Raindirk Concord opamp swapping thoughts......JLM99V's etc

[karloff70]

Hi Chaps, been a long time.....

I have bought a 20ch Raindirk Concord and am looking to up its ante a wee bit as she needs a bit of love anyway. I'll probably let Cyril recap the master/busses and do the channels myself over a while, but a few thoughts need solidifying and I need your help/advice.

Three things I want to change:

One, I'd like to open up the sound and drop the noise on say 4 or 6 mic pre's by help of new opamp. They sound great, but pretty vintage and it would be nice to have an even lower noise/more open alternative on a few channels. The pre starts with a Pikatron NTM4 1:4 tranny and then into a Signetics NE5534AN, which I gather is a good'en (and definite keepers if I pull some...), but what could I swap straight to lower noise/open the sound up? Straight, as in ideally not much more current draw and no need for extra caps to stop oscillation.....

Two, I want to change the eq a little. The top shelf is at 10kHz and I might try it at 12 instead, and while I'm in there might try some different cap types for more glassy/shiny top. Very neutral at the mo (styro caps), which is good, but top shelf wants to sing a little I reckon. Also the top shelf and the hi mid sweep are a little on the noisy side when boosting loads. They have TL072' or 5532's in them. What is a good'en here to kill the noise? Again, don't really want to fuzz around with extra caps/opamps that cost buckets, just less noise that still sounds as good.

Three, and here is where Cyril is going to come into it, is the busses/Master section. I'll give this to Cyril to recap, but before I do I'd love to hear some opamp swap possibilities for these. There'll be 5532's and 5534's in there at the mo. Would like to clear it up a bit and lose some noise. And THEN I would love to try a set of JLM99V's on the main and control room outputs!! To have the Neve-ish but clearer Malone-lens over the whole thing.....anyone tried them in that capacity? Feedback of your experiences would be very appreciated!!! I think its active summing in there, but not sure, have to check with Cyril....


So......sorry for the lengthy post and the many questions......any wisdom coming my way would be utterly appreciated!!!! Trying to get it all together and not confuse Cyril with rubbish talk, so to sort all this out before hitting him with the plan.....not looking forward to asking the man to 'bastardise' his own creation.....

 

[pucho812]

carfull when swapping chips as you may get oscillation. as for replacing the 5532 why? it's a perfectly good opamp.  maybe try an opa2604?

 

[abechap024]

carfull when swapping chips as you may get oscillation. as for replacing the 5532 why? it's a perfectly good opamp...

2nd especially the old Signetics NE5534ANs.

 

[karloff70]

Thanks guys. Aware the Signetics are good stuff and like I say, if I end up pulling any I'm definitely keeping them. Just keen on losing a bit of noise from the eq/master/busses and also try to see if a different chip would open up the sound plus lose noise in the mic amp as an alternative flavour on a few channels.

Is the OPA2604 drop in replacement, no need to add caps to stop oscillation? Current draw similar?

Any thoughts on JLM99V's on the outputs?

 

[pucho812]

the 2604 and 5532 share the same pinout. As for current draw wouldn't know off hand..


here is a 2604 link

http://focus.ti.com/docs/prod/folders/print/opa2604.html

and here is a basic 5532 link

http://focus.ti.com/docs/prod/folders/print/ne5532.html

As for doa on the output,  if you ask me a perfectly good  IC opamp works fine and can sound as good or better then a doa in some cases.

 

[karloff70]

Thanks, I'll check it out!

Any other thoughts on 99V for desk output, anyone? Or low noise 5534 replacements?

 

[jensenmann]

2604s are FET input dual opamps, 5534 BJT input single opamps. They are not interchangable.
If you want to keep noise low you need a BJT input opamp with a similar OSI (optimum source impedance) as the 5534 has. The combination a 5534 plus 1:4 tranny (Focusrite was using a 1:5 Lundahl in their ISA110) gives the best input noise behavior for a microphone as source. FET input opamps have a very different OSI than BJT input hence creating much more input noise if dropped into this particular circuit. Using FET input amps for mikepres only makes sense (from a noise-poit-of-view) with a high ratio tranny or external input transistors to match impedances better.
5534s are not unity gain stable and have a compensation cap added externally. That should be removed with other opamps.

5534s are low noise and low distortion in my book. There are very few opamps which beat them performance wise.

 

[abechap024]

I have a discrete opamp that is interchangeable with the ne5534. I have one that I stupidly covered in epoxy (thinking I was somehow thermally coupling everything) And it works fine for about 30 minutes then everything heats up too much and squeals off to who knows were. let it cool off its good for another 30 minutes.

No use to me, but i would be happy to send it along to you want to do tests with it. Send me a pm if u don't think it will be more trouble than its worth!

I should keep my opinion to myself, cause no matter what I say it will seem biased...but if you want clean and pristine modern ICs do that very well. You want mojo and other "goodness" I would go discrete.

All very subjective, and possibly sometimes not worth the switch. But like everything else music related those are very personal choices that you will have to make yourself.

I've had goodluck changing the opamps in my console to some more modern chips (opa228, 227s) and then discrete opamps for mix buss amps. I then have some modern ad797 on main mix amps. For me and my console it seems to be a nice amount of mojo while still keeping it somewhat clean.

 

[karloff70]

Wow! Superb info! Thank you!

Jens, you just saved me fecking around with the wrong chips in the mic pre then....nice one! With the mic pre it actually is very quiet already, only the top end is very 'vintage'. This in general I really like, but it would be nice to have a handful channels where the top end response is more open for things like fingerpicked nylon, where I am finding once I open it up with eq it borderlines the noise.....a more open preamp and no eq= sorted. Any idea what type of opamp would basically perform like the 5534 in this circuit but be more open sounding in the top end?

Abechap, thanks for the offer but that does indeed sound like more trouble....I was thinking the mix bussing in your vein though, in theory at least, as in open up with more modern opamps and then DOA on the end for a flavour, like JLM99V or Red dot 2520 e.g. Whether I'll go there, let's see....would a DOA work in the mic pre circuit, Jens? That could be sweet if so........for say 4 channels.

 

[pucho812]

my bad I misread that it was a 5532 in the mic pre and not the 5534 :-[

 

[jensenmann]

Any idea what type of opamp would basically perform like the 5534 in this circuit but be more open sounding in the top end?

Give a LME49710 a try. It needs additional PSU decoupling (0,1uF caps from v+ and v- to ground) as near to its pins as possible. It is possible that you need to tweak the bandwidth limiting cap. Since it´s a very fast chip you should check if the circuit is oscillating, even in the MHz range.

Not only chips are a source of noise. The circuit is important, too. You can improve noise by changing resistors, for example.

 

[karloff70]

Hmmm, resistors....been thinking that...the whole desk is brim full of carbon......but I really don't fancy going there if I can help it. Get a feeling they do a part of the sound I am liking too.

What about a DOA in the mic pre? There are no transistors, does this mean with luck I could swap the 5534 straight for a DOA like a 2520 or such without altering the circuit? I can scan and post the schemo if need be....

And what about e.g. LT1358 or LT1352 in the high shelf eq instead of 5532/TL072? Would they need caps to prevent them oscillating?

 

[Rob Flinn]

A Raindirk Symphony, probably one of the lowest noise consoles money can buy, is full of 5534 & 5532.

 

[karloff70]

I am aware of that. This thing however at the moment is not 'one of the lowest noise' things money can buy.

And also, really I am looking for 3 things, a few channels with more open (and maybe even lower noise...) mic pre, the top eq bands to be less hissy when at lots of boost (and please don't say "you shouldn't boost that much anyway....") and to open the mix buss and the busses in general up a bit, plus maybe hang a set of DOA's on the end for a colour.

Now, a Symphony is a design holding 5534's and 5532's. This thing is too (actually most were originally TL072's). I do not want to redesign the desk. I am looking for ways to achieve my 3 objectives, by way of opamps if possible. So whether a design with 5534's can be very quiet does not really help me here......

I also need to still recap the PSU, which hopefully will remove some hiss (maybe most of it). Maybe after that I will only bother with the master section /some DOA's on the end. But the eq is hissy on boost, even old reviews at the time state this, so if I can improve that I want to, and the pre's are nice but dark, so a few brighter ones would also be great....so there we are again............

 

[abechap024]

Do you have the schematic?

Maybe changing out a few key carbon resistors will help on noise. (Sum busses??)

The higher impedance the resistor the more noise it will most likely generate is my understanding.

It will be a very cheap fix parts wise.

Also, you haven't recapped the thing yet have you? I would do that, then you know what your dealing with. Often times old caps make for a nosier board.

 

[abechap024]

....And what about e.g. LT1358 or LT1352 in the high shelf eq instead of 5532/TL072? Would they need caps to prevent them oscillating?

Asking questions like that is anyone's guess. No one will know unless they actually get inside your board and switch one out. There are lots of variables. It depends on power, filtering, the circuit (big one), what sort of compensations are already built in, layout etc etc...

One thing I will warn, is that even if an opamp "appears" stable but not properly compensated it can have spurious oscillations. Example: a while back redid parts of my board with opa228 (a notoriously unstable opamp) well It sounded fine, looked ok on the scope so I left it in a few channels uncompensated. Did some recordings and those channels got the duty of toms and yea....once I started compressing the toms I'm like, whats that high frequency whistling sound? The transient from the toms was setting off the opamps...

 

[karloff70]

I do have the schematic, but no easy way at this moment to get it in here....

Either way, I think I'll go for recap of the PSU and Master section first to see what's really bad enough to want to bother after that. It's only that I don't really feel comfortable doing the master myself first thing, so was thinking Cyril at Raindirk is the obvious man for it. And since he'd be in there I wanted to do some homework on what other things could be maxed while he's in there ....like the DOA on the end idea.....stuff that I can't easily do.

Tryng a chip for a mic pre on a channel and a different cap on the top shelf and some resistors is within my remit of comfort, puttin DOA's in the master of the desk is not. Basically, recapping and playing around with channels after I don't mind so much. Wouldn't shut down the whole desk if I f*** up once or twice.....

So really this is a fact finding mission to present to Cyril as ideas to integrate ......I guess I'll just talk to him about where in the bussing the carbons could beneficially go and whether it would be easy to put the DOA's on the end. Just didn't want to mess with his head with lots of loose unformulated ideas about opamps for the master/busses. Also skint as at the moment, so having him spend less time doing it is essential rather than messing with options for ages....can't afford that just now. Getting the desk itself cleaned me out. Need to regroup, but also need this beast smiling a bit more asap.....

 

[abechap024]

Nice. Good thinking. If you think of it you should come back here and let us know what he recommends. It would be interesting to hear.
I can understand not wanting to mess anything up. But when it comes down to it, most things are very fixable. Half the fun is learning...(sometimes)

Sounds like your going to have a great board!

 

[karloff70]

Indeed will have. It sounds good already, but you can tell it wants recapping...random differences between channels, etc. The sound is a bit on the dry side though, fat, but dry.....which is why I am ogling the JLM99V flavour over the whole thing.........question is how much a couple of those on the end of the active summing will actually do.....have to try it though I reckon. Always fancied that as a concept (99V on mix outs) and now I have the desk to try it with....

Ok, thank you all, fact finding mission I guess kind of aborted then. Will recap first and then see......

 

[abechap024]

Yes, unfortunately people can give you a lot of good advice, but your going to have to endup doing most the footwork yourself when it comes down to how much compensation etc etc.well if your looking for color, aren't the jlm99v supposed to be pretty clean? There are lots and lots of opamps that you can try and switch out...

Also heres a pretty nice chart of some opamps you can try:

http://tangentsoft.net/audio/opamps.html


And often times all an opamp will need if its unstable is to increase the value of the feedback cap (usually a small value 10pf to 47pf) if your opamp isn't stable you can increase this up to 100pf, 150pf...haha. just depends! Sometimes with these new high speed opamps you might want to remove the compensation that was needed for the ne5534/2s cause it won't be needed.
To replace the TL072/71 TI has some TLE2072/71 that are meant as drop in replacements for the tl072/71 and they are much faster and less noise. But you could probably find something that sounds smoother and put it in there (opa2107, opa2132)

somethings to keep in mind:

tl072s are FET input and are often used in the higher impedance parts of the circuit as they are generally less noisy in higher impedance circuits. so you generally want to find a fet type input (di-fet works too and often better) to replace it with

Ne5534s are Bi-polar input and are usually used in the lower impedance parts of the circuit so you generally want to find a similar to replace it with. But with a lot of modern opamps, they have noise specs, so personally I don't feel as constrained by these rules.

I like to look at the spec sheets for a bit, but then grab a handful of different types and then replace some in a channel, record the results (both on paper and the audio). Then go back and do everything you can to trick yourself into no knowing which is which, blind test style. and then you should be pretty informed on what you like.

You might be surprised. I did this for an old Urie inductor based graphic EQ and found that the original 741s sound just as good as the new modern fancy ones, if not better in some cases. Let the Specs be thrown in the trash, no one you record is going to say "Oh wow, are you using those new gold encrusted opamps?" If it sounds good it is good.

Sometimes "FAST" can mean more "detail" other times it can mean more "harshness". At least thats what i've found.

OK sorry for ranting, and this information can be subjective, so use at your own discretion.