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Old 19th August 2005, 09:48 AM   #1
Electrons are yellow and more is better!
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Default Current feedback headphone amp

What do you think of my SMD current feedback amp?

At the moment I have only pdf's but if you'll check my QRV-06 amp you will have all info about the amplifier itself.

Page 1
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Page 6

Partslist

Solder layer
Component layer
Component print
Groundplane layer
Thermo pads layer
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Old 19th August 2005, 10:46 AM   #2
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Hi P E R A N D E R S,

I liked your current feedback amp very much!

How about publishing the specs......It would be great to see your revelation......

Cheers and enjoy!
K a n w a r
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Old 19th August 2005, 11:00 AM   #3
anli is offline anli  Russian Federation
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Try to move T12/T11 collectors to T13/T14 emiters respectively. Such way you will reduce AC part of Vce for T11/T12. Some resistors values rearrangement is needed, of course. The same idea may (must?) be applied to (pre)output stages.
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Old 19th August 2005, 11:06 AM   #4
Electrons are yellow and more is better!
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Quote:
Originally posted by Workhorse
How about publishing the specs......It would be great to see your revelation......
Some hints can be found here .
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Old 19th August 2005, 11:09 AM   #5
Electrons are yellow and more is better!
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Quote:
Originally posted by anli
Try to move T12/T11 collectors to T13/T14 emiters respectively. Such way you will reduce AC part of Vce for T11/T12. Some resistors values rearrangement is needed, of course. The same idea may (must?) be applied to (pre)output stages.
Yes, but I don't have much voltage and also _how_ much will I reduce?

In order to get good performance the R10 and R11 must be kept as low as possible, preferable zero ohms!
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Old 19th August 2005, 11:23 AM   #6
anli is offline anli  Russian Federation
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Quote:
Originally posted by peranders

Yes, but I don't have much voltage and also _how_ much will I reduce?

In order to get good performance the R10 and R11 must be kept as low as possible, preferable zero ohms!
AC part of T12/T11 Vce will be virtually null. I don't see any reason to make R6/R7 (R10/R11) as low as possible. There isn't one :-)

Such way amp's Rin will be much linear (try with non zero Rout signal source) and input (preoutput) stage will have less THD.
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Old 19th August 2005, 11:53 AM   #7
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R6, R7 is a part of the input buffer. Only R11, R12 is involved in the current feedback circuit.
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Old 19th August 2005, 12:14 PM   #8
anli is offline anli  Russian Federation
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Quote:
Originally posted by peranders
R6, R7 is a part of the input buffer. Only R11, R12 is involved in the current feedback circuit.
For page 1 - R10, R11 probably? OK, they are inside FB loop. R6/R7 are beyond one.
And .. what? You have more reasons to make input stage (and amp's input impedance) more linear, I think
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Old 19th August 2005, 12:30 PM   #9
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R10, R11 of course. How much more linear do you think it can be? Right now the THD is below 0.008%, below my soundcard.
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Old 19th August 2005, 12:44 PM   #10
anli is offline anli  Russian Federation
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Try with, say, 30K output resistance signal source - as for input linearity and THD. And measure input buffer power dissipation deviation in both case - as for input buffer thermal distortions.

P.S. Of course, I don't insist on anything. No more rather "I would modified this topology this way".
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