MXL 603s mod

[Marik]

[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.

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

 

[Category 5]

I think he meant that the 991 with the cap on the back of the board repolaced blew away the 603s that didn't yet have that cap replaced.

Shane

 

[tmbg]

yes, that's exactly what I meant. The stock ceramic capsule-gate caps seem to contribute the most to noise and poor top-end response. The 991 I had put a mylar in place there.

Now all three of those mics have polystyrenes in them, and sound even better.

 

[Flatpicker]

[quote author="tmbg"]Now all three of those mics have polystyrenes in them, and sound even better.[/quote]Preach it, bro! :thumb:

Gus, looks like you have another disciple. :green:

 

[zebra50]

[quote author="tmbg"] The stock ceramic capsule-gate caps seem to contribute the most to noise and poor top-end response. [/quote]

Yes! This isn't too surprising when you think about it - this is where the smallest number of electrons are carrying the information. Any degradation to the signal will be most noticable at this stage.

I'll fix it and send Stewart a new jpg.

Cool!

Stewart

 

[Category 5]

I just ordered the Xicon 1000pf polystyrenes from mouser but they are on bakorder until the end of the month. Which other caps ought I change out?

Shane

 

[Flatpicker]

[quote author="Category 5"]Which other caps ought I change out?[/quote]C4, C9, and C13.

 

[Category 5]

Which values and which brand should I get? Do you know of a great quality replacement that shouldn't have trouble fitting? I am just going to order htem now, and I'll strat swapping when I get the Xicons.

i am planning on doing the 990s too. I have been using the 990 for female vox through the 1272 and it has been sopunding excellent already.

Shane

 

[tmbg]

I hope I didn't buy the last of the polystyrenes...

good thing I bought a few

 

[longsoughtfor]

Can someone point me to a resource or briefly explain why different composition caps are better or worse then others in particular situations?

For example, why is a poly cap better then a tantalum or ceramic in the 603?

I realize that manufacturing cost may be why the maker used one over another but is that the only reason?

Thanks
Kevin.

 

[Flatpicker]

edited

 

[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.

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. When I get them both modified I?ll compare them and see if I can hear any difference.

 

[tmbg]

I have two 603s's

The first one I got was from Gutar Center, and I bought it at the same time as my 991. They're identical.

The second 603s is from Musicians Friend, it's the older PCB with the FET trimpot.

So apparently there's a revised design on that board... but the new 603s and 991 are indeed identical, except for the color and mogami wire.

 

[Guest]

my 990's dont have trim pots either...

 

[tmbg]

990 and 991 should be identical circuits, only with a different PCB layout to accomodate the different shaped body.

I did the same mod on my 990 as on the 991 and 603s's.

 

[Gus]

I have not been inside one but if like other china microphones like that

unscrew the bottom

There should be two screws that hold the grill to the metal plate

Lift the grill off.

 

[tmbg]

also, take note that the capsule is identical to the 991

 

[ebartlet]

[quote author="longsoughtfor"]Can someone point me to a resource or briefly explain why different composition caps are better or worse then others in particular situations?

[/quote]

Here is an article that may be helpful to you:



http://www.audience-av.com/on_capacitor_dielectric_material.htm

Another thing to remember is there are practical capacitance limits depending what type of capacitor you use, i.e. Generaly speaking everything above 1uf will use some form of electrolyte and everything below will use some form of film, and for really small values ceramic is all that is availible. HTH

 

[Category 5]

Check this out. I opened my MXL 600 to see if the mod might work on this one too.

http://www.pbase.com/image/38548660.jpg

http://www.pbase.com/image/38548661.jpg

http://www.pbase.com/image/38548662.jpg

C13 has a Wima in its' place. It's soldered tight so I can't see the value.

Does this mean we might be able to do the same to the 603s? Wouldn't you guys think a WIMA would sound even better than the polystyrenes?

Also, is there much point to swapping out C3 and C4? I mean, will it make a noticable improvement? I only ask because obviously MXL sprung for the WIMA on C13, I imagine they would have used something more robust for C3 and C4 if they thought there would be a significant benefit.

Shane

 

[Gus]

Caps at the values we use don't cost that much. I would suggest that you buy some of different types and try them. Find what your ears/brain like.

Someone here likes polypros at the capsule grid/gate of a microphone more than polystyrene. I like polystyrene. Sometimes it is a taste issue.