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Old 15th February 2010, 07:02 PM   #1
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Default Output level of TDA1545

Anyone who knows what output level at 0dB to expect from a TDA1545 with passive I/V, 2,2k?
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Old 16th February 2010, 10:38 AM   #2
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OK,
Then I respond to my own question:
It is in the ballpark of 0,7mV rms/ohm. So with 2,2k loading will will get ruffly 1,5V rms.
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Old 16th February 2010, 10:39 AM   #3
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Thank you Lars!
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Old 16th February 2010, 11:39 AM   #4
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You're welcome.

BTW are you making a separate DAC or is it in a cdplayer ?
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Old 16th February 2010, 11:53 AM   #5
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Default DAC output compliance

Quote:
Originally Posted by revintage View Post
OK,
Then I respond to my own question:
It is in the ballpark of 0,7mV rms/ohm. So with 2,2k loading will will get ruffly 1,5V rms.
Not likely! If you look at the datasheet for the TDA1545 you'll notice the output voltage compliance extends from 2V to [VDD-1]V. With a 5V supply, that's going to give you 2V p-p at best, around 0.7VRMS.
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Old 16th February 2010, 12:55 PM   #6
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Hey Jean Paul,
Will rebuild a simple NOS 1543 to 1545. DHT-tube buffer.

abra....
You´re correct about clipping. If we suppose the info I´ve got is correct 1k should be max. But as you seem to know the answers, tell us what the correct figures are!
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Old 16th February 2010, 02:01 PM   #7
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Default Output level

Well I just got the answers from looking carefully at the datasheet

I'd not use passive I/V myself for this DAC, there's no telling how much the distortion will increase when moving away from the optimum 2/3rds VDD bias point mentioned in the data. The lower the resistor value you use for I/V conversion, the lower the distortion, but go too low and the noise from the following amplifying stage goes up. Its not a very low noise DAC (~100dBA) so, if I really had to go for passive I/V, I'd try 150ohms as a first attempt, giving around 50mVRMS output.

Peufeu has a nice design using the TDA1545, here:

The Extremist DAC
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Old 16th February 2010, 03:22 PM   #8
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Actually the 2/3 Vdd would be held due to the grounded grid tube input would be biased at 2,9V.

As I see it my figures where double of yours. That way 2,2k makes sense as it gives 770mV fs at 2,2k. The loading from above will be ca 400ohm giving an output of above 100mV.

Just discovered my DAC to be rebuilt has a DIR9001, not compatible with this chip, as I understand it.
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Old 16th February 2010, 04:39 PM   #9
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Hi,

Quote:
Originally Posted by revintage View Post
Anyone who knows what output level at 0dB to expect from a TDA1545 with passive I/V, 2,2k?
First, I would not recommend a large value I/U resistor, I find around 150mV are tops for the 1545, the 1543 can handle a lot more level.

Second, try setting the chip to Iout = 2mA peak-peak (see datasheet).

Third, reference the I/U resistors to Vref, not to ground.

Fourth, the TDA1545 needs EIAJ dataformat, not I2S. This is normally easily obtained from any modern receiver by setting the dataformat appropriately.

Ciao T
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Old 16th February 2010, 07:39 PM   #10
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Hey Thorsten,

Quote:
First, I would not recommend a large value I/U resistor, I find around 150mV are tops for the 1545, the 1543 can handle a lot more level.
Got the 2,2k from a sketch you did quite a while ago. But using ca 400ohms as in the amp I have drawn must be OK.

Quote:
Third, reference the I/U resistors to Vref, not to ground.
Also found that on the above schematic. But it must be the same if you use a Grounded Grid with Ug being the same as 2/3 Vdd ?

What I haven´t figured out yet is how to set Iout=2mA that you mention. Any clues?

Quote:
Fourth, the TDA1545 needs EIAJ dataformat, not I2S. This is normally easily obtained from any modern receiver by setting the dataformat appropriately.
Just what I meant by mentioning that my DIR 9001 isn´t compatible(or is it?). Suppose the CS841...´s will work though.
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