MXL 603s mod

with some helpful coaching from Gus, I have been messing with these MXL mics, I have two 603s and a 991 (which seems to be identical to the 603s except for the mogami wire )

One of my 603s's is completely stock, one has panasonic V's in place of the monoliths in the amplifier and in place of the rf shunt caps, but it has the stock monolith capsule to gate cap.

My 991 has both the pan V's and a polystyrene (I think, it's that green pillowy one I stole from that mixpak) in place of the capsule to gate cap.

The upgraded 603s sounds marginally better than the stock 603s, but the 991 blows them both away, in terms of lower noise and high end clarity. I'm guessing that when I get my polystyrene cap order from mouser tomorrow and put one in the upgraded 603s, it'll blow away the stock 603s by a large margin.

Next to tackle the MXL2003

[quote author="tmbg"]...it's that green pillowy one I stole from that mixpak) in place of the capsule to gate cap... Next to tackle the MXL2003[/quote]That cap description sounds like mylar - not polyseyrene.

The 2003 is basically the same circuit with room for bigger caps. The same mod really opens it up!

this is it:



oi, you people and your red exxesss....


better now?

Where is the picture? I see the red X.

Shane

I've been messing with these recently.... they are nice sounding mics... and amazingly sensitive to dirt... keeping the board clean makes a BIG difference. Actually, one of the ones I bought was overly noisy out of the box, some cleaning fixed it right up. The cap from gate to capsule makes the biggest difference in sound I think... especially in the high end.

[quote author="JCMaudio"]...keeping the board clean makes a BIG difference. Actually, one of the ones I bought was overly noisy out of the box, some cleaning fixed it right up... [/quote]Yep. They are nasty, aren't they? I can't believe they don't clean the flux off those things!

[quote author="buttachunk"]hey--

has anyone traced this thing yet ? looks to me like that S Dorsey 'mod', doesn't it ??

[/quote]

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

:wink:

z50

Z50,

D1, D2 looks like they're the wrong way around?

Or do we source the vorking voltage through the 2N5401's?

Jakob E.

Jakob,

I didn't draw this circuit out, someone sent it to me (possibly Flatpicker or AdrianH - apologies to whoever it was). I know it looks wrong but I just has a looked inside the mic and I can confirm that the diodes are that way around.

It must be sourced through the 2n5401s.

Stewart

I drew it and yes, voltage is sourced through Q3 and Q4.

Speaking of the 603s, I want to try putting a higher voltage on the capsule. Do you think there's enough current to drive another multiplier stage?

Oh, meant to say that this isn't exactly like the Dorsey mod - he didn't include the voltage multiplier in his modification. He told me that he left it out because he was of the opinion that the Shanghai capsule sounded better without it.

Thanks Tim and sorry I'd forgotten it was you - I got sent a few and couldn't recall who sent which.

z50

Speaking of the 603s, I want to try putting a higher voltage on the capsule. Do you think there's enough current to drive another multiplier stage?

Click to expand...

Interesting Tim... I like a lower voltage on the capsule myself. It sounds clearer to me than stock... But how much voltage are you looking to put on it, 60v? I am curious as to how that would sound.

[quote author="zebra50"]Thanks Tim and sorry I'd forgotten it was you...[/quote]No need for apologies - for a second there I couldn?t remember myself!

[quote author="JCMaudio"]...I like a lower voltage on the capsule myself. It sounds clearer to me than stock... But how much voltage are you looking to put on it, 60v? I am curious as to how that would sound.[/quote]IIRC, Marik liked a lower voltage on it too. I'll have to give it a try that way.

I think the best way to do that would be to disconnect the D1/D2 junction from the rest of the circuit, and run a wire from there straight to R12, lifting the end of R12 going to C11/D6 off the board and soldering the wire straight to it. Next remove R10 - this isolates the voltage multiplier from the circuit. Of course, now you have to replace D1/D2 with 100Ks to get phantom power straight to R12 - about 35V at this point.

I don't know how it will sound with a higher voltage. Just curious like yourself. Not sure how much voltage another cap and diode will add...

Stewart;
I am glad Tim fessed up because it was not me.

There's a small error in the schematic - R5 (the trimpot across the source resistor in the phase splitter) should be either 500Kohms or 1MegOhm. It needs to be very high in relation to R6 (the source resistor) and very low in relation to R8 (the bias resistor)
The Schoeps Collette circuit that this is a copy of uses a 1Meg trimpot here.

[quote author="adrianh"]Stewart;
I am glad Tim fessed up because it was not me.[/quote]

:grin: But you have sent good things in the past :thumb:

Dayvel - thanks for the correction.

[quote author="zebra50"][quote author="adrianh"]Dayvel - thanks for the correction.[/quote]Yes - Thank you. I'll fix it and send Stewart a new jpg.

[quote author="tmbg"]

The upgraded 603s sounds marginally better than the stock 603s, but the 991 blows them both away, in terms of lower noise and high end clarity. [/quote]

I cannot find an explanation for that, as both 603 and 991 are the same mics. Is it possible that your 991 has a better capsule sample? Try its capsule with 603--interesting what you'd get.

IIRC, Marik liked a lower voltage on it too.

Click to expand...

Yes Tim, I completely bypassed the DC-DC converter, getting lower voltage on the capsule, and liked it better that way.