MXL 603s mod

[Gus]

the mxl600 looks like a 797 build, The red 1gigs

 

[Flatpicker]

[quote author="Gus"]Someone here likes polypros at the capsule grid/gate of a microphone more than polystyrene. I like polystyrene. Sometimes it is a taste issue.[/quote]Yes, I need to try some polypros. Do they have that "open" sound like the polystyrenes?

 

[Marik]

[quote author="Flatpicker"][quote author="Marik"]...as both 603 and 991 are the same mics... [/quote]I?ve got a friend?s 991 here and was just now comparing it to my 603S. There are a few small differences such as the 991 PCB doesn?t have a pot for FET adjustment and the long wire jumpers have been replaced with long curvy traces. [/quote]

:shock: :shock: :shock: --my 991 has this pot.
Also, newer 603's I saw, have PCB with traces instead of wire jumpers.

One other difference that could possibly affect the sound, is that the grille mesh-weave appears to be more open on the 991 and more dense on the 603S.

That's the only thing I failed to pay attention to, I have to admit. It would be easy to check though, just swaping capsules from 991 to 603 (or vs. vrs.)

 

[Flatpicker]

[quote author="Marik"]...It would be easy to check though, just swaping capsules from 991 to 603 (or vs. vrs.)[/quote]Good idea - I keep forgetting that the capslues unscrew off these things...

 

[Flatpicker]

I just finished re-capping a bunch of mics and found a bad polystyrene cap in my lot. I thought I?d warn you guys about it in case it happens to you. The symptom is that the mic either doesn?t work at all, or is very faint. And I could only hear the faint sounds when the gain was really cranked. I?m sure it was bad off the shelf, because I always tin the nodes first and never hold the iron on it longer than it takes to melt the solder - about .5 to 1 sec.

 

[Category 5]

I got the panasonic .22u films. While I wait for the polystyrenes I was thinking of trying a polypro on my 990.

Would I benefit from a value larger than 1000pf since there is plenty of room for it?

Also, I remember reading that the two .22uf caps are labeled differently on the 990. Wouls any of you guys mind calrifying which two caps get hte swap on the 990 (and just for reiteration in he same thread the one on the 603 too)?

I think it is C3 and C4 on the MXL600 whose pictures I posted above.

Shane

 

[Category 5]

Actually I just realized this was already posted. Sorry!

So, in 990 and 600 replace c3 and c4 with .22u films and c13 (or it looks like c7 in the 600) with 1000pf polystyrene

"On the 603s replace c9 and c4 with .22u films, and c13 with 1000pf polystyrene"

Actually, My 603s have .22s in C3 and C4 just like the 990 and 600, so if yours is new change those. I can't comment on changing C9. It looks like a .022uf in all the mics I have, and I can't see why somebody WOULD change it.

Shane


[quote author="buttachunk"]note;

on the 990, c9 is called c3. so replace c3, c4, and c13 in the 990.

:!: Don't change c9 in the 990 with a .22uF. :thumb:[/quote]

 

[Flatpicker]

[quote author="Category 5"]Would I benefit from a value larger than 1000pf since there is plenty of room for it?[/quote]No, but you might benefit from a value larger than .22uF. I just finished modifying one with a 1000pF polystyrene and a couple of AVX 1uF, 63V multilayer metal films. Probably not as good as Panasonic, but they were small enough to fit in there. I have not listened to the modified version yet. I'll give it a try tomorrow and let you know what it did.

 

[Flatpicker]

Ok ? just modified a friend?s 990 with 1000pF polystyrene and 1uFs instead of .22uFs...

A noticeable improvement - much more real. Fixed that ugly harsh sound in the upper mids. Still has the highs (this is a bright mic!) but they are much easier to listen to. I didn't noticed a difference as much at first, but after listening to the new clip and going back to the old one, the old one is just so un-pleasant! That?s when I noticed the harshness was gone. Moving in up close gives a nice proximity effect. I was all prepared to hate this mic, but if you tamed the high-end with a little eq, you could get some nice tracks from the modified version. I might have to get me one...

 

[Category 5]

Would you say the 1uf made a significant difference compared to the .22? Also, I saw some photos of a 603s somewhere and the two caps (1 and 2 I think) at the bottom of the board just above the XLR assembly were also changed. Any reason to make those .22uf films too?

Glad to hear about the 990. I have 2 and was already surprised to hear them stock. they are nothing more than a side address 603, but they do sound pretty different.

Shane

 

[Flatpicker]

[quote author="Category 5"]Would you say the 1uf made a significant difference compared to the .22? ... Any reason to make those .22uf films too...[/quote]Hard to say about the 1uF, but going from ceramic to mf sure helps. As far as the other .22uFs, they are just there to keep out RF. I seriously doubt you could hear much of a difference since they probably have a minimal effect on audio. That's just MHO tho...

 

[Rossi]

I'm surprised to hear you think the 990 is a bright mic. I had one for review last year, and that one sounded rather neutral, maybe even mellow, not as bright as a 603.

I just modded a Thoman t.bone SC150 which is similar to the SE Electronics small diaphragm mics. Their capsules (the SC150 comes with three) are similar to that in the the MXL 603, but the electronics are diffent. The SC150 (like the SE one) has a transformer coupled output. Other than that there are but two transistors, a FET at the capsule and a bipolar one (I think; I forgot the number). I did the ever popular capsule to FET capacitor mod. I didn't have a styroflex one handy so I settled for polyprop. Although the change in sound wasn't dramatic, perhaps, it did, as you guys put it, open up the sound. There is slightly more top end.

Given the very bright sound of these mics, that alone would not have been worth the mod. But the subjective change was more distinct. The treble range sounded cleaner and more pleasant. The multilayer ceramic seemed to have introduced some distortion. The polyprop seems much cleaner. So it's not just about more or less top end but good or bad top end. Also that slight murkiness in the mids disappeared with the polyprop. Especially the low mids sounded bigger, "freeer", without any level increase. All in all the mod transferred the mic from "okay in certain applications" to "very usable bright mic."

Next step would be to swap two 1µ electrolytics for same value WIMA MKS-2. Although I don't expect too much from that mod.

Well, anyway, thanks for the inspiration.

 

[cprieb]

[quote author="Category 5"]Would you say the 1uf made a significant difference compared to the .22? Also, I saw some photos of a 603s somewhere and the two caps (1 and 2 I think) at the bottom of the board just above the XLR assembly were also changed. Any reason to make those .22uf films too?
[/quote]
603 stock C1 and C2 are .022uF. I changed mine to .01uF but couldn't notice any difference.
When changing 603 C3 and C4 for fat film capacitors, mouting R9 on the solder side may help to make room for C4.
Greetings
César

 

[Flatpicker]

[quote author="Rossi"]... and that one sounded rather neutral, maybe even mellow, not as bright as a 603...[/quote]Hi Rossi.
I actually never compared it to a 603. I was testing the 990 with vocals and comparing it to clips made with my M20, V93, and 319 (all modified) LDCs. I tested the 603s (and the 991) as instrument mics using my acoustic guitar. I think we are using different points of reference here.

Your review of the SC150 mod results pretty much nails what I thought about the 990. It didn't really change the frequency response that much - it just cleaned up the sound and made it "freeer" as you said.

 

[Rossi]

Actually, the 990 isn't a bad mic for acoustic guitar. I think it's a pretty good allrounder/utility mic. If I could get them as cheap in Germany as they are in the States, I'd get a few "just in case." And for modding experiments, of course. :wink:

 

[Flatpicker]

[quote author="Rossi"]Actually, the 990 isn't a bad mic for acoustic guitar...[/quote]I will definitely have to try it on my acoustic before I give it back, then. :thumb:

 

[Marik]

I am sure many folks could find 990 very usable with some sources. To me the mic sounds kinda weird, and I think the problem is in that "acoustic" brass ring around the capsule, and grill construction. Definitely, with this capsule, the grill should not be that dense. I'd tear off inside finer layers of mesh. Instead of brass jobie I'd experiment with different gauze silks glued to wire mesh ring--the trick well known from ribbon mics construction. It will help to preserve HF response, while maintaining the LF one.

 

[Flatpicker]

[quote author="Marik"]...I'd tear off inside finer layers of mesh...[/quote]If it was mine, I would. MXL did sort of "grille" it to death, didn't they? Sheesh, you can't even hardly see through it!

 

[Rossi]

Of course there is some body/grill resonance. In this particular case it's pretty obvious, because it doesn't sound like the 603. But wouldn't making the grill sound more transparent turn the 990 into a 603 with just different cosmetics? To me the 990 sounds quite fine as it is, and its "added flavor" seems quite useful at times.

 

[Bear]

[quote author="Flatpicker"][quote author="Marik"]...I'd tear off inside finer layers of mesh...[/quote]If it was mine, I would. MXL did sort of "grille" it to death, didn't they? Sheesh, you can't even hardly see through it![/quote]

Allowing Banjo Mart to sell it as a large diaphragm condensor. Now I know I'm going to have to do it: go down to buy some to mod, have the weasel say how it's a great set, since you get the LDC and SDC both, purchase, take out the screwdriver, disassemble both and show him the capsules, and scream at him for being not only a moron, but also full of crap. That sounds like a fun Saturday.

Bear