MiniMax DAC - best opamps to replace stock ones?

[Audio Maniac]

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!

 

[Audio Maniac]

Some one has also recommended these ones: LME49710NA/NOPB (NE5532) and LME49720NA/NOPB (NE5534).

 

[Mooly]

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,
http://www.diyaudio.com/forums/anal...u-have-checked-see-its-stable-havent-you.html

 

[Audio Maniac]

Thanks for the reply Mooly!

Aren't those opamps lower grade than previously listed ones?

 

[vdi_nenna]

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

 

[abraxalito]

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).

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.

 

[Audio Maniac]

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!

 

[Audio Maniac]

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.

 

[Audio Maniac]

Mr. Vince,

Thanks for your help!

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

ºÍ§Ó*µ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."

 

[vdi_nenna]

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

 

[Mooly]

Thanks for the reply Mooly!

Aren't those opamps lower grade than previously listed ones?

There's a million answers to that...

Some aspects of performance are worse and some better by many magnitudes but it's how they sound that matters. The opamps I mentioned are FET types (both that I have used in various designs) and these do seem to perform well in the analogue stages of DAC's etc.

These is some reasoning that the 5532/4 types have a poor reputation for sound quality because being bjt types (ordinary transistor) that the input transistors can behave in a non linear way when faced with high frequency "hash" and noise from the DAC causing the transistors to act like diodes and demodulate the hf noise. How much truth there is in that I can't say but it does sound plausible because my own conclusions are that the FET opamps are superior in audio quality in that kind of application and yet when using the NE5532 as a simple linear amplifier the difference is far less obvious.

Why not fit sockets and see what you find.

You can always add a small cap (in the 4.7 to 22pf range) from opamp output to inverting input if you suspected any instability.

 

[vdi_nenna]

Why not fit sockets and see what you find.

Excellent suggestion.

 

[Audio Maniac]

Thank you again!

I'll do that. I'll order 2 or 3 sets of op-amps and thy them.
In fact I was in under the impression FET type op-amps perform better than BJT type.

There's a million answers to that...

Some aspects of performance are worse and some better by many magnitudes but it's how they sound that matters. The opamps I mentioned are FET types (both that I have used in various designs) and these do seem to perform well in the analogue stages of DAC's etc.

These is some reasoning that the 5532/4 types have a poor reputation for sound quality because being bjt types (ordinary transistor) that the input transistors can behave in a non linear way when faced with high frequency "hash" and noise from the DAC causing the transistors to act like diodes and demodulate the hf noise. How much truth there is in that I can't say but it does sound plausible because my own conclusions are that the FET opamps are superior in audio quality in that kind of application and yet when using the NE5532 as a simple linear amplifier the difference is far less obvious.

Why not fit sockets and see what you find.

You can always add a small cap (in the 4.7 to 22pf range) from opamp output to inverting input if you suspected any instability.

 

[Audio Maniac]

Molly and Vdi_nenna,

I did a quick search and found out OPA627 is also a FET type op-amp. What do you think of using it on the output stage and adopting OPA604 for I/V conversion? I guess OPA627 can be used on the I/V conversion stage as well, right?

 

[Mooly]

Personally I would go with the OPA604 or OPA134 but by all means try the OPA627.

Remember to check which are duals and singles too...

 

[vdi_nenna]

My only experience with opamps is between the NE5532, OPA2134 and LM4562. Mine were used in an active crossover. See pic (test phase). It has 8 opamps per channel. To my ears, the LM4562 is a winner. However, you should outfit your board with a nice set of milled DIP sockets. It's not a question of "if", but "when" you'll feel like switching out the opamps. It's too much fun not to try different types...and maybe those discrete ones too!

Also, it was suggested to use less costly opamps for the low pass and possible higher priced ones for the high pass for the XO.
I tried it and found I was missing a lot of information in the low pass by using the NE5532 and OPA2134 on high pass.
In my opinion, unless the design calls for it, use the same type opamps through out the board.

 

[Audio Maniac]

Minimax DAC already comes with DIP socket for all op-amps.

6moons audio reviews: Eastern Electric MiniMax DAC

As regards LM4562, is it a BJT or FET type op-amp?

Thanks again for your reply!

My only experience with opamps is between the NE5532, OPA2134 and LM4562. Mine were used in an active crossover. See pic (test phase). It has 8 opamps per channel. To my ears, the LM4562 is a winner. However, you should outfit your board with a nice set of milled DIP sockets. It's not a question of "if", but "when" you'll feel like switching out the opamps. It's too much fun not to try different types...and maybe those discrete ones too!

 

[vdi_nenna]

I want to say FET, but not 100% sure. It's high speed, but that doesn't exactly mean it's jfet input.

 

[SoNic_real_one]

LM4562 has a special input stage, is not a plain jfet. Anyway, for me was the best sounding OpAmp from the dual ones that I tryed. Low noise, low distortion. Close was AD8599.
If you don't belive me, maybe you belive the ESS guys (one of the best DAC's today):
Link. LME49720 is LM4562 renumbered per the new system.

 

[Audio Maniac]

Very useful link! Thanks a lot!
My Minimax uses an ESS 9018 DAC chip.

LM4562 has a special input stage, is not a plain jfet. Anyway, for me was the best sounding OpAmp from the dual ones that I tryed. Low noise, low distortion. Close was AD8599.
If you don't belive me, maybe you belive the ESS guys (one of the best DAC's today):
Link. LME49720 is LM4562 renumbered per the new system.