Official C12 Clone - Build and Support Thread
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Category 5
Well-known member
Not to complicate this further, but I was so blown away by the differences between tubes I have been exploring more.
12AV7 seems much closer in gain to the 6072, but does use 50% more heater current. Thing is there are a lot of cheap NOS 12AV7s out there. Think these might make a good sub? I know the AT7 variants are extremely plentiful, and probably a better alternative but I was curious what issues might arise if trying the AV7.
12AV7 seems much closer in gain to the 6072, but does use 50% more heater current. Thing is there are a lot of cheap NOS 12AV7s out there. Think these might make a good sub? I know the AT7 variants are extremely plentiful, and probably a better alternative but I was curious what issues might arise if trying the AV7.
Matador
Well-known member
12AV7's are also popular in the NYDave builds documented here, so no worries!
It's medium-mu much like the 12AT7, and will probably run fine if you follow the 12AT7 mods. The supply should be able to handle up to about 500mA heater current so a bit more heater current isn't an issue.
It's medium-mu much like the 12AT7, and will probably run fine if you follow the 12AT7 mods. The supply should be able to handle up to about 500mA heater current so a bit more heater current isn't an issue.
chunger
Well-known member
I've been talking back and forth with Matador in the last couple of days and am finalizing purchase of a couple small items at volume for the webstore that should be very low cost and supplement our available options:
1. ELA M251 parts kit (add-on to the C12 parts kit)
2. ELA M251 12AT7 conversion (trying to decide if I pack separate kits or roll them all together)
3. C12 12AT7 conversion (will be included in upcoming C12 parts kits, but I will pack a few loose ones as well to make available individually)
Also, I have a batch of capsules coming in from China due in early December and should be able to supply:
4. Budget build complete kits (turn-key kits)
Also waiting for tskguy to finish development of his reproduction capsule (prototype has been undergoing rigorous testing in the last couple months). At that point, I should be able to go live with what I've wanted to do the entire time:
5. Premium build complete kits (all-inclusive)
On my end, I will begin the official build documentation for the ELA M251 configuration very soon as well as modify the C12 documentation to reflect the 12AT7 option.
1. ELA M251 parts kit (add-on to the C12 parts kit)
2. ELA M251 12AT7 conversion (trying to decide if I pack separate kits or roll them all together)
3. C12 12AT7 conversion (will be included in upcoming C12 parts kits, but I will pack a few loose ones as well to make available individually)
Also, I have a batch of capsules coming in from China due in early December and should be able to supply:
4. Budget build complete kits (turn-key kits)
Also waiting for tskguy to finish development of his reproduction capsule (prototype has been undergoing rigorous testing in the last couple months). At that point, I should be able to go live with what I've wanted to do the entire time:
5. Premium build complete kits (all-inclusive)
On my end, I will begin the official build documentation for the ELA M251 configuration very soon as well as modify the C12 documentation to reflect the 12AT7 option.
Category 5
Well-known member
All cool stuff Chunger. Are you still involved in jessJackson's 251 project? It was looking really clean and I love the idea of the pattern switching happening in the mic with relays.
BTW, sent an email regarding the PSUs you mentioned.
And on a highly positive note, I finally came up in line for Tim's capsules and mine should be on their way today! It took a long time but as promised Tim came through so to those others in the queue, good things are to come.
BTW, sent an email regarding the PSUs you mentioned.
And on a highly positive note, I finally came up in line for Tim's capsules and mine should be on their way today! It took a long time but as promised Tim came through so to those others in the queue, good things are to come.
Category 5
Well-known member
Also, in prep for Tim's Capsules I was wondering...
I used a resistor lead to join the two backplate connection terminals together at the mic. Should I remove this and make the junction at the capsule instead for some reason? I can't think of why it'd matter, but who knows. I've heard weirder things. I'd rather solder on my CT12's less if possible. ;-)
I used a resistor lead to join the two backplate connection terminals together at the mic. Should I remove this and make the junction at the capsule instead for some reason? I can't think of why it'd matter, but who knows. I've heard weirder things. I'd rather solder on my CT12's less if possible. ;-)
Woot
Well-known member
Hey Guys,
So after rectifying my n00bish mistake of missing the two underside ground pads, one of the mics has fired up perfectly but the other is still not working.
Still have no output when the preamp is up really high.
I have had a read through the thread and changed c13 as it looks to have sustained a minor burn during capsule change but stil no love. I have double checked all connections and the trafo wirings.
Interestingly the mic transmits body noise when the amp is dialled up ie if I tap on the mic body lightly it comes through headphones nice and clear.
My voltages on the PSU are spot on.
The voltages on the tube are:
5: 6.3v
6: 67.3v
7: -0.9v
8: nil reading
9: 0.5mV
Any advice on where to start would be great.
Kind Regards,
Matt
So after rectifying my n00bish mistake of missing the two underside ground pads, one of the mics has fired up perfectly but the other is still not working.
Still have no output when the preamp is up really high.
I have had a read through the thread and changed c13 as it looks to have sustained a minor burn during capsule change but stil no love. I have double checked all connections and the trafo wirings.
Interestingly the mic transmits body noise when the amp is dialled up ie if I tap on the mic body lightly it comes through headphones nice and clear.
My voltages on the PSU are spot on.
The voltages on the tube are:
5: 6.3v
6: 67.3v
7: -0.9v
8: nil reading
9: 0.5mV
Any advice on where to start would be great.
Kind Regards,
Matt
chunger
Well-known member
Category 5 said:
I have no affiliation with JessJackson's 251 project. We are developing our own ELA M251 solution which for now is to use the hybrid configuration retaining the C12's 9 pattern setup. Both the "regular" C12 pcb's and the proto pcb can accomplish this. If we do go to the original ELA's 3 pattern switching in the future, we will likely do so by altering the body to accommodate a physical switch.
chunger
Well-known member
I'm thinking I should probably ask Matador to start a build/support thread for the Proto PCB sometime, but since I started posting about it here, I'll finish out the build.
This is a continuation of a completely teflon isolated C12 build based on the Proto PCB that recently went live on the webstore.
I complete the remaining connections to the 7 pin XLR, and the mic is now all buttoned up. The capsule connections are hooked up on the stock capsule and an Electron Harmonix 6072A installed for function testing. Notice as usual, I am using all "expendable" or at least easily replaceable components to verify microphone function before putting in premium capsule and NOS tube.
Next, I build up another PSU kit. . . it all went together by the numbers without any hitches whatsoever. It amazes me how fast the kit can fly together when not making photos
.
I set my Heater to 6.3V, idling bias to -1.0V, and B+ to 120V.
Next, I power down, install the outer tube, plug the mic into a mixer and do a "check, check, one, two, one two". Patterning works. The mic is quiet and clean. I will run the mic for a few hours like this in front of a speaker playing some music so the caps aren't completely new when I do critical recording tests, but it appears this mic is ready for premium components. I have a Tim Campbell CT12 capsule and a matched pair of NOS 1956 GE 6072A tubes to use for testing.
This is a continuation of a completely teflon isolated C12 build based on the Proto PCB that recently went live on the webstore.
I complete the remaining connections to the 7 pin XLR, and the mic is now all buttoned up. The capsule connections are hooked up on the stock capsule and an Electron Harmonix 6072A installed for function testing. Notice as usual, I am using all "expendable" or at least easily replaceable components to verify microphone function before putting in premium capsule and NOS tube.
Next, I build up another PSU kit. . . it all went together by the numbers without any hitches whatsoever. It amazes me how fast the kit can fly together when not making photos
. I set my Heater to 6.3V, idling bias to -1.0V, and B+ to 120V.
Next, I power down, install the outer tube, plug the mic into a mixer and do a "check, check, one, two, one two". Patterning works. The mic is quiet and clean. I will run the mic for a few hours like this in front of a speaker playing some music so the caps aren't completely new when I do critical recording tests, but it appears this mic is ready for premium components. I have a Tim Campbell CT12 capsule and a matched pair of NOS 1956 GE 6072A tubes to use for testing.
Woot
Well-known member
Hi 'Chung,
Looks awesome. Is the proto board the same length as the C12 board? I have some Beesneez bodies here but the c12 board is too long by a couple of mm.
It looks like I could probably cut the top off anyways near the capsule holes on the proto board and relocate them a bit "south".
Cheers,
Matt
Looks awesome. Is the proto board the same length as the C12 board? I have some Beesneez bodies here but the c12 board is too long by a couple of mm.
It looks like I could probably cut the top off anyways near the capsule holes on the proto board and relocate them a bit "south".
Cheers,
Matt
aamicrophones
Member
- Joined
- Mar 1, 2009
- Messages
- 7
The CM2480 has to low a turns ratio to be used with a single plate output circuit. It only has a 10:1 ratio and you need something like the T14 which has a 17:1 ratio.
The plate resistance is upwards of 22,000 ohms the CM2480 has an impedance ratio of 100:1 (square of the turns ratio). This means the 1.2K high mic input impedance of a 1073 would present a 120K load to the tube which wants to see a load of >220K to have no loading effect on the plate. The T14 has a impedance ratio of 286:1 which will not load the single 6072a plate circuit.
Now, you could get away with the CM2480 if you were going into one of the new transformerless preamps with a 5K input impedance but most folks want the vintage microphone sound and preamp.
The 2-stage CCDA circuit is a much better option as it is more HiFi than the original C12 circuit having an output impedance of 600 ohms.
You can use a transformer with a ratio of 5:1 ( impedance ratio of 25:1). You can use the CM2480 with impunity when driving it from 600 ohms... look at the specs on the Cinemag site.
Cheers, Dave
aamicrophones.com
The plate resistance is upwards of 22,000 ohms the CM2480 has an impedance ratio of 100:1 (square of the turns ratio). This means the 1.2K high mic input impedance of a 1073 would present a 120K load to the tube which wants to see a load of >220K to have no loading effect on the plate. The T14 has a impedance ratio of 286:1 which will not load the single 6072a plate circuit.
Now, you could get away with the CM2480 if you were going into one of the new transformerless preamps with a 5K input impedance but most folks want the vintage microphone sound and preamp.
The 2-stage CCDA circuit is a much better option as it is more HiFi than the original C12 circuit having an output impedance of 600 ohms.
You can use a transformer with a ratio of 5:1 ( impedance ratio of 25:1). You can use the CM2480 with impunity when driving it from 600 ohms... look at the specs on the Cinemag site.
Cheers, Dave
aamicrophones.com
jandoste
Well-known member
Hey guys,
I finished my build but no love... Its sound is very low! and I check everything so all good now!
I am not sure just wiring the T14 ... I didn't check the "-" "+" for XP1 (+) and XP2 (-)
it was the same values as like Chunger's T14
"The blue wires read 930R and will connect to the pcb to the terminals labelled XP1 (+) and XP2 (-)."
Do I must find the sides "-" "+" ? I didn't think the T14 has these sides....
Thanks
Jan
I finished my build but no love
... Its sound is very low! and I check everything so all good now! I am not sure just wiring the T14 ... I didn't check the "-" "+" for XP1 (+) and XP2 (-)
it was the same values as like Chunger's T14
"The blue wires read 930R and will connect to the pcb to the terminals labelled XP1 (+) and XP2 (-)."
Do I must find the sides "-" "+" ? I didn't think the T14 has these sides....
Thanks
Jan
micaddict
Well-known member
aamicrophones said:
Hi Dave. I'm not sure if everyone will agree a CCDA circuit is a much better potion per se (tranny regardless), but it's good to see you here. This community is getting richer and richer.
chunger
Well-known member
It's no secret Dave has been a long-time advocate of the CCDA circuit and it is a view shared by many other mic builders.
I'm less technical and am happy with a vintage circuit as long as it gets the job done well for the task at hand. . . kicker for me though was the prospect of extending tube service life by only utilizing one triode on a NOS tube type that is starting to get picked over and hard to find. Then, swapping over to the other triode.
In our testing, the T14 in this circuit stood out noticeably as being more natural and transparent. . . Cinemag 2480 had a bigger bottom, but felt a bit more boxed in everywhere else. . . whatever that means. . . which is why I settled on the AMI T14 even though the 2480 is quite a bit less expensive. 2480 didn't sound "broken" but AMI T14 in this mic just seemed to work a little better by ear in our recording/listening environment. If our loading is off for CM2480 implementation in this mic, it might explain the findings. Curious if Matador has an opinion.
I'm less technical and am happy with a vintage circuit as long as it gets the job done well for the task at hand. . . kicker for me though was the prospect of extending tube service life by only utilizing one triode on a NOS tube type that is starting to get picked over and hard to find. Then, swapping over to the other triode.
In our testing, the T14 in this circuit stood out noticeably as being more natural and transparent. . . Cinemag 2480 had a bigger bottom, but felt a bit more boxed in everywhere else. . . whatever that means
. . . which is why I settled on the AMI T14 even though the 2480 is quite a bit less expensive. 2480 didn't sound "broken" but AMI T14 in this mic just seemed to work a little better by ear in our recording/listening environment. If our loading is off for CM2480 implementation in this mic, it might explain the findings. Curious if Matador has an opinion.
jandoste
Well-known member
Hey guys,
Ok, I re-checked everything so all is good!
I see 120V / 6,30V and the Polar V is 49V etc etc
Result: No Sound ( very low ) why? it's because that I used a Electro Harmonix 6072A? and the Cap is Peluso CEK-12...
Thanks
Ok, I re-checked everything so all is good!
I see 120V / 6,30V and the Polar V is 49V etc etc
Result: No Sound ( very low ) why? it's because that I used a Electro Harmonix 6072A? and the Cap is Peluso CEK-12...
Thanks
jandoste said:Hey guys,
I finished my build but no love
I am not sure just wiring the T14 ... I didn't check the "-" "+" for XP1 (+) and XP2 (-)
it was the same values as like Chunger's T14
"The blue wires read 930R and will connect to the pcb to the terminals labelled XP1 (+) and XP2 (-)."
Do I must find the sides "-" "+" ? I didn't think the T14 has these sides....
Thanks
Jan
pasarski
Well-known member
- Joined
- Jan 29, 2010
- Messages
- 482
jandoste said:Hey guys,
I finished my build but no love
I am not sure just wiring the T14 ... I didn't check the "-" "+" for XP1 (+) and XP2 (-)
it was the same values as like Chunger's T14
"The blue wires read 930R and will connect to the pcb to the terminals labelled XP1 (+) and XP2 (-)."
Do I must find the sides "-" "+" ? I didn't think the T14 has these sides....
Thanks
Jan
+ & - only affects on polarity. Try to "flip" the trafo. Some T13's have in and out backwards, maybe T14's also.
jandoste
Well-known member
Thanks Pasarski for your response!
Which red is +/- I didn't check that but I really want to know why the mic's sound is very low
http://www.tab-funkenwerk.com/id76.html
Thanks
Which red is +/- I didn't check that but I really want to know why the mic's sound is very low
http://www.tab-funkenwerk.com/id76.html
Thanks
pasarski said:jandoste said:Hey guys,
I finished my build but no love
I am not sure just wiring the T14 ... I didn't check the "-" "+" for XP1 (+) and XP2 (-)
it was the same values as like Chunger's T14
"The blue wires read 930R and will connect to the pcb to the terminals labelled XP1 (+) and XP2 (-)."
Do I must find the sides "-" "+" ? I didn't think the T14 has these sides....
Thanks
Jan
+ & - only affects on polarity. Try to "flip" the trafo. Some T13's have in and out backwards, maybe T14's also.
Category 5
Well-known member
[/quote]jandoste said:Thanks Pasarski for your response!
Which red is +/- I didn't check that but I really want to know why the mic's sound is very low
Doesn't matter. As long as you maintain polarity between the primary and secondary.
jandoste
Well-known member
FIXED!
Thanks Category!
FB and RB linked by a jumper!
Thanks
Thanks Category!
FB and RB linked by a jumper!
Thanks
Category 5 said:jandoste said:Thanks Pasarski for your response!
Which red is +/- I didn't check that but I really want to know why the mic's sound is very low
Melodeath00
Well-known member
- Joined
- Jun 7, 2012
- Messages
- 416
I thought I'd chime in and say my kit is working perfectly right now. I spent Wednesday building the PSU, and I finished up the mic today. I'll admit I made a dumb mistake while building the polarity switch, but I corrected it immediately, and the PSU fired up perfectly on the first try with correct voltages. I was very pleased with myself haha
Since the PSU connections were already shrink tube wrapped, I decided NOT to cut the connectors and rewire. Does Alctron not use high quality cable, or is it perfectly ok to re-use most of the cable connections? Same thing in te mic. I kept the B+, heater, and polarity control wires in tact. I added my own silver teflon for ground and bias. I did not shrink tube around the connections, but I bought some on Amazon just now, and will re-do those connections if need be.
The mic works as well. I am home for Thanksgiving and have no audio interface, but my brother is here with a portable stereo recorder that has an XLR input, so I know the mic passes signal fine. Polar pattern switching is not working, but I realized I forgot to bridge the rear and front backplate of the tester Alctron capsule, so I assume that would be why. I assume no damage would arise from my mistake, right?
I did not pay attention to which transformer wires went where. I still don't fully understand how you would keep track of polarity in regards to the transformer. All I know is Red goes to XLR and blue goes to the PCB. I will test the polarity when I get back to my studio and swap the blue wires if need be. That's all that matters, right? I noticed the Alctron was inverted polarity compared to my other mics in general, and I did not want to swap the audio wires in the PSU XLR connector since they were nicely shrink wrapped already,
I will probably install the Tim Campbell capsule tomorrow. Why do we test heater voltage at the mic, while we test B+ and Bias in the PSU? Shouldn't we test everything at the mic?
I'm also still confused about the capsule teflon stand-offs. Since the metal pin goes through the teflon and makes contact with the PCB, how does the teflon have any effect whatsoever? Why would it even matter to float those capsule connections, and why are we using the teflon standoffs? It seems all we're doing is wrapping teflon around the connection that is made to the PCB. How is this different from using teflon wire?
I also ordered some Go2 Glue to dampen the headbasket. Mine seems to ring at 150Hz, not 400Hz.
Since the PSU connections were already shrink tube wrapped, I decided NOT to cut the connectors and rewire. Does Alctron not use high quality cable, or is it perfectly ok to re-use most of the cable connections? Same thing in te mic. I kept the B+, heater, and polarity control wires in tact. I added my own silver teflon for ground and bias. I did not shrink tube around the connections, but I bought some on Amazon just now, and will re-do those connections if need be.
The mic works as well. I am home for Thanksgiving and have no audio interface, but my brother is here with a portable stereo recorder that has an XLR input, so I know the mic passes signal fine. Polar pattern switching is not working, but I realized I forgot to bridge the rear and front backplate of the tester Alctron capsule, so I assume that would be why. I assume no damage would arise from my mistake, right?
I did not pay attention to which transformer wires went where. I still don't fully understand how you would keep track of polarity in regards to the transformer. All I know is Red goes to XLR and blue goes to the PCB. I will test the polarity when I get back to my studio and swap the blue wires if need be. That's all that matters, right? I noticed the Alctron was inverted polarity compared to my other mics in general, and I did not want to swap the audio wires in the PSU XLR connector since they were nicely shrink wrapped already,
I will probably install the Tim Campbell capsule tomorrow. Why do we test heater voltage at the mic, while we test B+ and Bias in the PSU? Shouldn't we test everything at the mic?
I'm also still confused about the capsule teflon stand-offs. Since the metal pin goes through the teflon and makes contact with the PCB, how does the teflon have any effect whatsoever? Why would it even matter to float those capsule connections, and why are we using the teflon standoffs? It seems all we're doing is wrapping teflon around the connection that is made to the PCB. How is this different from using teflon wire?
I also ordered some Go2 Glue to dampen the headbasket. Mine seems to ring at 150Hz, not 400Hz.
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