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Old 20th January 2014, 03:04 PM   #4171
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Quote:
Originally Posted by mcd99uk View Post
Yes, all my CFA amps share a lot with the MCP amp. IMHO the CMLC system is significant in it's improvement to sound. Wish more would try it...
Diamond buffer input stage + CMLC + beta enhanced VAS + 2 pole compensation + various output stages = Nice sounding amps.
[..]
Hi Paul,
You have mail.
Cheers, E.
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Old 20th January 2014, 03:49 PM   #4172
mcd99uk is offline mcd99uk  United Kingdom
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Originally Posted by Edmond Stuart View Post
Hi Paul,
You have mail.
Cheers, E.
Hi Edmond,

So I see... You + one other have mail too.

Cheers

Paul
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Old 20th January 2014, 04:10 PM   #4173
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by Edmond Stuart View Post
Hi Godfrey,

There are better and simpler ways.

Cheers, E.
Very nice design .. esp the front half. What could you do for the OPS to drive 4 Ohm load??

Thx-RNMarsh
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Old 20th January 2014, 07:03 PM   #4174
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Hi Richard,

Bod Cordell's error correction OPS is a strong candidate, that is, with at least two pair of power MOSFETs.

Cheers, E.
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Old 20th January 2014, 09:23 PM   #4175
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Originally Posted by Bonsai View Post
This simply raises the gain of the LTP at HF - not sure what the specific benefit of this is..
It allows you to improve the phase near ULGF if the zero is properly placed i.e. a Bode step.
Cherry discusses the use of this capacitor too in JAES but the maths is opaque despite several reads, more effort required.
Anyone understand this? I don't think he means a Bode step.

I reread my post in your reply and realised it was poorly written, could be read that I meant you when I wrote of phoney claims.
What I meant was that I had learned from and appreciated the thread and that, unlike JCX, I didn't even mind the dubious posts.
I don't think your contributions fall into that class, quite the contrary.

Best wishes
David

Last edited by Dave Zan; 20th January 2014 at 09:35 PM.
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Old 20th January 2014, 11:23 PM   #4176
Bonsai is offline Bonsai  Taiwan
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Quote:
Originally Posted by Dave Zan View Post
It allows you to improve the phase near ULGF if the zero is properly placed i.e. a Bode step.
Cherry discusses the use of this capacitor too in JAES but the maths is opaque despite several reads, more effort required.
Anyone understand this? I don't think he means a Bode step.

I reread my post in your reply and realised it was poorly written, could be read that I meant you when I wrote of phoney claims.
What I meant was that I had learned from and appreciated the thread and that, unlike JCX, I didn't even mind the dubious posts.
I don't think your contributions fall into that class, quite the contrary.

Best wishes
David

Dave, I tried that technique when I was developing the e-Amp with low capacitance values (as I note in my reply, high values are another matter). It still does not stop the fact that you have to close the loop where the phase margin is adequate. I doubt in a high loop gain VFA it allows you to push the ULGF up significantly - but of course I am open to correction - I may need to revisit it. And, IMV we are now getting into advanced comp tecniques.
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Last edited by Bonsai; 20th January 2014 at 11:26 PM.
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Old 21st January 2014, 02:55 AM   #4177
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by ostripper View Post
He also suggested a 3rd- order filter for the servo. Dang ! I found a filter
from heaven (below 1). In according with "KISS" (keep it stupid simple) ,
I am at 1 IC and 8 little passives.

What I have is a "cliff -like filter" ( 60db/decade) and good gain below 5Hz
to decimate any DC.


OS
Set -3dB corner to below 1hz.

THx-RNMarsh
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Old 21st January 2014, 04:15 AM   #4178
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Quote:
Originally Posted by ostripper View Post
He also suggested a 3rd- order filter for the servo. Dang ! I found a filter from heaven (below 1). In according with "KISS" (keep it stupid simple), I am at 1 IC and 8 little passives.

What I have is a "cliff -like filter" ( 60db/decade) and good gain below 5Hz
to decimate any DC.
I suggest you check LF stability wih your zillion dB/decade servo .. or at least design your PCB so you can revert to a simple 6dB/8ve roll-off.
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Old 21st January 2014, 04:21 AM   #4179
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Originally Posted by Edmond Stuart View Post
Edmond, do you have a link to the additional circuitry is necessary to ensure a decent behavior at overdrive conditions you mention in that link and also the subsequent one with bad overload recovery?
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Old 21st January 2014, 05:35 AM   #4180
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Quote:
Originally Posted by RNMarsh View Post
Set -3dB corner to below 1hz.

THx-RNMarsh
Yes , I will do ....

I have been sick (flu ) ... That got me thinking tempco.

As was mentioned (the blameless) is (almost) perfect , the two CCS's for
the LTP and VAS nearly negate themselves. It is not TOTALLY perfect , as
the 2 CCS's have different Ic and device types.
Still , it will be pretty accurate from a cold house to a hot summer day.

I sort of "lucked out" with my first CFA design , the hawksford's led cascode bias
negates the led IPS CCS's I used (real close). I found that a string of 2 led's for
the cascode could perfectly offset the use of a 2Q CCS at the input stage.

I wondered why my HK680 could be put outside (-10C) ... brought inside ,
and still measure within a mA of my set OPS bias. They "fine tuned" the
IPS (near perfect tempco) and matched it with an exceptional OPS Vbe setup .

It might be "anal", but I like that kind of performance . Most amps will never
see this extreme ambient swing or have their stages biased "hot" to override
external conditions.

I like cool .

PS - I thermally simulated 5 of my favorite VAS's in isolation , the hawksford
has 1/5th the Ic "drift" of the others.

OS
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