Best resistors For I/V Conversion?

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#82
Hello to all,
a crazy idea. 😀

Say I would want to implement a volume control at the I/V resistor level by replacing the current 1.3K resistor with a 24 step rotary switch. (I assume the TDA1543 would be fine with lower resistor values which would reduce voltage swing ).
What type/brand would you suggest ? Any other suggestions ?
 
#84
DF96 said:
If the resistor goes to ground then there are both minimum and maximum values, which some circuits violate. You can't simply put in a lower resistor value to get less volume. Read the TDA1543 datasheet.
Click to expand...


Yes the resistor would go to ground...
"there are both minimum and maximum values"... You are referring to the compliance voltage ?
I would remain within this voltage even if I lower the IV resistor...

I did actualy read the datasheet, so maybe there's something I'm not getting right..
 
#85
The best and cheapest alternative to special resistors at the I dac output (with certain sound degradation, audible no matter how special your resistor is) is to first send that I to a transistor, you then place any I/V resistor controlled with the transistor which are not sensitive to it. Then a final stage, some feedback and voilà.
 
#86
Bartb said:
Any other suggestions ?
Click to expand...

If you have a resistor connecting the TDA1543's output (pin 4) to ground to provide a passive I/V circuit, there's a DC voltage on pin 4.

If you already have a DC blocking capacitor in the circuit, your volume control needs to go between that capacitor and the pre-amp or power amp the DAC is driving.

I've had excellent results controlling the levels from both TDA1541- and TDA1543-based DACs using a stepped attenuator (IOW, your basic idea is sound) but the DC voltages must be blocked.

OTOH, if I've misunderstood your circuit, can you explain it more fully?

HTH

D
 
#88
Ryelands said:
If you have a resistor connecting the TDA1543's output (pin 4) to ground to provide a passive I/V circuit, there's a DC voltage on pin 4.

If you already have a DC blocking capacitor in the circuit, your volume control needs to go between that capacitor and the pre-amp or power amp the DAC is driving.

I've had excellent results controlling the levels from both TDA1541- and TDA1543-based DACs using a stepped attenuator (IOW, your basic idea is sound) but the DC voltages must be blocked.

OTOH, if I've misunderstood your circuit, can you explain it more fully?

HTH

D
Click to expand...


Hello, thanks for your reply. I made some wrong assumptions and it cannot be done the way I was thinking. Will consider the attenuator after the capacitor as per your suggestion. 🙂
 
#89
gabdx said:
The best and cheapest alternative to special resistors at the I dac output (with certain sound degradation, audible no matter how special your resistor is) is to first send that I to a transistor, you then place any I/V resistor controlled with the transistor which are not sensitive to it. Then a final stage, some feedback and voilà.
Click to expand...

Ahaa that is probably what I am already doing because the DAC's output feeds into a BC327. What I did not know is that in this case resistor quality is less important (or unimportant 😀 )
 
#91
#92
Bartb said:
Ahaa that is probably what I am already doing because the DAC's output feeds into a BC327. What I did not know is that in this case resistor quality is less important (or unimportant 😀 )
Click to expand...

Yessssss! unimportant 😀

I built 3 boards for my first diy dac tda1541.

El cheap o metal film 1 cent each
Flame proof from India 3 cent each
PRP 1$ each

I did the same thing with 2 Pre-amp boards PRP vs India cheapo, 0 feedback design

In both cases the Flame proof coated from India had the best sound.
The el chopo metal film didn't sound good.
The PRP sounded good but I preferred clearly the sound of the Flame Coated
 
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