fao null tester believers

Steve didn't get an answer from the resident accuracy manics,(term of endearment),so I won't harp on,but I do have a genuine question.

have 'null tested' amps ever been 'reverse' dbt'ed? ie have 6 amps (as an example) 3 that show low levels of distortion,and 3 than don't been dbt'ed to see if the null test belivers can actually HEAR this concept? (its the same question as Steves,so copyright is still his,but I am hoping this gets an answer)

 

Saab, I'm not going to answer your question directly but I'll just point out the very well known "Carver Challenge":

Another reference to the challenge in AA:

http://www.audioasylum.com/audio/general/messages/312177.html

The upshot of this is, if two amps have the same null test result (ie measure the same) then they will sound identical. Carver made his $700 solid state amp indistinguishable from a $12K Conrad Johnson tube amp to a group of Stereophile "golden ears". It could quite possibly have been done for a lot less than $700.

The fact that this challenge occured and that Bob Carver "won" is completely indisputed but it doesn't seem to have changed anything.

Michael.

 

It's hardly surprising that they couldn't tell the amps apart - if there was a -70dB null between the two amps then to all practical intents and purposes their outputs were completely identical.

 

Precisely, but what's interesting about the challenge is that Carver was able to make his relatively cheap amp sound identical to a $12K Conrad Johnson, and he would presumably have been able to do the same for any given amp. Makes you wonder what you get for your $12K

Michael.

 

thanks for that Michael,interesting stuff

but no reply from the trolls,yep,they must be trolls,because they ignore direct questions.Their only intent is to disrupt the forum by making contentious statements,they have no intent of having a sensible conversation

so 2 amps will identical null test results will sound the same? so accuracy is meaningless? what matters is your own flavour of distortion ie what sounds good to your own ears? what a surprise

accuracy just seems like an ubergeeks charter,persuing science for the sake of impressing your friends in the pub and for trolling the internet to massage your own ego

 

saab,
to continue my analogy from the other thread on this it's like the 0-60 numbers that car mags bandy about. the way they produce these numbers is down to driving skill and treating the car in an extremely brutal manner - something someone who's just spent 30k+ on a car is unlikely to ever do, so are pretty meaningless in the real world. also a top speed over about 90 mph is immaterial too unless you are suicidal with a desire to loose your license. but still the pub game of car top trumps continues.
cheers


julian

 

Hang on guys - some wrong ends of sticks being grasped here. As I read it, while the "Carver" test is actually doing one aspect of what Saab asked (DBT testing different amps that measure the same) it is totally different from what has been discussed as a null test elsewhere. In that test (e.g. re the Tube Dude amp), the null is between the input and output of a single amp - i.e. testing how closely the amp matches the "straight wire with gain" model. This test though is matching the outputs of two different amps (implicitly given the same input). So this result then goes as a signficant piece of evidence in favour of the objectivists point - i.e. "if it measures the same then it sounds the same". What Carver was doing was matching the distortions of the C-J amp, but rather more cheaply, rather than trying to get the cheap amp to be accurate.

And remember that the objectivists of the adb-tendency have only ever said that (until any reliable evidence to the contrary is produced) the sound is explainable by standard engineering and there is no magic - but have never said that the more accurate or flatter the frequency response/phase dispersion/whatever the better sounding the kit (that seems to be the TD facion with support from BD and Oedipus - in a non-objective alliance with he-whose-name-shall-not-be-mentioned ).

The Carver approach seems a pretty good way for a manufacturer of cheap amps/CDPs to get a leg up on the high-$ competition - get a Wadia/ML/CD12/Lamm/Ongaku/whatever and just null your own clone against it (always assuming you can actually match the high levels of distortion produced by the valve amps ).

 

Thanks for those clarifications Graham, saved me the bother

 

You clearly haven't been paying attention to what the 'null test' means. So what's the point in engaging with you?

Merlin has come out and said that he wants his amp to distort pleasantly, what about you?

Paul

 

who mentioned Merlin?

I am genuinely interested in Steves original question,this has nothing to do with Merlin,fwiw I agree with him,I also want a system to sound good to my own ears,the measurement of distortion,accuracy,null test,whatever,is irrelevant.

however,if a guy can change a cheap amp and make it sound like an expensive amp,then there must be something in it.I am going for a long read out of respect to BD.

 

The second statement / question doesn't really follow from the first. Am I missing a connection somehow?

If I understand correctly Carver achieved a -70dB null between his own amp and the Conrad Johnson, which is to say the outputs were similar to the extent that the differences were 70dB below the signal. Now that's really pretty damn close to identical AFAICT - anyone happen to know what the typical variation is between two engineering samples of the same design?(although it might well be much less than that again for all I know ).

As Graham said though this isn't the same null test that BD keeps harping on about. Again, Carver's exercise says nothing about the absolute accuracy of either amplifier, just that he was able to tweak his own design so it distorted (or not) the signal exactly the same way as the CJ and hence was indistinguishable blind.

 

ok,thanks for clarifying that,as I said,I need to go and have a read.

 

As usual people thinking they are being logical when they are missing important facts.
Of cource two things that measure the same will sound the same , who says otherwize?
Amps operate under dynamic conditions , to measure the same they would have to no matter what volume or what they were driving or what was going into it.
That is what you pay for.

 

And that is what the 'null' test demonstrates...

Paul

 

whatever the null test demonstrates is ultimately validated by your own ears,so after reading all those links I'm back to square one

 

A null test can demonstrate that an amp driving a real load with any signal is not distorting significantly. You can choose to use an amp that does distort significantly, but this is not the pursuit of 'hifi' and I think will end up in eternal chasing of the ultimate colouration. You can choose an amp that doesn't distort because you like the styling or the marketing spiel. You can choose to worry about such ephemera.

Or you can just buy a competent amp and use it until it expires.

Paul

 

a suitable statement to end this thread i think,seeing as the main protagonists have gone quiet

 

Great word!

Great advise!!

 

Almost everyone in the subjectivists camp! Have you not read any of the hundreds of posts made on this forum claiming that measurements are pointless because the unmeasurable effects of DCT, umpteen 9s pure copper and various other varieties of fairy dust, etc. etc. etc. make so much more difference.

...which point seems to be pretty well covered by G.J.Holt - one of those in the Carver challenge...

I do find it interesting that virtually none of the subjectivists have anything to say about this test (which was conducted in the late-80s) - which seems to completely destroy their argument.

 

Me too

Michael.