MXL tube mic experiments using 5703

[SparkleBear]

Hey y'all,

I've been experimenting with some MXL tube mic conversions. Using the MXL 990 and MXL991/804/603 Ive had some pretty lovely and promising results. I really like the tone of this tube and they are pretty affordable!

I thought I'd share some of my results....

Calling this one the "Mini49"... It's an m49c circuit with a relay to force cardioid only mode when the pattern selector is on the cardioid position. I used SQ's flat 47 capsule and an AMI t13 transformer. Head basket is from Mic-parts.com. Thanks for a great capsule @soliloqueen !




1920s lyon and healey terz guitar
https://www.dropbox.com/s/4i6641dy8nmla6r/M(ini)49 - 1920's Lyon&Healey.mp3?dl=0
Vocals mini49, guitar Mono KMV254 m70 nickel capsule. Recorded at the same time.
https://www.dropbox.com/s/82no3au65pvr9ae/Teia De Renda - no verbs (rough) 1.16.23.mp3?dl=0

Next was kind of a semi failed build of the MXL to M221b. This didn't really work out because the PSU was not filtered enough. This circuit basically ties the kathode to the heater... so filtering is super extra important here. This psu works fine for the cathode biased designs i've been mostly working with lately. I will be redesigning the PSU to see if this is a viable design... but the tone is nice. This was 3u capsule omni, chinese ali express t13 transformer. It has a 3uf wet tantalum capacitor for the output as any other composition would be too big for the body.



Same terz guitar -
https://www.dropbox.com/s/1uudt6c0mukm0iv/M221b (3.0uf output t13 chinex traffo)OMNI.mp3?dl=0


Newest one is a km54c circuit with out the feedback section of the circuit. This is also the cheapest build of all the three... Used a neutrik 10/3 transformer, 3u Cardioid capsule... Im actually quite pleased with how this one turned out.



https://www.dropbox.com/s/on1uash66dcxmro/MXL to KM54c 3u cardioid nte10-3 5703 (ompw).mp3?dl=0

I hope you enjoy the sounds. I am curious to hear your impressions.

CHEERS!

 

[SparkleBear]

Just built a second MXL to KM54 this morning. Here is a stereo guitar recording. XY 90deg coincident. 3U Cardioid capsules.

https://www.dropbox.com/s/s010dxu8r6l2cy0/MXL to KM54c stereo pair test..mp3?dl=0

 

[Chrisfromthepast]

@SparkleBear, For the km54, how did you deal with the diaphragm being tied to ground through the body?
Did you use a capacitor between backplate and grid and insert capsule voltage in between like the km84?

 

[SparkleBear]

@SparkleBear, For the km54, how did you deal with the diaphragm being tied to ground through the body?
Did you use a capacitor between backplate and grid and insert capsule voltage in between like the km84?

Yeah, just like the km84. It's more of a KM54c inspired mic rather than the real deal. My M690 to KM54 is following the circuit to the T (except for ac701 and using a higher polarization voltage than 40v)... but this mxl mod had to make compromises. No feedback circuit and grounded diaphragm. I think it sounds wonderful though.



Although, the gefell mod sounds much better with the old iron and the nickel capsule. But i wanted to be able to make some sdc tube mics that didn't cost $1000 in donor parts. This mxl mod does the trick.

 

[soliloqueen]

the vocals sound really good, glad you like the capsule

 

[SparkleBear]

The KM54(ish) tube sdc pair was finally finished with its own dedicated dual supply and hard case from amazon. The dual supply is really nice because it will maintain the same calibrated value whether one mic or both are connected. Well filtered and regulated.

Proud of the kit!



Oh! And a bunch of the MXL bodies came back from the powder coater! Super stoked on how they turned out! Im epsecially thrilled with how the "Patriot edition" Of the mxl 990 turned out. I have still yet to design anything that will utilize its two switches... but im excited for that, whatever it turns out to be...

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