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Old 19th April 2002, 05:19 PM   #1
nar is offline nar
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Unhappy D1.I/V conversion

Hey.Anyone Knows about D1 I/V conversion mosfet,IRF 610.But to which current are they matched?I calculated Q3 runs at 10,6mA and Q2 at 9.3mA.But still one the source pin of Q3 where is attached the I out of the DAC,still remains a 2V continious which should deserve the precision of the conversion!!!!...
I would like to adapt this solution to a TDA1549 but the chip may get angry about the DC at its I out....
Anyone,HELP!!!!
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Old 19th April 2002, 07:31 PM   #2
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Default read the fantastic manual!

The source voltage (input) is regulated to 0V by the trimpots.
To use the voltage output of your dac
(it has voltage output of +-2V or so),
just use resistors in series (ca. 2k2 or a bit
less, I connected it this way to a CS4390).
As you only have one output on your
dac, you only need the positive half of the output
circuit. And the negative input should probably be
left open (?)

I matched Q3 with Q6, Q2 with Q5 as described on passdiy.com.

martin
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Old 20th April 2002, 11:46 AM   #3
nar is offline nar
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Lightbulb TDA 1549 T

I think it is a TDA 1549 T inside the CD Philips 720.Haven't opened it yet.Uses same board than Marantz CD5000.

I plan to use this DAC , but anyone seeing the internal schematics see this horrible " precision op-amp" used by Philips to make the conversion I/V.
Theoricaly I can swap it using the pin reserved by Philips for the external capacitor (to make a 6 dB/oct low pass).In fact,Philips says it can be omited.This pin would go directly to the point of the entry for I/V.(minus in of this OP-amp integrated.)
The problem is...the Pass I/V conversion would parallel the already network hardware.It might result less current than initial,critical problem.But I really want to get rid of OP-amps !!!

Anyone concerned???Do you think the DAC will suffer?And what about the dynamic range (should be less extended)?

Sorry,as you can see I'm a neophyte...Perhaps Panos can Zenlite me?
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