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Old 25th September 2011, 05:15 PM   #1
Gudmund is offline Gudmund  Iceland
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Default No - feedback amplifier

Search for a no-feedback amplifier showed the attached circuit from

TUBEAMP

What about the design? Want's to built a new amplifier.
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Old 25th September 2011, 05:32 PM   #2
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Well I'm sure it will sound good.
Technically, it isn't a no-feedback design - there's lots of local feedback / degeneration; has to be to get good sound.
But it certainly is a non-GLOBAL-feedback amp.

jan didden
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Old 25th September 2011, 05:47 PM   #3
Gudmund is offline Gudmund  Iceland
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Default Local feedback

Quote:
Originally Posted by janneman View Post
Well I'm sure it will sound good.
Technically, it isn't a no-feedback design - there's lots of local feedback / degeneration; has to be to get good sound.
But it certainly is a non-GLOBAL-feedback amp.

jan didden
Ok, thanks.

I was told that amplifiers without FB sounds well. So - local FB can not be avoided concluded out from your statement.

Gudmund
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Old 25th September 2011, 06:03 PM   #4
Gudmund is offline Gudmund  Iceland
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Default Symmetrical

Quote:
Originally Posted by janneman View Post
Well I'm sure it will sound good.
Technically, it isn't a no-feedback design - there's lots of local feedback / degeneration; has to be to get good sound.
But it certainly is a non-GLOBAL-feedback amp.

jan didden
Forgot to ask.....do you prefer a symmetrical solid state design?

Just short....symmetrical or ?
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Old 25th September 2011, 06:25 PM   #5
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Quote:
Originally Posted by Gudmund View Post
Forgot to ask.....do you prefer a symmetrical solid state design?

Just short....symmetrical or ?
Well, I find it difficult to say that a particular topology is better or not. You can make great symmetrical amps and great non-symmetrical as well.
So much depends on the circuit details and the implementation.
Things like the grounding layout, (remember, not all grounds are created equal!) or power supply decoupling, and supply routing probably have at least the same impact as the topology.
If you are not experienced in those issues, your best bet for a successfull implementation is to selct a design that you like and where the designer gives info about how to put it together, and follow those.
With a circuit like the one you showed, and good implementation practise, your amp will certainly sound very well.
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Old 25th September 2011, 07:23 PM   #6
Gudmund is offline Gudmund  Iceland
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Quote:
Originally Posted by janneman View Post
Well, I find it difficult to say that a particular topology is better or not. You can make great symmetrical amps and great non-symmetrical as well.
So much depends on the circuit details and the implementation.
Things like the grounding layout, (remember, not all grounds are created equal!) or power supply decoupling, and supply routing probably have at least the same impact as the topology.
If you are not experienced in those issues, your best bet for a successfull implementation is to selct a design that you like and where the designer gives info about how to put it together, and follow those.
With a circuit like the one you showed, and good implementation practise, your amp will certainly sound very well.
Understand....well , I have made some amplifiers, and know that the wire connection from PSU to the PCB might affect the stability of the outputstage...also depending on the ground layout as you mentioned.

I shall stay with the symmetrical design...it looks good... from my point of view.

Thanks
Gudmund
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Old 25th September 2011, 07:42 PM   #7
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Just a shame the parts are not physicaly as symetric as the schematic would imply....
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Old 25th September 2011, 07:45 PM   #8
Gudmund is offline Gudmund  Iceland
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Quote:
Originally Posted by digits View Post
Just a shame the parts are not physicaly as symetric as the schematic would imply....
Which parts do you refer to?
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Old 25th September 2011, 08:21 PM   #9
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That amp was sold as a kit and it sounds fantastic in class-A. It was offered in a low power (40watt) class-A amp, or as a >100W class-AB amp. I havent heard the high power AB version, but the 40watter was plenty loud and sweet sounding.
My two Ýre.
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Old 25th September 2011, 08:44 PM   #10
jaycee is offline jaycee  United Kingdom
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Plenty of feedback, just not the usual type. Looks like current rather than voltage feedback. Why on earth would you choose to use crap like the TIP41/42 as drivers to 2SC3281/2SA1302's...
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