DAC 2496 (AK4393) DAC KIT With CS8416+AK4393+5532 - Page 233 - diyAudio
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Old 17th December 2012, 11:01 AM   #2321
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Default op amp continued

I have found that the higher the slew rate of the op amp was high, at more dynamic listening decreases.
Treble quality MC1458 (dual 741 !) are not very good but the dynamics and focus instruments are great! Very close to the sound of tubes, very life and presence.
Treble and harmonics are much more respected with OPA 2604 or LM4562 for example but the dynamics is very flat, the sound is lifeless, it is not very musical, i can't listen as is !.
Someone has an idea about this? I do not understand this phenomenon. I think the decoupling capacitors which certainly have a greater effect on an fast op amp while the MC1458 is too slow to be affected by a poor decoupling. I have not made ​​these changes.
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Old 17th December 2012, 11:21 AM   #2322
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I think there are many reasons...

Firstly you may just like the sound you hear with the 1458, there's no shame in that. Also we don't (I think... haven't read the whole thread) know what your points of reference are, what your system is, what speakers/amp etc you are using.

Drop a 741 (used correctly and within its limitations) into a €$10,000 system and it isn't quite the doom and gloom that many assume.

Also, are you sure the faster opamps are totally stable,
Swapping Op-Amps... you have checked to see it's stable haven't you ?
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Old 17th December 2012, 11:52 AM   #2323
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Hello Mooly, thanks for your answer.
My system is:
AMP : JLH class A 15 Watts diy amp / DIY 300 B 10W amp with Lundahl Output SE 1623
SPEAKERS : KLIPSH RF82 (98 db/1w)- FOSTEX FE103S TQWT
SOURCES (digital out use only): SQUEEZEBOX TOUCH / MARANTZ CD42 MKii
SOURCES ANALOG : LENCO L75 with Denon DL110 cartridge - DIY TUBE SRPP Riaa preamp like Hiraga.
DAC : TNT CONVERTUS 1543 x4 in // with triple psu and more than 100 000 uF filter caps
AK4396 DAC KIT bought on Ebay as is.

The sound of TNT Convertus is very very dynamic in comparison with AK4396.
The dynamic is in comparison when i use a mc1458 but not the sound.
Regards
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Old 17th December 2012, 12:08 PM   #2324
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Seems like a very decent set up and one thats capable of showing the differences in components.

I would perhaps take the Marantz as a kind of reference... and so maybe the sound you experience with this DAC is "how it is".

I would really expect something like the OPA2604's to be better than the 1458 on extended listening so maybe something is going on stability or "compatability" wise.

Don't know what to suggest... it might just be the way it is for this DAC.
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Old 17th December 2012, 12:24 PM   #2325
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I have tested the OPA2604 and i don't like it. Flat dynamics and too much highs. I prefer the 2134, the sound is more "live" and warm but dynamics are too flat too. I have tested the OPA2604 and i don't like it. Flat dynamics and too much highs. I prefer the 2134, the sound is more "live" and warm, good focus too, but dynamics are too flat . Original 5532 is very bad , i prefer a TL072 instead !
I'll test a good decoupling for the opamp, I'll see if that changes anything.!
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Old 17th December 2012, 03:45 PM   #2326
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Best advice I can give is to trust what you hear

Listen for an extended time, perhaps a few days or more to each. And go with what you like. At the very least you need to scope the opamp and check stability. You could also try a small (in the 5.6 to 22pf range) cap across each opamp from output to inverting input. So thats two caps per opamp.
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Old 17th December 2012, 04:02 PM   #2327
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Your suggestion to add a capacitor is to prevent oscillation?
For now it is the OPA 2134 which seems to me the best balanced choices.
I'm waiting Christmas for my new digital oscilloscope, I know what I'll do and measure during my vacation!
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Old 17th December 2012, 04:05 PM   #2328
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The cap would tame any tendancy to oscillate. You might also be interested in this if you like experimenting,
A Different Opamp Compensation Technique.
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Old 17th December 2012, 05:43 PM   #2329
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Ok but there's already a 1 nf cap between output and inverting input on the op amp. I don't think there's an oscillation but a design problem . Have a look on the shema: HobbyAudio.Com: CHEAP DAC KIT MINI2496 AK4396
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Old 17th December 2012, 06:32 PM   #2330
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Those opamps are wired as low pass filters. So the small cap I suggested would have no effect.

I think this is coming down to just listening preferences. The fact you like the sound from the 741 type opamps is fine. Without testing that's the only real conclusion that can be drawn.
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