Op Amps

[MikeCzech]

OK, so let's say you buy a cheap preamp with BA4560 Op Amps and you want to mod it.. How does one know which OpAmps will be compatible? Are they all compatible if they fit in the socket? When I go to order, how do I know which ones will fit in the socket??

I'd like to get something with character.. I'm gathering that Burr Brown is the way to go. I undestand the OPA2132 is a good replacement but is a cleaner Op Amp in comparison to some of BB's other OpAmps.

Is TI the same thing as BB now?

Sorry, I'm just getting into DIYing a MODing, but I must admit, I really don't have much of a clue.

Oh, and what purpose does an OpAmp serve and what makes them so different?

[mrc]

I like the LT1469 over the BB2134, it's much better.
mrc

[soundguy]

OK, so let's say you buy a cheap preamp with BA4560 Op Amps and you want to mod it.. How does one know which OpAmps will be compatible? Are they all compatible if they fit in the socket? When I go to order, how do I know which ones will fit in the socket??

I'd like to get something with character.. I'm gathering that Burr Brown is the way to go. I undestand the OPA2132 is a good replacement but is a cleaner Op Amp in comparison to some of BB's other OpAmps.

Is TI the same thing as BB now?

Sorry, I'm just getting into DIYing a MODing, but I must admit, I really don't have much of a clue.

Oh, and what purpose does an OpAmp serve and what makes them so different?

please dont fuck with your gear until you get at least HALF a clue, you can turn a box that is usable, but not so exciting souding into something that is just broken.

Not all opamps that fit into the socket will be compatible.

You have to find the datasheet for the opamp that is in there. Look at all the specs, namely the pinout, power requirement and current consumption, then try to find a list of others that are close.

the thing you gotta realize, this is maybe more pertinent with old older gear but still, the circuit was designed around or for a given opamp. There are sometimes lots of components in the circuit which serve no purpose other than to make the given opamp chosen work more efficiently or sound better or keep it from oscillating, etc. When you drop in another opamp chances are usually pretty good that it wont be operating completely efficiently. Sometimes you can drop it in and it will immediatley sound better, but sometimes you really do need to redesign lots of the compensation around the opamp to make the most of it. One other important point is that newer audio opamps tend to have higher current draw than older stuff, so you have to make sure your power supply can supply the current needed. If you are swapping one or two chips, it probably wont be the end of the world, but in the case of somethign like a console where you could be changing 60 chips or many many more, this is a huge point.

opamps are amplifiers and can be configured to do many things in a circuit but keeping it simple, they are little amplifier circuits. Its completely not the same thing, but thinking about a block diagram of your box, thinking about this very very simply, an opamp sorta acts like what tubes did in older stuff, they are the amplifiers in most cases. That statement is incredibly incredibly flawed (for instance not all tubes are amplifiers, some are diodes or rectifiers) but for the sake of trying to get a basic grasp you can sorta look it like that to get you going. Opamps are different for a million and eight reasons but again, keeping it simple, like tubes can have different tonal qualities, so can opamps. Unlike a tube or a transistor, which is a single amplifier element, opamps contain an entire CIRCUIT inside that little package so you can imagine how they can vary tonally. Its not just the opamp in a vaccum though, you've got the sound of the opamp itself but then really how it interacts in the circuit. I was talking about some valley people stuff in anotther thread and the gates and compressors sound really good to me and Im pretty sure they use 5534's or 5532's. Those chips kinda sound pretty good on their own, but the gainbrain2 is a real good example of how that chip (or wwhatever chip is in it) can be made to work in a circuit to sound real cool. Putting a burr brown into a circuit that was designed to compensate for a really slow shitty chip is probably not going to sound all that great until you remove the compensation and update it for the new chip. thats design, and that shit is way over my head for what I am able to do with the knowledge I currently have about electronics.

Its very chic to talk about rechipping stuff and Im certainly not suggesting its a bad thing to try to do, but its more complicated than just taking out the old chip and putting in a new one. Sometimes you get lucky and thats all it takes but there's generally more to it than that.

anyhow, read up on this stuff and start to learn about the different chips available and you'll be headed in the right direction.

dave

[operator_tape]

OK, so let's say you buy a cheap preamp with BA4560 Op Amps and you want to mod it.. How does one know which OpAmps will be compatible? Are they all compatible if they fit in the socket? When I go to order, how do I know which ones will fit in the socket??

I'd like to get something with character.. I'm gathering that Burr Brown is the way to go. I undestand the OPA2132 is a good replacement but is a cleaner Op Amp in comparison to some of BB's other OpAmps.

Is TI the same thing as BB now?

Sorry, I'm just getting into DIYing a MODing, but I must admit, I really don't have much of a clue.

Oh, and what purpose does an OpAmp serve and what makes them so different?

please dont fuck with your gear until you get at least HALF a clue, you can turn a box that is usable, but not so exciting souding into something that is just broken.

Not all opamps that fit into the socket will be compatible.

You have to find the datasheet for the opamp that is in there. Look at all the specs, namely the pinout, power requirement and current consumption, then try to find a list of others that are close.

the thing you gotta realize, this is maybe more pertinent with old older gear but still, the circuit was designed around or for a given opamp. There are sometimes lots of components in the circuit which serve no purpose other than to make the given opamp chosen work more efficiently or sound better or keep it from oscillating, etc. When you drop in another opamp chances are usually pretty good that it wont be operating completely efficiently. Sometimes you can drop it in and it will immediatley sound better, but sometimes you really do need to redesign lots of the compensation around the opamp to make the most of it. One other important point is that newer audio opamps tend to have higher current draw than older stuff, so you have to make sure your power supply can supply the current needed. If you are swapping one or two chips, it probably wont be the end of the world, but in the case of somethign like a console where you could be changing 60 chips or many many more, this is a huge point.

opamps are amplifiers and can be configured to do many things in a circuit but keeping it simple, they are little amplifier circuits. Its completely not the same thing, but thinking about a block diagram of your box, thinking about this very very simply, an opamp sorta acts like what tubes did in older stuff, they are the amplifiers in most cases. That statement is incredibly incredibly flawed (for instance not all tubes are amplifiers, some are diodes or rectifiers) but for the sake of trying to get a basic grasp you can sorta look it like that to get you going. Opamps are different for a million and eight reasons but again, keeping it simple, like tubes can have different tonal qualities, so can opamps. Unlike a tube or a transistor, which is a single amplifier element, opamps contain an entire CIRCUIT inside that little package so you can imagine how they can vary tonally. Its not just the opamp in a vaccum though, you've got the sound of the opamp itself but then really how it interacts in the circuit. I was talking about some valley people stuff in anotther thread and the gates and compressors sound really good to me and Im pretty sure they use 5534's or 5532's. Those chips kinda sound pretty good on their own, but the gainbrain2 is a real good example of how that chip (or wwhatever chip is in it) can be made to work in a circuit to sound real cool. Putting a burr brown into a circuit that was designed to compensate for a really slow shitty chip is probably not going to sound all that great until you remove the compensation and update it for the new chip. thats design, and that shit is way over my head for what I am able to do with the knowledge I currently have about electronics.

Its very chic to talk about rechipping stuff and Im certainly not suggesting its a bad thing to try to do, but its more complicated than just taking out the old chip and putting in a new one. Sometimes you get lucky and thats all it takes but there's generally more to it than that.

anyhow, read up on this stuff and start to learn about the different chips available and you'll be headed in the right direction.

dave

Well put

[MikeCzech]

Well, only one way to learn what I'm doing..

This might seem sarcastic, but seriously, I appreciate your pessimistic response, Dave. I guess it's what I expected, but nonetheless it was full of good usefull information.

It's certainly not going stop me from screwing up some cheap gear I'm not using anyway - because maybe one day I can be the cocky bastard trying to make someone hesitant to do something educational.. I say that with nothin' but love!

I put together a pair of 7th Circle A12's, and had no clue, so why not try to get a clue and take another couple of steps?

When I put the OpAmps in the A12's I had to put the meter on the OpAmps and adjust the caps until I got certain readings, are these typical adjustments that would need to be made when changing OpAmps?

[Milkmansound]

well, before you do anything look at the datasheet and application notes. The new IC might draw more current than the PSU of your preamp can handle - causeing a voltage sag and ruining some shit maybe - unlikely, but keep in mind that if its got cheap IC's its probably got a cheap supply.

also, oscillation is a bitch - in any opamp datasheet you will note that one application is to be used to generate a waveform. So, the wrong IC in the wrong place might just do that - dump a consistent sine wave or square wave right into the audio path! Thats not so good.

However, if you take the time and know your shit (I don't think I am at this point myself) then you can analyze the current circuit - make sure the new IC will work, and make any changes to the relevant components in the circuit in order to make the "better" amp jive with the other electronics.

basically - if you see an upgrade on the net, do it. If you are trying to chart new territory you better know your EE.

[soundguy]

This might seem sarcastic, but seriously, I appreciate your pessimistic response, Dave. I guess it's what I expected, but nonetheless it was full of good usefull information.

jesus, that was a pessimistic response?

I guess you have to fuck with this stuff for a while before you see the reality of the situation.

dave

[matta]

Mike,

I don?t think Dave is being pessimistic at all. While certain op-amps by
certain manufactures are designed as straight drop in replacements, you
can?t just go dropping in any old opamp.

Think of it this way. If you had a Ferrari would you go stick in a Hummer
Engine? It is still an engine, but there are serious factors to consider
when doing this kind of mod!

By all means, mod away! But I like to say Zeal without knowledge can be a
dangerous combination, and a little bit of research will give you a better
understanding.

Cheers

Matt

[MikeCzech]

No, no, I do appreciate everyones help..

I agree with all of you in a sense. I don't want to fly blind here, I wish I had a clue, and that is why I am asking questions - in hopes to get one.

I don't post much, but I haven't missed many threads on TapeOp in at least a year (even though it was down for 4 months). I know Dave is very knowlegable and can probably tell me more about OpAmps than the manufacturers can.

I say pessimistic because rather than just telling me what I need, or a good place to start looking, the initial advice given was 'Don't Touch It'.. Well, then the following sentences were several valuable clues... kinda funny really..

OK, back on subject.. Here's the deal, I have a Bellari MP105, I never use it, it's collecting dust. I've seen the mod on BlackLion for it, but I read somewhere about someone who used a Burr Brown OpAmp instead of the suggested OpAmp, and had better results.

I'd like to do something like this, but I'd also like to learn as I go. I don't want to do the Mod that I read was a good idea; I want to experiment with it to figure out what I prefer.. In the process I gain a little knowledge.. Whether I end up with a functioning Pre or junk, I get something out of it.

[Milkmansound]

well with that pre, yeah - there are some options. I mean there is only the one amp in the audio path cause the tube is there too... I used an analog devices opamp in there cause it was free and Matt Newport recommended it. The tube made more of a difference though - the stock tube was some low emmission Sovtek - I put in a nice old Philmore 12AX7 and also expirimented with Mullard and some others. Even a 4558 sounded better than the stock IC!

just check the datasheets, use Matts mod as a guide, and see what you can afford or get for cheap/free and spend the big bucks on the tube and you will be more than satisfied with that "mod"

[eeldip]

the bellari 105 does indeed respond to different opamps in interesting ways. ive had bad luck dropping in opamps for fun in other boxes.. but not this guy

its a really weird amp. i like it.

get those stock pots out of there next.

[mrc]

The BB2134 and LT1469 will drop in, and both are quieter than the BB2604. The LT is very nice, they might even send you a sample
mrc

[joeysimms]

Chippers and would be rechippers may find this series of threads about rechipping a console to be interesting, from Ted Spencer at rec.audio.pro -

http://groups.google.com/group/rec.audi ... 17272a9249

http://groups.google.com/group/rec.audi ... a64cdbf705

http://groups.google.com/group/rec.audi ... d31b72bdc0

[mrc]

That was all interesting reading, but this unit has an actual tube in the circuit. I would suggest a 12AU7, if you don't need a real high output. I've tried NOS Telefunkens and Mullards, and though I prefer the Tele, both it and the Mullard were much quieter than any of the new or vintage 12AX7's I had on hand. The opamp exchanges I read about in Joeysimms links all seemed to be solid state circuits, instead of hybreds.
My simple experimenting has been with AD275, BB2604, BB2134, BB627's on Brown Dog single to dual adaptors, LT1469, LM6172 and of course the stock 4580's Or 60's (I tossed them and don't remember) that were in the Bellari RP503 when I got it. Its a tube channel with opto comp and 3 band (swept mid) eq.
I found the Tube made a huge difference. The next largest difference is in the input opamp, then the compressor. The last 3 opamps make the least difference. The 2604 and LM6172 both put out a lot of hiss to my ears. The 1469 is clean and tight on the input and works well in the opto compressor. The AD275 sounds fine in the compressor, but it seems a bit loose, a bit more squishy sounding than the 1469. I'm running the BB2134 chips in the eq's and output sections, because I don't have any more LT1469's on hand, and am waiting to put together a larger order to cut down on the shipping cost.
The BB627s on the adaptors need to be coupled, they do the oscillation trick that was mentioned in the fine links Joeysimms put up for us, I just haven't had time to mess with it. They are very expensive little buggers, and may be great when tamed with proper coupling.
Puff Pastry has mentioned he is working on further mods for the RP to improve headroom, so I'm guessing it involves Powersupply and other changes. I'll bet his mods for the 105 will take it further, as well.
mrc

[ram3n]

Is this Bellari one of the starved plate designs? Or a "real" tube preamp design? I'm getting confused with all this hybrid tube/solid state talk.