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Old 18th April 2010, 05:10 PM   #21
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I have found tube/semiconductor amps with many strange kind of design, but I think that hybrid amplifier can be good.
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Old 18th April 2010, 05:30 PM   #22
amp_guy is offline amp_guy  United States
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There are some pretty highly regarded hybrids out there now, some examples are Pathos, Vincent, Unison Research and I think there is one made by Lamm.
The counterpoint amp has a nasty reputation of going volcano, which is strange as I have found the Hitachi mosfet's to be very robust.
However Iam not sure the SRPP is the way to go as the circuit tends to have a rather high output impedance to be driving the gate capacitance of mosfets.
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Old 18th April 2010, 05:38 PM   #23
amp_guy is offline amp_guy  United States
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First decision, are you planning on a normal design with lots of global feedback or low or no global feedback? if you are looking at a no feedback design simpler circuits can be used because of need for lessor amounts of gain.
There is a hybrid over in the hafler dh200\dh220 thread that looks promising.
Although I think I will add a bias regulator if I go that way.
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Old 18th April 2010, 05:39 PM   #24
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Why two VBE multipliers in series bias?

Valve V2 WCF seems wasteful/redundant.
Or maybe its V1b that is the redundant valve?
Only needs one style unity follower or the other.
Two or three twin triodes at most for stereo,
rather than four.

I'd even be tempted to replace V2b with solid
scrape transistor. That valve acts upon strong
local feedback and not behaving much like you
expect from the plate of a triode anyway...

If poster above is so worried that 240/9240
might not sound good as compliments? You
could abuse your BC327/337 current limiters
as crossing error correctors. And add a pair
of Schottky diodes in series with your 0R47
to act as the square law current detectors.
No problem to make diodes match, and any
power compliment mismatch is corrected.

The source resistor linearizes both MOSFET
square law curves too much anyway, that
smooth AB crossing without some form of
additional error correction near impossible.

240/9240 mismatch is not the main problem,
excessive crossing linearity is the problem.
You get that same issue with any device but
maybe lateral mosfet, because you need the
source or emitter resistor for other reasons...

Plenty of amps built with no corrections aside
from NFB hide the problem acceptably. But I
see no global feedback loop in this amp. So you
are gonna want to smooth out the crossing for
sure...

----------

"Error correction" is probably a misleading term.
"Complimentary curve correction" makes more
sense...

Last edited by kenpeter; 18th April 2010 at 06:00 PM.
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Old 18th April 2010, 05:40 PM   #25
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Quote:
Originally Posted by amp-guy View Post
First decision, are you planning on a normal design with lots of global feedback or low or no global feedback? if you are looking at a no feedback design simpler circuits can be used because of need for lessor amounts of gain.
There is a hybrid over in the hafler dh200\dh220 thread that looks promising.
Although I think I will add a bias regulator if I go that way.
Please go to post #17,
Regards
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Old 18th April 2010, 05:55 PM   #26
amp_guy is offline amp_guy  United States
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o.k I should have looked at your drawing in post 17 .
BTW is this a DIY project or are you developing a commercial product?
they are two different animals you know.
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Old 18th April 2010, 06:05 PM   #27
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Quote:
Originally Posted by amp-guy View Post
o.k I should have looked at your drawing in post 17 .
BTW is this a DIY project or are you developing a commercial product?
they are two different animals you know.
When amplifier was tested, I will share schematics for give idea to other people, but PCB and other specification is not for share.
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Old 18th April 2010, 06:12 PM   #28
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No difference of concern to me. So long as he's sharing/
teaching/learning and not simply marketing. Development
of commercial products is interesting when it completely
open to DIY on the side (like PASS). Apex has the right
attitude, I appreciate that moderators give him leeway.
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Old 18th April 2010, 06:12 PM   #29
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Quote:
Originally Posted by kenpeter View Post
Why two VBE multipliers in series bias?

Valve V2 WCF seems wasteful/redundant.
Or maybe its V1b that is the redundant valve?
Only needs one style unity follower or the other.
Two or three twin triodes at most for stereo,
rather than four.

I'd even be tempted to replace V2b with solid
scrape transistor. That valve acts upon strong
local feedback and not behaving much like you
expect from the plate of a triode anyway...

If poster above is so worried that 240/9240
might not sound good as compliments? You
could abuse your BC327/337 current limiters
as crossing error correctors. And add a pair
of Schottky diodes in series with your 0R47
to act as the square law current detectors.
No problem to make diodes match, and any
power compliment mismatch is corrected.

The source resistor linearizes both MOSFET
square law curves too much anyway, that
smooth AB crossing without some form of
additional error correction near impossible.

240/9240 mismatch is not the main problem,
excessive crossing linearity is the problem.
You get that same issue with any device but
maybe lateral mosfet, because you need the
source or emitter resistor for other reasons...

Plenty of amps built with no corrections aside
from NFB hide the problem acceptably. But I
see no global feedback loop in this amp. So you
are gonna want to smooth out the crossing for
sure...

----------

"Error correction" is probably a misleading term.
"Complimentary curve correction" makes more
sense...
There will be some change to keep amplifier simple.
Only one bias transistor is on heatsink.
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Old 18th April 2010, 06:22 PM   #30
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Quote:
Originally Posted by kenpeter View Post
No difference of concern to me. So long as he's sharing/
teaching/learning and not simply marketing. Development
of commercial products is interesting when it completely
open to DIY on the side (like PASS). Apex has the right
attitude, I appreciate that moderators give him leeway.
Thank's for understand, I not advertising and sell anything on this forum, just share what I want to share, that only can be useful for other people.
Regards
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