Very good i/v converter

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istipisti

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Joined 2005
#1
Hi!

I've tried some i/v converter to my (dual TDA1541A) dac, but, this is the best. Look at the schematic:

An externally hosted image should be here but it was not working when we last tested it.


Very-very good dinamic smooth sound. The high and middle frequencies are very good too.

Adjusing:
adjust T1's emitter resistor value. Set DC 0V to the TDA1541A output

Comment:
- the output condensator is paper in oil type
(the input resistor is for protecting the DAC output when the i/v converter's T1 dies.)

This is inverting he input, and this is good! We need to invert it to the correct phase! So every TDA1541A's converter need to do this.

Sorry for my bad english...
Is there somebody wants to try this?
Istvan
 
#2
istipisti said:
Hi!

I've tried some i/v converter to my (dual TDA1541A) dac, but, this is the best. Look at the schematic:

An externally hosted image should be here but it was not working when we last tested it.


Very-very good dinamic smooth sound. The high and middle frequencies are very good too.

Adjusing:
adjust T1's emitter resistor value. Set DC 0V to the TDA1541A output

Comment:
- the output condensator is paper in oil type
(the input resistor is for protecting the DAC output when the i/v converter's T1 dies.)

This is inverting he input, and this is good! We need to invert it to the correct phase! So every TDA1541A's converter need to do this.

Sorry for my bad english...
Is there somebody wants to try this?
Istvan
Click to expand...


Hi

Nice circuit, reminds me of the circuits I built for MC cartridges.

I'd suggest to remove the input resistor, as you want a low input impedance, the resistor degrades performance.

You can protect the DAC by adding antiparallel diodes (I use 1A Schotkky types), so the DAC never sees mre than say +/- 0.3V at its' output. This shouldn't be a problem.

You may want to replace R6 by a current source and add some emitter resistance to T2, this improves linearity.

best
 
#3
Hi Guido!

Thank You. The Schotkys are good solution for the protection! 🙂 The bottom resistor was current source in my first simulation, but... I believe in the "minimal concept". Maybe it is better.
I think my circuit sounding similar to the John Linsley Hood Class A.
But, we can put in some resistors and transistors and...

An externally hosted image should be here but it was not working when we last tested it.


I think, my version is better. 🙂
 
#4
istipisti said:
Hi Guido!

Thank You. The Schotkys are good solution for the protection! 🙂 The bottom resistor was current source in my first simulation, but... I believe in the "minimal concept". Maybe it is better.
I think my circuit sounding similar to the John Linsley Hood Class A.
But, we can put in some resistors and transistors and...

An externally hosted image should be here but it was not working when we last tested it.


I think, my version is better. 🙂
Click to expand...


Hi Istipisti,

Well, I like minimal too, so why adding 2 transistors ?

I myself have designed a tube based IV converter with less than 1 ohm input impedance to mate with PCM1704.

best
 
#9
Re: Re: Tube I/V

Guido Tent said:


Hi Arthur,

It is a mixed bag of everything, tubes intrinsically do not achieve 1 ohm input resistance.

best
Click to expand...


Hello Guido

Have you ever been tempted to build an all valve I / V stage which achieves low input resistance, and it would also be nice if it was direct coupled.

Reagards
Arthur
 
#10
Re: Re: Re: Tube I/V

PHEONIX said:



Hello Guido

Have you ever been tempted to build an all valve I / V stage which achieves low input resistance, and it would also be nice if it was direct coupled.

Reagards
Arthur
Click to expand...

Hi

All valve is possible, but I use transistors where they come in handy, e.g. biasing tubes. To me, valves are not a goal as such.

Mine is DC coupled. It has antiparallel Schottky diodes at the input to protect the DAC chip output........

best
 
#11
Guido Tent said:


Hi Terry,

There's many transistors around the tube, mainly for biasing

best
Click to expand...

Hi Guido,

Yes, I understand 🙂 This is a very good approach to I-V.

I think generally it is cleaner (more linear) but maybe a little less
euphonic than the usual dac into small value R into tube grid.

We have been using various iterations of the theme for about 5
or 6 years now.

If you can DC couple it then this is maybe the ultimate I-V I think.


Cheers

Terry
 
#12
Re: Re: Re: Re: Tube I/V

Guido Tent said:


Hi

All valve is possible, but I use transistors where they come in handy, e.g. biasing tubes. To me, valves are not a goal as such.

Mine is DC coupled. It has antiparallel Schottky diodes at the input to protect the DAC chip output........

best
Click to expand...

Guido,

Have you managed to do it (DC coupled) without a servo?

If so that is very impressive.

Cheers,

Terry
 
#17
Re: Re: Re: Re: Tube I/V

Guido Tent said:


Hi

All valve is possible, but I use transistors where they come in handy, e.g. biasing tubes. To me, valves are not a goal as such.

Mine is DC coupled. It has antiparallel Schottky diodes at the input to protect the DAC chip output........

best
Click to expand...

Hello Guido

Why use a valve at all if it is not a goal as such. You can build the I/V stage totally with silicon Direct Coupled and no valve issues.

Regards
Arthur
 
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