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Old 30th June 2007, 12:34 AM   #1971
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Quote:
Originally posted by Graham Maynard
Hi Carlos,

In your post#1956 you wrote,

>> Sound was "undecided".... something that was afraid to get out from the speaker. <<

That is exactly the way I described sound from a blameless type amplifier many years ago.
Every bit of the sound was there, and you could tell it was very low distortion, but it sounded as if it could not enliven a room by breaking free of the loudspeaker.
It made me stare at the loudspeaker and say - 'that's not right!', whereupon I used a different amplifier with that same loudspeaker and was happy.

Strange you should say the same.

A question about anyone not already having heard better - would they realise that they were missing out?

Cheers ........ Graham.
Hello

I never try that blameless amp, I have the text about it and it was look promissing, local nfb, etc...

What could be the principal cause of that failure from that amp ?

Gaetan
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Old 30th June 2007, 12:56 AM   #1972
sandyK is offline sandyK  Australia
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Default Destroyer X

Gaetan
I gave up on chip amplifiers many years ago.
They aren't TOO bad for surround sound rear amplifiers .
SOME DTS Surround Music Videos deserve better though.
SandyK
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Old 30th June 2007, 07:31 AM   #1973
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Default Yes friends, i am following the thread were you discuss sound stage


I am learning a lot there.

A different world may leave those folks that select recording to top quality.... a very narrow group of options too i think.

I have one exceptional recording that Graham Maynard sent me last year...really the sonics are much better, and because of that i use them during my tests.

I see you have deep belief into your modified Silicon Chip amplifier.

Is that schematic you sent me the modified version Andy?

I had the curiosity to construct to listen, despite i turn red when i observe that kind of circuit that remembers me Blameless..... maybe one day.

regards,

Carlos
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Old 30th June 2007, 08:31 AM   #1974
sandyK is offline sandyK  Australia
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Default Dx amp

Carlos
I would have given you the modified version, but did I give you the original published version ?
You may have noticed the added emitter follower in the modded version. The English designer Graham Slee from GSP Audio, told me that I should try removing the collector resistor that I added to reduce dissipation in the emitter follower , although he said that it may still be necessary to slow the amp down a little.
I reduced it in the similar Class A preamp to 2K2 ,with a further improvement in soundstage and an easier listening type sound. Another friend of mine heard it on Friday, and agrees. I didn't want to fully remove it, as the soundstage was becoming even bigger.Today I reduced the same resistor in the Class A Amplifier circuit you have, to half the value. Digital TV audio now has even more spatial information. I will try to reduce it further soon, BUT, I am concerned that I may end up with too BIG a soundstage !
I am not pulling your leg !
I will see if I can arrange for our mutual friend to obtain his impression of the latest changes
Alex
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Old 30th June 2007, 08:34 AM   #1975
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Default All rigth Sandy, our mutual friend seems to be busy those days


Yes, please, arrange that audition, and comparison with the Dx amplifier will be very interesting to me.

regards,

Carlos
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Old 30th June 2007, 08:48 AM   #1976
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Hi Gaetan,

And Carlos, first off my apologies for jumping in your thread with a non-DX topic, but the problem with the blameless lies very much around the VAS stage, the beta enhanced idea looks good but I found doesnt sound half as good as a simple common emitter single bjt. Second problem is its rather crude miller compensation as the only compensation used. In its original form from Doug Self sounds very cold
and as others have stated, it produces a clean sound that is planted between the speakers rather than extending beyond the speakers which makes anything close to a 3D soundstage its weakness. Other than that the basic topology is very sound to start from, but it does require big ears and lots of experimenting to get to sound like music.



Colin
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Old 30th June 2007, 09:53 AM   #1977
sandyK is offline sandyK  Australia
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Carlos

You have mail

SandyK
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Old 30th June 2007, 10:30 AM   #1978
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Default Yes.... this i have concluded too...not only the VAS but the fact it is mirrored too.


Not exactly a mirror, just a CCS counterpart i think.

No problem to go off topic for some time....it is good to produce a "period"...a pause into the main subject.

Of course we have to obbey rules.... if we insist too much we can have problems...so, we go limiting...do not worry, when i perceive excesses i use to publish texts about the Dx amplifier, pictures, tests, details, non succeeded modifications and all that stuff that interrupt the off topic continuity..... creates a pause only.

Your ideas, conclusions, opinions and posts are interesting Sandy, also Gaetan is very interesting too.

We have some nice friendship, a starting one as we use to mail directly having some personal conversations..also Gaetan.

So...here is our meeting place too, the care needed, is to avoid the idea that is only ours...hundreds are reading, and i do not know if they accept off topic so gladly as i use to accept.

thank you,

regards,

Carlos
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Old 30th June 2007, 11:01 AM   #1979
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Hi vynuhl.addict,

I am sure Carlos will be pleased at you jumping in with non-DX comment, because the concept of his DX was to construct an amplifier which did not have the audible weaknesses of other apparently more theoretically correct ultra low distortion designs.

Yes the Darlington VAS creates so much gain for 'desirable NFB' that the gain bandwidth must then be limited to ensure stability. The action of the VAS C.dom which becomes necessary then limits open loop bandwidth and this leaves internal amplifier behaviour at risk for non-linearity or discontinuity when the output stage cannot match dynamic loudspeaker system generated current demands.

Of note in relation to the C.dom at the 'blameless' VAS is that its VAS base drive is a minute fraction of the current necessary to charge the C.dom with respect to slewing VAS collector voltage. This means that input stage currents primarily drive the C.dom, and thus the input/error sensing differential stage can no longer transconduct linearly.

Input/VAS operation within individual 'blameless' type circuits are thus loudspeaker system load dependent, they operate independently in time, not together - as is necessary for accurate stereo image reproduction.

A 100pF C.dom on Carlos' VAS does not behave the same as a 100pF C.dom on a 'blameless' VAS. The DX and 'blameless' might appear to have similar value C.doms, but they do not act upon the differential input pair in the same way !!!

Cheers .......... Graham.
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Old 30th June 2007, 11:30 AM   #1980
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Default Re: Re: Destroyer X

Quote:
Originally posted by gaetan8888

Btw, most chip amps do have much higher distortion at very low output level, so the soundstage are lost in crossover distortions.
can you give an example?
this is a typical arguement in the valve vs. silicon debate.
However, everytime I look onto published THD charts, the THD vanished into noise at low levels.
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