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Old 12th September 2004, 02:10 PM   #1
Fuling is offline Fuling  Sweden
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Good afternoon

After reading Nelsons article about transconductance amps and fullrange drivers I got inspired to try this concept with my fresh
Fostex horns.

I donŽt want to spend any considerable amounts of time or money, so I got the idea of using cheap TDA 20XX power opamps.
TDA2050 seems to be the newest of them and the one with the least discouraging specs

Another major reason for using these chips instead of the popular LM38XX are that these ones only have five legs, so point to point wiring should be easy.

Feedback would be arranged by a current sensing resistor (some 0,5-1 ohms) connected between the speakers negative terminal and ground instead of the usual voltage divider from the output.
This should give a very high output impedance which is attractive here.

What do you think?
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Old 12th September 2004, 03:13 PM   #2
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Fuling,

The principle of current sensing feedback to create a high-impedance output works with any amplifying 'black-box' so there is no reason why it wouldn't work with the amp you propose.
There may be an issue with stability so you may need some other compensation then the standard data-sheet one, but maybe you should just try it out.

Jan Didden

PS Did you receive my mail on the 1-clap transistor?
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Old 12th September 2004, 04:16 PM   #3
Fuling is offline Fuling  Sweden
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Hi

I think IŽll give this one a try soon. I donŽt have any high end ambitions, just want to see (hear) how the speakers behave when they are driven by a high impedance source.
If the experiment turns out good IŽll try something more delicate later, like a single ended amp or maybe even a pentode amp without feedback.

Yup,I got your mail
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Old 12th September 2004, 05:19 PM   #4
316a is offline 316a  England
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Hello ,
You're a valve man aren't you ? Use a pentode in SE

cheers

316a
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Old 12th September 2004, 05:49 PM   #5
Fuling is offline Fuling  Sweden
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Quote:
You're a valve man aren't you ?
Sure!
IŽm thinking AL1, very linear direct heated pentodes.

I just want to try the concept before I pay the cash involved in a tube project (even though I have almost everything except for the acual tubes)
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