The newsletter mentioned a monoblock versions of the poweramp is in the works.

Paul, can you elaborate/ Will it be the same design but delivering more power? If you don’t need the power, would there be any merit in getting the mono’s instead of stereo? Any indication of price and estimated shipment date?

There are monoblocks in the works. They will follow shortly thereafter the launch of the stereo. They will cost the same, $7,500 each. They are identical to the stereo inside, only difference is one less tube, a few different PCBs and a different back panel. They have minimally more power 300 watts instead of 250 into 8 Ohms. This isn’t a power thing. Let’s face it, 300 watts into an 8 Ohm speaker and near twice that into a 4 Ohm is plenty for any situation.

No, the deal is impedance, current, isolation. Instead of 20 MOSFET outputs on the stereo, the mono has twice the number at 40, thus the output impedance is cut in half, the damping factor double. Instead of sharing a power supply between two channels, the beast is dedicated to only the one and for any given output signal, just loafing along with massive current headroom available. Lastly, two power cords, two transformers, the physical isolation of two chassis - all play into achieving a serious step above the stereo single piece.

Thanks for clarifying. I was planning to do a shootout of the new amp against my incumbent Spectral 360 SS Series II monos, but I’ll probably wait for the monos to ship.

Do you have a working prototype validating superior sound quality of the monos?

This question immediately came to my mind as well.

Nope. It’s next on the queue. But I have enough experience in these things to know pretty much how it’s going to respond. If you double the power supply in any power amp the sound improvement is extraordinary.

Engineering are working on getting a pair built for me.

Keep us posted.

Out of my price range, but I’m curious how this would fair against my Decware amp.

Completely different animals, 40 watt tube vs a big Mosfet monster - but the power supply concepts ring true. So it has me curious, even though I’ve not used solid state power amps in 16 years. :slight_smile:

I am looking at the post from Paul regarding the BHK Signature 300 Monoblock amp and find that the number of MOSFETs mentioned per channel was not quite correct. Not to make Paul wrong but in actuality, the stereo channels have 2 phases of 4 up and 4 down for a total of 16 outputs per channel. Therefore the Monoblock version which rearranges the stereo channels to parallel the outputs of their two phases will form one phase of the final two phase bridge circuit. So the Monoblock amp will have a total of 32 MOSFET output devices or two signal phases of 8 up and 8 down.

In your estimation; how much better will the monos sound on a relatively easy to drive speaker? Worth the extra $$$?

So it has even been made yet and my new (stereo) amp is already missing 8 MOSFETs. pulling-hair_gifitwasntme_gif

I think my Classic 250 has 20 MOSFETs per side with similar rated power. Maybe that’s what Paul was thinking of.

How many class-A watts (@ 8 ohms) are the stereo and mono versions anticipated to provide? Any chance of a switch or control to allow the user to choose between a lower or higher class-A bias level for everyday listening versus take-no-prisoners sessions? Thanks

BHK on the subject of bias. The Class A range of the BHK Signature 250 with the bias set as we are setting it so far is actually a bit less than 1W per channel. One thing that I have found with this kind of MOSFET output circuitry over some time is that the sound is surprisingly independent of the actual bias idling current above some lower amount where crossover type distortion is too much. This no doubt will bring up cries of foul, blasphemy, off with his head, and such from some. The proof is in the pudding so to say and the sound of this amp is such that technical thoughts about it’s Class A output power seem inconsequential. The bias setting of the BHK Signature 300 Monoblock will be about double for 4 times the Class A output power.

A point of interest, The standby power consumption of both versions of the amp, with the rear panel power switch on and the front panel button turned off, and thus output stage idling current is going to be somewhat less than the operating power or bias so as to keep everything more warmed up for quick return to optimum sound when the amp is enabled with it’s front panel switch.

To answer the actual question above, there are not any plans at present to offer several operating biases to be selected but that is a doable type of thing if needed.

I can chime in with a little info. Perhaps Bascom can elaborate. First, we will not be able to provide a switch or an easy method of going between stereo and mono. The units will be dedicated and somewhat different inside.

The wattage will be close to the same for both, the mono slightly higher. The current available in the mono will be twice that of the stereo.

As Paul says, the current capability will be about twice that of the stereo channels so that in itself will be a plus for more difficult loads. Further, with the two channels now really separate that will be another sonic plus. Even with easy loads, all of this is going to likely sound better. I have one of the three original prototypes and I am very thrilled with the way that one sounds - and in comparison with the prototypes, the production version is better yet!

I like all PS fans really appreciate having the designers like Bascom and Ted participate in the forums and be able to elucidate why certain design choices were made and their impact on sonics.

i know this may be difficult to quantify, but if I were running the stereo version and high pass filtering from say 50HZ on up, would that negate some of the benefits of going to the monoblocks, since they wouldn’t be driven full range?

I’m looking forward to getting this amp running on my TAD CR1’s.

BHK here. This would depend somewhat on how much strong bass energy below 50 Hz there would be in the material being played. For material with most of the bass energy above 50 Hz, it probably would not make much difference. However, since it has been said “that everything makes a difference” and the stated advantages of the mono version, the pair of BHK Signature 300 amps would still be audibly superior.

Hello BHK,

Regarding bias in the new amps, I agree that the proof is in the performance of the whole package and look forward to hearing the amp. Any chance it will be making music at April’s Axpona? Thanks

We’re not currently planning on attending the Chicago show.

Paul McGowan said We're not currently planning on attending the Chicago show.
Paul, sorry to hear you will not be in Chicago. It was great to see you last year.


Are there plans for an early adopter (beta) program for the monoblocks? If so, how does one go about getting on the list for consideration?

“We’re not currently planning on attending the Chicago show.”

Disappointing, I missed last year. I’d like to run out to Boulder to hear this beast some time, though. Wonder how I can convince the wife that this is a necessity? I’ll have to check the Red Rocks schedule for a show she might like.

DenisD said Paul,

Are there plans for an early adopter (beta) program for the monoblocks? If so, how does one go about getting on the list for consideration?

Yes there are and if anyone is interested in getting an invite, email me personally and I’ll add your name to the list.