RuudNL

Schematic Sanken CU-41
« on: October 14, 2014, 11:37:06 AM »
I am looking for a schematic of the Sanken CU-41 microphone.
The microphone I have here produces no sound, only a terrible loud unregular noise.
I will first replace the capacitors and see what happens, but it would be a lot easier to find the problem with a schematic diagram in my hand!
There is a solution for every problem!

http://www.vansteenisaudio.nl


peterc

Re: Schematic Sanken CU-41
« Reply #1 on: October 14, 2014, 03:50:10 PM »
Hey Ruud

I am also looking for this. I could not open mine, any advice?

Peter
If opportunity doesn't knock, build a door.

RuudNL

Re: Schematic Sanken CU-41
« Reply #2 on: October 15, 2014, 04:50:20 AM »
To open the microphone, I used a 'tool' made out of a thick paperclip. (Any piece of thick steel wire will do.)
You put the helper tool in the two small holes in the bottom and twist the threaded bottom part.
(I didn't make the scratch!!!)



By the way: I contacted Sanken and they say that they have the schematic diagram, but they are not allowed to give it away.
GRRRRRRRRRRRRR!!! I bought their stuff, why can't I have the schematic? Bad customer service!
Well, I will reverse engineer their microphone and have the schematic anyway. Huh!
« Last Edit: January 15, 2016, 04:06:16 PM by RuudNL »
There is a solution for every problem!

http://www.vansteenisaudio.nl

peterc

Re: Schematic Sanken CU-41
« Reply #3 on: October 15, 2014, 03:57:07 PM »
Thanks for that, will try it in the morning.

Peter
If opportunity doesn't knock, build a door.

ChrisEverett18

Re: Schematic Sanken CU-41
« Reply #4 on: January 12, 2016, 02:29:30 PM »
Have you by chance created that schematic?  I have been trying to work on mine with little success because I don't know what I'm looking at!!...lol. 

RuudNL

Re: Schematic Sanken CU-41
« Reply #5 on: January 15, 2016, 04:08:00 PM »
Sorry, no schematic.
The owner took the microphone back and he would send it to Sanken for a repair.
(I know where the problem is, it is in the potted circuit where the impedance converters are, but I did not want to remove the potting.)
There is a solution for every problem!

http://www.vansteenisaudio.nl

radardoug

Re: Schematic Sanken CU-41
« Reply #6 on: January 22, 2019, 10:09:37 PM »
Old post, but did your client get anywhere with it? I have one doing the same thing.

RuudNL

Re: Schematic Sanken CU-41
« Reply #7 on: January 23, 2019, 02:18:30 PM »
Sorry, no idea. I haven't seen him for years!
There is a solution for every problem!

http://www.vansteenisaudio.nl

RuudNL

Re: Schematic Sanken CU-41
« Reply #8 on: December 04, 2020, 07:55:28 AM »
That is: I haven't seen the client for years, until today!
He brought me the CU-41 again, because Sanken couldn't repair it.
I found a schematic in the technical documents section, but unfortunately no information about what is going on inside the impedance converters. I will open the microphone again and have a renewed look!
(Unfortunately the link posted by dirty1_1garry doesn't work anymore.)
There is a solution for every problem!

http://www.vansteenisaudio.nl

Gus

Re: Schematic Sanken CU-41
« Reply #9 on: December 04, 2020, 04:04:44 PM »
what is the potting compound made of?

Looking at radardoug link in another thread https://groupdiy.com/index.php?topic=71815.0

 I would guess it might be two followers inside

Interesting
The blue looks to be the smaller capsule HPF noniverting follower, build out resistor
Yellow the large capsule inverting then LPF noniverting follower
then the outputs feed the opposite windings on the output transformer
both followers run at different currents

Have you unsolder the blue and grounded the input of the output stage
then unsolder the yellow and grounded the input of the output stage 
and/or lifted the red DC to DC wire
That should give a hint as to what might be bad in the potted circuit


RuudNL

Re: Schematic Sanken CU-41
« Reply #10 on: December 06, 2020, 08:02:04 AM »
Today I have removed the impedance converter module and started to 'unpot' it.
The potting material is a kind of 'gel' like material, that can be removed in small pieces with a bit of care.
What I can see inside is the following:
- two SMD-like resistors (probably with a very high value, maybe 1 G.ohm or so)
- one 220 pF capacitor
- two 'normal' metal film resistors
- one FET.

Everything times two, one circuit per capsule. As far as I can see now, both circuits are identical.
I suppose one high value resistor for the polarisation voltage of the capsule, a coupling capacitor to the gate, another high value resistor to the gate of the FET. And one (or two in series) source resistor(s).
Since the other (3) FETs in the circuit are 2SK184, I have a feeling that the FETs in the impedance converters might be the same, but I 'm not sure about that at the moment.  Will be continued!
There is a solution for every problem!

http://www.vansteenisaudio.nl

Gus

Re: Schematic Sanken CU-41
« Reply #11 on: December 06, 2020, 08:28:26 AM »
I would guess the high value resistors are values around 3gig because of the 220pF caps.

This thread is interesting I looked for images
http://recordinghacks.com/microphones/Sanken/CU-41
and saw how there appears to be a certain size plate the LF capsule is mounted in and it offset from center. The  capsules mounting and design of the mount is interesting.

There is also the HPF and LPF and slightly different output stages to the transformer.

I wonder if different builds of this microphone has different parts selected for the different capsules frequency response and sensitivity?
I see two places with dual caps, that can be for a non standard value or a way to get close to a desired value due the cap tolerances by trimming or selected from a number of pre-measured and sorted caps

Is the rest of the circuit like what radardoug linked?

RuudNL

Re: Schematic Sanken CU-41
« Reply #12 on: December 06, 2020, 08:32:31 AM »
I didn't check the rest of the circuit, because I am certain the problem comes from the impedance converter.
This is what is inside the potted module. (No rocket science...)
There is a solution for every problem!

http://www.vansteenisaudio.nl

Gus

Re: Schematic Sanken CU-41
« Reply #13 on: December 06, 2020, 08:37:34 AM »
I am curious about the 220pF. I wonder why they did not use a 470pF or higher?

The one resistor is bootstrapped to a higher resistance so maybe that is good enough.

Any pictures of the circuit and capsule mount and grill design?
« Last Edit: December 06, 2020, 08:45:04 AM by Gus »

RuudNL

Re: Schematic Sanken CU-41
« Reply #14 on: December 06, 2020, 10:43:01 AM »
I noticed that there is a difference between the schematic and the microphone I have here.
As far as I see, there are 3 electrolytic/bipolar capacitors on the schematic, but I have 5 of them...
I can't imagine that the unmarked wire (orange in reality) to the impedance converter and connected to R15, R23 and R24 doesn't have a decoupling capacitor.

UPDATE: The microphone works again. After replacing one of the 220 pF capacitors everything is fine now.
(It was a time consuming repair, so I didn't compare the rest of the schematic with the electronics of the microphone.)
« Last Edit: December 06, 2020, 02:27:34 PM by RuudNL »
There is a solution for every problem!

http://www.vansteenisaudio.nl

Re: Schematic Sanken CU-41
« Reply #15 on: December 13, 2020, 04:10:11 PM »
Hmmm...
CU-41 is a two capsule LDC. Mine guesses was that it use two individual impedance converters for each capsules and only then X-overed adn summed together.
But relatively to Ruud schematic looks like two capsules connected together right before impedance converter. Or you shown just one impedance converters schematic of two?

RuudNL

Re: Schematic Sanken CU-41
« Reply #16 on: December 14, 2020, 03:32:14 AM »
There are TWO impedance converters.
"Everything times two, one circuit per capsule." (Reply #10)
(The signals are summed after the impedance converters.)
There is a solution for every problem!

http://www.vansteenisaudio.nl

Re: Schematic Sanken CU-41
« Reply #17 on: December 31, 2020, 08:53:08 AM »
There are TWO impedance converters.
"Everything times two, one circuit per capsule." (Reply #10)
(The signals are summed after the impedance converters.)

Can you check my redrawn schematic?

RuudNL

Re: Schematic Sanken CU-41
« Reply #18 on: December 31, 2020, 09:58:44 AM »
As far as I can see that looks right. (The microphone is already back to the owner.)
I have the impression that the capacitors are selected during production.
In the microphone I had here, there were some small capacitors connected in parallel (with the existing ones on the PCB) and these were soldered on the back of the PCB.
There is a solution for every problem!

http://www.vansteenisaudio.nl

Re: Schematic Sanken CU-41
« Reply #19 on: December 31, 2020, 11:39:08 AM »
Sucks that companies won't share schematics. Doesn't surprise me with Sanken though. I messaged them about their super short 4" shotgun mic, asking about how it handles interiors, because if it has an interference tube there's always the chance of comb filtering, and what I got back was a message about how the side rejection is much better than other mics, without addressing my actual question, and telling me if the room is too noisy I should be using one of their longer shotgun mics, which will be even less ideal in an indoor reverberant space. Not really on topic, but that pretty much turned me off buying any of their mics. Deity also gave me a similar reply about how their S-Mic 2S tube is short enough that it shouldn't cause issues even though they acknowledge it will in a video on their YouTube channel, but they didn't tell me their mic is superior, and that's a $300 mic vs like $900 or whatever the Sanken costs.

Definitely not what I would call good customer service (from either, but at least Deity shows theirs is still vulnerable to comb filtering/phase issues), because it tells me that their sales reps either don't know their stuff, or care more about one sale than a repeated relationship and actually informing and helping the consumer.