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Old 18th October 2011, 07:02 PM   #1
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Default MiniMax DAC - best opamps to replace stock ones?

This is my first thread in this forum!

I would like to know the best opamps for the following applications:

1 - I/V conversion stage. The stock opamps are 2 x NE5532. After this opamps, there're 2 outputs stages, one based on a single tube (12AU7) and other SS with the opamp NE5534

2 - For ss output satage. The stock unit is a NE5534 (also 2 units).

Although I used to work as electronic technician in the past, I am a newbie in audio modifications. I found some dual mono AD825, AD827 and also OPA627 and would like to know if I can simply take off the stock units opamps and then stick the new opamps in?

I'll appreciate any help!
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Old 18th October 2011, 08:27 PM   #2
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Some one has also recommended these ones: LME49710NA/NOPB (NE5532) and LME49720NA/NOPB (NE5534).
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Old 19th October 2011, 07:56 AM   #3
Mooly is offline Mooly  United Kingdom
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You have many choice...

I would suggest OPA2604 and OPA604 or OPA2134 and OPA134

As always and without seeing a circuit I always advise you check for stability,
Swapping Op-Amps... you have checked to see it's stable haven't you ?
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Old 19th October 2011, 12:59 PM   #4
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Thanks for the reply Mooly!

Aren't those opamps lower grade than previously listed ones?
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Old 19th October 2011, 01:29 PM   #5
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May I suggest the following. They sounded better than the OPA2134 in my active crossover. Also replaced NE5532 in a phono pre.

LM4562 - Dual High Performance, High Fidelity Audio Operational Amplifier

LM4562 dual opAmp
LME49880 dual opamp
LME49710 single OpAmp

Price is reasonable and the improvement was very obvious.

If you are able, you should build your own discrete opamps.
See Pass Diy for a PDF on DIY Opamps in the Projects sections.
No monolithic opamp will top a discrete opamp. Very good quality and low parts count.

Vince
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Old 19th October 2011, 01:43 PM   #6
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Quote:
Originally Posted by Audio Maniac View Post
1 - I/V conversion stage.
This needs wide bandwidth as standard. LM6172 works well, OPA2890 might be worth a punt for where low supply current is a requirement. The 2890 is low supply voltage though (12V).

Quote:
2 - For ss output satage. The stock unit is a NE5534 (also 2 units).
Something with fairly beefy output drive. Could try LM6171. NE5534 isn't so bad in this position as in I/V.
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Old 19th October 2011, 02:39 PM   #7
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Mooly, nice thread!

I've seen many threads on internet where DIY hobbyists replace op-amps on their tastes. At first I thought there would be possibility of stability issues but as nobody talked about it, eventually I accepted the idea it wasn't a deal. Now I discovered swapping op-amps it's not that simple.

I was about to replace the stock op-amps of my MiniMax DAC, but because of your warning I will rethink it as I don't have a scope.

Thank you very much indeed!
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Old 19th October 2011, 02:41 PM   #8
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I don't care about the op-amp price as long as it doesn't cost $50 each. A expenditure of $100 plus shipping for the whole package is acceptable.
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Old 19th October 2011, 04:06 PM   #9
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Mr. Vince,

Thanks for your help!

What do you think of a Audio-GD discrete op-amp?

ͧ*响

"If you are able, you should build your own discrete opamps.
See Pass Diy for a PDF on DIY Opamps in the Projects sections.
No monolithic opamp will top a discrete opamp. Very good quality and low parts count."

Last edited by Audio Maniac; 19th October 2011 at 04:08 PM.
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Old 19th October 2011, 04:48 PM   #10
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Most likely they will sound better than a monolithic opamp, but I don't like that they have so many parts as seen in your link/photo. That's a personal preference. With that in mind, if you look at a schem of a monolithic IC opamp, they have many transistors also. The difference is that a discrete opamp's transistors are bigger and can handle more power. They can also be chosen for audio grade properties. One can also use better caps and resistor in discrete builds. The down-side it that discrete OAs cost much more $$. You will have to decide. Just be sure your PCB and case have space for a discrete opamp.

DEXA Technologies Discrete Audio Op-Amp

The Pass DIY Opamps only use 3 active components, and those components are audio grade jfets. Problem is you'll have to do some jfet matching, designing, building and testing yourself, but I bet it will sound terrific. If you are unsure about building them, just buy ready built discrete opamps.

I used the National opamps in place of building my own opamps. Too many project, so little time! However, it's the one thing in my system which needs to change to discrete!

Enjoy and let us know how it turns out!

Vince
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