Thanks Paul, email sent.
Paul, any more information you’re ready to share on the early adopter program for the stereo version?
We will have an unspecified number of BHKs available to ship in April for beta. The deal will be this: full production finished units. They will come at an early adopter/beta price directly from us to a limited number of invited people who are on our list. Each person will be asked several things in exchange for a somewhat lower price: a written honest review, and cooperation of working with us if there are problems that require changes. In other words, you will be asked to be understanding. If the amp’s doing something funny we don’t like, we will ask you to return it so we can look at it. We will, of course, pay all associated costs with shipping. But, for example, you may be asked to pack the thing up and shlep it somewhere. And then we need the written evaluation. In exchange you’ll get it at a reduced price.
I haven’t any more solid details than that.
Looks like the monoblocks will be more suitable for speakers with “funny” impedance, like Martin Logan. Not that I most listen to whistles with overetones, but when the impedance gradually drops to 0.5 Ohm, you have to be careful with choosing a proper amp… However, $15,000 is quite steep…
Euro is very close to dollar now. So, $15,000 will translate to around €20,000 for the customers in EU 
Alekz said Euro is very close to dollar now. So, $15,000 will translate to around €20,000 for the customers in EUIf it turns out to be a world-class product it will be a bargain at that price point....
I can’t imagine it being better than my Halcro dm88 mono blocks, but I’m keen to make the comparison.
Are any BHK-beta units going out into 240 volt land? I assume you’re doing a 240 volt Export variant of the amp and not a universal voltage to keep the International distributors happy?
brodricj saidMarketing is something I'm not good at ;) PSAudio is expected to deliver world-class products, but I'm not sure if it's expected to be in that price range.Alekz said Euro is very close to dollar now. So, $15,000 will translate to around €20,000 for the customers in EUIf it turns out to be a world-class product it will be a bargain at that price point…
This is what I’ve just found (NL prices):
PassLabs x350.8 14,500€
PassLabs x600.8 27,900€ (pair)
PassLabs x60.8 13,900€ (pair)
PassLabs x100.8 20,500€ (pair)
PassLabs x160.8 27.900€ (pair)
What are the other direct competitors?
@Alekz I’m curious why you mentioned those PassLabs amps. I know they are recognized as a high-end brand, and they review well, but from the numbers I’ve seen they don’t measure as well as the reviews suggest. I would hope the BHK monos measure better than anything PassLabs. There are so many amps that the BHK is competing with, e.g. Krell Solo 375/575 (the new Class A iBias amps). The Krell also reviews well, but the performance numbers measure rather ordinary as well. If recall correctly, Paul mentioned a while back he is aiming for the best of the best with this amp, putting it north of PassLabs and Krell performance.
For the BHK to be world-class best-of-the-best the main numbers I’d be looking for are slew rate in the order of 100V/us, and THD @1 kHz < -140dB at full output power. I’d also hope to see the BHK with a very solid set of amp protection measures, e.g. short-circuit proof, over current limiting, protected against input overloads, if a continuous DC offset appears on the output, etc.
@scotte_1, for as much as I admire a well engineered and measuring product, it won’t guarantee something sounds better than something else. I don’t know how the Pass X250.8 measures in comparison to the X250.5, but the X250.5 is one of a very small handful of the best amps I’ve ever heard.
The marketing people, and some (if not many) customers, love good numbers…
For the numbers that are of particular interest to me:
PassLabs x250.8 : 1% distortion @ full power @ 1kHz, slew rate 50V/us
Krell Duo 300 : 0.045% distortion @ full power @ 1kHz, slew rate 40V/us.
Halcro dm88 (my current reference amp) : 0.0009% distortion @full power @ 1 kHz, slew rate 100V/us.
Whilst the Krell and PassLabs review well their performance numbers don’t come anywhere close to something like a Halcro. I hope the numbers for the BHK fall closer to the Halcro than the PassLabs or Krell.
Halcro is an interesting product. The amps were specifically, and expressly, designed to measure with the lowest possible distortion. This begs the question whether they sound good because they measure well, or incidentally sound good.
While Halcro amps sound very nice, other amps with less impressive book specs sound great also.
There appears to be some correlation between specs and sound, there are other things going on as well. Perhaps things we have not yet learned to measure. 
According to some high end designers, if a product sounds superb but doesn’t measure well then maybe we are measuring the wrong things.
With the PassLabs amp spec @ 1% distortion you are hearing an aberration of the input signal. These amps review well, but you are hearing an interpretation of the input. With the Halcro @ 0.001% distortion you are not. They both sound good, but obviously for different reasons to different people. I would not buy a PassLabs amp simply because they do not measure well. But I would still contemplate buying the BHK even if it didn’t measure so good simply because of my loyalty to the brand.
The first transistor amps measured perfect, but sounded awful 
1% distortion at full power is, actually, nothing. Usually tube amps have higher distortion, but mostly even harmonics. Transistor amps have lower distortion, but mostly odd harmonics. So this parameter will not tell you much. And if you use your amp at full power, probably it’s not powerful enough and you have to move one step up. Halcros tend to sound overly analytical, so it’s up to the rest of the system.
Then the system synergy. For example, Magnepans sound better with Classe and Logans with PassLabs (I checked the lower segment of them, not the monoblocks).
About the specs, check this post http://www.psaudio.com/forum/new-power-and-pre-amp-forum/checking-in/page-3/#p39751 about Class A wattage. Based on this parameter I wouldn’t bother with BHK amp 
brodricj said With the PassLabs amp spec @ 1% distortion you are hearing an aberration of the input signal. These amps review well, but you are hearing an interpretation of the input.On paper yes, but not in the real world. First, this is as full power, you do not listen to an amp at full power and retain the ability to hear anything - distorted or not.
Second, 1% distortion and below is regularly considered inaudible - especially if the distribution and relationship of harmonics is related to the signal, which is typical.
And what are we going to listen to them on which will precisely reveal these differences? Not our 5% distortion speakers.
We are listening to an interpretation of the input with every component we buy. The trick is to buy those with an interpretation we like. Thus Pass amps review well; they sound good. As do Halcro, although it is a different sound.
Buy and enjoy the one you prefer.
Alekz said1% distortion at full power is, actually, nothing. Usually tube amps have higher distortion, but mostly even harmonics. Transistor amps have lower distortion, but mostly odd harmonics. So this parameter will not tell you much. And if you use your amp at full power, probably it’s not powerful enough and you have to move one step up. Halcros tend to sound overly analytical, so it’s up to the rest of the system.
1% distortion might be nothing, but it’s still 1000 times more distortion than the Halcro.
Halcro power amps were described by some as being overly analytical, simply because they impose virtually no sonic signature on the input signal at all. This would be a criticism of the Halcro if what you were seeking was a device which adulterated the input to make it more sonically pleasing. But it would be high praise if what you were seeking was an unadulterated representation of the input. Which is why the PassLabs and the Halcro both get good reviews, they simply sound good despite measuring very differently.
Elk saidHa! I typed it ... and then deleted to not to provoke another side discussionAnd what are we going to listen to them on which will precisely reveal these differences? Not our 5% distortion speakers.
Speaking of Pass Labs “distortions”:. x350.5 (350W stereo) http://www.audioholics.com/amplifier-reviews/x350.5-review/x350.5-measurements
"In fact, the measured distortion spectra were excellent for the entire Class A operation of this amplifier (up to 40 watts peak). You can see how down in the mud the distortion components are (-96dB for the 3rd harmonic below the fundamental).
At 420 watts, 8 ohms (which is above the 350wpc power rating) the X350.5 displayed a not so pretty distortion harmonic spectrum. I observed the 3rd harmonic (35.251 + 37.57) dBV being 72.8dB down from the fundamental. This unusually high distortion product is likely somewhat a deliberate result of employing minimal feedback in this amplifier design.
Although the amp was showing 1% distortion driven at full power into 4 ohms, the analog waveform was still very smooth and unclipped."
I wouldn’t call -72.8dB from the fundamental at x1.2 max power high
The measurements show: 0.1% @372W and 1% @405W.
Halcro dm88 (200W monoblocks): http://www.stereophile.com/how-is-ted-coding-the-fpgaent/halcro-dm88-reference-monoblock-power-amplifier-measurements
“The measured output power at 1% THD+N was greater than specified, at 295W into 8 ohms (24.7dBW) and 525W into 4 ohms (24.2dBW). The dm88 is less happy driving 2 ohms, however, clipping at 266W (18.2dBW).”
Halcro indeed shows a bit better measurements but at 4 times higher price tag. What does it tell us? Apart from that most likely Halcro will not like Martin Logan speakers? Nothing.
I recently had the pleasure of trying out 4 very different but similarly priced amplifiers in my system. They included my own Audio Research ref 150, a Vitus RI-100, a Pass Labs X250.5 and a pair of MolaMola Kaluga monoblocs.
It was fascinating to hear how different each amplifier could make my system sound. There was nothing in the measurements that would tell you that the Audio Research threw the biggest, deepest soundstage of the bunch… Or, that despite a frequency response that extends well beyond 50kHz, that it was less “airy” sounding than some of the competition. The measurements also did nothing to tell me how sensitive to cabling (particularly power cords) the Kalugas were.
If you are going to buy a new amplifier, auditioning on your own system is a must. Not only is it fun, but educational as well.
brodricj said Halcro power amps were described by some as being overly analytical, simply because they impose virtually no sonic signature on the input signal at all. This would be a criticism of the Halcro if what you were seeking was a device which adulterated the input to make it more sonically pleasing. But it would be high praise if what you were seeking was an unadulterated representation of the input. Which is why the PassLabs and the Halcro both get good reviews, they simply sound good despite measuring very differently.I know this is the accepted tagline of amplifiers we consider neutral or overly analytical; that they present 'no sonic signature' and thus it explains their analytical sound, but I would argue that is not necessarily true. In fact, I would go so far as to say this may be somewhat inaccurate. To be clear, I am not referring to the Halcro, an amplifier I have never heard, but greatly respect as a marvelous triumph of engineering. No, this is in general with regards to sonic stamps of equipment.
I do not believe it is possible to make an amplification device without a sonic signature. Certainly not a power amplifier, perhaps THE most difficult piece to get right in the entire chain. If you look at what is going on inside and what is being demanded of the device, I would suggest it is close to impossible to have it not affect the way the speaker sounds. There are simply too many variables. For example, the Halcro had remarkable specs: no measurable distortion, high damping factor etc. But at what cost? It could not have achieved those things without benefit of complex circuitry and that circuitry places its stamp on the sound.
In my experience you cannot take a power supply and modulate it from 10Hz to 100kHz perfectly and without any deviation from the input circuitry, which is the task assigned to the most under appreciated piece of equipment in the reproduction chain, the power amplifier. That any power amplifier measures ‘perfectly’ and therefore has no impact on the sound it produces when driving a speaker, only suggests to me we haven’t figured out all there is to measure.
I believe there is no amplifying device ever invented that does not place its sonic stamp on the sound. Certainly none I have listened to in the last 40 years.
BHK adding commentary - All of what has been said in this and recent previous posts about measurements good and bad about amplifiers and their sound has some truth in each of the thoughts. My take on this being a design engineer, measurer, and listener is that it is first about the music and how real and engaging it is. There are many attributes about the reality of music reproduction and we all have our individual list of them that are important to us. That said, the BHK Signature amplifiers bring beauty and reality to the music with wonderful detail, delicacy, speed, and space. Will everyone agree that it does that, probably not, but many if not most people will.