DIY Tube Mic

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Hello,
after I have done some amps and speakers, I would like to make my first microphone, as Im not an expert in eclectronics I build most of my stuff from kits.
Can any one tell me what to expect from this kit?
DIY Vacuum Tube Condenser Microphone Kit

I will need two mic for stereo recording, mostly it will be pure solo instrument or two instruments, may be instrument + voice. Just for info I will conect the mic to a E-MU 0404 USB card and than to my loptop. I could buy some mic but doing it self is more fun and let say "unique"

What do you think of the kit? There is a 12AX7 tube unfortunately no mentioned which one. I hope its the russian not a China one.
 
Try this way:OTL

Aproven in praxis and sound good.

For balanced out(XLR) second half of ecc83 tube have to be rewired to form DC coupled Concertina phase Inverter,for Volume You have to use than double 100k Pot.
For even strictly standards You have to use Van Scoyoc phase inverter for balanced(XLR) output stage.

Good Luck
 

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I think I'd be inclined to cut R7 by a factor of two, parallel the plates, grids and cathodes, and get lower noise and better output capability with that kit.

Tubes are cheap enough that you can change whatever you use as there are only one tube per mic.
 
The kit is basically a knocked-down unfinished $200 Chinese tube mic.

Your E-MU 0404 has line inputs. You'll need a mic preamp between the mic and 0404 if you use a standard tube condenser microphone circuit, including the kit mic circuit.

There is a lot of DIY mic and mic pre action on Prodigy Pro DIY:

Meta-Meta: Look here for overview..

The schematic posted is very strange. I don't understand the floating cathode connection to the condenser capsule. How could this possibly work? :confused: Also no way a 100K pot will drive a standard 1600 ohm mic amp input. Even a little high for a guitar amp if you ask me...

Cheers,

Michael
 
Well, im not very knowlegeable about electronics therefore I can not say how good or bat it is just from the diagram... so far I read it seems not to be a good choice. Even thou a 200$ mic should not be bad at all...
I have no equipment to make my own PCB´s thats why I use the kits so if there is a other kit some one can recommen im more than happy to take a look on it.
How much distortion it will have, what do you think?

As for the preamp I beliwe once to get a nice low noice kit there is a lot of them out there.
 
Well, im not very knowlegeable about electronics therefore I can not say how good or bat it is just from the diagram... so far I read it seems not to be a good choice. Even thou a 200$ mic should not be bad at all...
I have no equipment to make my own PCB´s thats why I use the kits so if there is a other kit some one can recommen im more than happy to take a look on it.
How much distortion it will have, what do you think?

As for the preamp I beliwe once to get a nice low noice kit there is a lot of them out there.

Maybe you misunderstood slightly. I mean the schematic posted in this thread post #2 is strange.

I think the Auracle A5500 mic kit is probably a decent way to go and I may in fact spring for one myself just for grins. It may be hit or miss with the capsule but if you get a bad one they should exchange it for you. The circuit looks fine. Just getting the body and grill in a raw form is easier than gutting out a $50 FET mic and trying to retrofit a 5 or 6 pin XLR.

Word on the preamp. There are many good affordable kits out there.

Cheers and good luck!

Michael

I see they got some A5500 mic kits in on 9/27 and they're sold out today. Must be a popular item...
 
It is strange but work OK:).Actualy first half of ecc 83 is GG(grouded grid) based input stage,so cathode of that first stage have double function:first function is to DC suply condenser capsule(FET) and in same time same stage cathode is modulated with AF from same MIC capsule(FET),actualy this is hibryd cascode stage,upper stage is triode and lower stage is MIC(FET).

Second stage(half of ecc83) is actualy voltage gain stage.It cood be rewired in many way:For lower SE(unbalanced) impendance output(and voltage)cood be rewired to be Cathode follower, so that depends from what you want(and where) to conect Mic preamp output.

BTW I developed and succesfully use this MIC preamp design long time ago,newer have the problem,work very stable and sonic performance mostly depend from Condeser FET Capsule quality.Best Regard
 
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It is strange but work OK:).Actualy first half of ecc 83 is GG(grouded grid) based input stage,so cathode of that first stage have double function:first function is to DC suply condenser capsule(FET) and in same time same stage cathode is modulated with AF from same MIC capsule(FET),actualy this is hibryd cascode stage,upper stage is triode and lower stage is MIC(FET).

Second stage(half of ecc83) is actualy voltage gain stage.It cood be rewired in many way:For lower SE(unbalanced) impendance output(and voltage)cood be rewired to be Cathode follower, so that depends from what you want(and where) to conect Mic preamp output.

BTW I developed and succesfully use this MIC preamp design long time ago,newer have the problem,work very stable and sonic performance mostly depend from Condeser FET Capsule quality.Best Regard

OK I understand. The "capsule" has a FET stage in it. So the first stage will have a lot of gain based on a cascode with a 100K load resistor. It's a lot of extra circuit and stages compared to a simple tube mic circuit like the Auracle mic (which is the same circuit used by Neumann, AKG, etc.). Why 2 gain stages in a tube mic? (unless you want to drive a line input directly)

Where do you get this capsule and what's it's cost, performance, etc. ? What's the selection available? The only advantage I see is you don't have to deal with the giga-ohm impedance of the capsule in your circuit, but at what cost? There are plenty of excellent standard condenser capsules readily available at low cost.

What did you plug your mic into for an amplifier?

If you want to drive a standard mic pre you'll want ~ 200ohm output impedance. At that point you might as well parallel the sections of the ECC83 and use a 12:1 step-down transformer. Or use a 6072 with a 10:1 stepdown. Or a 5840 with a 7:1 etc... There is little to be gained by removing the output transformer if you end up with 100K ohms output impedance.

So it still looks a little strange to me and I wonder what's the advantage over the circuit everyone else uses? It certainly has some drawbacks...

Cheers,
Michael
 
Can any one tell me what to expect from this kit?
DIY Vacuum Tube Condenser Microphone Kit
.


I looked at that page and I am more interested in the FET microphone kit.
Does anyone know if it is sold in Europe or in Asia, since shipping from US to EU is prohibitively expensive ?
Maybe these kits are sold under different names by different companies, much like the Chinese mics are.
They might also be sold on Ebay.
Any info you might have will be appreciated.
 
I have no experience with those mic capsules with built in FETs, but I think they are to be powered by a few volts, and loaded with a low impedance. So using a tube's cathode that way is pretty smart I think since it does both give it a few volts to work from, and amplifies the signal (and presents a low impedance). The rest of the circuit I agree isn't optimum, but I'm sure it works ok if farely short cables are use to a high Z input.
Nothing wrong in having lots of gain at the mic, better S/N ratio.

That kit sure looks like a good deal to me. Nice mic chassis and a capsule that is likely no worse than what we'll find in mics up to xxx money. Not the circuit I'd use tho, but that's just me.
 
OK I understand. The "capsule" has a FET stage in it. So the first stage will have a lot of gain based on a cascode with a 100K load resistor. It's a lot of extra circuit and stages compared to a simple tube mic circuit like the Auracle mic (which is the same circuit used by Neumann, AKG, etc.). Why 2 gain stages in a tube mic? (unless you want to drive a line input directly)

Where do you get this capsule and what's it's cost, performance, etc. ? What's the selection available? The only advantage I see is you don't have to deal with the giga-ohm impedance of the capsule in your circuit, but at what cost? There are plenty of excellent standard condenser capsules readily available at low cost.

What did you plug your mic into for an amplifier?

If you want to drive a standard mic pre you'll want ~ 200ohm output impedance. At that point you might as well parallel the sections of the ECC83 and use a 12:1 step-down transformer. Or use a 6072 with a 10:1 stepdown. Or a 5840 with a 7:1 etc... There is little to be gained by removing the output transformer if you end up with 100K ohms output impedance.

So it still looks a little strange to me and I wonder what's the advantage over the circuit everyone else uses? It certainly has some drawbacks...

Cheers,
Michael

Think even Auracle Mic condenser capsule have FET built in,but suply for that FET capsule goes via resistor network/divider from B+ voltage, and Mic(FET) output is than conected traditionaly to the tube grid, personaly never like the sound and stability of condenser(FET) MIC from that way of conection to the tube grid.

From old radio/tape recorder You can have cheap Condeser(FET)capsule for first circuit probe:),but on the market is so many excelent other`s FET built in condenser capsule,more expencive too.(Auracle)

I developed this Tube Mic preamp circuit under next condition/circumstances:

When I emiting(Pirates) on AM band(1600-1800khz) with DIY high power Tube Modulator/ Transmitter ordinary dynamic Mic allways goes `crayze `due huge surounding electromagnetic fields, but this type of Mic conected this` my way`(cascode) always work extreme stable, with extreme audio sensitivity and modulation quality.But for some proffesional studio/recording use this design is good too.Special without stepdown transformer on the preamp output(OTL)

Best regard
 
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...
I have no equipment to make my own PCB´s thats why I use the kits....

Not really a comment on this microphone. But I just had to say that decades ago when tubes were the only way to build electronics no one used PCBs. The classic and I think still best way to build with tubes is "point to point" or with turret boards.

Not being able to make a PCB is in fact one good reason to build with tubes.

How will this sound when you are done? Well you really are not building a microphone. All the parts that determine the sound are contained in that condenser capsule.

You were planning to build tow for stereo recording, people typically don't record a vocalist in stereo. They pan the track to stereo in the mix later, same for most instruments. Stereo might be used to record an ensomble
 
Think even Auracle Mic condenser capsule have FET built in,but suply for that FET capsule goes via resistor network/divider from B+ voltage, and Mic(FET) output is than conected traditionaly to the tube grid,

No, the Aurycle mic doesn't use a FET capsule, it's a straight condenser capsule polarized by 60VDC through a 1G ohm resistor.

" personaly never like the sound and stability of condenser(FET) MIC from that way of conection to the tube grid."

?? Virtually all recordings are made with mics using this circuit

"From old radio/tape recorder You can have cheap Condeser(FET)capsule for first circuit probe:),but on the market is so many excelent other`s FET built in condenser capsule,more expencive too.(Auracle)"

No, I don't think so. I think you're guessing. Please point me to one.

"When I emiting(Pirates) on AM band(1600-1800khz) with DIY high power Tube Modulator/ Transmitter ordinary dynamic Mic allways goes `crayze `due huge surounding electromagnetic fields, but this type of Mic conected this` my way`(cascode) always work extreme stable, with extreme audio sensitivity and modulation quality.But for some proffesional studio/recording use this design is good too.Special without stepdown transformer on the preamp output(OTL)"

Cool. If I ever build a high power pirate AM station I'll remember that. My current interest is in high fidelity microphones for use in a recording studio. i have doubts about general high quality capsule availability.

What about the output impedance of your circuit? How does it drive a 1600 ohm load of a balanced mic pre? How does it even drive a 10K line input? It must be for a high impedance input of some kind.. Radio transmitter?

Good quality mics use output transformers to get a low impedance output. From a condenser capsule, gain is not needed at the mic. A lot of condenser mics also use follower outputs with no gain at all (and low impedance). There's enough gain in the mic preamp.

Really, you should look into the schematics of some classic mics linked to on the Prodigy Pro page I referenced. A good base of information won't hurt.

Cheers,

michael
 
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No, the Aurycle mic doesn't use a FET capsule, it's a straight condenser capsule polarized by 60VDC through a 1G ohm resistor.

" personaly never like the sound and stability of condenser(FET) MIC from that way of conection to the tube grid."

?? Virtually all recordings are made with mics using this circuit

"From old radio/tape recorder You can have cheap Condeser(FET)capsule for first circuit probe:),but on the market is so many excelent other`s FET built in condenser capsule,more expencive too.(Auracle)"

No, I don't think so. I think you're guessing. Please point me to one.

"When I emiting(Pirates) on AM band(1600-1800khz) with DIY high power Tube Modulator/ Transmitter ordinary dynamic Mic allways goes `crayze `due huge surounding electromagnetic fields, but this type of Mic conected this` my way`(cascode) always work extreme stable, with extreme audio sensitivity and modulation quality.But for some proffesional studio/recording use this design is good too.Special without stepdown transformer on the preamp output(OTL)"

Cool. If I ever build a high power pirate AM station I'll remember that. My current interest is in high fidelity microphones for use in a recording studio. i have doubts about general high quality capsule availability.

What about the output impedance of your circuit? How does it drive a 1600 ohm load of a balanced mic pre? How does it even drive a 10K line input? It must be for a high impedance input of some kind.. Radio transmitter?

Good quality mics use output transformers to get a low impedance output. From a condenser capsule, gain is not needed at the mic. A lot of condenser mics also use follower outputs with no gain at all (and low impedance). There's enough gain in the mic preamp.

Really, you should look into the schematics of some classic mics linked to on the Prodigy Pro page I referenced. A good base of information won't hurt.

Cheers,

michael


Aurycle Mic model A620,A630 and A218p does have built in FET,I never use that Models but some Philips,JVC and Panasonic FET capsule Mic

``Virtually all recordings are made with mics using this circuit``-

-So what? is that the only reason to not try another alternative better design Way.

Inside ewery old radio/tape recorder usualy exist Condeneser FET capsule-cheap one,in diameter 6-8mm,it is good for first time circuit probe but for some other Audio apllication is good too.Thats is what I mean actually but not for using in serious Studio Recordings

For low impedance balanced output(1600 ohm) and best Sonic results I sugest everybody to use pure Tube low impedance output(OTL).You know for sure about Sonic limitation/degradation of OPT in tube amps it is same here with stepdown transformer on the Mic Tube preamp output but much worse. To drive 10k line input is not the problem for atached schematic

Prodigy pro page for some Mic information-I don`t care

BTW I have lot of fun emiting on the AM band using that My Mic preamp(Pirates for Ever:))

Best regard
 
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Aurycle model A620,A630 and A218p does have built in FET,I never use that Models but some Philips,JVC and Panasonic FET capsule Mic

``Virtually all recordings are made with mics using this circuit``-

-So what? is that the only reason to not try another alternative better design Way.

Inside ewery old radio/tape recorder usualy exist Condeneser FET capsule-cheap one,in diameter 6-8mm,it is good for first time circuit probe but for some other Audio apllication is good too.Thats is what I mean actually but not for using in serious Studio Recordings

For low impedance balanced output(1600 ohm) and best Sonic results I sugest everybody to use pure Tube low impedance output(OTL).You know for sure about Sonic limitation/degradation of OPT in tube amps it is same here with stepdown transformer on the Mic Tube preamp output but much worse. To drive 10k line input is not the problem for atached schematic

Prodigy pro page for some Mic information-I don`t care

BTW I have lot of fun emiting on the AM band using that My Mic preamp(Pirates for Ever:))

Best regard

Rock on, my friend!

Michael
 
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