The website says: “The BHK Signature 600 Mono Amplifier is unique in all the world. It is the only fully linear power amplifier of this size that is fully balanced from input to output.“
That’s a big claim, and it doesn’t mention N and P’s at all. What is fully linear, other than gain with minimal distortion? My dealer sells equally or more powerful amplifiers that I’ve heard that measure extraordinarily well, the Soulution 701 and Naim Statement. They are a lot more expensive than BHK600, but the Chord Ultima mono are around the same price, more powerful and measure extremely well.
The claim made strikes me as one that could easily attract derision and disbelief in equal measure.
A little research shows that Bascom King also used this idea in a headphone amplifier, where it is described thus: "The King’s circuitry is very different from the typical complementary output topology; it uses the same polarity N-channel MOSFET outputs as these are more alike and complementary than N- and P-channel MOSFETs. Just before the output stage is a two-stage differential amplifier using a dual-triode tube for the input stage followed by a P-channel MOSFET differential driver stage. "
Mike Creek sold his original amplifier business to a speaker manufacturer and set up a new business, Creek Audio Ltd, in 1993. It is still in business. He employed Alexander Nikitin as his Chief Engineer, he remained with Creek for 10 years.
As explained in the above article, Nikitin’s N-channel design was made into the Creek 4330 amplifier, which was a big success, being voted ‘Budget Component of the Year’ by Stereophile in 1998. A larger version, the 5350 SE, won the 2000/2001 Stereophile Component of the Year Award. This was quite something for a small North London company. The Stereophile reviewer called it revolutionary and bought one.
At this time Mike Creek bought EPOS, makers of brilliant speakers, I had a pair of EPOS ES14 for many years, which is when I became aware of Creek, although Creek are based only a few miles from me.
So it certainly seems an uncommon design, but it has been used very successfully in the past. Mike Creek is still running the business and his current offering apparently uses a similar MOSFET design.
Mr Nikitin moved on to another area of industrial electronics. Mike Creek seems to have taken credit for these highly regarded designs, but then his name was on the tin.
Bascom King seems to have taken this design to a whole new level of power. Creek was aimed at the budget market, the 5350SE is RCA solid state and looks like a typical UK integrated amp, but was a true giant killer. The output amp design does not appear to have been patented, so I wonder why if it is so good, no one else seems to have used it.
10 years ago I owned Constellation Centaur monoblocks, topology N-channel MOSFETs*. (*paragraph 6) (Bascom King was one of the top team signed up in the design of the Constellation amplifiers)
Is that the case? When I was looking for a good amplifier for Harbeth I tried a Plinius P10 for a few months, as a fried had an SB-301 for years. I found it incredibly punchy and detailed, a little too dry for my tastes. I went back to using Quad.
They were better known for making A - A/B hybrids, but were big, very heavy and ran incredibly hot, hence you could switch off the Class A if preferred. Most people did as they sounded almost and possibly as good in Class A/B and consumed half the power.
It seems that many amplifier designers lock into a certain way of doing things, that BHK locked into these N-channel MOSFET for PS Audio, Audeze and Constellation (thanks @Dirk), Peter Walker with current dumping (also not his original concept), Chord with their high frequency power supplies (because that’s what John Franks did in his previous avionics life), Bruno Putzeys made Class D work after Clive Sinclair didn’t. Even my own Devialet can rightly be accused of being a digital version of Quad’s current dumper, but it’s taken the idea to a whole new level using telecoms tech (because it was designed by someone at Nortel).
I suppose it’s taking a workable idea, sometimes discarded, sometimes successful and forgotten, and pushing it to the limit.
It’s very healthy, very creative, the only downside is that everyone thinks their approach is the best! Which of course they all are!
I’ve no doubt the BHK600 are magnificent (unless you have a bad back). If you look around in that stratospheric level, they also appear to offer excellent value.
-I received my BHK 600s this week and have been enjoying them ever since. Did the 24 hour tube burn in as recommended. They replaced my BHK 300s which have served me faithfully for many years now. I use a full suite of PSA gear in my system and the amps are hooked up with balanced interconnects. The amps sounded good right out of the box but they are definitely getting better over time. First thing I noticed was a dramatic increase in the spaciousness of the soundstage. Side and back wall reflections within the recording venue are now more apparent and provide a very realistic sense of the space itself. This was accompanied by a palpable sense of air surrounding individuals and instruments within that soundstage leading to a more 3D experience of the performance. Then came a newfound sense of ease to the sound when playing dense orchestrations at higher volumes. Next was the explosiveness of transient attacks and the tautness of bass response from my speakers. All traces of overhang are now gone. Finally, there is a level of clarity to the overall presentation which is noticeably better than with the BHK 300s. I would not call it etched but rather low level details being heard for perhaps the first time that add a sense of reality to the presentation. Kind of like what you experience when you first see a movie displayed on a 4k screen. When all of these improvements are added up, the BHK 600s represent a very significant upgrade to my system.
-A few things to note: The BHK 600s have a switch on the back which allows you to choose between 2 different levels of output gain. PSA recommends using the lower setting. I may end of there but it does require some getting used to because it makes the output of the BHK 600s lower than the fixed output of the BHK 300s, requiring you to turn up the volume control on your preamp to achieve equivalent loudness levels from your speakers. I am using a 5 number higher level on my BHK Preamp to provide a close approximation to what I was used to with the BHK 300s. Then there is the heat they generate. These things must spend a good deal of time in Class A because even without music playing, when the amps are powered up, the heat sinks get very warm. Finally, if you remove the cover over the tubes and take a look at the components inside, you will see a very noticeable upgrade in parts quality including the tube sockets which are now very tight and secure. I’m sure this flows through to the rest of the components used to build these babies and it looks to me like the idea that no expense was spared in their construction is far more than marketing hype.
-When you take into consideration the extremely generous trade-in program PSA offers on these amps, especially when you trade-in your BHK 300s, the value for dollar is extraordinary in my opinion. Congratulations to Bascom King for leaving behind this crowning jewel on his legacy and for PSA for all of their hard work and dedication to make it possible.
Thank you for the comprehensive overview and assessment of the BHK-M600 monoblocks. I should be receiving my pair within the next couple of days and look forward to having similar results. I will be replacing a Luxman M900u stereo amp. The new amps will be driving a pair of Magico A5’s. The Luxman’s paired very nicely with The Magico’s, in terms of soundstage& Imaging, but I felt it lacked a little bit in terms of impact & dynamics. The Luxman’s shortcomings should be resolved by the 600’s.
I’ll let you know how things progress following the break-in period.
Nice report. If good ears listen alike, it seems we have come to similar conclusions…spacious, deep, detailed, effortless. More than an improved BHK 300. A different and better beast. I did report to PSA exactly what you have seen with the 600’s gain structure. I also have too increase the BHK pre by about 5 steps to get the same output as the 300’s. Not a problem but I’m curious.
A few more things I can report. The BHK 600s consume app. 130 watts of power each in Idle mode and 297 watts in Play mode. Of course, power consumption will go up when music is playing but with my relatively efficient speakers, I find these behemoths are just loafing most of the time so they really don’t demand a whole lot of power above and beyond their resting level. If your speakers present a difficult load and are relatively inefficient, your mileage will vary. I have mine plugged into a pair of P-20s on dedicated 20amp lines, along with my other components, and total watts consumed averages around 500 on each, so plenty of power available when there is a demand for it. One thing I would caution when reading the owner’s manual: the pictures showing how to change the tubes are very well done but I was taught that whenever you handle vacuum tubes, you should always wear gloves to avoid leaving behind any oil on the glass bottles which can cause spot heating issues.
Hey guys, I tried to edit my initial review post so it would show separate paragraphs but when I resubmitted it, the thing is totally messed up and some of my original post has been lost. Any suggestions on how to fix this problem?
In the upper right you should see a orange pencil with a number. When clicked on this gives you access to your post’s history. You can choose an earlier version if you would like.
The odd looking formatting occurs when one adds a tab or multiple spaces before text. Just delete the spaces before the odd looking format and it should go away.
OK. Found another way to edit the text which didn’t cause it to go haywire. Still have no idea what the problem was but at least all of the text is back.
By the way, you can get a carriage return/new line by hitting “enter.” Unlike other text editors, such as on Facebook, you get a new line without sending the post.
I don’t think the hot spots on the glass of a tube would present any problems to the internals of the tube, but it could collect dust easier and then cause the tube to get too hot.
Did you compare the sound quality of the low with the high gain setting? Such a much higher need of preamp level might be difficult to achieve in some setups, if even the PSA solution of pre/power amp in a recommended setting (low), driving efficient speakers needs such extreme preamp levels with possibly little preamp level headroom left then?
I did compare the sound quality with the amp gain setting on low and BHK preamp gain increased vs amp gain setting on high and preamp gain lowered. Frankly, I couldn’t hear a difference once the overall output levels were matched. I did discuss this issue with PSA and they told me that they feel the BHK preamp sounds its best when used in the middle of its volume range, so wanted to give people a way to increase their BHK preamp output level if they wanted to. My biggest concern with this approach was the potential to hear more tube noise, especially when using a phono preamp, when the preamp gain was run at a higher level, so I went back and forth multiple times to see if that would be the case. As I said before, I couldn’t hear any difference between the two approaches, including listening with my ear close to the tweeter where tube noise would be most apparent. Since everyone’s system is unique, I think it would be best to make the comparison yourself to see if one approach sounds better than the other. Obviously, if you have to run your preamp at a very high gain level to compensate for the lower gain level on the BHK 600 amps, you might lose some headroom in the process, but I believe the difference between the two level settings on the amps is app. 5 dB, which is not going to push a preamp into clipping unless it is already running close to wide open. In my system, the average level setting on my BHK preamp was 35 and now I run it at 40, out of a possible max level of 100, so really not a huge difference.