miktek cv4 diy mod?

[micaddict]

I didn't use K7 from Beesneez, but maybe it's just sound of it?

It is or should be plenty brilliant.

My guess is the problem lies elsewhere.

 

[ln76d]

It is or should be plenty brilliant.

My guess is the problem lies elsewhere.

Hi Henk!

Did you make comparison with any other M7 - if so, could you tell something about differences?

I remember that there were some minor problems in the past with capsules from groupbuy - maybe simple eye inspection on the capsule could give some answers also? Of course with applied polarisation voltages

 

[micaddict]

I don't have one here. But one of the strong points of a good K47, or M7 for that matter, is the high mid band.
This is where brilliance resides, hence my earlier remark.

The BeesNeez K7 has a very good reputation and Klaus Heyne spoke highly of it when he tested the thing.
And he's not easy to please in this regard.

BTW, this is the second time today I mention Klaus.
That is a coincidence. 

 

[McIrish]

With C1 you should  get completely different result, if any - so rather not.
Try to find any additional film or ceramic capacitor in the circuit, count the amount and compare with schematic.
The only place where it should be, is from plate to ground - walues from 100pF - 1nF.
I didn't use K7 from Beesneez, but maybe it's just sound of it?
Measure polarisation voltages before R1 and R2! It's the best way to see why cardioid have similar level from both sides.
With omni usual lack of proximity effect gives that impression.

Could you rephrase the first sentence? Are you saying that the value of C1 won't make a difference or it will?

 

[ln76d]

Ah, sorry

If you will notice any difference, you should notice (in my opinion - some will not agree with it) more hi frequencies than less.

Set pattern on PSU to omni, disconnect one side of C1 and check.
Without the cap and setup to omni you will get "true" cardioid

 

[McIrish]

Thank you for the clarification. I unfortunately do not see any other caps in the circuit. I'm starting to believe that possibly I got a bad capsule. I sent Ben a note and he said he would replace it.  Very odd. I would think that by the way it sounds, there must be a LPF in there somewhere but I've gone over it a lot and don't see anything like that.

 

[ln76d]

Do you have any other capsule (beside original) to make test?
If there would be cap from plate to ground (LPF), there would be probability to find it direct on tube socket or near it.

 

[McIrish]

I only have the original and the replacement readily available. I've gone over the circuit dozens of times to make sure I'm not missing something. It's pretty straightforward. I just don't find a cap from the plate to ground or anything else that appears to be a filter.  I even checked the power supply but the output from the transformer goes right to the 3 pin XLR. There are 15K resistors from the outputs to ground but nothing else.

I appreciate all the help you have given me. I've disassembled it all again to double check my schematics.

 

[McIrish]

I gave my schematics and the microphone to another technician at the company I work at. The schematics I drew are 100% accurate. It's very similar to Olivers Alternate U47 with remote schematics. There are just a few changes in the tube bias and heater circuitry.

Funny enough, I did find the front and back screws of the capsule loose. I'm not sure how they got loose but they needed to be tightened.  I double checked everything physically at this point. Now, to double check voltages to the capsule (before the 1G resistors. I'll write more later.

 

[micaddict]

Funny enough, I did find the front and back screws of the capsule loose. I'm not sure how they got loose but they needed to be tightened.  I double checked everything physically at this point. Now, to double check voltages to the capsule (before the 1G resistors. I'll write more later.

Please do.



Yesterday, as we were having this discussion, someone posted the following on the slutz forum:

"For what it's worth, I just got in a BeesNeez K7 and used it to replace a Peluso PK47 in a frankenstein mic that I have. The mic is unique, with a 12AU7 based circuit, so it's not a good point of reference except to me because I've been using it for about 8 years.

So far the K7 sounds much better to me than what we hear in the shootout. The PK47 had that familiar high end sizzle that I've grown to really dislike, but the K7 has really smooth but present and detailed highs. I am looking forward to putting it through its paces when I get some good vocalists over soon."

 

[ln76d]

So we can assume that there's something wrong the capsule, especially when the front and back screws of the capsule loose.

 

[McIrish]

From everything I've read, the K7 should sound great. In this case, in a Miktek CV4, this particular capsule makes an Oktava MK-319 sound bright.  I really don't know what's happening here.  The screws did seem loose on the diaphragm. I'm not at all sure what the proper torque should be but I just snugged it up so the wire wouldn't spin. Ben Sneesby said I sould have just left it alone, that it was tested before it left. With how it sounds, I didn't think I could make it any worse. He asked me to put it in another microphone to test. Maybe the CV4 has an issue. The only other tube mic I have is a Wunder CM7GTS/M7. I'm not going to touch that mic. I had to pay a small fortune to have it repaired at Wunder last year.  Ben has been kind enough to offer to send a replacement capsule.

I did have to remove his K7 capsule from the mounting that it came on, as the CV4 uses a single hole mount and Ben's has two small screws. I didn't want to mess with the top plate to use his mounting bracket so I used the one that came with the original capsule. It seemed to go fine so I don't believe I damaged anything.

I wish someone else had a CV4 with a replacement capsule, so I could know where the problem lies.

 

[ln76d]

Ok, i'm confused...

It's too bright or too dark?

If it's too bright - remove C1 (can be even one leg), put pattern switch in omni position and check - this what i mentioned before.
Really - do it  - then we will see is it capsule or preamp itself
If it's too dark, probably capsule!

 

[McIrish]

Sorry that I wasn't clear. The CV4 with the K7 is way too dark. I don't see anything in the circuit that would cause that so my guess is that it is the capsule. I did measure votages before the 1G resistors and everything is fine there. I'm not sure how a capsule could be damaged in a way that makes it dark. It looks perfect.

 

[ln76d]

Diaphragm can be too lose.

What's the polarisation voltage value?

 

[mics]

Diaphragm can be too lose.

What's the polarisation voltage value?

Your capsule is an m7,not a k7.

 

[McIrish]

Ben is absolutely correct and a great guy about this. I messed up the order. I thought I ordered a K7 but actually ordered a M7. It's a long boring story, but in the end, it was my mistake. Ben's working to get this sorted out with me. I will post back once I have a K7 installed. I feel kind of like an idiot right now but I guess that's how we learn.

Thank you everyone for you help and advice.

 

[ln76d]

Diaphragm can be too lose.

What's the polarisation voltage value?

Your capsule is an m7,not a k7.

Definately not my, but thanks for clarification

We were talking here about completely different things

 

[McIrish]

The CV4 has the front at 0v, the backplate at 60v and the back side varies from 0-120vdc.
Does that tell you anything?

 

[ln76d]

The CV4 has the front at 0v, the backplate at 60v and the back side varies from 0-120vdc.
Does that tell you anything?

Yes, many things
For example:
- voltage value is decent  and usable for most capsules, rather you would not stress the capsule or destroy it.
- For M7 or K47 type capsules you could try go little higher like 65V if PSU let you do that - usual it's a change of two resistors, one inside microphone, other in PSU