Presnous Firestudio Project XMAX Preamp Modicifaction

[Bart1cm]

Hey folks,
New to the forum here. I'm fairly new to modding, but I've done a handful of mods of some of my mics based off of information that I read here. They turned out great so I figured someone may have the know-how to help me out with a question.

I have a Presonus Firestudio Project which uses Presonus' XMAX preamps. I'm not very thrilled with the sound I get from the sound I get with these preamps. It has a very boxy mid-range tone and I almost always have to make a big mid cut in the mix down to alleviate it. The issue doesn't change all that much from mic to mic. Of course they sound different, but I feel the pre could be holding some of my mics back in their capabilities.

Has anyone ever modded one of these? I read about a guy who changed the op-amp on another forum but there wasn't enough info to give a good idea of what this did to the overall sound. I cracked it open and it appears that all of the pres are using Chang electrolytic capacitors. I couldn't really find a lot of info about Chang caps, I figure there might be a reason for that.

How can I tame some of the mid-range boxyness of the preamp? Should I change the op-amp? And will changing the capacitors to a different material or brand make a noticable difference?

Any words of advice are greatly appreciated!

 

[MrZpliff]

Hi !

I doubt that the boxiness comes from the preamps... I haven't noticed it on mine at least. The preamps are bit boring maybe, but not boxy.
Have you checked the room you're recording in and mic placement ?

Best regards
Magnus

 

[Bart1cm]

Well I know it's coming from something inside the unit. I've been pretty mobile with it, recording in various different locations and I always get the same sound. Its a little bit muddy in the low-mid section. I've also used my mics on other boards and got cleaner sounds. I would agree that the sound of these preamps are slightly boring. I was just asking if anyone knows of any mods that can tame the low-mid or give the pres a more real to life sound.

 

[Andy Peters]

Well I know it's coming from something inside the unit. I've been pretty mobile with it, recording in various different locations and I always get the same sound. Its a little bit muddy in the low-mid section. I've also used my mics on other boards and got cleaner sounds. I would agree that the sound of these preamps are slightly boring. I was just asking if anyone knows of any mods that can tame the low-mid or give the pres a more real to life sound.

Perhaps external preamps are the ticket?

 

[Bart1cm]

I have been looking into external preamps. Seems like my best bet for a better sound. Does anyone know a good stereo preamp build? FET would be ideal. I was also looking at the aphex 107. I still don't understand a great deal about preamps so any advice is welcome.

 

[gemini86]

Why would fet be ideal? Just curious...

I recommend the 9k pre or a THAT1512 type preamp, also known as the $5 pre... Both are very clean and neutral, but definitely not boring or boxy...

 

[MrZpliff]

I use the G9 as often as I can, a really nice one...
Not FET I know but you can compare between them here...

From a test I made with a couple of modified ribbon mics.

This one is a modified ribbon straight into the Presonus micpres:
http://www.bitterend.se/Ribbon - PresonusMic - Norm.wav

And this one is the same but through the G9 and then the Presonus line in:
http://www.bitterend.se/Ribbon - G9 - PresonusLine-Norm.wav

from this thread:
http://www.groupdiy.com/index.php?topic=46378.0

 

[Bart1cm]

The SSL 9K pre seems to be a good idea. I don't know why it would be called the $5 pre though, it seems that it costs a bit more than that. I know Gustav is selling the PCB's for these. Is there anyone that sells the completed channels individually?

 

[gemini86]

The SSL 9k isn't the $5 pre. The $5 pre uses an all in one preamp ic that is around $5. The 9k is a great pre most of it is cheap. The most expensive part (excluding any psu parts) is the gain pot

 

[abechap024]

I think I've heard that low mid "boxiness" before, or lack of clarity. I would suspect changing out the electrolytic coupling capacitors to a higher grade (panasonic FCs or the like) will clear it up for you.

 

[1sound]

I'd have to agree with abechap024 on that one.  Modded my older Firepods (1st gen) by putting in Panasonic FC's throughout (amongst a few other things) and got a huge improvement in clarity, even before swapping out the opamps and doing and PS upgrade (the stock supply really stinks in the older ones).  Not a huge fan of those "chang" caps to begin with.  They've been using them for ages (mine had them as well).

After that, the power supply is really one of the better things you can fix in those units IMHO.  A cleaner supply helped my box out tons as well and not just the analog side either...  More depth of field, less noise...

Hope that helps a bit!

1sound

 

[okgb]

The way i hear things , I like to notch out a little narrow bit around 180 - 220 hz
on allot of things . Sounds like you've come to a plateau , if you want to be a scientist
start with the cheapest option and extrapolate from there , good luck & skill

 

[Bart1cm]

Thanks Abechap and 1sound! I just wanted to be reassured that I might hear a difference before I put the time into doing it. 1sound, did you switch out all the caps? Or just the ones in the preamp section?

I also ordered 2 SSL 9k PCB's from Gustav, I'm excited to see how those will differ from the Presonus pres. That'll take a while though, so I'll start with recapping.

 

[Johan]

Have you checked the room you're recording in and mic placement ?

+1
never underestimate the room...I allways had problems around 130-150Hz untill I (finaly) realised...speed of sound devided by room hight was exactly where my problems lay.. speed of sound 340meter/second,  typical room hight in sweden=2.4meter  340/ 2.4=141Hz
...that said. I'm sure the solutions others mentioned will help too...
J

 

[Bart1cm]

No doubt about the room playing a crucial role in the sound quality. Its a pretty basic concept, I've been recording long enough to understand how environment and mic placement effects the end result. Not to say that I don't have anything to learn, you never stop learning when it comes to audio. Like I've said though, I've recorded in various locations ranging from theater classrooms to auditoriums and the same problem has followed me everywhere.

I took Abechap and 1sound's advice and ordered a bunch of Panasonic FC caps. I'll start from there and see where that takes me. I'll do before and after recordings so everyone gets an idea of what I'm talking about. I'm very excited to build the SSL 9k preamp as well. People seem to love them. Gustav is having a 3 for 2 deal through the end of 2011, so I'll be building a 3 channel mic preamp to start with and add on when I have more cash to cough up!

-Bart

 

[Bart1cm]

Magnus, I just listen to your pre comparison tracks. The G9 sounds great! There's a lot more detail to the sound, more nuances of the room sound. Less low-mid mud. I've been wanting to mod a ribbon mic too, specifically the Nady RSM-4. I want to replace the ribbon with 2.5 micron foil and replace the transformer with a Lundahl 2912, but one project at a time! I already have too much going on!

 

[MrZpliff]

Would be great to hear some soundsamples of "before and after" your mod 
I seldom use the built in micpres. I either use the G9 and/or a couple of old telefunken pres.
Good luck with your build