MXL 990 mod question from Norway

[Frdfrode]

Hi there. I have a mxl 990 donor, and are looking for a nice capsule and circuit mod for this. I already own a 40 year old AKG C 414 B ULS and would like this DIY project to be an alternativ sounding microphone compared to the AKG. I have before build a few simple michrophones as fun using copperpipe etc. I am ok with a soldering iron, but do not have enough knowledge to design my own circuit.

Best regards
Frode

 

[micolas]

Hi there. I have a mxl 990 donor, and are looking for a nice capsule and circuit mod for this.

Hi Fredfrode
Is your MXL990 the through hole or SMD version?
I recommend the Arienne FlatK47 capsule

 

[rock soderstrom]

Besides the usual solid state mods, how about tubes?

My suggestion, SELA T12 or Royer Mod. You can keep the capsule for initial tests and then upgrade as required...

 

[Frdfrode]

Hi Fredfrode
Is your MXL990 the through hole or SMD version?
I recommend the Arienne FlatK47 capsule

Thank you for answering. The donor is still in post to me, I have to wait and see. What does SMD version mean?

Frode

 

[Frdfrode]

Besides the usual solid state mods, how about tubes?

My suggestion, SELA T12 or Royer Mod. You can keep the capsule for initial tests and then upgrade as required...

Thank you, found some info on it. Looks like a good project.

Frode

 

[Khron]

What does SMD version mean?

https://en.wikipedia.org/wiki/Surface-mount_technology

 

[micolas]

Thank you for answering. The donor is still in post to me, I have to wait and see. What does SMD version mean?

Frode

 

[micolas]

Besides the usual solid state mods, how about tubes?

No offense, A tube project especially in such a limited space exceeds Frdfrode's electronics experience

 

[Frdfrode]

Got it, thank you for your time helping with this

Frode

 

[RuudNL]

The MXL capsules are not the best. (To put it mildly...)
Since there is no frequency correction in the circuit, a K47 capsule would be the only option, or a CK12.
(But most capsules sold as 'CK12', are nothing else than an edge terminated K67 capsule.)

 

[Frdfrode]

The MXL capsules are not the best. (To put it mildly...)
Since there is no frequency correction in the circuit, a K47 capsule would be the only option, or a CK12.
(But most capsules sold as 'CK12', are nothing else than an edge terminated K67 capsule.)

I have som stuff from 30 years back, see attached pictures. Maybe some of this can be used, if not in a mx990 body but for a later project? The capsule is the same on all pictures. I also have other tubes in variable sizes.

 

[Frdfrode]

I have som stuff from 30 years back, see attached pictures. Maybe some of this can be used, if not in a mx990 body but for a later project? The capsule is the same on all pictures. I also have other tubes in variable sizes.

 

[micolas]

I have som stuff from 30 years back, see attached pictures. Maybe some of this can be used, if not in a mx990 body but for a later project? The capsule is the same on all pictures. I also have other tubes in variable sizes.

Frdfrode,

That's the DIY spirit!
What you have there can be used for various projects.
I also look for old equipment at friends and recycle the components.
The capsule is type k67, the tube
TFK EF86 if it is within the parameters is beautiful.
The Lundahl transformer can be configured 2:1 and used in classic topology:
k67j+Fet+BJT+Transformer 2:1
And you probably have other useful components.

 

[rock soderstrom]

No offense, A tube project especially in such a limited space exceeds Frdfrode's electronics experience

I do not know Frode's skills, it is true that a FET circuit is less dangerous and would also fit better into the existing microphone.

On the other hand it would work, the Royer Mod has the transformer in the PSU housing and the Sela T12 can also be built with 5840.
So they do not need that much space.

 

[rock soderstrom]

I have som stuff from 30 years back, see attached pictures. Maybe some of this can be used, if not in a mx990 body but for a later project? The capsule is the same on all pictures. I also have other tubes in variable sizes.

Hmm, mee like!

You got almost everything you need for two tube mics!

The 5840 and the Lundahl for the Royer Countryman Cathode Follower mic and the 1:10 Beyerdynamic bean is a perfect fit for a Sela T12 or the other Royer Mod with plate out...

 

[micolas]

I have som stuff from 30 years back, see attached pictures. Maybe some of this can be used, if not in a mx990 body but for a later project? The capsule is the same on all pictures. I also have other tubes in variable sizes.

From my knowledge:
Beyerdynamic
BV 310 010 00*
Studio grade transformer, dual in-line pcb mounting,
single primary,
1:10 turns ratio, 200ohm

It can be tried in the U87 circuit, inverted primary with secondary(Less dangerous with jFets than tubes).

 

[rock soderstrom]

From my knowledge:
Beyerdynamic
BV 310 010 00*
Studio grade transformer, dual in-line pcb mounting,
single primary,
1:10 turns ratio, 200ohm

That’s true, this mini transformer can be used in countless circuits, FET and tube. I have used the same model with wire bushing, and this small guy really sings! 10:1 is good for a lot of triode wired pentodes, my favorite is the 5654/E95F/6AK5w family! (=bigger brother of the 5840)

 

[rock soderstrom]

BV 310 010 00*

BTW, for those who don't know, the three marked numbers in the Beyer code indicate the step up ratio of the transformer.

 

[micolas]

BTW, for those who don't know, the three marked numbers in the Beyer code indicate the step up ratio of the transformer.

Exactly.

 

[Frdfrode]

Building a tube mic sound exiting, but may be a to big project to start with. I would have to build the PSU also I guess.
I was thinking about a sweet vocal mic, sparkling without being to rough in the top end, with a solid mid/low mid.

I do not know if the k67 is the right for that? With or without the beyer transformer?

Maybe there is someone on this forum that have pcb´s for i nice circuit, or I can solder on project plate. I have plenty of components, wima condensors and metal film resistors etc. Some I am sure I will have to buy.

I have 4 pieces of the 5840 tubes if someone would want some, I do not 4 of them.

So on to a tube mic for next project, but one at the time