Official C12 Clone - Build and Support Thread

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mrgrooves666

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Feb 1, 2021
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Unfortunately Studio 939 been out of stock on them for a while now. I have not been able to find another source for them. Chung did a great job to get them customized.
 
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marked

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Aug 22, 2016
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Gothenburg Sweden
Yes, the headbaskets are of good quality. Studio 939 has only the three other baskets in stock now it seems.
I will probably try to move around the mic with the one mesh basket in the room to see how it works out. But the sound of the two mesh basket is also very good in the circuit I now am trying out, so no worries there 😎
 

Delta Sigma

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Dec 4, 2010
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Winnipeg
You can do that - it's easiest. If you want to run the tube the same, however *only* change the polarization voltage, you can lower R13 in the microphone from 499K down to 390K.
Thanks! How significantly would the R13 swap change the cardioid and fig-8 patterns? I'm using the Lorlin switch in the standard 9 position, stepped. Has anyone tried this?

I'm in an awkward position as I completed this build, but I can't test it out at home. I tried to switch music computers and interfaces in one go to switch from a PCIe setup to Thunderbolt and by new interface is defective, spewing garbage into my headphones. I have to get this thing replaced under warranty before I can test mics at home!
 

Matador

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Feb 25, 2011
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How significantly would the R13 swap change the cardioid and fig-8 patterns?
Not significantly. The backplate and rear diaphragm will have ~5V difference which may tend to favor one side of the capsule (mainly the back), but it probably isn't enough to be very audible (especially if you run the microphone in cardioid mode most of the time).

If you lower B+ by 10V, then everything will scale equally along with it (pattern switch included), and the tube won't care one way or the other, and you don't have to de-solder anything, just turn a pot.
 

mjlaudio

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Jul 9, 2014
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I have a Power supply build that I inherited mostly finished. The issue I have is that the b+ travels up to 140v then drops down to 115v or so. Then it travels back up.
I have checked the orientation of the caps, and diodes they seem correct. Any suggestions?

I am testing with a 180k resistor across the correct pins as well.
 
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colin_maybe

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Apr 25, 2014
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3
Hi @Matador ,

I built the Matachung 251 kit with a 12AT7 build back in 2014. Years later I've decided to spring for a new BeesNeez CK12 capsule. While I'm at it, I figured I'd revisit the circuit, to make sure I have everything as good as it possibly can be.

As I recall my build was a minority -- with both the 251 and 12AT7 conversion options.

I followed this schematic posted earlier for the 251 conversion. Set the R3 bias pot to 0R, and made the following tweaks for the 12AT7: R1/R2 (91K -> 33K), and R17 (100K -> 47K).

I left the cathode resistance at 1.8K since I didn't have a 1K metal film resistor to try.

The mic worked fine but I recall you mentioned in this post that lowering the cathode resistance to ~1K would be a more appropriate starting point. I guess I don't know if I'm missing anything by having the cathode resistance at 1.8K.

My question is -- since 2014 do you have an opinion on the best or correct cathode resistance for the 251/12AT7 build?

I'm also curious if the cathode resistor should be the same quality Dale metal film resistor, or if a regular carbon film 1/4 watt would work. If so that would be great because I have a bunch of them lying around.

Thanks!
 

wrentema

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Dec 16, 2020
Messages
20
Location
Berlin
Starting my build soon (ish) But is there a special trick to get in touch with Tim Campbell? I would like to order two capsules but email doesn't work so far.
 

Delta Sigma

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Dec 4, 2010
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415
Location
Winnipeg
Starting my build soon (ish) But is there a special trick to get in touch with Tim Campbell? I would like to order two capsules but email doesn't work so far.
You're not going to like it but I think you'll need some patience. If you're anxious to get building, find the cheapest edge terminated capsule you can to get going and wait for Tim. It'll be worth it in the end.
 

wrentema

Member
Joined
Dec 16, 2020
Messages
20
Location
Berlin
You're not going to like it but I think you'll need some patience. If you're anxious to get building, find the cheapest edge terminated capsule you can to get going and wait for Tim. It'll be worth it in the end.
All good :) Not in a rush. Was just wondering because I didn't get a reply at all. But will wait patiently :)
 

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