SM Pro PR8 E - Opamp suggestions?

[Halkbi]

Hello!

This is my first post here. I stubled on this forum while doing some research about the SM Pro PR8 E preamp, and I was stunned to see how simple it seems to mod the design. First, just let me say that I'm pretty novice when it comes to electronics. I've got some experience, but not a lot. I really can't understand what most components in a signal path does and why they're there. Some kind of walkthrough would be nice if you've got the patience for it (and if I can find a scheme for the PR8E), otherwise this is what it all comes down to.

From what I understand, the design issues of the original PR8 has been taken care of in the PR8E and I guess that's why the Black Lion mod isn't available anymore, since it would only include changing the opamps. Correct?

Basically; I'm looking for opamp suggestions for the PR8E's input and output stages,both which has JRC4558Ds in it's original state. The BLA mod has LM6172 for the input and NE5532 for the output and seems to have been getting a lot of praise over the boards. The LM6172 however is quite expensive (at least here in Sweden) and pushes the costs up to the point where I could just pick up a used Presonus Digimax D8 and be happy from start instead of spending the same amount of money + hours of soldering and desoldering ICs (and possibly f**king up the PCB.)

So all in all, I'm looking for advices for which opamps that would be suitable here and which sonic qualities/alterations they would provide. Please give me your opinions/experiences!

Best Regards,
/Halkbi

Edit: Of course, the first thing I do is post in the wrong forum. Please move this thread.

 

[abechap024]

Hello!
Welcome to the forum. It has an amazing search function that will probably lead you to more knowledge then I could show you, but I'll try to share my thoughts on "modding" gear in general. Take it for whatever its worth.

I've never modded an SMpro but I imagine it could benefit sonically from a few things.

Also take note, you mention you might like a digimax, well you should spend some thoughts considering selling your smpro and just upgrading to a digimax or whatever. I've never used either and can't say if the sound quality, but price wise i notice the digimax isn't that much more then what you could sell your smpro for and what you would spend on parts. Plus don't ever count on getting the money back that you've put into your unit if you ever want to sell it. I've noticed, that all but very rarely that "upgraded" or "modified" pieces of gear that are in the lower consumer realm seem to go for LESS than ones that haven't been tampered with, because no one can vouch for the quality of repair, voided warranty, other unforeseen problems that the "upgrades" have caused.

ANYWAY

assuming you want to continue cause hey its more fun to tinker anyway. Start by replacing the electrolytic capacitors. All of them until you can figure out which ones are in the power supply and which ones are in the audio path, because usually the majority of sonic benefits come from replacing the ones directly in the audio path. Then after that you can try putting in new opamps, they are all fairly interchangable, as long as you learn about Single channel opamps, and dual channel opamps. At first glance they look the same, but will blow up if you don't get the correct kind in. Beyond that the worst thing an opamp can do that doesn't like the circuit, is oscillate, or not work optimally, but it won't destroy anything. If it sounds good it is good.

Also the SMPro isn't surface mount right?

 

[Halkbi]

Thanks for your reply!

Been reading everything I could find about the PR8E here (and elsewhere) before I've started this thread. To make things clearer; I don't own the PR8E. I mentioned the Presonus because I've gotten some great results from their XMAX pres before, and therefore I've been eager to get the Digimax (as I've never really needed a 8ch preamp before.) I'm very much aware of modded cheap gear's second hand value. It's just a tough choice between getting it right from the beginning and gaining some experience. I'm studying music production and this little thing could be a part of a school project. But as I really need a decent pre, usability comes down most important here. If someone with experience of both the Digimax and modded low end preamps, it would be worth a lot to get some first hand opinions/experiences on how they would compare.

To get technically, why do I want to keep the electrolytics out of the audio signal path? What makes them inappropriate there?

I've gotten that far into understanding opamps. What I'd like to hear about is people's experiences of pulling out and replacing JRC4558s, what kind of chips that won't get me into oscillation hell in a circuit designed for the 4558 and about how different opamps work in the input vs. output stage.

And no, it isn't surface mont.

 

[abechap024]

Ok...so you are set on wanting to change the opamps. Good good. NE5532s OPA2107, opa2227, opa2134, opa2132, opa604...

There are literally TONS of opamps. If you looking for someone to give you a "safe" choice you can't go wrong with opa2134 or opa2132, NE5532 are nicely musical and would be an upgrade...but everyone has their own pet opamps, that they swear by and each one does have a different sound subjectively. So its really up to you...there are a lot of new opamps that I'm sure sound great if you want to spend $$

But you ask why do you want to change the electrolytic caps? To me, the sound of older opamps can be cool sometimes. Low slew rates, different distortion etc. Not ALL the time, and NOT on EVERYTHING but my point is to me, crappy opamps are not as offensive as CRAPPY ELECTROLYTIC Capacitors.

To my ears electrolytic tend to "mush" and "smear" the audio, while bad opamps still tend to sound "sharp" but sometimes they have grungey ness to them (like the 4558s)

Anyway I'm sure you can see much improvement, but don't forget to change the electros too....
just my 2 cents