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Old 2nd December 2002, 01:04 PM   #11
halojoy is offline halojoy  Sweden
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Quote:
Originally posted by hugonot
--------------------- ..... --------
There is a great amount of negative feedback in last two stages, I,m affraid it could oscilate.
-------- ........ ----------
Dobra Lenny pogadamy na Aikido.
I have seen small capacitor
across R27, 33 ohm
in this type of output stage with a voltage gain

Also is good, maybe nessesary,
with a separate Power Supply for the output stage
for Current Feedback Amps.
They are more sensitive for such feedback.
This is already done here.

DC-servo. Why?
Nelson said somewhere that he can tolerate some 0.500 volt.
How much watt is that?
Would it ruin your speaker?
I know that I would give such a speaker away to charity
or better to destruction!

You will get far, far less DC-offset than 0.500 volt,
if you trim your amplifier.
Isn't it better to use some delay and a relay,
until DC-offset settles?
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Old 11th December 2002, 01:37 AM   #12
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Quote:
Originally posted by peranders
Lenny if you want to study the concept of current feedback, check ON and National.

http://www.national.com/search/searc...ack&full=1#App

Have some trouble to find at ON but I know they have good documents.
check out www.ti.com also
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Old 11th December 2002, 03:07 AM   #13
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Quote:
Originally posted by halojoy
Nelson said somewhere that he can tolerate some 0.500 volt.
Only as a short term proposition (warming up). 100 mV is
my acceptable limit for most speakers, and I like a lot less
than that.

BTW, 0.500 V is 1/16 watt into 8 ohms.

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Old 11th December 2002, 03:11 AM   #14
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When I turn on my A75, DC offset is 300mV or so and starts slowly going down to approx. 20mV after 20min. if I remember correctly.
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Old 11th December 2002, 05:20 AM   #15
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My 50w class A has 325mv offset all the time. Is the dc drop across the output choke @ 3.5 amps. Would be nice if it didn't but I don't think it has any real detriment to the sound, especially if you don't know about it. That last bit sounds funny but I think it has quite some truth to it.
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Old 11th December 2002, 06:31 AM   #16
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Hi Lenny

I once performed simulations on a circuit that was a little similar to yours.
The main difference is that mine is inverting and it's input stage is a little simpler than yours. The simulation results looked promising.


Yet another complementary amp

I particularly like the output stage on your first schematic. The first reason (as you already mentioned) is that it can be driven very close to the rails. The second reason is that lower Vce driver transistors can be used.

I don't think that this is topology is very critical regarding stability.

I haven't found the time to try my circuit out so far but a workmate of mine is very curious about it's performance and will most probably try it out.

Good luck with yours

Charles
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Old 11th December 2002, 04:05 PM   #17
halojoy is offline halojoy  Sweden
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Quote:
Originally posted by phase_accurate
Hi Lenny
Yet another complementary amp

I particularly like the output stage on your first schematic.

I haven't found the time to try my circuit out so far but a workmate of mine is very curious about it's performance and will most probably try it out.
Good luck with yours
Charles
in't it nice we can give "sound advices"
to anyone person surrounding us

i do it a lot - specialy my eldest brother asks me many advices about his soundsystem
- i have designed, my own, hifi headph-amp
custom made to suit his headphones - he bought model after advice given (Sennheiser 600)

watch me know - i am the american dream

some links on amplification design tubes/transistors at

Music&Mp3 Page of Groman the Swede
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