gogolox

Looking for MXL 440 PCB Upgrade
« on: April 22, 2020, 10:55:21 PM »
Hey everyone!  I'm new to Group DIY and am just getting into mic DIY.  I have experience soldering and have an MXL 440 as my donor body.  I have a new capsule, but was wondering if there is a seller of a better pcb for the mic.  I know microphone-parts.com has something, but was wondering if there was someone else who does this here.  I looked at the White Market and found mostly compressors and mic pre's.  Any help would be great! Thanks!


Khron

Re: Looking for MXL 440 PCB Upgrade
« Reply #1 on: April 23, 2020, 11:33:32 AM »
Define "better (pcb)".
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

Re: Looking for MXL 440 PCB Upgrade
« Reply #2 on: April 24, 2020, 01:13:09 PM »
Hey everyone!  I'm new to Group DIY and am just getting into mic DIY.  I have experience soldering and have an MXL 440 as my donor body.  I have a new capsule, but was wondering if there is a seller of a better pcb for the mic.  I know microphone-parts.com has something, but was wondering if there was someone else who does this here.  I looked at the White Market and found mostly compressors and mic pre's.  Any help would be great! Thanks!
The PCB is fine. You'll probably want to change the FET out, maybe upgrade capacitors, and possibly use quieter diodes. Definitely a different capsule, unless you want to add corrective EQ or just build a new circuit. But there's nothing wrong with the current circuit, it looks like it's probably the Schoeps circuit. Put in a K47 style capsule or edge terminated capsule (on that's flatter than a K67) and you should have an improved mic.

But there's nothing wrong with the stock PCB or circuit, it's just using cheaper components and a capsule that needs de-emphasis.

I'm pretty sure a lot of the Mic-Parts offerings will be the same circuit anyway.
« Last Edit: April 24, 2020, 01:17:08 PM by Icantthinkofaname »

RuudNL

Re: Looking for MXL 440 PCB Upgrade
« Reply #3 on: April 24, 2020, 03:28:38 PM »
This is how a MXL440 looks inside:



They use a 17 mm capsule with a brass ring around it.
All SMD components...
« Last Edit: April 24, 2020, 03:32:29 PM by RuudNL »
There is a solution for every problem!

http://www.vansteenisaudio.nl

analogguru

Re: Looking for MXL 440 PCB Upgrade
« Reply #4 on: April 24, 2020, 05:30:06 PM »
Looks nice.... as long as there are no 0402 parts used.....

Yes, I ordered 100pcs 2,2µF/50V MLCC and didn't look carefully enough, I thought they would be 1206 with this capacity/voltage..... so I got them in 0402 size (1mm x 0,5mm).  I wonder if I ever will use them....
« Last Edit: April 24, 2020, 05:35:15 PM by analogguru »

Re: Looking for MXL 440 PCB Upgrade
« Reply #5 on: April 24, 2020, 11:20:03 PM »
This is how a MXL440 looks inside:



They use a 17 mm capsule with a brass ring around it.
All SMD components...
Oh they're doing SMD now. The Recording Hacks picture shows an older through hole variant (sometimes I forget how much that site is missing, or the amount of opinionated information on it). It may be worth building the Mic Parts circuit just to get through hole, but there are probably free schematics floating around.

Or OP, why don't you just build a mic in the BM-800 body with a different PCB? You can probably do the Alice build for really cheap.

You might be better off just buying a better mic to put the capsule in. Maybe an MXL 2010 or something. Maybe the older Behringer B2 Pro as well. Also what kind of capsule is it? A K67 capsule isn't going to be good in the circuit. If it's a K47 or "CK12" it should be fine.

I wonder how many MXL mics are still through hole. Surprisingly, the V67G was still through hole as of 2017.
« Last Edit: April 24, 2020, 11:24:13 PM by Icantthinkofaname »

RuudNL

Re: Looking for MXL 440 PCB Upgrade
« Reply #6 on: April 25, 2020, 05:20:34 AM »
This is how I modified the microphone: new microphone capsule, Schoeps circuit on a new PCB and a DC/DC converter on another PCB on the backside. Now it is a very acceptable microphone:

There is a solution for every problem!

http://www.vansteenisaudio.nl

rogs

Re: Looking for MXL 440 PCB Upgrade
« Reply #7 on: April 25, 2020, 07:39:15 AM »
Or OP, why don't you just build a mic in the BM-800 body with a different PCB? .....

I took it one stage further back and built my first  LDC project onto stripboard - so no PCB. (Only takes a couple of hours to make). Gave me the opportunity to try out my own version of the Schoeps circuit....

I posted some project notes here:  www.jp137.com/lts/LDCX2.notes.pdf
www.amx.jp137.com - A DIY RF condenser mic project

Re: Looking for MXL 440 PCB Upgrade
« Reply #8 on: April 25, 2020, 07:48:18 AM »
I took it one stage further back and built my first  LDC project onto stripboard - so no PCB. (Only takes a couple of hours to make). Gave me the opportunity to try out my own version of the Schoeps circuit....

I posted some project notes here:  www.jp137.com/lts/LDCX2.notes.pdf
How's the longevity of a build like that? I've heard varying opinions.

rogs

Re: Looking for MXL 440 PCB Upgrade
« Reply #9 on: April 25, 2020, 09:42:43 AM »
How's the longevity of a build like that? I've heard varying opinions.

Well, the oldest of my own mics built like that is now around 3 years old ... and shows no sign of any deterioration.
As you can see from the photos and description, the  IG resistor is fitted directly to the FET gate  on the top side of the board, so the extreme HiZ parts are  kept away from the stripboard tracks.
The flux from the soldering of the remaining components was removed with a  sharp tip, and the whole board cleaned with isopropol alcohol.
As I say, so far so good .....  I've several mics built like it - some with K67 type capsules, some with K47. 
I even tried one with a 3 micron edge terminated capsule, but I needed to reduce the polarisation voltage  to stop the capsule collapsing.
Simple task -- I just removed  one multiplier capacitor !
It's also very simple to vary the design with stripboard if you fancy experimenting
Obviously not a suitable technique for mass production -- but for a simple hobby project??
I've been very pleased with the results so far...
www.amx.jp137.com - A DIY RF condenser mic project


RuudNL

Re: Looking for MXL 440 PCB Upgrade
« Reply #10 on: April 25, 2020, 11:59:38 AM »
The only point in the circuit that is critical, is the connection to the gate.
All other points have a pretty low impedance.
Removing flux from the board makes it looking better, but I doubt if there would be an audible difference if you would leave the flux on.
By the way: what is the polarisation voltage that you got with all the voltage multiplier stages in place?
(I usually don't go higher than 55-60 Volts.)
There is a solution for every problem!

http://www.vansteenisaudio.nl

Gus

Re: Looking for MXL 440 PCB Upgrade
« Reply #11 on: April 25, 2020, 12:00:43 PM »
I have worked on the MXL SMD PCBs like in the picture. I use  good temp controlled irons and tweezers. IMO the pads held up OK if you have some skill soldering.

I installed bias potentiometers, adjusted the circuit design, changed resistor value and/or type, increased the DC to DC voltage etc.

I would use the stock board to start experimenting and change the capsule if that is what you want to do.
What kind of capsule?
What do you want to change in the sound?
That will help you figure out what circuit you want after the capsule grill is selected.

Being one sided you can remove the parts and solder or drill and solder if the pad is big enough for leaded devices, if that is what you have to build with.


rogs

Re: Looking for MXL 440 PCB Upgrade
« Reply #12 on: April 25, 2020, 05:46:38 PM »
By the way: what is the polarisation voltage that you got with all the voltage multiplier stages in place?
(I usually don't go higher than 55-60 Volts.)

 With a 9v zener and all multiplier stages in use, I get around 60V.
Removing one charge capacitor will reduce that by around 8 volts as I recall.
You could of course use a higher voltage zener to increase the max available voltage, but like you I tend to go with somewhere between 50 and 60 V as a general rule.
And if you do go higher you need to remember to use 100V capacitors in the later stages, rather than 63V ones ....
www.amx.jp137.com - A DIY RF condenser mic project

Re: Looking for MXL 440 PCB Upgrade
« Reply #13 on: April 25, 2020, 07:29:43 PM »
This is how I modified the microphone: new microphone capsule, Schoeps circuit on a new PCB and a DC/DC converter on another PCB on the backside. Now it is a very acceptable microphone:



Is this the usual linear version of the circuit?

RuudNL

Re: Looking for MXL 440 PCB Upgrade
« Reply #14 on: April 26, 2020, 04:36:52 AM »
Is this the usual linear version of the circuit?

Yes.
There is a solution for every problem!

http://www.vansteenisaudio.nl

gogolox

Re: Looking for MXL 440 PCB Upgrade
« Reply #15 on: April 27, 2020, 07:44:34 PM »
Thanks for the responses guys.  The Alice idea is really cool after looking into it a lot more.  With the MXL 440,  I was asking about the upgrade because I saw a circuit kit at microphone-parts.com that looked really good for it.  Problem is with shipping and tax it goes to about $155, which seems a bit steep to me for a pcb and circuits.  That's why I was wondering what other options there could be.  I do know about www.vintagemicrophonepcbkit.com, but the 87T pcb has their holes for the screws in a position that makes the pcb touch the roof of the body kit.  Not sure if that's fine or not.  I have an AK67 from Advanced Audio that was given to me a few years ago and figured I would pair it with a pcb that would fit it better.  Figured it would be a great project for my first mic diy.  I do have experience soldering and have done different small diy projects in the past in case someone was wondering

Gus

Re: Looking for MXL 440 PCB Upgrade
« Reply #16 on: April 28, 2020, 11:37:18 AM »
Thanks for the responses guys.  The Alice idea is really cool after looking into it a lot more.  With the MXL 440,  I was asking about the upgrade because I saw a circuit kit at microphone-parts.com that looked really good for it.  Problem is with shipping and tax it goes to about $155, which seems a bit steep to me for a pcb and circuits.  That's why I was wondering what other options there could be.  I do know about www.vintagemicrophonepcbkit.com, but the 87T pcb has their holes for the screws in a position that makes the pcb touch the roof of the body kit.  Not sure if that's fine or not.  I have an AK67 from Advanced Audio that was given to me a few years ago and figured I would pair it with a pcb that would fit it better.  Figured it would be a great project for my first mic diy.  I do have experience soldering and have done different small diy projects in the past in case someone was wondering

The Alice microphone is not any better than the stock MXL circuit in this microphone.
Look up the SMD JFET used it is not bad.
Check the PNP balance
There was also a Yahoo group with lots of good information on this type of circuit. Does anyone know what happened to it after yahoo dropped it?

The stock board can be reworked it is not hard to trace being one sided.

Change the capsule if you want then add a bias control then replace some of the SMD parts if you want.

Do a search for this type circuit a lot has been posted on the web over the years some of good some not so good.



Khron

Re: Looking for MXL 440 PCB Upgrade
« Reply #17 on: April 28, 2020, 11:50:57 AM »

There was also a Yahoo group with lots of good information on this type of circuit. Does anyone know what happened to it after yahoo dropped it?

All(?) the ex-Yahoo groups seem to have been transferred to groups.io - at least the LTspice and the MicBuilders have.
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

rogs

Re: Looking for MXL 440 PCB Upgrade
« Reply #18 on: April 28, 2020, 12:14:37 PM »
The Micbuilders group is here now: https://groups.io/g/MicBuilders
www.amx.jp137.com - A DIY RF condenser mic project

Gus

Re: Looking for MXL 440 PCB Upgrade
« Reply #19 on: April 29, 2020, 02:07:17 AM »


 

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