banana plugs? For feck’s sake, just a bit of vibration in the environment and they start to unscrew and then they are even worse than the spring loaded ones. Z-plugs forever!!!

 

[mocenigo]

Do you have any pointers to measurements or studies showing those effects? Where would the noise be coming from?

I do not, but when both Benchmark and Purifi claim the same thing, and we know that are quite anal about getting noise and distortion down, well, this is plausible. However, anything ferromagnetic AROUND a conductor has a measurable detrimental effect on sound (as a signal — audibility is another matter).

 

[JimB]

locking banana plugs? For feck’s sake, just a bit of vibration in the environment and they start to unscrew ...

Not in my experience (but then, we haven't had a major earthquake just recently...).

I don't have Z plugs, but I have recommended them! (Well, BFA, actually.)

 

[restorer-john]

including @restorer-john (who is looking surprisingly feminine these days ).

An ad I came across in a 1977 electronics magazine for Beltek 6x9" car speakers. I remember everyone at one point seemed to have Beltek speakers in their cars.