Function of 2 caps in MCA SP1 (MXL 603) circuit?

I didn't find the answer searching the archives concerning the 603, so I thought I'd ask.

I have a couple MCA SP1 mics (almost the same circuit as the MXL 603)
For those of you who have been replacing caps on these mics, did you replace C8 and C9?
They're ceramic caps of pretty hard to find values in films.

C9 (on the SP1) is actually C8 on the 603 schematic, and C8 (on the sp1) is C7 on the schematic.


The schematic has C9(C8) listed as a 6.8pF, but I think the ceramic cap in my mic is 10pF. C8(C7) is 27pF.

My question is, is it worth it to dig up some replacements for these caps or should I just leave them? What's their function in the circuit?

http://www.sdiy.org/oid/mics/MXL-603S.gif

DC to DC section is the top left part of the linked schematic.
You can leave the stock caps in there.

The following schematic has a few errors:

http://www.sdiy.org/oid/mics/MXL-603S.gif

D5, D6 and D40 are 6.2 volt zener diodes.
The D30 12 volt zener does not exist in the actual circuit.
The R50 trimpot should be shown as a 500k trimpot.
C30 should be a 47 uFd 50 volt cap

This schematic has similar errors:

http://www.omnipressor.com/MicSchLib/MXL603S.jpg

ZAP

http://www.groupdiy.com/index.php?topic=5156&highlight=mxl+603+mods

eD)))

The mca sp-1 doesn't look anything like that. It has 2 circuit boards inside. I'll take a pic after I finish my coffee.

Here's a couple pics:




Not much to it. It screams: Please Mod ME!!

Are you sure you'not talking about the MXL 2001 ?

Another thing about these. I heard they were made of plastic. Mine are all metal. Did they change them?

top picture is the DC to DC section

[quote author="Stagefright13"]Another thing about these. I heard they were made of plastic. Mine are all metal. Did they change them?[/quote]
That's what I read as well, in the Harmony Central review IIRIC.
But mine have an alu-body as well. Probably they mistook the alu for plastic, I was only sure myself as well after disassembling it.

Regards,

Peter

The base-plate of the capsule-section seems to be prepared for more wiring.
I heard about the SP2, might that be a multi-pattern version then perhaps ?
For some reason the TapeOp-review considers the SP2 to be not as nice as the SP1.

The very same circuit/layout could be found in the mxl v57m, and I'm sure several other mxl models.

The body, capsule baseplate, and metalwork are all identical to the mxl, as well. I gutted the mxl and put in the Royer cathode follower circuit. Still got the mxl boards to tinker with.


Hmmmmmmm....

http://www.groupdiy.com/index.php?topic=17753

[quote author="clintrubber"]The base-plate of the capsule-section seems to be prepared for more wiring.
I heard about the SP2, might that be a multi-pattern version then perhaps ?
For some reason the TapeOp-review considers the SP2 to be not as nice as the SP1.[/quote]
As I understood in the meantime the SP-2 can also be battery-powered ('on its own').
So while the capsule will be the same probably, they need to have made some circuit-adaptions - apparently resulting in
a less nice sounding mic for phantom. OK, FWIW.

Would have been nice if a multipattern version of this mic had been, or is that for some reason a no-go for medium sized diaphragms ?

I have a great drummer coming from Irvine California in a week and a half will try the sp1's and my mics and the rentals and will see what happens soundwise. Will be my first test of them.

But I don't have time to mod them by then so...

But my first impressions are they may make good overheads or very good tom mics. Except I would use LDC on floor tom myself. But we shall see.

I do rock mainly and some Jazz. And 75% VO and commercials so don't go buy me. But it will be a hard rock band shortly.

[quote author="Stagefright13"]Will be my first test of them.

But I don't have time to mod them by then so...

But my first impressions are they may make good overheads or very good tom mics. Except I would use LDC on floor tom myself. But we shall see.[/quote]
Sounds good. I realize well I shouldn't get too carried away with this mic to be the thing of all things, but for this price it wouldn't hurt to have a spare one to keep a stereo-pair going. And/or to compare mods against.

But it will be a hard rock band shortly.

Click to expand...

Used them on something loud as well (no 'hard rock', but comparable busy) and I was pleased by the sound - remained 'open' (...). That might say more about previously used mics, but OK... it's an improvement nevertheless.

Cheers,

Peter

Well at 39 bucks US they are great. Everyone starting out recording could benefit from a bunch of them. And some 57's

I haven't tried it yet but I think they would be an awesome Tom mic. Will let you know.

Thanks guys! I'm the original poster.

I replaced the .22uF's with 1uF Panasonic films, and the tants with Wimas, and the .001uF tant with a Panasonic film.

I also took out D1 and D2, and C1 and C2 on the output. This was according to reccomendation from a guy named DCoyle on tapeop.

These mods are probably already detailed here under the MXL series mods, but I thought I'd mention that what is a little bit unique about these SP1 mics is they have 2 extra .001 caps right before the output transistors, shunting the highs to ground.

DCoyle reccomended taking these out as it opens the mic up a bit, and the other MXL mics don't have them.

I tried it with and without these caps, (replaced again with Panasonic .001 films) and I decided the mic sounded smoother with those caps in. Just going with my ears here. I imagine what may have attracted some people to this el cheapo mic in the first place is that it seems to lack some of the high end harshness of a lot of other cheap mics, and keeping those caps, but upgrading from the ceramic seems to retain that quality.

Anyway, just thought I'd share.

Thanks JW! I will try it. Your advice is appreciated. :thumb: :thumb:

Did you remove D1 and 2 and C1 and 2? or did you put in jumpers to replace them?

And yeah I have plenty of mics with the high end boost. A pair of flatter condensers is much appreciated.

I removed them. Good luck!