Topic: MXL 990, 991 and Oktava 319 Mods

[raymonda]

Attached are pictures of the finished mods to these mics. I didn't post pictures of the internal mods to the Oktava's since the are not as easy to take a part and it was an after thought to shoot them.

I have used the mics on a few live sessions with very good results. One live session will be released as an upcoming cd. I'll let folks know when it becomes available.

[raymonda]

More pics

[raymonda]

More Pics

[Fatah Ruark (aka MIKE B)]

FYI:

You can post those other pictures as a REPLY to this thread. It will be easier for people to search for in the future.

Very cool stuff though!

[Kindguy]

What mod is on the 319?

[raymonda]

Physical:
1) one layer of screen removed
2) foam around base of LD to remove reflective sound
3) Side metal brasing on basket removed
4) Resonator filter around LD removed

Electrical:
1) Many caps and resitors replaced with higher compliance and better grade.
2) 1o db pad and high pass filters removed.

[chris319]

How difficult was it to remove the inner layers of mesh from the MXL 990?

[raymonda]

Simple! Needle nose pliers and pull. Also, I would take off the brass ring that surround the SD. I'm not sure why they have it there but my guess was to create a shadow and make it look like a LD.

FYI The 990/901 and 993 share the same cap, circut topolgy and components. They are identical mics. However, the 990 is side address, or course. So you can skip paying any extra for the 603's and go directly to the 990/991 for usually half the price of 603's.

Look for Frank Vagnola and Bucky Pizerelli CD to be release soon. On that session I used the 991 as ORTF, and the 990 as spaced Omni along with the other tracks in the multi track mix. I think you will like what you hear.

Ray

[michaeljoly]

In all of these mics, upgrading to a faster FET with less capsule capacitive loading, then biasing for optimum operation makes a big difference as well. There is one manufacturer making a particular version a very stable capacitor that is my choice for the critical capsule to FET input location (no, its not a WIMA Polypro). Its also possible to squeeze 1 uF coupling caps into the 603 bodies for better bass extension.

Similar comments about the 990. In addition I prefer to modify the capsule into a little "saddle" with tapered edges to reduce diffraction effects. Hard to tell from your photos, but the mesh can be completely removed from the capsule to reduce top end resonance in the 990 application because of the sheilding effects of the headbasket.

I didn't realize you Tapers are such crafty DIY'ers!

[raymonda]

Hey Mike,

Great to have you step in side since your work on the Oktava's and MXL's inspired me to work on mine to begin with. I hold your work and technical experience in high esteem.

I left the screens on the 990's because I change the caps, depending on the purpose, from omni to card and it can help protect it from foreign objects and fat fingers.

Thanks for the recomendation of further improvements, which I'll certainly act on. 

[raymonda]

I'm glad the adjective you used was crafty and not crappy.

[michaeljoly]

I left the screens on the 990's because I change the caps, depending on the purpose, from omni to card and it can help protect it from foreign objects and fat fingers...

Great idea! Its great to see recordists get under the hood like this. Its really old-school and really how the legends approached their gear.

[raymonda]

Mike,

Does this look like the caps you were talking about? They were used in the 990's but not the 991's, due to a limited supply. Or, take a closer look at the 990's above, since this picture is so bad.

[michaeljoly]

I can't tell from that pic, but all these mics have two .22 uF caps, usually polypro, near the output transistors. Those should be replaced with 1 uF polypro to extend the bass response.

[Javier Cinakowski]

I was looking over your webiste Michael, those Oktava kits look like a really nice value. 

Off topic, but have you looked at doing anything to the Rode NT5 (NT55, Nt6 etc)  ?  I've got a pair of Rode NT6's here that would like to be experiemented with!  :-)