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Old 24th November 2012, 03:09 PM   #1
freax is offline freax  Australia
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Default Brainstorming over different methods to convert op of TDA1543's

I was just thinking that if you were to parallel many TDA1543's (say 10) and then take their R + L outputs which are generating current, wire them in parallel and then put the sum of this output onto the leg of a capacitor for each channel that you would charge the capacitor using current alone THEN dischage this capacitor into a grounded resistor inorder to generate voltage.

What would be the benefit of this? Every design I see has the resistors before the capacitors, but I think that by massivley paralleling TDA's then using them to charge a single capacitor which then feeds into a resistor would be far more powerful/transparent.

What do you guys think?

Also... Another idea. using vacuum capacitors instead of ordinary types, is it possible to use this with the output of a TDA chip? Has anyone done it before?

Thank you if you contribute.
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Old 24th November 2012, 03:30 PM   #2
freax is offline freax  Australia
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Another idea I've had, is this.

Lets say you have the single output of one side of a TDA1543. you then parallel 10 of these outputs but add capacitors instead inbetween each junction inorder to produce a cumulative effect.

Example:
Click the image to open in full size.

Has anyone done something like this?

The squirrely thing is a resistor.

The box things to the far left are single dac current output chips.

and the two flat line things are capacitors.
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Old 24th November 2012, 03:59 PM   #3
DF96 is offline DF96  England
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Discharging a capacitor into a resistor produces current; you already have voltage due to the charge on the capacitor.

I don't understand what you are trying to achieve. The output current from the DAC chip (or parallel chips) is the signal. Why create an HF slope by putting it into a capacitor?
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Old 25th November 2012, 12:09 AM   #4
freax is offline freax  Australia
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I'm trying to produce a lot of current then dump that into a vacuum tube. I would think that by adding capacitors that there would be a coupling effect and each circuit (1543) would be properly matched and therefore produce a far more stronger output while at the same time increase precision by averaging the values.

I think that by properly matching each chip that there would be a substantial increase in precision, but as you say it introduces a HF slope, interesting.

Sorry it was an idea that i came up with last night at like 3am.. haha

Has anyone cooled these dac chips using liquid nitrogen and using higher voltages? or peltiers.

what were the effects?

I should think that there would need to be some kind of shielding (grounded copper tape) between the dac chip and the peltier device inorder to reduce the possibility of inducing current from the peltier unit into the dac chip because of the constant turning on/off of a peltier unit inorder to maintain an accurate temperature.
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Last edited by freax; 25th November 2012 at 12:13 AM.
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Old 25th November 2012, 02:36 PM   #5
DF96 is offline DF96  England
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To produce lots of current you parallel the chips. This is a standard technique with 1543 as it helps cancel random errors. The danger is that you can end up with too much current for most valve stages. The proper match for a current-output DAC is a short-circuit sitting at the correct DC level.

The usual opamp virtual earth input provides this, but opamps can struggle to handle the HF stuff on a raw DAC output. Resistors (passive I/V), unless very low in value, usually generate too much voltage so exceed the AC voltage rating for the chip output and generate distortion or even clipping. The fact that some people miscalculate the resistor values does not help. See my website for some pointers on this.
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