Choosing an opamp for guitar direct box.

[Giora]

Hello, everybody.

I am a relative novice in op-amps usage, so here is the question that I have :

I would like to record guitar through my sound card to do all the signal processing on the sound in the software.

1. Sound card (Audiophile 2496) has 24 bit A/D and JRC5532 op-amps for pre-amplification.

When I listen to recorded music through this sound card, it sounds good enough to me.

It indicates to me that guitar sound recorded in professional studios through tube amps, compressors and so on is not degraded significantly by these JRC 5532 opamps, or at least acceptable to my ears

Now I need a direct-box type of device to preamplify my guitar signal before it's going to the sound card.

I have a direct box (from Midiman) that uses NJM4580 and NJM4560 type of opamps. My feeling, which I can not quantify , that these opamps sound bad.

I hope after reading this you understand what type of problem I want to tackle and can give me some hints or direction

For instance: I could construct direct box using FET-input stage opamps TL072 - it is used in my Fender transistor guitar amplifier after all.

Wold that be good ?

Or take high-quality low noise CMOS opamp ?

Or just to be in line with my sound card, find JRC5532 opamps and construct the preamp using this device.

Or replace JRC 5532 in the sound card and use some other device all togehter ?

P.S I am not goind to use Tube electronics - this is too expensive and troublesome, but other than that - I am open to any ideas as how to improve the sound quality of this recording chain.

Regards, George.

[azira]

Douglas Self's website suggests that 5532s are much better than TL072s. I think they are pin compatible too. If you're looking for low distortion it seems like you can't beat 5532s for price/performance. There are some OPAs (OPA624 IIRC) that are quite expensive and also very good.

[Giora]

Azira, by the way, here is another thing:

On my sound card I have JRC5532 ( which is the same thing as NJM5532). It seems their sound quality is o.k for me.

People often talk about NE5532, which Texas Instuments part.

Are they the same thing ? Because by looking at their internal schematics in the spec they look different

[azira]

You know, that is a good question to which I don't have an answer.. I would use the NE5532 if you are in doubt, that is the one that Self tested.

I wonder the same thing about different brands of transistors though: Is a MJE3055 the same as a 2N3055?
--
Danny

[Giora]

Yeah, Danny, I read one post on this forum with regards to NE5532 and JRC5532, the guy said they sound different. He claims that TI made external pins from harder metal than JRC did. This is why he thinks the sound is different.

But just looking at two data sheets from these devices - you see that they are just plain different.

It's interesting because different fabs should really use the same design if they call the chip the same name

[cheater]

Hey Giora, get anywhere with your DI investigations? Maybe a circuit of your own?