Purifi Class D

[Rexp]

1 hour ago, fas42 said:

Speaking of that specific Belafonte LP, I had an interesting session at the Sydney audio club meeting many, many years ago. A supposedly pretty decent vinyl rig was set up, and played the copy that someone had ... God, it was awful!! The vinyl tracking distortion was atrocious - for me, it was, unlistenable ... yet other members around me were listening with a rapt expression on their faces ...

 

And every now and again someone claims I'm against audiophiles - oh dear, 😆.

You're wired different... 

[fas42]

Just now, Rexp said:

You're wired different... 

 

True ... I like my system to make sounds that mimic live music - unlike some, 😄.

[RickyV]

I tought this thread was about Purifi class D amplifiers or at least class D??

[John Hughes]

So I got an email today that My Starkrimson has shipped!  Coming cross country, First Class mail so it might take a while to get here though.  I'll be comparing this GaN amp to my VTV Purifi amp. 

[Qhwoeprktiyns]

On 3/10/2021 at 5:32 PM, jaytor said:

The Purifi modules have an input impedance of 4.4K across the differential inputs (2.2K to ground). The general rule of thumb is that you want to have a source output impedance that is at least 10 times lower than the input impedance. So if your source has a differential output impedance under about 450 ohms and plenty of drive, and you are using short interconnects, you might be happy with the results. 

 

I tried bypassing the input buffer, and even though I have a low 66ohm differential output impedance from my preamp, I thought the sound was more dynamic with more weight with the input buffer active. However, I do have long balanced interconnects (~8M). So your results may be different. You won't hurt anything by trying it. 

 

I forgot to give some feedback on this. Bypassing the input buffer with my DAC gave excellent results: https://www.ecdesigns.nl/en/shop/powerdac-r

It has 32 ohm output impedance, and the volume control is very transparent. Interconnects used are 1 meter long. The sound was really dynamic, no issue at all, and the amp was dead quiet. 

My speakers are 90db, and lowest gain is OK. 

 

This was with the Audiophonics HPA-S250NCI. did not try other modules, but concluded  that the input buffer is really the weak link in that purifi implementation.

[Matias]

FYI this leaked and is about to be released.

 

 

Purifi 1ET7040SA
Output Power: 950W(2Ω), 500W(4Ω), 250(8WΩ)
Output Current: ~40A
THD+N: <0.00035% @ 200W, 4Ω, 1kHz
Dynamic Range: ~129 dB(A)
Output Noise: ~14µV(A)
Gain: 13dB
Output Impedance: <13µΩ @ 1kHz
Efficiency: 94% @ 500W, 4Ω, 1kHz
Idle losses (output stage): 2.8 W

[57gold]

Matias - Thanks for the heads up.

 

Wonder what kind of power supply will be required to supply the juice to output 40 amps of current?

 

I guess there is the one that is used to power the Hypex Ncore NC1200.

[Matias]

41 minutes ago, 57gold said:

Matias - Thanks for the heads up.

 

Wonder what kind of power supply will be required to supply the juice to output 40 amps of current?

 

I guess there is the one that is used to power the Hypex Ncore NC1200.

Yes, the regular Hypex SMPS1200 should do, I suppose the higher voltage version, SMPS1200A700.

 

By the way forgot to post the excellent measurements. Almost as fine as the 1ET400A but with tons of current, probably more expensive though. Bruno really outdid himself.

 

1ET7040SA

 

 

1ET400A

 

[57gold]

Haven't seen anything more on this new unit.

 

Given its capabilities, you'd think amp builders would be jumping on board, scrambling to announce a new unit?

[Mike48]

On 10/3/2021 at 6:29 AM, 57gold said:

Haven't seen anything more on this new unit.

 

Given its capabilities, you'd think amp builders would be jumping on board, scrambling to announce a new unit?

 

I don't think PuriFi has released it yet. It's not on their Web site.

 

[Al Jones]

I have just been informed by Australian March Audio that everyone is still waiting for Purifi to actually start mass production of the new module, which should be “very soon.”

 

Al Jones

[Al Jones]

This just in direct from Purifi re the new module:

 

“Hopefully early in the new year. But it’s difficult to say for sure due to the ongoing component scarcity situation.”

[Matias]

 

[Mike48]

More power, otherwise similar specs. Does that sum it up?

[mocenigo]

1 hour ago, Mike48 said:

More power, otherwise similar specs. Does that sum it up?

yes

[DuckToller]

recent YT with Bruno ...
Thanks for the link at FB Lars Risbo!

 

[PYP]

Is the Purifi 1ET7040SA ( High 40A Current Output) for "professionals" only?  I don't see it on the Purify website, only the 1ET400A.   

[barrows]

6 minutes ago, PYP said:

Is the Purifi 1ET7040SA ( High 40A Current Output) for "professionals" only?  I don't see it on the Purify website, only the 1ET400A.   

Yeah, no DIY option with the higher power modules it seems.  I might just purchase an affordable build from a manufacturer and then DIY it to be better.

[ssh]

https://apollonaudio.com is having a Black Friday sale. 10% off.

No connection other than a very satisfied customer.

[Allan F]

On 11/11/2022 at 12:06 PM, barrows said:

Yeah, no DIY option with the higher power modules it seems.  I might just purchase an affordable build from a manufacturer and then DIY it to be better.

 

Apart from the higher current, do you know if the sound quality of the Purifi 1ET7040SA module is superior to that of the 1ET400A? As you note, there are manufacturers offering Class D amplifiers using this new module.

[Jud]

3 minutes ago, Allan F said:

do you know if the sound quality of the Purifi 1ET7040SA module is superior to that of the 1ET400A?

AFAIR, no.

[barrows]

1 hour ago, Allan F said:

 

Apart from the higher current, do you know if the sound quality of the Purifi 1ET7040SA module is superior to that of the 1ET400A? As you note, there are manufacturers offering Class D amplifiers using this new module.

Bruno Putzeys is on record as saying that when one increases available power/current, there will always be a slight rise in distortion, and that this is unavoidable, but considering that the distortion of all of these amplifiers is at levels generally considered to be inaudible, I suspect that is merely a technical concern.  My own experience suggests that a more powerful amplifier of the same general design quality and implementation, always seems to sound better in my system, even if the loudspeakers do not technically "require" the additional power.  This may be because the higher power amplifier is operating in its more linear range when being asked to deliver a lower percentage of its overall power (look at distortion curves of amplifiers), or it may be because musical dynamics and transients, require gobs of current delivery to be rendered realistically in the very short term.  I do not know the answer here for sure, but have heard, for instance, the NC-400 vs. NC-1200 based amplifiers in my system, and the NC-1200, despite nominally having higher distortion, sounded better (enough that I wished I could get my hands on a Mola Mola set of mono blocks), eventhough my speakers do not technically "require" the increased current/power.

There are plenty of reports out there in audiophile land of a high degree of amplifier current/power headroom leading to better sound quality, even at moderate volumes where one is mostly operating in the first few watts (long term) of amplifier power.  My own experience leads me to conclude that I would like to have the higher power Purifi option here.

[John Hughes]

@Barrows. This is a smart answer!  My speakers are super efficient so these differences won't be audible.  But I'd bet the higher power modules would make a difference in speakers at 4ohms and less than 88db efficiency.

[barrows]

3 hours ago, John Hughes said:

@Barrows. This is a smart answer!  My speakers are super efficient so these differences won't be audible.  But I'd bet the higher power modules would make a difference in speakers at 4ohms and less than 88db efficiency.

Yeah, I suspect there is some level of efficiency where more headroom will not bring improvements, but without trying one never knows for sure.  My own speakers are 4 ohm, and rated 90 dB for 1 watt, but I suspect that rating is a bit generous, as the speakers do appear to like some more power.  Theoretically, the 400 Watts at 4 ohms should be much more than enough, but the amp with even more headroom has sounded better in the past.

[Miska]

12 hours ago, barrows said:

Yeah, I suspect there is some level of efficiency where more headroom will not bring improvements, but without trying one never knows for sure.  My own speakers are 4 ohm, and rated 90 dB for 1 watt, but I suspect that rating is a bit generous, as the speakers do appear to like some more power.  Theoretically, the 400 Watts at 4 ohms should be much more than enough, but the amp with even more headroom has sounded better in the past.

 

Usually it is the loudspeaker's complex impedance that matters from amplifier perspective. Not the absolute resistive impedance power. And that combined with amplifier's damping factor.

 

If you don't have complex impedance curves of the loudspeaker, minimum EPDR gives a good idea how difficult the loudspeaker is to drive. Something like 2.5 ohm EPDR is not unusual, and these appear usually around mid bass frequencies for conventional dynamic speakers. And around treble area for electrostatic speakers (electrostatic is essentially a capacitor, higher the frequency, closer it gets to short-circuit). Magnetostatic speakers have their own unique behavior.

 

High damping factor vs minimum EPDR is best comparison if you want to get idea of how much the amplifier has control over the speaker.

 

If you have electrostatic, it is essentially a short-circuit for class-D's switching frequency.