Apparently, low distortion has been a selling point for longer than we may realize. Here’s a powered loudspeaker from 1930, and no distortion!
stereophilus said 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...It is incredible, is it not, that carefully designed units which do the same thing accomplish it so differently. And even nuttier, they often measure very similarly.
With rare exception, modern amps measure quite well making specs even less useful.
My experience has been that predicting amplifier sound based on a few specs is like judging a car based upon its final drive ratio and its curb weight. You can guess a few things about it, but there will be so much more to learn when you try it out.
I find preamps to sound more different than amps, but this may well be simply a function of my experience.
brodricj said @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.
Specifications have to be understood within the context of the amplifier designer’s goals and the tradeoffs made to achieve those goals. Specs can sometimes provide some insight into an audio product’s sonic performance, but you usually need to understand how a particular spec relates to the total design. For example, Pass Labs’ amp designer Nelson Pass addressed the reason for the X600.5’s lower slew rate here:
"Of course we agree that if we want a fast circuit whose distortion remains low at high frequencies we need to toss current into the Gates. I don’t place as much emphasis on this as you do, but I address it by running more current through the Vas. In the X600.5 the symmetric voltage gain stage will peak out at about 100 mA. We also take advantage of balanced output stages (halving the slew requirement), and last but not least, we bias the amplifiers high.
To answer another question, the X600.5 (monoblock) has 48 devices arranged in 4 groups, each 12 in parallel. Anticipating the next question, we rate the slew rate as 50 V/uS, but I took a look at one on the bench today and saw about 80 V/uS. You can get a sloppy 160 V/uS if there’s no load."
I posted this separately on a new topic but for those of you following this thread…
Okay, warning!! Spoiler alert. This is a rave and I just walked in from Music Room One holding my jaw in place. I am pumped up beyond description so take what you read with a boulder of sand. I have been accused of exaggeration and hyperbole in the past, it shall not end here.
Holy f*ck what has this change from stereo to mono wrought? I went into the first listening session of the BHK monos expecting better separation, possibly better soundstage as is normal with monos of the past. Immediately something was wrong. Center image specificity was all wrong. Spacious to the extreme, the mono part all wrong. I suspected a setup problem, none to be found. I played the Stereophile test disc and one channel’s was out of phase with the other. Ok, production units yes, but testing by hand without procedures and one channel obviously has wires crossed. Curses. Swap polarity on one channel, sit back to listen.
The first cut I put on is one I have heard so many times I rarely play it. But it came up on the iPad and away we went. Jane Monheit singing Alfie from an old Audiophile Voices CD. Wow. The reverb on her voice so obvious and detailed I remained transfixed in the seat. It was real. Not like she was in the room, but like I was in the studio listening to the playback. Weird. Not something I had experienced before. But I could not bring myself to turn on another track. I was transfixed. Near the end I heard something wrong, as if the sound ‘burped’. A glitch in the track? I went back to listen again. At precisely 29 seconds to the end it happened again, only this time it was as clear as day. A punch in! Holy crap. Clearly Monheit’s engineer punched the recorder in to have her fill in a phrase she had flubbed in the original recording. Now, so obvious that I cannot believe I had never heard it, but this time, perhaps my hundredth listen, I could not avoid its obviousness.
My friend Richard from Bit Perfect had sent me a track from the Vienna Philharmonic’s Das Rheingold, Solti conducting, and a DSD remastered copy. Not a Wagner fan, I have been trying my best to learn this track and so I have heard it many times, but I would not have normally chosen it; it was next on my playlist, so away we went. I turn up the volume, the soundstage opens in front of me and for the first time I get it. How could I have not loved this piece from the first listen.? It’s magnificent, and not just because the recording sounds so right, but because the music fills my soul as it never did before. I am in love.
Michael Fremer had sent me a recording of the Nutcracker taken from an album and now playing on my Mac Mini. Again, jaw dropping performance. I can’t leave the room. The surface noise of the record has become completely disembodied from the music, like the first time I heard Harry Pearson’s system and never again, until today. The fairies dance, the world on stage lays before me, separated from the record surface noise in the most natural of ways. The noise is obvious, yet not part of the music. It’s spooky. I am hooked.
The BHK Mono is a parallel BHK stereo. That means internally every tube, transistor, capacitor and resistor is doubled up, working together as one. And this has made some magic none of us would have guessed until we heard it. To suggest the mono is twice as good because it is doubled would be an injustice to my excitement of the moment. Perhaps it is only twice as good in reality and I will come down from my cloud to see this clearly tomorrow. But today, I will go back and listen into the night, confident it would be wrong to say it is only twice as good, when a magnitude is a better description. As good and revolutionary as the BHK Stereo is, an eye and ear opener to anyone able to audition it, the Monos are something to behold and words cannot do it justice.
I am posting this copied from tomorrow’s Paul’s post.
Paul McGowan said . . . I have been accused of exaggeration and hyperbole in the past, it shall not end here.But at times like this, it is needed to express the excitement.
Thanks Elk, it really is something almost exhausting it’s so good. I haven’t heard anything this extraordinary in a long, long time. And I thought I was excited with the stereos!
I hope you’re exaggerating because I’m loving the BHK stereo and two monos are not in the budget, even if I returned the stereo. Still, great for those with the budget (and the room–I don’t really have that either) for the monos.
steve, I sent you a PM. I’d love to hear the new amp.
I’m not too thrilled with PS Audio right now. Looks like I’ll be eating dog food for years to be able afford the mono’s. I’ll name a hernia after Paul, moving these babies
O
stevem2 said I hope you're exaggerating because I'm loving the BHK stereo and two monos are not in the budget, even if I returned the stereo. Still, great for those with the budget (and the room--I don't really have that either) for the monos.Oh,I exaggerate not, but understand. Look, this is nuts. One BHK is expensive, two twice as much. And the stereo was the best amp I had ever listened to in my life!
Of course on the other hand, one (unnamed) amp, designed by Bascom, is than bi-amped Signature 300 monos with room left over!
Just saying.
emailists said steve, I sent you a PM. I'd love to hear the new amp.I’m not too thrilled with PS Audio right now. Looks like I’ll be eating dog food for years to be able afford the mono’s. I’ll name a hernia after Paul, moving these babies
Sorry.
Can we run a BHK stereo amp from a P10 with no problems? What about running a pair of BHK monos from a P10?
Yes and yes. I just ran a pair of monos from one P10 and it worked flawlessly. It also sounded amazing, stunning really. I have yet to spend the time to experiment if it would be better running a separate P10 with each, but for now I haven’t the room nor the inclination because it sounded so damn good I don’t want to mess with it!
You’re killing me Paul. Monos still aren’t going to happen though. I’d also have to get new cables for a mono set-up (so add a couple grand at least, maybe more, for that, and maybe new furniture to hold the amps). Also, my listening room is small, which limits how much soundstage I can get anyway–if the speakers weren’t almost against the wall they would be near-field. (If you can’t tell I’m trying to convince myself the benefits would be limited in my case.) Then there’s the usually understanding spousal unit to consider. Maybe I’ll win the lottery. And get a new house to go with the new amps.
emailists said steve, I sent you a PM. I'd love to hear the new amp.I PM'd you back with contact info.
Paul McGowan said Yes and yes. I just ran a pair of monos from one P10 and it worked flawlessly. It also sounded amazing, stunning really. I have yet to spend the time to experiment if it would be better running a separate P10 with each, but for now I haven't the room nor the inclination because it sounded so damn good I don't want to mess with it!Glad to hear one P10 worked well with a pair on monos. That is what I was thinking of doing (whenever my beta monoblocks arrive).
At this point I also have all my other equipment plugged into the P10 along with my current amplifier (Musical Fidelity Nu-Vista 300). Should I be thinking about a second P10, one for the monoblocks and one everything else? Particularly since I have two dedicated 20 amp lines in my room.
I would connect the monos to a single P10 on one circuit, and get a P5 for the front end components on the second circuit.
That is certainly an option, particularly since I have a P5 in my other room where I have my big-screen TV. I guess I could always move that P5 once I get the monoblocks. I have been used to excellent picture quality with the P5 in my family room. Tough choices…
Get a P3 for the video room…
Thanks, good suggestion. After springing for the monoblocks, that is the most cost effective option. 