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Old 19th October 2011, 05:21 PM   #11
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by Audio Maniac View Post
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.
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Old 19th October 2011, 05:52 PM   #12
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Quote:
Why not fit sockets and see what you find.
Excellent suggestion.
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Old 19th October 2011, 06:08 PM   #13
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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.


Quote:
Originally Posted by Mooly View Post
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.
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Old 19th October 2011, 06:12 PM   #14
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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?
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Old 19th October 2011, 06:33 PM   #15
Mooly is offline Mooly  United Kingdom
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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...
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Old 19th October 2011, 08:17 PM   #16
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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.
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Old 19th October 2011, 08:26 PM   #17
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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!


Quote:
Originally Posted by vdi_nenna View Post
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!
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Old 19th October 2011, 08:42 PM   #18
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I want to say FET, but not 100% sure. It's high speed, but that doesn't exactly mean it's jfet input.
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Old 19th October 2011, 10:23 PM   #19
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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.
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Old 20th October 2011, 12:03 AM   #20
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Very useful link! Thanks a lot!
My Minimax uses an ESS 9018 DAC chip.

Quote:
Originally Posted by SoNic_real_one View Post
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.
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