A cirucit to put Carlos anti-blameless stance to permanent rest. - diyAudio
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Old 21st March 2007, 08:12 AM   #1
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Default A cirucit to put Carlos anti-blameless stance to permanent rest.

and hopefully that doubled barrel shotgun might be put aside for this one.I really encourage the inquisitive builder out there to try this circuit. Its essentially a blameless with some changes in error correction and current sourcing. If you have access to the same parts as listed all the merrier as the vas transistor is somewhat critical..You will be rewarded with effortless and music tones, with images that can often jump out at you with startling realism. The best part is that they comewith no ear fatigue at all over long listening.
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Old 21st March 2007, 10:18 AM   #2
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Hi vynuhl.addict,

That is a similar topolgy to Douglas Self's 'Blameless', but it does not follow Self's closed NFB loop stabilisation strategy.

Your circuit does not have the single 100pF Miller connected C.dom which so slows VAS control of the output devices when driving real world loudspeakers.

Good to hear that you have this genuinely useful topology sorted, as indeed Carlos has in his own Dx thread with a more simple design. Your 2SA1360 needs overcurrent protection though, because with an inadvertent fault condition it could conduct itself and the top half of the ouput stage into instantaneous self destruction with that Darlington drive.

Cheers ......... Graham.
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Old 21st March 2007, 12:02 PM   #3
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Default Oh!...a new blamefest!....were is my gun?


Mine was not good...maybe other one constructing....maybe i have made some mistakes...sounded without salt...i turn very nervous..really i am still nervous with that design.

I was expecting beautifull sonic results...i felt myself stupid as a mule constructing that one and trying to make it sound fine.

Grrrrrrr!....i cannot see that...i turn nervous once again!

Kidding...Doctor Self is a nice guy with good designs...maybe i am deaf!

C'a marche soldat...defense l'arrière!

regards,

Carlos
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Old 21st March 2007, 01:20 PM   #4
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vynuhl.addict,

As pointed out correctly by Graham, the Vas transistor needs protection - you could take the cue from D.Self's many circuits.

Taking the cue from Self a little further, why not use bootstrapping for the input like he did with his Load Invariant Amplifier?

Your schematic does not show the transistor types for the Current Source and Vbe positions. The input stage decoupling resistor value is also not shown. (Can the same resistor not be replicated in the negative rail as well?)

The 20K resistors to ground from the current sources on the negative rail can be split into 10K+10K and the junction can be decoupled with caps.

Tell us more about the sound and to which amps did you compare.
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Old 21st March 2007, 06:54 PM   #5
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Default I remember that one i have made...not this one that seems to be good

But that one was terrible

I leave in front of the beach ...and i have recorded that sound...the sound of waves when they are intense... a digital high quality recording was made.

And i remember that i have reproduced that noise...and others too..but this one....result terrible!....the wave sound seemed to me to be air leakage from an automobile Gaz Station tire inflation machine.

This is the reasons of my scandalous reaction to "that" amplifier.

Observe my place....for sure i know the wave sounds quality... it is constantly playing inside my ears...and recording played with other amplifiers, as Symassym...GEM....mine and others sounded nice.

regards,

Carlos
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Old 21st March 2007, 09:47 PM   #6
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Graham, overcurrent potection such as a 10ohm resistor between emitter of vas and rail?. I took a hint in one of Hugh Deans posts to try out bare minimal lag, and secure with lead comp, needless to say this made a difference that was no less than stunning in sound quality differences, gone was that well documented solid state hardness. Even when I built the oiriginal blameless i used a 47pf cap instead of 100.


Carlos, you points on the original blameless are very valid, It is clean, very clean but unable to allow long listening without breaks.


The input stage decoupling resistor is 10ohms 1/4 watt. The VBE bjt in 2sd600k Sanyo, current source bjt are 2n5551 nos motorola. my goal was still aimed at simplicity while constructing, and in dougs designs he only decoupled one half with a resistor also but i am not sure of his reasoning. The original reason i did this was because i saw it done in the trimodal .. I suppose it could be replicated in the other rail but as far as tweaks go with this amp it sounds very finished. It is currently being run from a dual mono supply but using one 300va transformer and 24000uf per amplifier. The Rails sag very little at high levels(not ear bleeding), less than a volt +/- 500mv or less variation.
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Old 21st March 2007, 10:22 PM   #7
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Hi vynuhl.addict,

I would suggest half the value used in the opposite sink, which comes out closest to 33R, and use the voltage dropped across this to drive a current limit with emitter to rail and collector to the base of the 2SA1145. Use a very low capacitance PNP small signal transistor for this.

Enjoy your listening.

Cheers ........ Graham.
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Old 22nd March 2007, 12:38 AM   #8
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Darn Carlos!

I thought we had beautiful beaches in South Africa.

Regards.
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Old 22nd March 2007, 10:34 AM   #9
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Default No differences Johan...we have only the Atlantic Ocean between us.... the same

result is possible...difference may be the constructions we have around...brazilian style...but the beach beauty, by itself is not a Brazilian Monopoly.

Hawaii....Honolulu...Kaneohe....Waikiki is much better!

regards,

Carlos
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Old 22nd March 2007, 09:54 PM   #10
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Forgive my ignorance, but...
what does this circuit exactly?
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