Using three different op amps?

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Keala

Active member
Joined
Aug 22, 2017
Messages
42
Bought an old Yamaha RM-804 recording mixer, and i want to change the op-amps.  The three band eq uses 3 JRC3558's. I was wondering if i could use 3 different op amps. Sorry if this is a stupid question, but i'm new to this stuff.

So i'm thinking...

NE5532 for the highs
UA741 for the mids
AD8599 for the lows

is it even possible
or just complicated to do?
 
Yes it is possible, but I am inclined to ask why those 3 and why which ones where?

It is common for large mixers to use a handful of different op amps in different locations.  Something like the 5532 might be good for an output line since it can drive 600 ohms comfortably.

I am not familiar with the Ad8599 and I am too lazy to look it up.  (I did try to look up JRC3558 and couldn't find it).

I am very familiar with the 741 and it is a very early op amp, perhaps the first with internal compensation for unity gain. This also means it is rather slow , around 0.5V / uSec.  You might use the 741 for a LED driver, not an important audio path.

It is/was not crazy to use slower op amps in LF EQ sections that do not need to handle full bandwidth, but modern op amps  are cheaper and faster so parsing this way is generally not worth the trouble this century.

JR
 
found a gearslutz post that had a lot of info about what op-amps to swap out for the 4558 (3558 was a typo)

"AD8599 - warmer and darker sounding
NE5532= very organic, natural sound
UA741 - retro and generally groovy"

i'll change the 741 out with a LME49860NA


 
Keala said:
found a gearslutz post that had a lot of info about what op-amps to swap out for the 4558 (3558 was a typo)
the 4558 is similar to 1458 basically a dual 741 so also slower than dirt.
"AD8599 - warmer and darker sounding
NE5532= very organic, natural sound
UA741 - retro and generally groovy"

i'll change the 741 out with a LME49860NA
Sorry I can't help you with retro, groovy, and whatever. Those are not objective descriptive terms.

When used properly (with adequate loop gain margin) op amps do not have sounds of their own, but accurately follow what their negative feedback network tells them to do.

People on the WWW (say they) hear all kinds of things that I don't.  They swap op amps because that is something they can do without understanding design and some believe they have created some magic. In general the more hyperbolic their claims for how good a change sounds, the less likely it is to be true. At best a better op amp will only be marginally more accurate so sound slightly more like the original design intended. 

Better is always better but do not expect significant audible improvements. There will be diminishing returns from using op amps newer and more expensive than NE553x and TL07x that are a few decades old, widely available, and not very costly.

JR
 
All right. Thanks for the help. So shifting out op-amps to get colored sound, is just snake oil. But it will have a diminutive effect on the audio, but not in terms of coloring the sound. But it could have an effect on the noise floor?

What should i then do to get more "colored" sound? is it possible or is that just a myth aswell?
 
The '741 is a single, your 4558s are duals, so that needs more thought.

Of the many "dual 741" chips, the 4558 was among the best and the JRC-made ones work excellent for audio.

These Tascam boards work at -10dBv so do not need super hot or super fast chips.

Without a schematic, I can't know if a simple TL072 will have less or more hiss. Tascam tended to lower impedances so the 4558 may still be quietest. '5532 might be quieter, or its high input current may throw the circuit out of happy DC bias, or its high speed may incite supersonic troubles on what is a rather low-speed layout and decoupling.

I was always very pleased with Tascam's audio balance. IMHO, used wisely, they get close to the performance of much more expensive (at the time) mixers.

For "color", use cheaper (non-chip) circuits and beat them to the edge of distortion.
 
Keala said:
UA741 - retro and generally groovy"

to me the 741 sounds narrow, tinny and farty - retro it is, but the part of it that I wouldn't want back. 'information' like that is why I stay away from gearslutz and co. Just my personal experience though, to be sure you'd have to try it yourself - it might be exactly what shines in your application (though I'd be surprised).

Michael
 
I think you will find more improvement in your eq by changing the capacitors in the eq filter.  Can you post the schematic?

The capacitors will change the "tone" or colour of the eq more than the op amps imho.  Old yammies tend to have crappy Japanese polyester eq caps (like the green chicklet types which just sound terrible) and should be replaced.  Depending on the values they are using you can use wima fkp or mkp, or if the values are really high mks (they are lower quality but also smaller which you will understand when you order a large value fkp or mkp and find out what 27.5mm lead spacing looks like).

Other options to the polypropylene options listed above are polystyrene or silver mica, all depends on your budget and the values.  Some people like MIT multicaps and the like ... Or Russian surplus ... Or tin foil caps... So many options so many different sounds.  You can try pairs of channels and make your own comparisons.

I tried the op amp rolling.  While JR cannot hear the differences I find them to be apparent.  Maybe it's just the lower noise floor, or maybe the extended frequency range, or maybe it's just poorly compensated circuits misbehaving with different op amps sounding different and therefore must be "better" I don't know.  What I know is that 5532 generally sound better than 4558.  But it's rarely as easy as just changing them out one for one especially for the faster ones like lme49860.  Bypass caps need to me added on the power rails to stabilise them, plus you should probably look at the feedback loop and esp the cap there.  Oscilloscope is handy for that.

If you don't have the schematic post me some pics of the actual circuit and I'll id the caps for you.
 
I've been searching far and wide for the schematic, but without any luck.

https://ibb.co/f4tZbk
https://ibb.co/iwyd2Q
https://ibb.co/dqid2Q
https://ibb.co/my8BNQ
https://ibb.co/bsVEbk
https://ibb.co/njjJ2Q
https://ibb.co/dvBLGk
https://ibb.co/nzBj95
https://ibb.co/cVVNwk
https://ibb.co/ctYmNQ
https://ibb.co/jXtmNQ
https://ibb.co/nde495

Here's a ton of images of the components
 
From 1st glance I'd say they're the yellow gold caps by the pots (0.0018 and 0.0056uf).  Nice that everything is labelled!

Can you remove a channel ?  A picture of the entire top and entire bottom as well as a list of what each pot does would be helpful .

Consider recapping all the electrolytic capacitors

Contact Yamaha service dept online for the schematic.
 
enginefire said:
From 1st glance I'd say they're the yellow gold caps by the pots (0.0018 and 0.0056uf).  Nice that everything is labelled!

Can you remove a channel ?  A picture of the entire top and entire bottom as well as a list of what each pot does would be helpful .

Consider recapping all the electrolytic capacitors

Contact Yamaha service dept online for the schematic.

I can send pictures of a channel. I'm in Denmark, so i'll do it tomorrow afternoon.
I could replace the caps, but with what? polypropylene? what's best?

Friend of mine tried to contact Yamaha for the schematic, but they don't have it.
 
All good
Schematic is hard to find for sure.  Check with other Yamaha jurisdictions.  Yamaha Canada has been good to me for schematics when I was working on my pm700.

Polypropylene is a good choice.  Pick your distributor of choice and search for wima caps.  The values are a little odd for their current production.  Epcos (little blue box polypropylene caps) are good too.

Try to get 5mm, I like mouser.com because their search is very good.  Navigate to film caps then enter in the capacitance value and 5mm lead spacing (you can make 7.5 or 10mm work if you bend the leads) and see what comes up.  You are going to have to get values that are a little higher or lower (0.015 or 0.022 instead of 0.018, 0.0047 or 0.0068 instead of 0.0056 etc).  Which will change your eq points a bit.

I would suggest lowering the low eq from 100Hz and raising the high a mid eqs from 10k and 2k.  So, low as needs a slightly higher cap (maybe it's 0.022? You'll have to trace out the circuit a bit) and mid and high caps lowered (to 0.0047 and 0.0015?  Experiment a bit or use math to calculate).
 
enginefire said:
All good
Schematic is hard to find for sure.  Check with other Yamaha jurisdictions.  Yamaha Canada has been good to me for schematics when I was working on my pm700.

Polypropylene is a good choice.  Pick your distributor of choice and search for wima caps.  The values are a little odd for their current production.  Epcos (little blue box polypropylene caps) are good too.

Try to get 5mm, I like mouser.com because their search is very good.  Navigate to film caps then enter in the capacitance value and 5mm lead spacing (you can make 7.5 or 10mm work if you bend the leads) and see what comes up.  You are going to have to get values that are a little higher or lower (0.015 or 0.022 instead of 0.018, 0.0047 or 0.0068 instead of 0.0056 etc).  Which will change your eq points a bit.

I would suggest lowering the low eq from 100Hz and raising the high a mid eqs from 10k and 2k.  So, low as needs a slightly higher cap (maybe it's 0.022? You'll have to trace out the circuit a bit) and mid and high caps lowered (to 0.0047 and 0.0015?  Experiment a bit or use math to calculate).

I could try to contact Yamaha Canada. But now that i think about it, there is another console in the rm series called the rm 2408. I'm thinking that a lot of the circuitry is the same. It just looks like a bigger version of the 804.

schematics for the 2408
http://www.florian-anwander.de/yamaha_rm2408/

I'll be home in about 8-9 hours, so i can take a channel out and take some pictures.
 
PRR said:
Tascam tended to lower impedances so the 4558 may still be quietest. '5532 might be quieter, or its high input current may throw the circuit out of happy DC bias, or its high speed may incite supersonic troubles on what is a rather low-speed layout and decoupling.

I was always very pleased with Tascam's audio balance. IMHO, used wisely, they get close to the performance of much more expensive (at the time) mixers.

Do you mean Yamaha (rather than TASCAM) as the OP's desk is a Yamaha ?
 
Keala said:
found a gearslutz post that had a lot of info about what op-amps to swap out for the 4558 (3558 was a typo)

"AD8599 - warmer and darker sounding
NE5532= very organic, natural sound
UA741 - retro and generally groovy"

i'll change the 741 out with a LME49860NA

Well people say a lot of stuff on the interweb...

Basically op amps don't have an intrinsic sound but do perform in the context of the rest of the circuitry.
This really needs some design / analysis skills to make sense of.

I'd say better mileage going over the caps first - renew electrolytics and if you can see they are signal path ac coupling increase cap value if poss (keeping at least the voltage rating shown).
Then other caps.

Checking JRC data sheet for 4558 shows typical Rin at 5M (although min is 300K !)

Input Resistance RIN 0.3 5 - MΩ

so I'd say best bet to start if you do want to swap op amps would be OPA2134.

For 'colour' you probaly need to look at discrete circuits / transformers !

Op amp circuits tend to be designed to be 'clean' until they crash into the rails.
Having said that you may get somewhere by putting a 'hot' signal into a OPA2134 (so pushing the FET type input stage) whilst not pushing the output too much...
 
Newmarket said:
Well people say a lot of stuff on the interweb...

Basically op amps don't have an intrinsic sound but do perform in the context of the rest of the circuitry.
This really needs some design / analysis skills to make sense of.

I'd say better mileage going over the caps first - renew electrolytics and if you can see they are signal path ac coupling increase cap value if poss (keeping at least the voltage rating shown).
Then other caps.

Checking JRC data sheet for 4558 shows typical Rin at 5M (although min is 300K !)

Input Resistance RIN 0.3 5 - MΩ

so I'd say best bet to start if you do want to swap op amps would be OPA2134.

For 'colour' you probaly need to look at discrete circuits / transformers !

Op amp circuits tend to be designed to be 'clean' until they crash into the rails.
Having said that you may get somewhere by putting a 'hot' signal into a OPA2134 (so pushing the FET type input stage) whilst not pushing the output too much...

So could i change the 4558's out with dual discrete op-amps it could give color?
also, are these even available for under 40 bucks?

if i'm replacing 27 op amps, 1600 $ is maybe a tad too much for my budget
 
$40 per op amp?  2134s are more like 4 maybe cheaper if you are getting more than 25.  Same with the lme part.  I'm not familiar with the AD part but no op amp chip is  worth 40$ esp in this type of application.

I looked at the 2408 it seemed like the values of the eq caps differed from what I thought yours were so I figured it was a different circuit.  Yamaha used to do that, try out very different designs on slightly different model numbers.  Anyways let's check and be sure!
 
enginefire said:
$40 per op amp?  2134s are more like 4 maybe cheaper if you are getting more than 25.  Same with the lme part.  I'm not familiar with the AD part but no op amp chip is  worth 40$ esp in this type of application.

I looked at the 2408 it seemed like the values of the eq caps differed from what I thought yours were so I figured it was a different circuit.  Yamaha used to do that, try out very different designs on slightly different model numbers.  Anyways let's check and be sure!

I was talking about these little devils
http://www.tnt-audio.com/jpg/ss3602-dual-discrete-op-amp.jpg

I'll be home in about 2-3 hours. I'll send pictures of the ciruit
 

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