Official C12 Clone - Build and Support Thread

[cariocaman85]

Thanks. Good offer. Do you have any experience with them? How long is the production time and shipping approximately?

I ordered a transformer a few years ago. It was fine, a bit long delay though (1 or 2 month in my memory).

 

[johnchantler]

I just ordered custom transformers for this project from toroidy in Poland. €59 each for their ‘audio grade’ version. Regular version is cheaper. They quote 35 business days, but my last order only took two weeks.

 

[johnchantler]

diameter~65mm
height~35mm

not sure if these will fit in the alctron supplies or not — I'm going to use another case for mine

 

[andYz00m]

Alright, I’ve exhausted my troubleshooting ability. I have a build with low output and boomy/woofy sounding signal.

Heiserman capsule, AMI T14, 6072.

Tested voltages everywhere and everything I can find is correct. B+/plate voltage, bias, polar, heaters. Swapped capsules and tubes, tested transformer, etc.

Even though this build is set up for 6072, if I throw a 12AT7 in there, the output does go up.

Any ideas on where to look?

 

[soapfoot]

Have you cleaned everything thoroughly, particularly in the high impedance areas?

 

[dmp]

Alright, I’ve exhausted my troubleshooting ability. I have a build with low output and boomy/woofy sounding signal.

Can you post some pics?

Soapfoot's suggestion is common problem in builds. You can measure the correct capsule bias voltage 60v at R12/R13 but on the other side of the 250M, any leaky path to ground will lose the polarization. Clean with 99% isopropyl alcohol.

A few more troubleshooting steps:

Check the tube bias voltage at P4? Should be negative wrt ground. You need to measure it before the high meg resistors.

If you are using a styrene cap for C13, have you tried swapping it? Switch for a ceramic until you get it working. Heat from soldering can damage the styrene

If you have a signal generator, you can connect a sine wave at the plate with the mic off, and measure the signal out, to confirm everything downsteam of the tube is working.

If that works, you can replace the capsule with a 50pF cap and connect the sine wave to it / C13 to measure the full gain and frequency response of the mic amp

 

[andYz00m]

Soapfoot's suggestion is common problem in builds. You can measure the correct capsule bias voltage 60v at R12/R13 but on the other side of the 250M, any leaky path to ground will lose the polarization. Clean with 99% isopropyl alcohol.

A few more troubleshooting steps:

Check the tube bias voltage at P4? Should be negative wrt ground. You need to measure it before the high meg resistors.

I cleaned as I built but I have been swapping things around and resoldering, its totally possible that I blasted C13 in switching capsules and such. I'll put a ceramic in there until I can resolve the issue.

I have cleaned everything again as well as I can while things are in the mic, and have tested the bias at P4 which is correct at ~ -1 VDC. The pol voltage at R12/R13 is correct at ~57VDC and up to the 250M, but after the 250M it drops to ~2.35VDC.

Below are photos.

I will test the output post tube to see what's up there. To test the head amp, I replace the capsule with two separate 50pF ceramics to the bp gang? So FC to BP and BC to BP? How much sin wave voltage to send into C13? I assume a 1K sine?

Thanks for the help!

 

[plugged1]

Reading some of the new posts it’s important to note that the power supply for this build and the Mic Parts VPS are NOT compatible. The VPS uses the standard stock pin out NOT the modified pin out that this build uses. I have both and painted them to correspond to the correct mic.

 

[Nen'O]

Hi all,
I'm about to build new cables for modded Apex 460 (stock power supply) with Summer SC Octave Tube cable and neutrik 7 pin XLR.

I know that Pins 1-7 on the one end matched up to their corresponding pins on the other end.
Summer cable has a total of 7 conductors, two for the supply voltage and 5 more normal conductors.
What pins on XLR are for power supply?
Pins 2 and 4?

https://shop.sommercable.com/en/Cable/Bulk-Cable-Audio/Mikrofonkabel-SC-Octave-Tube-200-0186.html
Cheers

 

[mhelin]

The pol voltage at R12/R13 is correct at ~57VDC and up to the 250M, but after the 250M it drops to ~2.35VDC.

Your scope input impedance (10M or so) makes a voltage divider with the 250M.

 

[andYz00m]

Your scope input impedance (10M or so) makes a voltage divider with the 250M.

Im really at a loss here.

Been checking this thing out again trying to troubleshoot. Need some advice on how to test the head amp. Everything Ive tested seems correct.

 

[blackart777]

Great project, thank you very much,
Great Microphone.

 

[aaquilato]

Hi all.
I'm hopefully not going to hijack this thread.
Can anyone shed some light on the Lucas CS-1.
The microphone I'm looking at was built by Oliver so I thought I'd reach out to see all your thoughts.

Thanks...

 

[Recording Engineer]

Hi all.
I'm hopefully not going to hijack this thread.
Can anyone shed some light on the Lucas CS-1.
The microphone I'm looking at was built by Oliver so I thought I'd reach out to see all your thoughts.

Thanks...

What kind of light are you looking for on the CS-1?

 

[aaquilato]

What kind of light are you looking for on the CS-1?

Hi.
Thanks for replying. Any first hand info about them, the build, the components...
These (there are a pair for sale) were built by Oliver Archut for Terry Manning.
They supposedly have Tim Campbell capsules in them which is not what the "recording hacks" page states.

The seller has mentioned a safety circuit that goes bad but can be easily fixed by TAB.

This would be a very big investment for my small personal studio.
I have tinkered with the Apex 460 and built a C12 clone and a 251 clone.
I've also built one of Oliver's C12s from his kit but this mic seems to be something different.
I'm curious as I'll never be able to afford a C12 and clones or whatever you want to call them is as close as I'll get.

Thanks for your time with this.
Anthony.

 

[Recording Engineer]

Hi.
Thanks for replying. Any first hand info about them, the build, the components...
These (there are a pair for sale) were built by Oliver Archut for Terry Manning.
They supposedly have Tim Campbell capsules in them which is not what the "recording hacks" page states.

The seller has mentioned a safety circuit that goes bad but can be easily fixed by TAB.

This would be a very big investment for my small personal studio.
I have tinkered with the Apex 460 and built a C12 clone and a 251 clone.
I've also built one of Oliver's C12s from his kit but this mic seems to be something different.
I'm curious as I'll never be able to afford a C12 and clones or whatever you want to call them is as close as I'll get.

Thanks for your time with this.
Anthony.

I had #84, I believe it was, that I bought new. Sold it back in 2015 along with most all my gear.

Excellent mic all-around! However, no good at all for acoustic guitar in my experience. There, it’s way too dull!

If you can buy a pair for a fair-price, I wouldn’t hesitate. I haven’t heard anything about a supposed “safety-circuit” problem, but I never looked at the power supply. I know the CS1 is self-biased and use a single transistor buffer in its supply.

The capsule is a custom CK12-type, MBHO-manufactured and spec’d by David Bock of Bock Microphones. I’d find out for sure if the pair you’re considering are original capsules or Tim’s capsules… I wouldn’t hesitant with either, but I’d want to know for sure either way.

Lucas LMG-95-ES tube (made by Mullard), and labeled as such. AMI has replacements. Both sides are ran in parallel. There are arguments on whether other 9-pin tubes will work good-enough.

Super tiny, AMI T-1 transformer.

Dennis at AMI is super helpful and responsive. Don’t hesitate to ask him for any help!

I have a pair of CS-1 -inspired mics, made for me by Chris at Barbaric Amplification, with original tubes (bought from AMI when I still had the CS-1) and transformers (bought from AMI in 2020).

 

[Tim Campbell]

Hi.
Thanks for replying. Any first hand info about them, the build, the components...
These (there are a pair for sale) were built by Oliver Archut for Terry Manning.
They supposedly have Tim Campbell capsules in them which is not what the "recording hacks" page states.

The seller has mentioned a safety circuit that goes bad but can be easily fixed by TAB.

This would be a very big investment for my small personal studio.
I have tinkered with the Apex 460 and built a C12 clone and a 251 clone.
I've also built one of Oliver's C12s from his kit but this mic seems to be something different.
I'm curious as I'll never be able to afford a C12 and clones or whatever you want to call them is as close as I'll get.

Thanks for your time with this.
Anthony.

I never supplied capsules for that microphone so please get a photo of the capsules and find out why they have my capsules. Maybe the seller is mistaken. They should be MBHOs

 

[aaquilato]

Thank you for this info. It's very helpful.
The serial numbers of these mics are #33 & #37.
I've read most of this on the recording hacks page. I have a friend who knows Terry and has told me you can still order the CS-1 from him, which I did not know.
I will dig a little further...

 

[aaquilato]

I never supplied capsules for that microphone so please get a photo of the capsules and find out why they have my capsules. Maybe the seller is mistaken. They should be MBHOs

Thank you for jumping in here Tim.
btw... The AMI C12 I built has your capsule in it and it is by far the best sounding mic I own.

 

[Recording Engineer]

I have a friend who knows Terry and has told me you can still order the CS-1 from him, which I did not know.
I will dig a little further...

Hmmm… I was under the impression they were unofficially long-gone out of production and stock; much like most, if not everything, Lucas. Please let us know what you find out. I never would have had built a microphone-type still in production or stock.

Speaking of Lucas Engineering products, I’d love still to get my hands on the Tube Equaliser. Again, I am under the impression it is unofficially long-gone.