Zen I/V Converter

[Melon Head]

For your simulated circuit, you should consider changing :

1) C1,2,5,6 to 10uF minimum
2) R8,16 to 10k (using 500ohm to drive a 1k load is a bad idea)
3) add caps (100uF) to gnd after R9,10,17,18

I would use a complimentary follower with a single pair of 2SK170/2SJ74 and no source degeneration. Hardly any distortion with 10k load.


Patrick

I will try all of those suggestions

Regarding 1) I thought I could lower the caps because the circuit is now seeing 1 Meg as opposed to 10k or 20k.

 

[EUVL]

I misread your values of R8,R16. Sorry.
You could use 100k for those and then 1u for the caps.

Patrick

 

[EUVL]

> Or pick some bigger Jfets.
> Hint: Look at some of the switches.

You mean bigger in terns of package size than TO92 ?


Patrick

 

[Melon Head]

The only thing I can think of that Nelson might be suggesting here is the Power Jfets from Semisouth. So it would have to be a D1 circuit.

I will have a look around and see what I can find.

 

[Zen Mod]

seems that PCM63 have own internal diode(s) on output

 

[juma]

....
I would use a complimentary follower with a single pair of 2SK170/2SJ74 and no source degeneration. ...

It's worth noticing that such a buffer is topologicaly a push-pull and its' sound character is somewhat different. Its' input capacitance is significantly higher too. That's the price to be paid for higher drive capability...

 

[EUVL]

All correct, except that before I put a 4.7n at the output of the IV stage, I am not too worried about 41p at the input of the complementary follower.
A push-pull buffer stage has less distortion and lower output impedance.

But use what you fancy. All matter of taste.


Patrick

 

[qusp]

so biasing source at AVCC/2 (or close enough, the exact V doesnt seem to matter all that much) is no problem due t o being Vground right? for sabre users input Z really should be quite a bit lower, i'm not even sure paralleling the jfets will get us there for best DNR; but the sound is another matter I guess. I have DCB1 PCBsready and waiting for a reason and this seems like a good one, but I need to tick a few more boxes yet. BTW this would be for ackodac not buffalo II. same diff though as far as numbers that matter here.

linear systems JFETS would seem the logical choice here no?

 

[gaetan8888]

Hello

To use the Zen I/V Converter with a TDA1541A, do it need any modification ?

Thank

Bye

Gaetan

 

[Nelson Pass]

It's a current output DAC whose current is within the limits
of the bias, so I assume not.

 

[gaetan8888]

Hello

I can't find any 2SK170 and 2SJ74 here arround.

Do it need to be very low noise jfet ?

Bye

Gaetan

 

[juma]

... To use the Zen I/V Converter with a TDA1541A, do it need any modification ?....

It will work as it is but performance will be sub-optimal.

 

[Tea-Bag]

It will work as it is but performance will be sub-optimal.

That's too bad. There are lots of DIYdac's using that chip. We should focus on making it optimal, or better than resistor I/V

 

[Melon Head]

Can someone well versed in dac's, present a list here that would be a reasonable match with this circuit.

How do I determine whether 5 Ohms to 15 Ohms is going to be a problem for a particular dac?

 

[Nelson Pass]

It will work as it is but performance will be sub-optimal.

Do you have any data on that? The manufacturer does not
mention voltage degradation in the data sheet.

 

[juma]

Do you have any data on that? The manufacturer does not
mention voltage degradation in the data sheet.

TDA1541A datasheet (page 7) says:
"Notes to the characteristics
1.To ensure no performance losses, permitted output voltage compliance is ±25 mV maximum."

I made 3 DACs with that chip, tried various I/V solutions and found out that it really sounds best with DAC's output as close to 0V as possible.

Snap from datasheet:

 

[crt]

What about PCM1704
Still suitable with ZEN I/V ?

Regards
La Ode

 

[gaetan8888]

Hello

Normally, for the TDA1541A, wen using a resistor I/V, you need your resistor to be arround 30 ohm.

How much ohm impedance are the ZEN I/V ?

Anyone compared the ZEN I/V to the D1 ?

Thank

Bye

Gaetan

 

[Melon Head]

Try reading the article.

 

[EUVL]

@thanh1973

Did you receive my email thru the forum ?


Patrick