Buckeye Amps: 2nd Generation Purifi EIGENTAKT 1ET9040BA Amplifier

[atomek]

Very few, almost no people will use the low gain setting. Most people will need to use the medium or high gain settings to match their source equipment. 4 volt xlr or 2 volt rca. These are the gains where amps should be compared as its most relevant to most users. Otherwise just bypass the input buffer and just claim the Purifi module performance.

Could you tell more about this, I plan to buy this amplifier to power Dynaudio S25 (200W 4ohm) spekars. I calculated required gain: Vout = sqrt(200 * 4) = 28.3 Vrms, Gain = Vout/Vin = 28.3 / 5.2 (my DAC have 5.2 Vrms) = 5.44, so 14.7 dB which is below "low gain" settings of 15.5 dB (which according to calculations could power 240W 4ohm at 100% DAC volume output). Should I use medium gain anyway? Or can I use low gain and maybe even bypass gain?

 

[welwynnick]

Could you tell more about this, I plan to buy this amplifier to power Dynaudio S25 (200W 4ohm) spekars. I calculated required gain: Vout = sqrt(200 * 4) = 28.3 Vrms, Gain = Vout/Vin = 28.3 / 5.2 (my DAC have 5.2 Vrms) = 5.44, so 14.7 dB which is below "low gain" settings of 15.5 dB (which according to calculations could power 240W 4ohm at 100% DAC volume output). Should I use medium gain anyway? Or can I use low gain and maybe even bypass gain?

All your calculations are correct, on the condition that you only want 240W into a 4 ohm load, which would be under-utilising a very capable amplifier.

I wouldn't over-think it. You can change the gain and see for yourself. Set the gain to low and see if it goes loud enough for you. They're quite efficient speakers, so it probably will.

 

[quattro98]

There's a review of the Buckeye Purifi 9040 amp in Stereophile by Kal Rubinson. I saw it via an Apple News+ subscription, so I posted the link below. I assume it will show up on the Stereophile website (and be in the print issue). I couldn't see all of the measurement figures via Apple News+. Not sure why. Perfect for driving your Estelon X Diamond Mk II reviewed in the same issue.

EDIT: If you subscribe via Apple News+, the measurements are shown by scrolling left and right. User error on my part.

Buckeye PURIFI EIGENTAKT 1ET9040BA1 — Stereophile

Cover

apple.news

 

[Matias]

This will be fun. Can't wait to show up on the Stereophile website.

 

[Kal Rubinson]

This will be fun. Can't wait to show up on the Stereophile website.

Me, too.

 

[Buckeye Amps]

Let me just say, when I first started Buckeye Amps, never ever did I think it would be on the audio radar large enough to be noticed by a publication like Stereophile.

Thanks everyone!

 

[jacktracks707]

Purify Gen 2 three channel just arrived and hooked up. Sounds great for the LCR of Kef R11 metas and R6 Metas. Part of a 9.4.4 system. Denon 6800 is the main brain.

 

[yys310]

Let me just say, when I first started Buckeye Amps, never ever did I think it would be on the audio radar large enough to be noticed by a publication like Stereophile.

Thanks everyone!

Hi,
For this review I subscribed the stereophile for 3mo.
Is the 19kHz+20kHz-IMD measurement result within your exception?

Edit: CCIF --> 19kHz+20kHz

 

[Buckeye Amps]

Hi,
For this review I subscribed the stereophile for 3mo.
Is the 19kHz+20kHz-IMD measurement result within your exception?

Edit: CCIF --> 19kHz+20kHz

Let me look into this further

 

[Sal1950]

Me, too.

Good review Kal !
I got my copy of the Jan 2025 issue last week but just stated reading my way thru it.
Nice honest presentation of the amps great virtues, S-P needs more like this.

Dylan, Better gear up for some increased sales.
Sal

 

[jruser]

Can anybody with access to the stereophile review spoil what the 8-ohm 1% THD figure is? A rough guess of where the elbow on the 8-ohm graph is would also be helpful.

 

[Oniiz86]

@Buckeye Amps I was wondering why your Purifi 1ET9040BA amp wasn't sent in for review with Micro Audio's SMPS1K-SN power supply, for some reason I thought it was reviewed with the Micro Audio SMPS by @Kal Rubinson for Stereophile?

I saw this in another thread “This power supply limits the ultimate output of the amp to 1200W into 2 ohms. Buckeye offers an optional Micro Audio SMPS1K-SN power supply that offers Active Power Factor Correction, higher power output (a 0.67dB increase from 1200W to 1400W into 2 ohms)…” @Kal Rubinson, Buckeye Buckeye PURIFI EIGENTAKT 1ET9040BA1” fn. 6, Stereophile 1/2025 at 79."

 

[Buckeye Amps]

@Buckeye Amps I was wondering why your Purifi 1ET9040BA amp wasn't sent in for review with Micro Audio's SMPS1K-SN power supply, for some reason I thought it was reviewed with the Micro Audio SMPS by @Kal Rubinson for Stereophile?

I saw this in another thread “This power supply limits the ultimate output of the amp to 1200W into 2 ohms. Buckeye offers an optional Micro Audio SMPS1K-SN power supply that offers Active Power Factor Correction, higher power output (a 0.67dB increase from 1200W to 1400W into 2 ohms)…” @Kal Rubinson, Buckeye Buckeye PURIFI EIGENTAKT 1ET9040BA1” fn. 6, Stereophile 1/2025 at 79."

We didn't have the Micro Audio SMPS' on hand at the time. Since the SMPS doesn't affect the overall performance in regards to audible quality/what is heard, having the "base model" reviewed wasn't an issue.

 

[ggs]

Dylan, any thoughts on the IMD measurements yet? Stereophile's measurements don't seem to agree with Purifi's data sheet (if I'm reading them right).

 

[quattro98]

Dylan, any thoughts on the IMD measurements yet? Stereophile's measurements don't seem to agree with Purifi's data sheet (if I'm reading them right).

The Purifi IMD is 18.5 kHz + 19.5kHz with a graph that stops at 20k (400 W into 4R). The Stereophile one is 19 kHz + 20 kHz and goes up to 30 kHz (50 W peak into 8R).

I'm curious what those with a more technical background make of the 18 kHz peak at -70 dB.

 

[Julf]

I'm curious what those with a more technical background make of the 18 kHz peak at -70 dB.

Anything that is down -70 dB at 18 kHz will be inaudible.

 

[quattro98]

Anything that is down -70 dB at 18 kHz will be inaudible.

Agreed. I don't think it matters in use (listening to a class D amp right now). The level is quite different than what we see in Purifi's IMD measurements with sidebands at less than -125 dB.

 

[ggs]

Any possibility that the OPA 1612 is the source of the IMD? Stereophile may have made their measurements with the Buckeye amp gain set at high. (OP amp gain-bandwidth products are finite.) I also am curious about the 18 kHz peak, not the peaks above 20 kHz, even though they are all definitely inaudible to me.

 

[Buckeye Amps]

Any possibility that the OPA 1612 is the source of the IMD?

The 9040 uses the OPA1656

 

[ggs]

Rodents! I'd forgotten. Any insights into the IMD?