Art tube MP project series mod

Ember

New member
Ok, first of all I apologize ahead of time if i'm posting something that is already posted but I have read a lot about all of the art tube mp mods and all but i would like to add a little clarification before i start ordering parts for this mod.

Ok, well basically im replacing the tube on the unit and I plan on replacing the opamps on the unit as well, but heres the difference that i found between the two units, the (well at least my) mp project series has three JRC 4580D opamps on the unit compared to the two that the other unit has.

Is it ok if I replace all three of them with the OPA2134 opamps? if not please advise. thanks.
 
I socketed the opamps on mine and put the OPA2134s in there. I also replaced as many electrolytic capacitors as I could with same-value mylar film ones (some had too high of values to be able to fit a non-electrolytic one there, iirc) -- it sounded much better afterward. I also replaced the tube, but I don't think that had as big an impact.

It was really difficult for me to work on that board, especially getting the old opamps out.
 
I socketed the opamps on mine and put the OPA2134s in there. I also replaced as many electrolytic capacitors as I could with same-value mylar film ones (some had too high of values to be able to fit a non-electrolytic one there, iirc) -- it sounded much better afterward. I also replaced the tube, but I don't think that had as big an impact.

It was really difficult for me to work on that board, especially getting the old opamps out.
sweet. thanks for the help!
 
I am about to embark on a mod of that preamp this week. Going to replace all the opamps, tube, the 10uF 50v caps (Nichicon bipolar) and the 33 and 330pF caps.

Maybe some other ideas as well.
 
I am about to embark on a mod of that preamp this week. Going to replace all the opamps, tube, the 10uF 50v caps (Nichicon bipolar) and the 33 and 330pF caps.

Maybe some other ideas as well.

nice, im pretty good with an iron but not too incredibly knowledgeable about electronics, any chance you could post the parts that you are buying and where you are getting them from? it would be very helpful. For instance it says in the spec sheet for the OPA2134 that pin 8 sound be bypassed using a 10nF ceramic capacitors or larger, and honestly im not 100% sure what i should get for that. thanks in advance.
 
whew - now I remember that. I had long forgotten about those instructions when I took the iron to my unit.

Re-reading that PDF makes me wonder whether my changes will result in opamp burnout at some point. I rarely use the unit (and have some replacement opamps), so it's not a big deal, I guess.

But in order to follow those instructions to the letter, I'd need to focus as hard as Stimpy when he was building the happy helmet, and I doubt I'd get that much runway. Anyway, if you can mod at that level, my [hat,happy helmet] is off to you!

edit: and mine's an MP, not the project series - guess I had those confused earlier in the thread.
 
Well, I was looking for the original mod source, but can't find it. I don't remember where I got it, but I pasted it into a word document.

Here it is:

unknown web source said:
okay, here's the recipe;

one Art TUBE MP, Project series mic preamp.
one MXL 990 mic.

ha ! of course they sound pretty thin/harsh, right ? and some believe that "starved-plate" mic preamps can never sound good...

okay-- here is how you get them to sound good. in the MXL, replace the caps with WIMA polyprop's. It's up to you which to replace, but I recommend replacing as many as possible. I also recommend against using styrene for the capsule cap, as many modders can only find 50v styrene caps, and the voltage on the capsule is generally higher... Also, you can more than likely substitute an MXL2003 for the mic,,,,, may raise the cost a bit.

next; grab a JJ Tesla 12ax7, 3x MC33078s, 3x 8-pin sockets, 7x 33pf and 7x 330pf silver micas, and 10x Panasonic BP (bipolar) radial caps for the mic preamp. You may want to count the caps again before ordering/buying (this is how many I replaced IIRC)... I like to use solder wick for removing solder.

Be careful; remove one type of component at a time-- don't remove all of the caps at the same time or you may not know where the components go. The ceramics labelled 330 means 33pf, and 331 means 330 pf. The electrolytics I replaced are the tall thinner 10uf 50v caps, not the shorter chubby ones. Not having a schemo, I replaced them by checking the traces...

Okay, once you have these all in, try-out your newly modded vocal chain. I did this mod for someone,,, they just did a session with several seasoned session musicians, and they were all asking "what mic IS that ?!?!?!" The tracks were noise-free and sounded excellent-- leagues beyond the stock units (yes, we a/b'd the difference on guitars (DI) and vocals). The tracks had THAT sound, where I didn't even want to think about eq'ing anything. And now you can confidently dismiss when people say "it's just all design, components don't make a difference in sound". Heck Yeah!


I'm tracing the circuit and maybe I don't fully understand why he chose those parts, but now that I look at it, it doesn't seem to have a real rhyme or reason to it. I wish mshilarious or someone could see this board. It seems like some if the smaller capsm (33pF and 330pF) are for DC offset on the op amps. Some of the ones he recommends replacing don't seem to be in the signal path either, but I could be following the wrong traces.

I'm going to do one bit at a time and see how it sounds.
 
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