DOA comparison

[living sounds]

Here is a comparison of five DOAs in the summing position of a 16 channel console. The summing op amp  (usual inverting configuration with a feedback cap) drives an old German made transformer from which the output goes straight to the converter.  The mix was done with the AC sound op amp in place and then only the console turned off to change the op amps. The rest of the gear stayed on. There's one guitar on the right side mixing for half of the 1731 track. Only processing was quite a lot of limiting to get a realistic picture, as well as conversion to mp3.

Op amps used:

-AC sound 2520 (API type)
- GAR1731 (ClassicAPI Melcor clone)
- APP992 (discrete FET-based DOA)
- BB2521 TI (ClassicAPI hybrid op amp using a Texas Instruments NE5534)
- BB2521 Phillips (ClassicAPI hybrid op amp using a NOS Phillips NE5534)

Song is "Backroom In Tulsa" from Wesley Morgan for which the multitrack can be found here:

http://www.cambridge-mt.com/ms-mtk.htm


Tracks:

https://dl.dropboxusercontent.com/u/15815132/ACsound_2520.mp3
https://dl.dropboxusercontent.com/u/15815132/APP992.mp3
https://dl.dropboxusercontent.com/u/15815132/BB2521_5534_Phillips.mp3
https://dl.dropboxusercontent.com/u/15815132/BB2521_5534_TI.mp3
https://dl.dropboxusercontent.com/u/15815132/GAR1731.mp3


BTW: Don't bother trying to line up and null files, DAC and ADC ran on their own clock for better sound, so they are drifting out of sync.

 

[JohnRoberts]

Of course you could null say a left vs right bus in real time.

from several tests you could identify which are more different from the others.

I ASSume the ones that are more like each other are the more accurate.

JR

 

[abbey road d enfer]

I don't hear any difference.
I guess if there are, they are buried by the transformer's response and by the mp3 encoding (and by my aging ears).

 

[12afael]

what I can feel

ac sound - very lively
APP992 - a bit dull less lively
BB2521 phillips  - very acurated
BB2521 TI  - very acurated I couldn't tell any difference with the phillips
GAR1731 - a bit smooth close to the ac sound

The mix sound fantastic!

 

[living sounds]

Of course you could null say a left vs right bus in real time.

from several tests you could identify which are more different from the others.

I ASSume the ones that are more like each other are the more accurate.

JR

I've done that before here and routinely do it for testing, but this one is purely for listening.

 

[living sounds]

I don't hear any difference.
I guess if there are, they are buried by the transformer's response and by the mp3 encoding (and by my aging ears).

The transformer is fairly transparent (just adds a little low end bump, distortion measurements at higher frequencies are indistinguishable from transformerless outputs). Mp3 encoding is very high quality, it should be much harder to tell these mp3s apart from their wav counterparts than differentiating the different op amps.  But everyones ears and system are different. And sensitivity to these things might vary with time of day or other factors.

 

[living sounds]

what I can feel

ac sound - very lively
APP992 - a bit dull less lively
BB2521 phillips  - very acurated
BB2521 TI  - very acurated I couldn't tell any difference with the phillips
GAR1731 - a bit smooth close to the ac sound

The mix sound fantastic!

Interesting, keep it coming! I'll refrain from posting what I think (I've been reviewing these op amps for months now, so I know pretty well what to listen for).

And thanks, great you like it! The multitrack is pretty good (despite the excessive noise and bleed).

 

[DerEber]

I realy prefer the APP992!
Yes it is dark for me too, but don´t know. Just rocks to my ears.  ;D

 

[living sounds]

I realy prefer the APP992!
Yes it is dark for me too, but don´t know. Just rocks to my ears.  ;D

Interesting. 

 

[andybaker28]

HI There

So glad you posted this comparison. To me the AC sounds a bit more clear on top and on bottom too. But mostly my impression was that is quite a bit more 3D. Is this also what you find?

Thanks!

what I can feel

ac sound - very lively
APP992 - a bit dull less lively
BB2521 phillips  - very acurated
BB2521 TI  - very acurated I couldn't tell any difference with the phillips
GAR1731 - a bit smooth close to the ac sound

The mix sound fantastic!

Interesting, keep it coming! I'll refrain from posting what I think (I've been reviewing these op amps for months now, so I know pretty well what to listen for).

And thanks, great you like it! The multitrack is pretty good (despite the excessive noise and bleed).

 

[Humner]

What mixing desk did you use for this?

 

[ruffrecords]

I wonder whether the differences you hear are actually due to the op amps themselves or just their reaction to the circuit in which they are placed? Using regular op amps in a virtual earth bus can introduce all sorts of artefacts into the mix (check out Steve Dove's excellent articles on this topic). Stray capacitances can make a lot of difference. I don't know why more designs do not use a Transamp topology for the VE mixer op amp as this avoids most of the problems you get with regular op amps used as VE mixers.

Cheers

Ian

 

[living sounds]

It's a Soundcraft 200b, very heavily modified.

I guess it's probably both the differences from the op amps themselves as well as how they react in the circuit. But overall these results reflect quite accurately what I have heard from these op amps used in different positions, e.g. noninverting as a fader buffer or in the make up stage of a passive EQ.

 

[JohnRoberts]

I wonder whether the differences you hear are actually due to the op amps themselves or just their reaction to the circuit in which they are placed? Using regular op amps in a virtual earth bus can introduce all sorts of artefacts into the mix (check out Steve Dove's excellent articles on this topic). Stray capacitances can make a lot of difference. I don't know why more designs do not use a Transamp topology for the VE mixer op amp as this avoids most of the problems you get with regular op amps used as VE mixers.

Cheers

Ian

I wrote about using transamp for VE summing in my 1980 console design article. Paul Buff also described that in his application notes.

There are several possible explanations for audible differences between DOA in a VE summer operating at high noise gain. The higher the closed loop gain, the less open loop gain left over (loop gain margin), to force the op amp for follow the feedback network, revealing more of the DOAs raw open loop characteristics. The higher the closed loop/noise gain the more different they can sound.

JR

 

[ruffrecords]

Unfortunately it looks like Paul Buff is sadly no longer with us. Do you happen to have a link/copy to/of his application notes?

Cheers

Ian

 

[JohnRoberts]

Unfortunately it looks like Paul Buff is sadly no longer with us. Do you happen to have a link/copy to/of his application notes?

Cheers

Ian

Yes he passed away just about a year ago. RIP he was a good guy and smart as a whip (smart enough to leave the audio business decades ago.  8).  )

http://www.ka-electronics.com/images/pdf/valley_people_trans_amp_applications.pdf

Here's a link to the app note over on Wayne's forum. Lots of pearls like this over there. (Look at AN-2 for the VE summer)

I've been cleaning up and throwing stuff like that away the last few years... I think I sent Wayne a box full of manuals and app notes, for all kinds of stuff (maybe even that).  I knew Paul and used his VCA in a compressor I did at LOFT, back in the early 80's.

JR 

 

[bruno2000]

Wait..............you're asking for critical listening comparisons using mp3 files?????????????
Best,
Bruno2000

 

[surfkat]

OK, so I'm late to the party but here's my 2 cents if you are listening.
The GAR stands out above them all as the smoothest, most vintage sounding and the one I like the sound of.
The AC has that hyper realism that seems to be all the rage with the kids. It's like a poke in the ear with a sharp stick to me.
The APP is the second best of the bunch, pleasant but not as smooth as the GAR.
The other 2 were too close to tell much difference although both were good.
Not a bad one in the bunch but I gotta go with the GAR.

By the way cool song, unique sound and a nice mixing job.

 

[living sounds]

OK, so I'm late to the party but here's my 2 cents if you are listening.
The GAR stands out above them all as the smoothest, most vintage sounding and the one I like the sound of.
The AC has that hyper realism that seems to be all the rage with the kids. It's like a poke in the ear with a sharp stick to me.
The APP is the second best of the bunch, pleasant but not as smooth as the GAR.
The other 2 were too close to tell much difference although both were good.
Not a bad one in the bunch but I gotta go with the GAR.

By the way cool song, unique sound and a nice mixing job.

Interesting.  8)

Since I made the test I did a few more and made changes to the rest of the equipment.  The AC op amp had cheap Indian transistors in them, changing them all to Fairchild brand made it sound and measure a lot better. 

I ended up with TI NE5534, not only there but almost everywhere in the console (5532, too). Most transparent option, I now think it's better to not have a fixed amount of a certain mojo always in the console. I found the most most recent TI 5532/5534 to sound better than vintage ones, not only in the console but in other gear, too.

Yes, great song and great multitrack, I only did the mixing.

 

[MicDaddy]

Living sounds, did you happen to try On Semi 5534?