I explained how it should have been tested at the bottom of page 117. You can't place any probe on the negative speaker terminal, it will cause problems with the feedback loop. If that's what happened in ASR testing, then all the results are invalid because the amp was oscillating and unstable.
I already explained. YOU are wrong it was measured correctly.
Besides many knowledgeable people on here have also explained about the measurement and that what you believe must have happened in reality could not even have happened. Your tech guy made that error. Amir did not and could not because the AP555 has a floating input.
OK, so Bob didn't follow CE standards on this one. Did I not mention that they rushed it a bit to market? Also, he was working with a new young man who he was giving a start in audio electronics. Maybe the correct 'labeling' was overlooked and they should have used a 2-prong IEC plug but the fact remains that the amp is safe how it's designed electrically. If you plug any 3-prong cord connected to it into an outlet, it's going to place the neutral on the correct side regardless, you won't get a backwards connection to the amp.
This is no excuse... sorry.
Also you are wrong. In Europe you can plug in a plug upside down. Effectively connecting 230V live via a 1M resistor to the chassis. One might hope the rest of the used gear is connected to safety ground in a proper way. It is even possible that this may cause a ground loop.
I don't really care about what you think I should hear. I let my ears tell me if it's good or not. Would I be listening to tube amps or SS amps that sound like tube amps if I wanted 'signal purity'? I want a sound that has the emotion of the original performance, and in general that can't be had with a sterile signal path.
So YOU want an effect box that pleases. That's fine. Most people want an amplifier that amplifies and does not add nor remove.
If the measurements were taken incorrectly (for this particular amp) then the results are invalid. I'm listening to it as we speak, without KT-120's in it (RCA 6L6GC) and it's got plenty of volume, more than I can handle for a few minutes without turning the volume back down. Now, if 6L6GC can drive the output to uncomfortable levels, what do you think the KT-120 can do?
Does your personal opinion change anything about the technical performance ?
If you are so convinced... send it in to Amir.
I don't know why they didn't use a bigger mains transformer. I'm thinking that maybe they didn't test it 'both channels driven' and see that it falls short in that area. Keep in mind that it had been many years since bob designed a 2 channel amp, all of his prior tube amps post-retirement were monoblocks.
No excuse either.
Then why are we arguing whether it's capable of delivering the base performance of 75 W/Ch?
I am not arguing. You are merely stating I am arguing. I agreed.
Either. It has a 5yr warranty if there are any real problems. Everything else would be a perceived problem and he offered an unconditional refund, he doesn't want your money if you are unhappy with it.
You perceive things differently than I... must be audio.
I think Jordon who Bob gave most of the product packaging work (and board layout) to didn't know about the proper 'markings' or that the IEC should have been 2-prong. I'm not saying mistakes were not made, but electrically the product is safe because the chassis is tied to it's ground.
That's what you think. A manufacturer SHOULD no. This is no excuse. Just one you came up with.
As I said before, if the tests were done correctly there wouldn't be this discrepancy between what real world owners/users are experiencing and what ASR test 'results' are showing. In addition I've shown that there is a known problem with testing this particular amp and how to correct the error in testing it. Bob couldn't put the test lead attachment point outside of the amp, so attaching to the RCA shell is the only alternative.
This has been covered extensively. YOU are wrong. The input of the AP is galvanically separated so the issue your 'qualified tech' encountered did not happen here.
So.. you can keep believing the measurement was incorrect but in the real world it was done correctly.
What makes the AP555 so immune to causing a problem when it's known that attaching test leads to the neg speaker terminal will cause problems? Obviously it's a sensitive feedback system that keeps the amp stable, so why argue the issue, why not just accept that there could have been an error in it's testing?
Because there wasn't. The input is 'floating'. It is you that is not accepting that fact.
Which is more plausible? An audio designer/physicist with over 60 years designing amps created an amp that sounds great but doesn't 'work properly', or a mistake was made in measuring it? Thousands of these units were sold, I don't see many going back because they don't sound good.
I did not say these amps do not sound good. It measures poorly... and yes... it was measured correctly. Even if you don't want it to.
If you have evidence of the contrary please post the 'correct measurements'.
Again, who is wrong? Maybe if you or anyone testing it had listened to the unit they would immediately know that your testing results do not equate to the performance of the amp in an actual application of, you know, music?
The testing WAS correct. Your ears aren't analyzers. You can enjoy music with ears+brain though.
Don't worry, I won't be selling my main system amps of these within my lifetime. And I trust the unpublished results of my EE friend who works on amps for people out of sheer kindness.
Ah right... the guy that had test gear that shorted the current feedback loop.
Why don't you ask him if you can set Amir straight and actually show the measurements.
It does when your non-peer reviewed tests (and unwillingness to accept that they -may- be wrong) are incorrect.
I did not measure anything here. And you need to accept that he measurements were correct.
If Amir agrees, maybe he should suspend this thread until there is verification that his tests were or were not done correctly. If not, it's possible that a bunch of libelous stuff was stated/posted here, and damaged the reputation of an audio legend over the last year because of 'vanity'.
YOU have to provide the evidence measurements were incorrect.
So far only false assumptions and your opinion have been posted by you.
No real evidence, no redemption.
Did you ever think of the possibility that this thread so severely damaged the sales of it, so that's why they stopped selling it? Marketing a particular product at a particular price requires parts purchases in bulk, so it's possible that there was an inability to risk buying the next lot of parts because sales plummeted.
They did not stop selling it. They are still selling it under a different name (the
Black Magic 25) with more realistic specs.
No audiophool has ever been discouraged buying something that was tested on ASR. Reason: they do not visit this website and prefer NOT to see measurements. Mostly because they don't understand.