Buckeye 3 Channel Purifi Amplifier Review (2nd)

[jimk1963]

It won’t be the 0.5W as the Hypex SMPS will be on standby mode and not off it using Auto or 12v.

One change we hope to make late this year is better control of the SMPS to further bring down idle/standby wattage

Thanks, so I guess that means we're looking at 14 Watts using 12V trigger, like @amper42 measured in Auto mode.

Glad you're looking at making a change - green power saving initiatives are everywhere nowadays, and lowering thermals in cabinets during "off time" is always helpful for equipment longevity.

 

[jimk1963]

I don't think Dylan has a Kill-o-watt to measure watts used by the Buckeye Purifi in different configurations. I asked him for that data previously and it was answered with "a few watts" instead of exact measurements. I use the Purifi with the ADI-2 DAC FS and did not have a trigger. There will always be some power used by any amp in trigger mode as it needs to be waiting for a signal to become active. How much would require a measuring device and a DAC or AVR setup in trigger mode with the Purifi connected.

I would like to see power usage added to ASR reviews. In the case of the Buckeye Purifi the review could report idle power use in "On" mode, "trigger" mode and "Auto". My guess is the power use in trigger mode may be close to leaving the Purifi in "On" mode while idle. The 14W idle power use of the Purifi is significantly lower than the 23W idle power use of the Buckeye NC502MP.

Agree re: power usage, I posted a similar request on another thread, a few "likes" ensued. Power consumption should be added to all electronics under test - whether an amp, an AVR, or just a simple DAC. Two good things would come out of this: (1) consumers would get smarter about how creative (or lazy) various companies are, which drives (2) OEM's would pay more attention to power consumption (including Standby modes) and step up their game.

 

[mdunjic]

I got 2ch version of the exact same power amp from Buckeye based on Purifi Eigentakt modules. Using it in high gain setting, in a biamping config - Buckeye is driving tweeter and midrange, while Audiophonics nCore nc502mp based 2ch power amp is used for bass drivers. The two amps are working perfectly effortlessly and flawlessly together, and sound is always pure and relaxed, regardless of the volume settings. Never had so much (virtually unlimited) of the cleanest power available lol and speakers simply love it

Preamp is Benchmark LA4

DAC is SMSL SU-9n

 

[aphysically]

@Buckeye Amps Everything is still going great! One feedback I do have is the indicator LED is bright enough to cast shadows on the other side of the room. Indicator LED brightness is a personal pet peeve of mine and there's probably others that prefer the opposite. Overall great job!

 

[amper42]

@Buckeye Amps Everything is still going great! One feedback I do have is the indicator LED is bright enough to cast shadows on the other side of the room. Indicator LED brightness is a personal pet peeve of mine and there's probably others that prefer the opposite. Overall great job!

I use a small piece of black electrical tape to partially cover the Buckeye blue power light to match my desired brightness. It works like a charm and I can't detect the tape at a distance.

 

[Buckeye Amps]

Amazon sells light blocking dots that can either completely block the light or dim it by 75-90%

 

[Gruesome]

I got 2ch version of the exact same power amp from Buckeye based on Purifi Eigentakt modules. Using it in high gain setting, in a biamping config - Buckeye is driving tweeter and midrange, while Audiophonics nCore nc502mp based 2ch power amp is used for bass drivers. The two amps are working perfectly effortlessly and flawlessly together, and sound is always pure and relaxed, regardless of the volume settings. Never had so much (virtually unlimited) of the cleanest power available lol and speakers simply love it

Preamp is Benchmark LA4

DAC is SMSL SU-9n

I see lots of room to add more stuff!

 

[Gruesome]

It won’t be the 0.5W as the Hypex SMPS will be on standby mode and not off it using Auto or 12v.

One change we hope to make late this year is better control of the SMPS to further bring down idle/standby wattage

PC power supplies have this feature, with only a low current 5 V (or 12 V? It's a while since I looked) permanently on to provide power for the remote power switch that turns on the rest of the power supply. So it shouldn't be too difficult to have this feature added to a commercial audio power supply.

 

[mdunjic]

I see lots of room to add more stuff!

Indeed!

 

[jimk1963]

It won’t be the 0.5W as the Hypex SMPS will be on standby mode and not off it using Auto or 12v.

One change we hope to make late this year is better control of the SMPS to further bring down idle/standby wattage

A few follow-up questions:

Will the new Micro Audio 2kW SMPS also be used with the Purifi 3-channel design?

Re: the change you’re making for improved standby and idle, are those improvements related to this new SMPS?

The SMPS1200A400 has an SMPS standby pin on J5, appears it isn’t in use. If correct, wondering why? Guessing it would require another circuit for control/timing. Seems it could potentially solve the Auto/12V standby power consumption issue.

 

[Buckeye Amps]

A few follow-up questions:

Will the new Micro Audio 2kW SMPS also be used with the Purifi 3-channel design?

Re: the change you’re making for improved standby and idle, are those improvements related to this new SMPS?

The SMPS1200A400 has an SMPS standby pin on J5, appears it isn’t in use. If correct, wondering why? Guessing it would require another circuit for control/timing. Seems it could potentially solve the Auto/12V standby power consumption issue.

The 2kW will not be for the 3ch Purifi. But there is another version from Micro Audio that will be used.

 

[goryu]

Any updates on the 3 channel NCx500???

 

[Buckeye Amps]

Any updates on the 3 channel NCx500???

Final testing of the prototype will hopefully be done by end of the month and then production units would follow.

 

[mdunjic]

This is a second review of the Buckeye 3-Channel Purifi based balanced class D amplifier. First sample had an issue with its binding posts increasing distortion. It costs US US $1,595.
View attachment 279145
Typical of Buckeye amplifiers, focus on what is inside rather the case which is utilitarian. An indicator nicely shows status of the amplifier (on, fault or overload). Back panel sports a 3-way switch for setting the gain which is very nice to have:

Let's get right into the measurements to see if the issue with distortion is resolved (I ran full suite of tests).

Buckeye Purifi 3 Channel Amplifier Measurements
Let's start with our low gain dashboard:
View attachment 279146
Looking at the spectrum of the FFT we see a large reduction in harmonic distortion compared to the first sample. SINAD as a result improves a bit although it is mostly noise limited. Still, we match the reference design, landing the amp solidly in our top 20 best amplifiers ever measured (out of over 200):
View attachment 279147

You need pro type interface to drive the low gain to full power (as much as 7 volts for 4 ohm). Fortunately high gain hardly brings any penalty:
View attachment 279148

Request was made to show power with reactive loads as opposed to just resistive as is the norm in my reviews (and industry). Using my new PowerCube loadbox, I can do that:

View attachment 279149
Capacitive load doesn't change things but inductive loads it down a bit more. SINAD remains more or less the same so really, nothing of worry.

SNR is the same as before and excellent:

View attachment 279150

Frequency response is flat as always: (should say "NO load impedance dependency"
View attachment 279151

Oh, forgot to mention that I am testing channels 1 and 3. Due to larger distance, crosstalk is even better now (and was incredible before):
View attachment 279152

Multitone shows an improvement of 2 bits:
View attachment 279153

Let's dig into power measurement where we saw the rising distortion before:
View attachment 279154
Performance is far improved. No longer do we have a large hump in mid-power region. There is a small increase that exists but we can ignore it:
View attachment 279155

Power remains as before:
View attachment 279156

View attachment 279157

Here is the warm up behavior:
View attachment 279160

I didn't re-run the on/off pop test. Should be the same as before (which was very good).

Reactive Load Amplifier Power Testing
Let's use our fancy Powercube loadbox to simulate both capacitive and inductive loads ranging from 8 down to 2 ohms (amplifier goes into protection with 1 ohm):
View attachment 279159
(ignore the color differences.) Response is perfect. Regardless of load impedance down to 2 ohm reactive, the amplifier maintains the same output voltage. Can't ask for more.

Conclusions
It is great to see such responsive companies such as Buckeye that take the results of a review and instantly jump on the issue identified to resolve it. And resolve they have. Performance is essentially identical to Purifi reference design. Value added is provided in the form of a 3-gain buffer stage and powerful power supply that allows all three channels to produce near full power when driven simultaneously. Results is one of the cleanest/most transparent multichannel amplifiers you can buy.

I am happy to add the Buckeye Purifi 3-Channel amplifier to my recommended list.

------------
As always, questions, comments, recommendations, etc. are welcome.

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Got 2-ch version of the same from Dylan ... love it so far, no brainer

Paired it (in hi-gain mode of course), for bi-amping, with Audiophonic's nCore based NC502MP 2-ch power amp (Audiophonics is used just for the bass drivers) ... virtually unlimited power reserve per channel, brutal transparency, relaxed sounding at virtually any sound level ... room induced distortion is the only limit for me now ... what else to ask of a pair of more than affordable modern, high-efficiency class D amplifiers? And I am 20yrs Quad 909 sound fan ... which I still own, but not using it at the moment, as it is getting too hot in the summer lol.

 

[mdunjic]

Yes, Purifi is a newer, more advanced design than the original NCore. There's also the next generation Hypex NCoreX / Nilai that should be an improvement over the original NCore. That being said the NCores are still very very good and at this point it's more of 'how far can we perfect it' than actual audible improvements.

Agree ... however, those SINAD / THD+N differences are mainly demonstrated on a high quality test bench, like Amir's. In real life listening, from my personal experience, both sound very good and non-different, to 99.99% of audio lovers ... I have power amps, based on both of them. Just make sure you have high quality pre-amp and DAC upstream

 

[MicroAudio]

A few follow-up questions:

Will the new Micro Audio 2kW SMPS also be used with the Purifi 3-channel design?

Re: the change you’re making for improved standby and idle, are those improvements related to this new SMPS?

The SMPS1200A400 has an SMPS standby pin on J5, appears it isn’t in use. If correct, wondering why? Guessing it would require another circuit for control/timing. Seems it could potentially solve the Auto/12V standby power consumption issue.

Power consumption for the new 2KW & the new 1500W SMPS is less than 0.5W in standby mode.

Standby mode means your amplifier is fully off, and the ON / OFF control is done via the low-current standby switch.

A custom control port will be available for Buckeye to control the SMPS.

Hope that helps

 

[jimk1963]

Power consumption for the new 2KW & the new 1500W SMPS is less than 0.5W in standby mode.

Standby mode means your amplifier is fully off, and the ON / OFF control is done via the low-current standby switch.

A custom control port will be available for Buckeye to control the SMPS.

Hope that helps

Thanks MA, this is good to read. I assume/hope the custom control port will be toggled by the external 12V trigger on the Buckeye side of the design.

 

[emilkoz]

I got 2ch version of the exact same power amp from Buckeye based on Purifi Eigentakt modules. Using it in high gain setting, in a biamping config - Buckeye is driving tweeter and midrange, while Audiophonics nCore nc502mp based 2ch power amp is used for bass drivers. The two amps are working perfectly effortlessly and flawlessly together, and sound is always pure and relaxed, regardless of the volume settings. Never had so much (virtually unlimited) of the cleanest power available lol and speakers simply love it

Preamp is Benchmark LA4

DAC is SMSL SU-9n

I always wondered how these multichannel amps work with the tweeter. The hypex fusion amps had the nice option of 100 w channel. Eigentakt 250w< what will it do to a tweeter performance wise? Is’nt it totally overkill to use all those watts and dollars for the tweeter?

 

[MacCali]

I always wondered how these multichannel amps work with the tweeter. The hypex fusion amps had the nice option of 100 w channel. Eigentakt 250w< what will it do to a tweeter performance wise? Is’nt it totally overkill to use all those watts and dollars for the tweeter?

Not sure what you are getting at, please further explain. Since most speakers have two, three, or more drivers which produce sound.

Generally speaking a person wouldn’t buy a three channel amp and use it as a mono block

 

[Julf]

Not sure what you are getting at, please further explain. Since most speakers have two, three, or more drivers which produce sound.

Generally speaking a person wouldn’t buy a three channel amp and use it as a mono block

I assume @emilkoz is thinking about driving the speaker actively, with a separate amp/channel for each driver - and wondering if 250W for just the tweeter wouldn't be overkill.