Buckeye PURIFI 1ET9040BA Amp Review

[GavriloD]

Hello, I need an amplifier for my Dynaudio Confidence C1 speakers. The room is 38 m² and the listening distance is about 4 m. I am seriously considering a Class D amplifier. What I care about most is perfect control of the bass driver so it can reproduce frequencies around 30 Hz without any issues. It seems that typical commercial amplifiers class AB are not sufficient for this.

I am not a technician — could the problem be related to output current? Would the AUDIOPHONICS AP300-S500NC handle this, or would it be more reasonable to go for the latest Purifi, even though it is significantly more expensive?

You have a relatively large room and bookshelf speakers that are not made to reach as low as 30Hz. It is always a question for me why do you need a 30Hz response, given there are hardly any recordings that reach that low. Maybe some organs, not even a double bass, can reach that low.

If it is a matter of just not being able to get lower extensions in your room and the feeling of not enough bass response, the amp itself will not be the solution; you will need a sub.

 

[schali]

You have a relatively large room and bookshelf speakers that are not made to reach as low as 30Hz. It is always a question for me why do you need a 30Hz response, given there are hardly any recordings that reach that low. Maybe some organs, not even a double bass, can reach that low.

If it is a matter of just not being able to get lower extensions in your room and the feeling of not enough bass response, the amp itself will not be the solution; you will need a sub.

You are right, there probably aren’t many recordings like that, but some electronic music recordings do include it, and it’s quite an experience. Believe me, you would be surprised how low these speakers can go. I read somewhere that they measured down to 33 Hz.

The room is larger, but that definitely isn’t the reason why these bass frequencies aren’t playing now — the amplifier is responsible. I tried another one where it worked, but it was very expensive and I can’t afford it, so I’m looking elsewhere. With Class AB/A, you basically need a welder, and I’m wondering whether Class D can handle it as well. Are those just numbers, or not?

 

[Lars Risbo]

You have a relatively large room and bookshelf speakers that are not made to reach as low as 30Hz. It is always a question for me why do you need a 30Hz response, given there are hardly any recordings that reach that low. Maybe some organs, not even a double bass, can reach that low.

If it is a matter of just not being able to get lower extensions in your room and the feeling of not enough bass response, the amp itself will not be the solution; you will need a sub.

it’s true that few instruments have fundamentals down at 30Hz. However, unless we only want stationary long organ notes reproduced then we need extra bandwidth below the fundamental to reproduce the dynamics, ie the envelope of a bass tone turning on and off again. in other words, any rhythmic bass content.

 

[theREALdotnet]

it’s true that few instruments have fundamentals down at 30Hz. However, unless we only want stationary long organ notes reproduced then we need extra bandwidth below the fundamental to reproduce the dynamics, ie the envelope of a bass tone turning on and off again. in other words, any rhythmic bass content.

IME experience, anything that pops, clicks or taps has frequency components all the way down.

 

[Lars Risbo]

yes that’s down to mathematics. amplitude modulation of a fundamental gives spectral side bands which can extend down to 0Hz

 

[Rit]

In actual usage, you can safely run both monoblocks off of a single 15A circuit.

For reference, when I had a dedicated HT setup I had 3 channels of NCx500, 12 channels of NC502MP, a JVC Laser projector, room lights, and all my components (processor, xbox, etc) all running off a single 15A circuit and routinely watched movies at reference levels and never had a single issue.

Back in the old days!

 

[RickS]

@amirm, the 1.4kW spec you listed for the 2R load is for a 0.1%THD per the Purifi datasheet. The 1.6kW measurement you made is for 1% THD, so the amp does not exceed the rated spec by 200 watts as insinuated. Purifi does NOT spec their 9040BA modules at 1% THD, only at 0.1%THD. But their lesser power modules are spec'd at 1% THD. Not sure if you still have the amp, but what is its power at 0.1% THD into 4R and 2R?

While you have a point about Amir's claim, it is a bit of hairsplitting. If you look at the 9040 datasheet, you will find this....

This does show that 9040 spec is about 1500 watts at 1% SINAD for a 2-ohm load. So, Amir's measure of the Buckeye amp does seem to exceed the spec. Conditions matter though (gain, temp, duration, etc.) and am not absolutely sure about Purifi's conditions for the above. In any case 1.6 kW is (relatively) impressive. Personally, would look more at the knee where clipping starts rather than where the curve goes vertical. This is about 700-800 watts at less than .0001%. Still impressive.

In the end, unless conditions are matched identically, your best bet is to only compare between Amir's amp measurements. From personal experience, whenever you measure several hundred watts or more (even for a brief duration), it is stressing the measurement rig. Even things like termination torque and wire distances become critical when trying to make really low distortion measurements.

 

[David_M]

While you have a point about Amir's claim, it is a bit of hairsplitting. If you look at the 9040 datasheet, you will find this....

View attachment 510665

This does show that 9040 spec is about 1500 watts at 1% SINAD for a 2-ohm load. So, Amir's measure of the Buckeye amp does seem to exceed the spec. Conditions matter though (gain, temp, duration, etc.) and am not absolutely sure about Purifi's conditions for the above. In any case 1.6 kW is (relatively) impressive. Personally, would look more at the knee where clipping starts rather than where the curve goes vertical. This is about 700-800 watts at less than .0001%. Still impressive.

In the end, unless conditions are matched identically, your best bet is to only compare between Amir's amp measurements. From personal experience, whenever you measure several hundred watts or more (even for a brief duration), it is stressing the measurement rig. Even things like termination torque and wire distances become critical when trying to make really low distortion measurements.

You see 1.5kW, I see 1.6kW when you zoom in for further clarity. But my concern is your use of the word "spec" regarding power at 1% THD+N. That power spec does not exist from Purifi, even though the amp has been measured as indicated in the graph. Have you wondered why they decided to spec their module at 0.1% and not 1% as they did for lesser-powered modules? Wouldn't it have been better, from a marketing perspective, to say we deliver 1600W and not 1400W in 2 ohms? I'd say it would definitely be better.

However, I suspect they found that the necessary cooling requirements would be massive or untenable, at least not attractive enough to specify at that power level. Maybe they also found limitations in the switching power transistors at such high currents (40 amps peak). All in all, I suspect they chose not to spec at 1% due to decreased reliability in their modules.

You (legally) guarantee what's written in the datasheet. At 0.1%, they guarantee the 1400W all day as long as cooling requirements are met, as indicated in their datasheet. At 1600W in 2R, generating 40A peak current? Not so much, and probably that's why they set their overcurrent protection limit at 40A peak. They do not want their modules to operate anywhere near these current levels.

 

[Buckeye Amps]

OK....as Rick said, splitting hairs

 

[RickS]

You see 1.5kW, I see 1.6kW when you zoom in for further clarity. But my concern is your use of the word "spec" regarding power at 1% THD+N. That power spec does not exist from Purifi, even though the amp has been measured as indicated in the graph. Have you wondered why they decided to spec their module at 0.1% and not 1% as they did for lesser-powered modules? Wouldn't it have been better, from a marketing perspective, to say we deliver 1600W and not 1400W in 2 ohms? I'd say it would definitely be better.

However, I suspect they found that the necessary cooling requirements would be massive or untenable, at least not attractive enough to specify at that power level. Maybe they also found limitations in the switching power transistors at such high currents (40 amps peak). All in all, I suspect they chose not to spec at 1% due to decreased reliability in their modules.

You (legally) guarantee what's written in the datasheet. At 0.1%, they guarantee the 1400W all day as long as cooling requirements are met, as indicated in their datasheet. At 1600W in 2R, generating 40A peak current? Not so much, and probably that's why they set their overcurrent protection limit at 40A peak. They do not want their modules to operate anywhere near these current levels.

Not fully clear what your intentions are, but if your concern is with Purifi specs, contact them. I think we are agreeing that conditions matter and you want some details.

This thread is about review of one vendor’s amplifier based on the Purifi 9040. We have more appropriate ones that discuss amplifier ratings and regulations. If that is more your concern, then can point you there. As that goes, there are regional differences and enforcement considerations. In the US, enforcement is unlikely and is why ASR does independent testing to help make better purchase decisions.

 

[David_M]

Not fully clear what your intentions are, but if your concern is with Purifi specs, contact them. I think we are agreeing that conditions matter and you want some details.

This thread is about review of one vendor’s amplifier based on the Purifi 9040. We have more appropriate ones that discuss amplifier ratings and regulations. If that is more your concern, then can point you there. As that goes, there are regional differences and enforcement considerations. In the US, enforcement is unlikely and is why ASR does independent testing to help make better purchase decisions.

I have ZERO qualms or complaints about any of the Purifi modules or any of the amps they are used in. I repeat ... ZERO complaints!

My post was intended to clarify statements saying that 1600W in 2R is a Purifi spec, which is clearly not, and for good reason. It's not listed anywhere in their datasheets as a tested spec one should use to drive their modules. As indicated in my earlier post, that kind of drive will trip the OCP circuitry, which is not desirable.

My goal is to prevent users from thinking 1600W is a viable power output from the 9040BA modules. It is not. Purifi does not support that kind of drive. That's all ... just a correction for anyone interested.

 

[Buckeye Amps]

My post was intended to clarify statements saying that 1600W in 2R is a Purifi spec

Nowhere was it implied 1600w is Purifi spec. At least from my reading of what Amir wrote.

 

[David_M]

Nowhere was it implied 1600w is Purifi spec. At least from my reading of what Amir wrote.

I guess he referred to it as headroom over the 1400W spec and was rather excited about it. He simply confused the 1400W 4R max power with the 2R 1600W number from the power curves.

BTW, do you recommend your 9040BA amps for those with inefficient electrostatic speakers, which have capacitive impedances down to 0.5 ohms at 15kHz and beyond? I used to have MartinLogan's Spire series back in the day, and they needed lots of power to sing. Thankfully, my power amp (Bob Carver's Cinema 7400 series) was then able to handle it without shutting down once. His amps shone at delivering huge peak currents into super low impedances.

 

[Buckeye Amps]

I guess he referred to it as headroom over the 1400W spec and was rather excited about it. He simply confused the 1400W 4R max power with the 2R 1600W number from the power curves.

I still don't see what you are referring to. He clearly typed out spec for 2ohm as being 1.4kW on the Max Output test graph where his result was 1.6kW at 2ohm.

Nowhere do I see him referring to 4ohm spec as 1400w? Unless he edited the graphs from me just re-reading them again now.

 

[Mort]

BTW, do you recommend your 9040BA amps for those with inefficient electrostatic speakers, which have capacitive impedances down to 0.5 ohms at 15kHz and beyond?

You are the kind of customer I would prefer buy the competition.

 

[RickS]

Feel I should caution our less technical readers, not to take any datasheet "specs" as absolutes. Not only do conditions matter, but there is also often some wiggle room due to component tolerances, circuit designs and deratings. Protection circuits are rarely as exacting as many may think. Even a simple fuse has variability.

All these things can play into why a measurement may fall shy or exceed a specific number.

 

[David_M]

You are the kind of customer I would prefer buy the competition.

Sorry...I don't get what you mean. You suggest I look elsewhere from Buckeye?

 

[goryu]

BTW, do you recommend your 9040BA amps for those with inefficient electrostatic speakers, which have capacitive impedances down to 0.5 ohms at 15kHz and beyond?

I have a pair of Acoustat 6600's which don't quite dip down that low at higher frequencies but still present a challenging load for most amps. I drive them with the 9040 Purifi monoblocks and have had zero issues. The amount of actual power required at those high frequencies is rather low in any case. Purifi informed me when I asked this question that the 9040 amps are "stable into nearly a dead short"...

 

[jpslittleworld]

I was curious on your graph for power output at 40 HZ you didn't have any of the hypex ncx500 amps.

Would you happen to know what the hypex ncx500 mono was doing at 40 HZ power wise into 4 ohm

 

[welwynnick]

I was curious on your graph for power output at 40 HZ you didn't have any of the hypex ncx500 amps.
Would you happen to know what the hypex ncx500 mono was doing at 40 HZ power wise into 4 ohm

It's only a relatively recent addition to the test schedule, so there are few amps to compare.

Personally, I've long thought the NCx500 doesn't have any shortcomings in any respect.