Gus' MXL 603s mod - Pictures/Part numbers -thanks Flatpicker

[Flatpicker]

[quote author="jeffrey_burr"]When upgrading these caps, how important is it to have matched pairs of caps, if I want my matched 603s to remain matched?[/quote]As far as matching values for just the caps, I don't think it matters. I've tried 820pFs in place of 1000pFs and can't tell any difference. Just don't change the FETs, FET bias, capsules, or capsule bias and you should be fine.

 

[Gus]

No polypros I know of will fit. I picked pan V series PET because thay sound fine and FIT.

 

[Rossi]

[quote author="jeffrey_burr"]Rossi, thanks, but I think you misunderstood my question. I'll rephrase.

When upgrading these caps, how important is it to have matched pairs of caps, if I want my matched 603s to remain matched?[/quote]

As Flatpicker said, it's not that important. The capsule to fet cap is not critical and actually a bit oversized anyway. 1000 pf is a very safe value, 680pf would probably enough. Those caps don't have to match in two mics, they only have to be large enough.

The two 220n (or bigger) polyester caps are perhaps a bit more critical. 20% tolerance may be a bit much, although I doubt that you would actually hear the difference. You can get 5% caps, if you want to. Those caps form a hi pass, and the bigger those caps are the more the difference in cutoff frequency moves into the low bass frequencies where you can't hear the difference. So at 470n the difference is less important than at 220n.

BTW Those caps never were matched even on a matched pair. What they match is the capsule or perhaps the whole mic, but not the parts inside the mic. I've seen "matched pairs" of chinese electret condensers that hat different electronics inside.

 

[BackHand]

I have Studio Projects C4 mics, could anyone of you proos out there come up with an upgrade/mod of these? I would be haaaappy :razz: !

Would you guys prefer the MXL 603s (with mod) against the Studio Projects C4?

Please... :grin: !

Studio Projects C4

 

[Rossi]

I just got a pair of C4 mics. They're very small, so there's little room for bigger caps etc. I haven't investigated the circuit very closely, but I saw that the capsule to fet cap is ceramic. Again polysterene or polypropylene would be better, but I don't know if there's enough room. Doresy recommends NPO/COG ceramics for his circuit. Not sure that's as good as good as polysterene or polyprop, but those are smaller. Has anyone tried glimmer caps?

I like the C4 capsules. They're really low noise for ther small size. Excellent resolution without HF-Boost.

 

[Flatpicker]

[quote author="Rossi"]...Doresy recommends NPO/COG ceramics for his circuit...[/quote]All ceramics sound the same to me in the capsule-to-FET position. Polypropylene may be slightly smoother, but still sounds similar to ceramics IMHO. Polystyrene, OTOH sounds altogether different to my ears.

I love polystyrenes in all the LDCs where I've used them and also in the Oktava MC012s, but to be honest I wasn't very happy with how polystyrene caps changed the attack on acoustic guitar notes when used in the 603s. I liked the ceramics better there, even though they were more harsh.

As for the C4s, the first thing I'd do is try polystyrenes in the capsule-to-FET position, but who knows if there is an improvement. You'll just have to try it and see.

 

[Rossi]

I had good results with polyprop so far. I noticed an improvement not only on my modded mics, but also on mics that came with polyprop stock.

Perhaps the brand or voltage rating makes a difference. I used BC components. High voltage polyprops are actually several caps in series, so maybe that's not so good.

 

[Flatpicker]

[quote author="Rossi"]...Perhaps the brand or voltage rating makes a difference...[/quote]Good point.

 

[Gus]

I think brand and voltage make a difference.

 

[jeffrey_burr]

Hi everyone.

I got my pair of 603s finally, and all was well until I opened them. All I did was open them to look at how much room is available for cap upgrades, and after I put them back together again, they don't work at all - no sound. I did make absolutely certain I wasn't doing something stupid or forgetting anything or using bad cables etc etc. They were working upon receipt...

Can anybody think of something obvious that I don't know about, concerning the opening up of these mics? Any ridiculously delicate parts? Anything stick out as an especially likely occurance I should have tried to avoid? I did touch the pokey-out thing which contacts the bottom of the capsule assembly, was that an unspeakably oafish thing to do?

Thanks in advance. Trying to take this shit in stride,

 

[Flatpicker]

[quote author="jeffrey_burr"]...I did touch the pokey-out thing which contacts the bottom of the capsule assembly...[/quote]Take them apart again and push the "pokey-out thing" a few times and see that it springs back into place. Sometimes they hang up and don't put enough pressure on the bottom of the capsule.

 

[jeffrey_burr]

Thanks for the quick response Flatpicker! I hope it is something that simple, but I don't think that's it. Looking at it through the rear openings while screwing the thing together, it sure seems like it's making contact. I'll keep working with this idea. I can't see how it would be something more complicated since there are so few 'variables' in my case. How unlikely is it that the wire leading into the plastic from the board got disconnected? I just touched the thing gently, to feel it spring back. An impulsive, thoughtless action I suppose, but not violent. I had also unscrewed the capsule from the body, not being sure of the construction. I can't think of any other relevant bit of info. I did plug in another mic requiring 48V to make sure there's nothing else in my rig responsible for this maddening failure.

Naturally no one can make a long-distance clairvoyant diagnosis of my mics, I just thought something obvious might pop into someone's head, that's not popping into mine. It's from ebay, no chance of return! Woe be unto this fool.

 

[Flatpicker]

[quote author="jeffrey_burr"]...I just touched the thing gently, to feel it spring back...[/quote]Don't worry about being gentle, just exercise it a little. I had the same problem on a few occasions and that turned out to be the cause. Also, instead of unscrewing the connector and pulling the whole board out, just unscrew the capsule to get to the spring contact.

 

[jeffrey_burr]

Thanks again for your encouraging words. I'll keep working on it. I wonder if anyone has ever tried filing a millimeter or so off the top of the body, to ensure good contact to the capsule. One could run out of inside thread I guess and it might look poor if the capsule didn't screw all the way down on there, but it does seem silly that it would be so difficult to get enough pressure between these parts.

 

[jeffrey_burr]

I'm no troubleshooting genius. I am hopeful that my problem is as simple as you have said, Flatpicker, but totally vexed that I can't get it working again. I don't think the springy pokey thing is getting hung up; but the mic was screwed together REALLY tightly, so obviously I must return it to that state. I'm not sure I can do this without some kind of special wrench! I can't help but wonder if this is their way of discouraging tinkering of the sort espoused here at this forum. This mic is the "mogami" variety, with stamped logo.

So, does anyone have anything to say about this idea of filing off a little material from the bottom (xlr end) of the tube? This'll bring all the guts closer to the capsule, and probably alter the sound somewhat? since the volume of air behind the diaghram will be less? I'll be careful not to get any metal shavings on the critical bits.....

 

[Marik]

[quote author="jeffrey_burr"]
So, does anyone have anything to say about this idea of filing off a little material from the bottom (xlr end) of the tube? This'll bring all the guts closer to the capsule, and probably alter the sound somewhat? since the volume of air behind the diaghram will be less? I'll be careful not to get any metal shavings on the critical bits.....[/quote]

Nah, don't do that. If you become desperate, send it to me--I will troubleshoot it for you. Just pay shipping. PM me.

 

[synthetic]

I finally did this mod. I used 100V poly caps for the .22u and they barely fit in my 603s, but I managed to put it all back together. Nice mod, seems to open up the low end especially. :guinness:

 

[Category 5]

Went back in mine and replaced the .22's for .47's

I used panasonics from Digi-Key, and although it's tight they actually fit. It opens up the low end a little more. Your last post is what prompted to mention this.

If you haven't already, clean the boards until they are shiny and flux free. Mine were pretty dirty stock. It does seem to lower the audible noise floor when you do this.

I also replaced c1 and c2 with .01uf films. I can't decide if it made a diff. or not.

 

[Gus]

I have fit 1ufs in a microphone like the 603's problem is I forget what brand of cap it was.

I picked the .22uf brand and type because they FIT,sound fine and should be easy to find.

 

[Flatpicker]

I put AVX 1uf?s in a 990 and there seemed to be more sound improvement to my ears then putting the .22uf Panasonics in a 603 (same circuit, capsule). Don? t know about getting a 1uf in a 603, but you could certainly go higher than .22uf with the AVX. I started using the AVX in MC012 "Dorsey" mods that I sometimes do for people and I think they sound great there too.