I think BHK and or Mr. McGowan would like to reply with an answer as to why Mr Atkinson says that the Signature 300 will work its best with speakers having an impedance of 4 ohms and above.
Also why did the first one go unstable ?
I know alot of very good things were said but you dont end a technical review with that ending if you dont want people to read it…many people just skip to the end for a wrap up…
Lets not go back to a Fremer bashing, listening is subjective…bench testing is not…
BryanEye said
. . . why Mr Atkinson says that the Signature 300 will work its best with speakers having an impedance of 4 ohms and above.
Because, as Mr. Atkinson explains in his Measurements section, he found distortion increased slightly into four ohms and below, a common finding. Given this observation, his perfectly reasonable, objective conclusion is that the amp "will perform at its best with speakers having an impedance of 4 ohms and above.”
The distortion measurements at 4 ohms are still very low. So why does this offhand comment disturb you? Are you seriously concerned you will hear this level of THD? The amp exceeded its power output specs at both 8 ohms and 4 ohms, producing 620W into 4 ohms, and 950W into 2 ohms. Does this bother you? Do you really need more power?
I am also interested Paul’s and Mr. King’s reaction to the instability of the first amp. While, as Mr. Atkinson explains, this is the equivalent of measuring the g-force at which a car rolls over, I am still surprised the amp rolled over.
It bothers me because most modern amps seem to be stable at 4 ish ohms…to me that is an issue…it should be for eveyone.
I don`t want to pretend to hear the THD at that level…or could I ?..but there seems to be more to the story and PSA has gone dark on this issue.
I have followed this forum since my DS purchase and have had these amps on my short list , mostly because of the Mr. King videos and the beta testers reports.
Now not so much unless there is a follow up about this.
It bothers me because most modern amps seem to be stable at 4 ish ohms…to me that is an issue…it should be for eveyone.
I don`t want to pretend to hear the THD at that level…or could I ?..but there seems to be more to the story and PSA has gone dark on this issue.
I have followed this forum since my DS purchase and have had these amps on my short list , mostly because of the Mr. King videos and the beta testers reports.
Now not so much unless there is a follow up about this.
The BHKs, both 250 and monos, are extremely stable at impedances lower than 4Ω - and this is because most speakers dip their impedance as they’re playing. We test the amps for stability down to 1Ω, though I wouldn’t recommend driving 1Ω loudspeakers! The increase in distortion at lower impedances is consistent with the design, which uses lower amounts of feedback to maintain musicality. And the increase would, I suspect, not be audible. To be honest, I have never used the amplifiers at any impedance above 4Ω and I don’t know anyone that has - though I suspect there have been some. The vast majority of today’s loudspeakers are 4Ω. The amp was designed and voiced on 4Ω loudspeakers.
I am sorry if it appears we’ve “gone dark” as that’s not the case from my perspective - though you’re correct - I haven’t chimed in enough to the forums on the issue. I just kind of thought it was a non-issue - and easy mistake I suppose.
As for Atkinson’s instability in the one amp, and not the other. We got the amp back and could not duplicate the problem. Nor have we ever seen the problem. Our chief engineer got on the phone with John and went over exactly what he did to stimulate the instability. It only happened on a AP (Audio Precision) with a weird set of tests specific to John’s routine. We too have the same AP and found that we could, indeed, duplicate that instability using the same test. It happened only in that one amplifier and to this day, remains an edge event - something we’ve not seen again.
We’ve added John’s test to our battery of tests performed on every BHK leaving the building and have yet to see it reappear. So far, we’re chalking it up to the anomaly gods - should it ever show up again - we’ll consider it a trend and dig deeper.
It certainly is nothing any user of the BHK will ever encounter. The amplifier is as solid and stable as a rock.
BryanEye said
It bothers me because most modern amps seem to be stable at 4 ish ohms...to me that is an issue.....it should be for eveyone.
I am glad you are satisfied with Paul's response, but remain astonished that you read the Measurements section to indicate the amp is unstable at 4 ohms or has any issue at 4 ohms. Neither Mr. Atkinson's measurements nor his comments lead to either conclusion. Note, for example, that the preconditioning he always performs was into 8 ohms. And is an attempt to break the amp; no amp will ever be subject to these operating conditions in use.
Paul McGowan said
Our chief engineer got on the phone with John and went over exactly what he did to stimulate the instability. It only happened on a AP (Audio Precision) with a weird set of tests specific to John's routine. We too have the same AP and found that we could, indeed, duplicate that instability using the same test. It happened only in that one amplifier and to this day, remains an edge event - something we've not seen again.
Fascinating and weird. If you are ever able to determine why, please let us know. Your explanation above is already great fun.
We’ve added John’s test to our battery of tests performed on every BHK leaving the building and have yet to see it reappear.
Sorry, Bryan, but this does not answer any of the specific questions I have posed or the reasoning behind your conclusions.
You asserted “listening is subjective….bench testing is not.” Thus, my query as to the objective basis for your statements; they appear directly contrary to the available evidence. My curiosity was piqued.
But there does not seem to be any objective basis for your conclusions - which is perfectly fine; we are all entitled to our various biases, prejudices, inconsistencies of logic, leaps of faith, expressions of unfounded paranoia, and still more. And jumping to conclusions is great exercise.
As an aside, bench testing is as subjective as any other human endeavor. Our decisions as to what to test, why, what we value, and results interpretation are inextricably grounded in beliefs. Audio history alone is replete with examples of measuring both the wrong thing and misinterpreting results. The best we can do is to be consistent in how the test is performed.
BryanEye said
It bothers me because most modern amps seem to be stable at 4 ish ohms...to me that is an issue.....it should be for eveyone.
I am glad you are satisfied with Paul’s response, but remain astonished that you read the Measurements section to indicate the amp is unstable at 4 ohms or has any issue at 4 ohms. Neither Mr. Atkinson’s measurements nor his comments lead to either conclusion. Note, for example, that the preconditioning he always performs was into 8 ohms. And is an attempt to break the amp; no amp will ever be subject to these operating conditions in use.
Paul McGowan said
Our chief engineer got on the phone with John and went over exactly what he did to stimulate the instability. It only happened on a AP (Audio Precision) with a weird set of tests specific to John's routine. We too have the same AP and found that we could, indeed, duplicate that instability using the same test. It happened only in that one amplifier and to this day, remains an edge event - something we've not seen again.
Fascinating and weird. If you are ever able to determine why, please let us know. Your explanation above is already great fun.
We’ve added John’s test to our battery of tests performed on every BHK leaving the building and have yet to see it reappear.
Impressively thorough, you are.
One thing was not mentioned in Mr. Atkinson’s testing. The implication was that the amplifier “broke” under testing. In actuality, a power supply fuse blew which he could have found and replaced. I think it was wrong of him to not find this out and mention it. When the amp went back to PS Audio, replacing the fuse restored it to operation. And on using the amps on 4 Ohm speakers, absolutely no problem even when their impedance dips below 4 Ohms. On the subject of bass not having as much “slam” as others, that is one particular parameter of reproduction. The BHK amps were designed to realistically reproduce music which the great majority of listeners agree that they do in a very convincing manner. You can’t please all the people all the time
A fuse? Really? Odd he did not track this down. He is not afraid to open things up.
On the subject of bass reproduction, is there any reason to believe using the amps in balanced configuration would have any influence in this regard? I expect not, but have been wrong many times before.
Elk said
A fuse? Really? Odd he did not track this down. He is not afraid to open things up
And in fact, if I am interpreting the photo of the amp's rear panel correctly, the fuses are in nice little fuse holders that can be unscrewed without opening the cover -- unlike the DS DAC, for instance. Anyone as knowledgeable about audio as JA should have checked this, particularly when he deliberately stresses the amps (as he himself admits he does in his testing).
Memo to Paul & Co.: please, in future, don’t make us open the case just to change a fuse. Especially when you can’t just take a screwdriver to the bottom. Having to go on this site and locate a video about how to open the case is a bit much. Dampened my enthusiasm for trying aftermarket fuses considerably. Or maybe that was the idea.
magister said
Having to go on this site and locate a video about how to open the case is a bit much.
I just changed the little flat, round lithium battery in my fob for my BMW. I could not figure out how to open the case. It is far from intuitive. I similarly had to turn to YouTube for a how-to video. It is an elegant system once I saw how it works, but sneaky.
Memo to Paul & Co.: please, in future, don’t make us open the case just to change a fuse. Especially when you can’t just take a screwdriver to the bottom. Having to go on this site and locate a video about how to open the case is a bit much. Dampened my enthusiasm for trying aftermarket fuses considerably. Or maybe that was the idea.
After all the headaches our customers have gone through trying to get into the PerfectWave series to change fuses, I made a command decision and set a new policy for the company. All future products shall have outside accessible fuses. That’s now written in law at the company. So you’ll note that the BHK amplifier has all outside accessible fuses, so too will the upcoming products. All of them.
Once in awhile you have to make a big sweeping decision like that.
Funny thing is, when we designed the PerfectWave chassis, the team and I worked hard–really hard–at showing no external hardware. No screws to hold the top cover on. That was a pain in the butt to do, but it looks oh so clean. And one of our rationales was that the internal fuse would likely never blow - it is rare, in fact, that a PerfectWave fuse ever needs replacing. Sigh. Then, along comes the flood of aftermarket fuse upgrades. Valid? Yes, but by then we were locked into the chassis design.
The top covers aren’t hard to take off, but they’re not easy either. Oh well, live and learn.
One thing was not mentioned in Mr. Atkinson’s testing. The implication was that the amplifier “broke” under testing. In actuality, a power supply fuse blew which he could have found and replaced. I think it was wrong of him to not find this out and mention it. When the amp went back to PS Audio, replacing the fuse restored it to operation. And on using the amps on 4 Ohm speakers, absolutely no problem even when their impedance dips below 4 Ohms. On the subject of bass not having as much “slam” as others, that is one particular parameter of reproduction. The BHK amps were designed to realistically reproduce music which the great majority of listeners agree that they do in a very convincing manner. You can’t please all the people all the time
I agree with Bascom. But to shed some light on it, John did write us and let us know the testing caused the amplifier to blow a fuse and he was hesitant to just replace it and keep going. He knew it, he could have replaced it easily, but had the other amplifier available so he just went to that. It’s not that he didn’t know.
Funny thing is, when we designed the PerfectWave chassis, the team and I worked hard–really hard–at showing no external hardware. No screws to hold the top cover on.
Delightful design engineering and very elegant.
Removing the top is not difficult, but it is mysterious.
Paul McGowan said
John did write us and let us know the testing caused the amplifier to blow a fuse and he was hesitant to just replace it and keep going.
This makes more sense.
Just replacing the fuse when you do not know what caused the failure is not necessarily wise. Given the nature of his “pre-conditioning” process I am a little surprised more amps do not truly fail under this stress test, although there have been plenty which have done more than just blow a fuse.
Good decision, Paul. I certainly agree that the PWD/DS case is very elegant, with that nice polished top and no screws. Ironically I (and I suspect other owners) never remove the plastic, wanting to keep that beautiful finish intact but taking away part of the good looks. (Mine sits a rack shelf, where you don’t see much except the front, though.)
Hah!! Every time I see a PerfectWave with the plastic still on top I am reminded of a house I once saw in Long Island who had their couch covered in plastic so as to never damage the beautiful fabric below. The people who did that had the couch for more than 20 years, sitting on plastic the entire time.
The first thing I do is rip that plastic off and enjoy the hell out of that gorgeous finish.
But, I get it. It damages easily.
Hint. The material we use is HDF and it receives a thick coat of paint and then is polished to the piano finish in a series of steps on big buffing wheels. You can actually treat the finish as you would a car. Rubbing compound, car polish, wax, all work perfectly on the top cover.
