Buckeye 3 Channel Purifi Amp Review

[DonH56]

That assumes the distortion is even audible. And that’s why the “pleasing even order distortion” of tube amps (or any other component) is a red herring.

At some point it is always audible, but near clipping, so either you need a bigger (or better) amp or to turn down the volume. A long time ago I posted some test tones with varying amounts of distortion. For a single tone, 1% (-40 dB) was detectable by most folk, but it could take several percent using multitones. IMD was detectable at a somewhat lower level, perhaps 0.5%, but still... Almost nobody (may have been nobody, it was a while back and I do not recall) could detect 0.1% (-60 dB) HD though now and then someone would just break the error margin for IMD. This was through earphones or speakers which added their own distortion but still anything below -80 dB (0.01%) seems unlikely to cause problems. Always possible I and the other people who tried it have ears of clay, of course, that is the usual reaction (your hearing/DAC/speakers/whatever aren't "resolving" enough).

 

[pma]

0.1% H2 of 1kHz sine wave is audible with good headphones but the necessary condition is a proper volume level. It must be set below the point where the intrinsic ear nonlinear distortion prevails. Then, it is audible in the abx test.

 

[Billy Budapest]

At some point it is always audible, but near clipping,

I agree with that, but I am assuming “normal” listening levels where peaks do not go into clipping. I also think it’s far more likely that speaker drivers (especially at bass frequencies) will begin to distort at output levels lower than where the distortion associated with the amplifier becomes audible.

 

[Billy Budapest]

0.1% H2 of 1kHz sine wave is audible with good headphones but the necessary condition is a proper volume level. It must be set below the point where the intrinsic ear nonlinear distortion prevails. Then, it is audible in the abx test.

Another caveat—I am talking about audibility of distortion of speaker amplifiers. Headphones and headphone amps are a whole other world.

 

[DonH56]

I agree with that, but I am assuming “normal” listening levels where peaks do not go into clipping. I also think it’s far more likely that speaker drivers (especially at bass frequencies) will begin to distort at output levels lower than where the distortion associated with the amplifier becomes audible.

Agree except it depends upon the amplifier. A lot of AVRs only put out 100 W or less driving even just the front three, and with so many low-sensitivity speakers around clipping may be more common than I think (not something I have thought much about, though). I ditched a near-TOTL Sony AVR a few years ago because it was obviously clipping driving my Maggies, then found out in a review that the output dropped from rated 100+ W/ch to about 50 W/ch with three channels driven and 35 W/ch (!) if all five were driven, all into 8 ohms. It did not like my 4-ohm Maggies. I do not listen all that loudly, usually 65~70 dB or so at the MLP. It is doing OK upstairs driving somewhat more sensitive smaller Revels.

 

[Urvile]

Agree except it depends upon the amplifier. A lot of AVRs only put out 100 W or less driving even just the front three, and with so many low-sensitivity speakers around clipping may be more common than I think.

I whole heartedly agree -- I also think that manufactures are... less than honest? speaker manufactures about the power needs of their speakers, which compounds the problem. You have to look at recommended power range / Minimum Impedance / Sensitivity, to guide you to a realistic power need. And AVR manufactures who only give power ratings with one speaker driven at 8 Ohms..

 

[Feyire]

And the culprit is...

View attachment 263237

The binding post connection tab.

Unknown to @Buckeye Amps when he bought the binding posts, the tab is primarily made of steel. Steel is a relatively poor conductor and like a loose or oxidized connection can cause distortion. As with some others, I thought the culprit was the input board, but fortunately it was not. Honorable mention goes to @pma. Within his first few posts in this thread, he mentioned problems with ferrous materials in the signal path. We just had to find it.

Fantastic investigative work by all involved .

@Buckeye Amps , I'd perhaps suggest getting some small neodymium magnets, which you can use to easily verify whether or not any of the other materials used where the amplified audio signal passes through, is ferromagnetic or not. You'd be surprised for example, how common it is for the nuts on cheap bindings posts to just be gold covered steel. The same goes for a lot of speaker cable terminations - possible sources of added distortions everywhere!

As I've often shared in these forums, any ferromagnetic material in the amplified audio signal path will cause distortions, and these increase significantly with higher frequency due to hysteresis. This thread is a textbook example with empirical evidence.

If it was for a random guy saying that the binding post would make a difference lots of people here would put him in the snake oil territory.

That's very true. I'm glad that various professionals were here to assist in the diagnosis and also provide the before and after measurements.

 

[charlielaub]

Why use FASTONs at all? How about soldering the wires on to a binding post meant for that sort of connection? Like this:

 

[kevinsullivan]

Fantastic investigative work by all involved .

@Buckeye Amps , I'd perhaps suggest getting some small neodymium magnets, which you can use to easily verify whether or not any of the other materials used where the amplified audio signal passes through, is ferromagnetic or not. You'd be surprised for example, how common it is for the nuts on cheap bindings posts to just be gold covered steel. The same goes for a lot of speaker cable terminations - possible sources of added distortions everywhere!

As I've often shared in these forums, any ferromagnetic material in the amplified audio signal path will cause distortions, and these increase significantly with higher frequency due to hysteresis. This thread is a textbook example with empirical evidence.


That's very true. I'm glad that various professionals were here to assist in the diagnosis and also provide the before and after measurements.

It's great news if that's the correct and final diagnosis. A few pennies worth of parts to drop in sure beats having to manufacture new boards. In the end it will have been a scary but ultimately good lesson on the need for up-front assured adequacy of testing procedures. The magnet test is also a great and cheap solution to fix the gap in testing that seems to have produced this issue. Good news for Buckeye Amps, which also showed throughout a commitment to quality, transparency, and customer support and satisfaction. A great little engineering story to tell grandkids! (Phew!)

 

[Too Many Notes]

Why use FASTONs at all? How about soldering the wires on to a binding post meant for that sort of connection? Like this:

I am learning as I go here, so newbie question... Do fastons not make it easier for the end user to swap out a bad module for a replacement themselves, as opposed to needing to ship the unit back to Buckeye for repair? Personally, I have zero interest in learning how to solder. One of the reasons I went with Buckeye Amps is because these amps seem easier to self-service.

 

[Buckeye Amps]

I am learning as I go here, so newbie question... Do fastons not make it easier for the end user to swap out a bad module for a replacement themselves, as opposed to needing to ship the unit back to Buckeye for repair? Personally, I have zero interest in learning how to solder. One of the reasons I went with Buckeye Amps is because these amps seem easier to self-service.

This was one of the main reasons when I first set out designing the lineup back in 2020 I made sure no soldering was involved: the ability for the end user to either “repair/replace” parts easily if necessary. Along with the ability to upgrade if wanted (such as to a Rack case, etc) without needing to send back to me.

The Fastons are a great, secure connection. Closing in on 1000 total sales orders and never had one slip off during shipment or use. Aside from the steel tab issue, their performance is no different from soldering.

 

[restorer-john]

Closing in on 1000 total sales orders

What an awesome achievement. Congratulations.

 

[Buckeye Amps]

What an awesome achievement. Congratulations.

Thank you.

This never would have been possible without this community from the start. So a huge thank you to the ASR community.

 

[RickS]

This was one of the main reasons when I first set out designing the lineup back in 2020 I made sure no soldering was involved: the ability for the end user to either “repair/replace” parts easily if necessary. Along with the ability to upgrade if wanted (such as to a Rack case, etc) without needing to send back to me.

The Fastons are a great, secure connection. Closing in on 1000 total sales orders and never had one slip off during shipment or use. Aside from the steel tab issue, their performance is no different from soldering.

Can add a bit more about the Fastons:

1. I bypassed the Faston by soldering to the binding post tab and it does not fix the distortion issue.
2. They are more consistent than soldering. Most notably, soldering to a large metal mass like the binding post can result in cold solder joints or solder potentially spreading on to threads and making it difficult to replace a binding post.
3. Since it does take a good bit of heat to solder to the binding post, you can also melt the wire’s insulation or the plastic insulating washer. Have done both with the bigger posts so am speaking from experience.

Even if you are creating a high performing amp (like Hypex Nilai), you can see that good connections can be made without needing to solder. @Buckeye Amps use of Fastons is just like many manufacturers do inside speakers and other electrical connections that need to be reliable.

 

[Doodski]

Can add a bit more about the Fastons:

They are more consistent than soldering. Most notably, soldering to a large metal mass like the binding post can result in cold solder joints or solder potentially spreading on to threads and making it difficult to replace a binding post.

I've diagnosed and confirmed the repair on heavy solder joints from the factory(s) that where both in the power supply and at the binding post(s). The joints looked OK but the integrity of the joint(s) was poor and not conducting well. It's the nature of that beast.

Since it does take a good bit of heat to solder to the binding post, you can also melt insulation or the plastic insulating washer. Have done both with the bigger posts so am speaking from experience.

DittO. When I was servicing at component level I had 4 soldering irons. From SMD, through-hole PCBs, heavy gauge copper conductor and heavy PCBs that required some higher wattage irons. Trying to fake out a operation with a improper iron is not being effective.

 

[jhaider]

Which also means none of those who chose the speakON upgrade option are affected.

I’m still surprised that your clientele would deign to mess with lowly binding posts when you provide a much better option.

Not wanting to modify stuff just to upgrade to Speakon is one thing. But when something comes to you with the better in every meaningful way option, why willfully go the other way?

(Not that the difference, or your “distortion issue,” was ever an audible concern - though it’s good you fixed it when made aware of it. But still, better with no real downside is still basically always better.)

 

[kevinsullivan]

It's great news if that's the correct and final diagnosis. A few pennies worth of parts to drop in sure beats having to manufacture new boards. In the end it will have been a scary but ultimately good lesson on the need for up-front assured adequacy of testing procedures. The magnet test is also a great and cheap solution to fix the gap in testing that seems to have produced this issue. Good news for Buckeye Amps, which also showed throughout a commitment to quality, transparency, and customer support and satisfaction. A great little engineering story to tell grandkids! (Phew!)

Also, as an outsider, but a technical person, I'm impressed at how such a small flaw in the signal path showed up so clearly in the tests. Seeing this deepened my confidence in the proposition that this amp really is ultra-clean. Otherwise it'd show up in testing--as it did here. Pretty cool.

 

[restorer-john]

Not wanting to modify stuff just to upgrade to Speakon is one thing. But when something comes to you with the better in every meaningful way option, why willfully go the other way?

Once a few 'audiophile' speaker brands start putting them on their speaker terminal plates, others will follow suit and it could be the end of the 4mm banana on amps/speakers.

Speakons also force audiophiles to use sensible gauge cables instead of python-sized wire.

 

[JRS]

There appears to be several or more peeps looking for a class D amp with big VU meters. A common request although finding suitable big VU meters is apparently not so easy.

Wish this weren't so busy: https://www.ebay.com/itm/2558860344...6PEkGGTP1momI97HGWUe|ampid:PL_CLK|clp:2047675

 

[restorer-john]

If you want VU meters, buy something like this (pics below about $20 from China) to play with. You can easily build it into a box or even an amplifier, the driver circuitry PCB is prebuilt, comes with all the wires and the little 'vu' meters are very cute. They are LED backlit with adjustable brightness and meter range control.

It doesn't tell you anything really useful, but they sure look cool.

No afilliation:

https://www.aliexpress.com/item/1005002032529748.html?spm=a2g0o.order_list.order_list_main.136.4b571802UCXfIt