Best opamp for I/V conversion? (DAC)

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#222
I'm glad you revived this thread. It so happens that I have a design with an OPA2134 IVC that I'll build a couple copies of so that I'm able to compare components.

I'll try to get a hold of some samples of the parts that were mentioned before.

One thing I have done, though, is to put a large feedback cap into the negative feedback of the IVC that at least limits the dV/dt as the input current abruptly changes.

Gabdx1, I'm trying to quit op amps. So maybe there should be a thread on the best voltage follower. Personally, I'm looking for one with very high (or at least purely resistive and/or capacitive) input impedance. It must be capable of driving line outputs, but I have no prejudice on architecture other than keeping the offset low. I have a funky passive IVC where it might fit.

Cheers,
Borge
 
#223
Great, I don't know anything about audio circuits

But I understand what you say and we are on the same road.

Ill use the tda1541 (sorry no voltage out) directly to transistors, ill use some filters, maybe 2 resistances and one capacitor, and also a coupling capacitor to get the dc out.

I cant tell more now but after I try it this week we shall see.

Sorry for my newbiness 🙄

'I have a funky passive IVC where it might fit. '
wich is ???
 
#225
Question for everyone that look monolithic OP´s as standalone objects of discussion.

What type of power supply regulators you use and how long are supply lines between OP and regs?

I believe that proper use and implementation of every OP is relevant for objective estimation of their sound.

Low impedance, wide band regulators (Shunt) located near OP with proper coupling near power pins, short traces for NFB (VF or CR), use of OP mostly as voltage amplifier. Don´t use them to drive any low impedance, use some kind of buffer even for driving cables and high impedance loads.

Thank you for your time.:wave:
 
#226
I am using TDA 1541 with 16 bit 8 times oversampling using CS8412, SAA 7220 and 74HCXXXX.

The output stage is 4 x NE 5534 and after which the DC block by 2 x 10uF Solen Fast Cap. I tried replacing the OP 627 x 2 at the front and NE 5534 at the back and vice versa, I dislike both confi as they sound too analytical too me.

What is your recommendation.

attached output stage

1541output.jpg
 
#227
You can modify this :

R23 C39, you can add a 15uf + 1k // with 4.7uf ( implemented like the R23, C39)

Thats the only difference i have... I don't find my sound *analytical*
I find that all the opamps reduce 3d and do bad stuff...

I found out that the ad8599 ? (dont remember) was the most detailed and natural, I didn't compaired to any discrete / ad797

I will report complete modification to my cd player very soon, it includes :

1. stacking of tda1541 (yes, one on top of the other)
2. Digital filter with chinese 30$ clock
3. i/v with active resistor,
4. dexa regulators all over
5. discrete buffer class A output stage with dedicated supply
6. tantalum an resistors all over compaired with PRP and others
7. Improvement* or see if there is BS to the 4OS of the digital filter
8. Possibily 1 caps in all my audio system, no coupling transformers, All signal resistors tantalums, the only cap is in the speaker XO and is very big with barelly no effect on sound (80uf)
9. 14 BGates caps for the tda.
10. Upgrade power supply.

The cd player is a old crap sony 610esd 1987 with new laser Bu1 and recent service + oil and clean up of parts
 
#236
"The output stage is 4 x NE 5534 and after which the DC block by 2 x 10uF Solen Fast Cap"

ccschua,
You will get a big improvement by changing the 10uf solens to a better film cap; sonicaps or the more expansive sonicaps will sound much better if you are going to stay with that current oputput configuration.

Cheers.
 
#237
IMO, the easiest way to get good sound is to use OPA627BM or OPA627SM as I/V.
I won't say they are the best.
But they are easy to get, easy to use, and especially easy to sound good.

I think one can simply apply these OPA627s and spend more time thinking about other improvements in a system.
 
#238
a simple resistor is better as each OP-AMP that I know - please refer for the exactly value
http://www.dddac.de/pcm63/DAC_I-V_Resistor.htm
(easy to realize for check out the sound quality)

for ultimate sound quality you need the I/U converter from Papa Nelson Pass - please refer in this case therefore the follow URLs:
http://www.diyaudio.com/forums/showthread.php?threadid=9910
http://calab.kaist.ac.kr/~cgkim/audio/amp/zen/www.passlabs.com/d1_ua.htm
http://www.diyaudio.com/forums/showthread.php?threadid=78968
http://www.head-fi.org/forums/f6/pass-labs-d1-clone-kit-324197/
http://www.head-case.org/forums/do-yourself/3914-opinions-pass-d1-clone.html

Until this day I haven't discover an OP-Amp with similar sonic quality. For me it is amazing, that most of the hobby and commercial developers don't use this solution
 
#239
Well there is a reason why you should choose an active part with as little input impedance as possible. The current outputs from a dac is far from linear. They are only linear in a very narrow band.

But then again. This I/V converter can be made with current mirror and an output buffer with no feedback and the sonic performance will not suffer.... And in bonus you will get a far better performance than with resistors alone

Ask Jocko Homo if he still is arround here....

- Sonny
 
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