Audio Buffer 8 years after

[PMA]

Originally Posted by Ian Finch

This is the earlier OPA134 implementation, right? It's still absolutely capable as a wideband amp, as you indicate. Thanks for the post.

Hello Ian,

this is a modification for OPA637. If you take a closer look at 1MHz sine, you would see it has 26Vp-p. For this voltage swing, slew rate at 1MHz is 81.7V/us. The OPA637 has 135V/us, so it is capable to make that. And, it has ultralow distortion as well, and low noise. That's what we need - speed, low distortion and low noise, in case we seek for TRUE amplification, rather than for colorizers.

This circuit has voltage gain of 20dB, and I need it for accurate measurement purposes as well.

Bonsai, thanks for your kind words.

Best,

[stellavox]

Have you tried the OP633 as a buffer - it's fantastic

Charles

[PMA]

Hi Charles,

thanks for your kind words.
I have only a datasheet of the OPA633, in 1996/97 Burr-Brown Linear Products catalogue. Yes, it looks like a great part.

I have worked quite a lot with LH0033.

Regards,

[pooge]

Pavel,

Do you have circuit boards available now?

[PMA]

I will have several boards on January 7th, 2011. They are for the original version from 2003, i.e.

Audio Buffer in english

circuit diagram

http://web.telecom.cz/macura/buffer_old.gif

PCB



Regards,

[motiis]

I've aggreed with Pavel, ADA4898-1 is very nice part. It has not only great spec. but it has great tone also. I using it as a buffer

[dorkus]

thanks for the info Pavel - very interested in the ADA4898, haven't seen a lot about it.

so, the real test - how does it all sound?

cheers,
dorkus

[PMA]

The ADA4898-1 souds very good, with regards it is an opamp. Frankly speaking, I prefer sound of certain discrete topologies to any opamp. Anyway, good opamp + BUF make good sound solution. The circuit is compact, smaller size than discrete circuit, and very easy to build. For beginners, I would vote for opamp + BUF. For those who seek for highest sound quality, go for a discrete design.

[dorkus]

hi pavel,

thanks for the input. i agree with the "with regards it is an opamp" part. in my experience reviewing and auditioning commercial gear, there is a certain homogenized, grainy quality from the upper midrange on up that IC opamps have trouble shedding, relative to the best discrete (or tube for that matter) designs.

i assume we are talking about the distinction between IC and discrete though, and not necessarily the opamp topology? e.g., the discrete opamps in Bryston electronics sound very good, and not at all like IC's, though the sound is perhaps not as unencumbered and open as the best low or no-global feedback designs.

perhaps i will give the ADA4898 a try as a replacement in existing circuits though, e.g. my Onkyo CD player which sounds very good despite the use of 5532's. it will be tricky optimizing things... i may need to proto up some DIP daughtercards to i can get the bypassing and layout right.

cheers,
dorkus