Just bought 2 diy tube mic kits, i´m gonna switch some components and need help

hey i just bought two of these diy tube mic kits http://www.diymic.com/  i´m thinking of a lundahl transformer and m7 capsule in one of them, and maby a campbell ct12 capsule in the other.

What i need help with is which components should i chance tubes,capacitors,transformers etc.

IF you ask me, I would put it together with what it comes with first. Give a listen and then change out parts you don't like

madsim..

build em stock.....then throw out the chinese 12ax7 and experiment with different tubes.... I have been running telefunken ax's with the 2pf cap accross grid and plate of the tube....RCA's sounds really nice too. One of mine has a brightness which is from the capsule itself (like all chinese capsules there is a bit of variation here - quality control at manufacturing)....

generally i didnt find that much difference with other components in the path (quality from the kit was acceptable to start with)....

I played with some Rifa caps but no big changes in sound.

Trafos would be interesting mod, but I think the capsule is the major limitation with these.
Probably better to spend your dough on a G7 with a great capsule.

have fun...Mac.

Yeah the g7 was the mic i got the idea from to build a mic in the first place.
The thing with this mic is that it seems to be a good first diy kit.
Maby i´ll just build one stock and upgrade one
If i don´t like it i´ll put in the stock capsule and save the good one for a g7.
The g7 is very tempting! maby the next project?
Do you like the mic mac?

looking forwards to getting started!!

You can make most mic circuits with that PCB.

The Shanghai capsule is pretty crap and is the main limiting factor. 12AX7 is not a great choice, but still works I suppose.

the 12ax7 tube is stock in these mics. which tubes should use if not 12ax7, and what  do i have change to make other tubes work properly?

thanks for replying people

madsimilius said:

the 12ax7 tube is stock in these mics. which tubes should use if not 12ax7, and what  do i have change to make other tubes work properly?

thanks for replying people

Click to expand...

An American 12AX7 instead of the Chinese one.

Capsule and transformer should be the only other things worth changing. Does this thing follow the Apex 460 circuit? Is there a schematic somewhere?

I'd go for an ecc81 or 82 instead. The gain of the 83 is unnecessary and it's plate impedance is too high unless using a cathode follower.

If you want to make something in a C12 style then try copying the 1/2 a C24 circuit. Not the same, but works well. For using an M7, maybe look at the bulldog upgrade circuit designs for inspiration (and their C12 inspired one too).

wow so cheap!

I had no idea.  I was thinking of getting a 460 to mod but I think I'll go for one of these!

Keep in mind that these are cardiod only stock.  If you have an supply from one of the other Chinese mics, you can make it multipattern with the right capsule.  I'm doing a C12 with the Ela M451 cathode bias with one I bought.

Craig

It is not a C12 with 251 cathode bias.

Why do people still build the G7?  This is not meant in a bad way.  It was an early tube microphone build on the web and not bad:however I would have guessed people would have changed the power supply part and maybe other things by now.

There is a picture of the schematics in the link but it´s in poor quality. If it´s the same ass the 460 i´ll just stick with the 1/2 c24 mod.
If not i think i´ll just try switching parts and see what i can do with it
I know, it´s cheap!  I belive it´s better quality then the 460 to?
Do i have change some parts to be able to  use a ecc81/82 instead of the 12ax7? 
I mainly need a cardiod so it´s ok. 
i´ve only heard good things about the g7 so why not ? the ioaudio mk7 looks interesting to ! http://www.groupdiy.com/index.php?topic=30124.0

Gus said:

It is not a C12 with 251 cathode bias.

Click to expand...

Really?  Please explain.

I just bought one...

even with the shipping to France it's cheaper than the cheapiest tube mic from Thomann the T.BONE SCT700 wich is body donnor for the MK7.
so at least I have a blank body to make whatever mic I want, just for cheap.

and a psu box too!

it worth the money IMO.

cheers.
Jr.

Its just such a drag that it s not a multi pattern supply. Otherwise it would be the most perfect donor ever

deuce42 said:

Its just such a drag that it s not a multi pattern supply. Otherwise it would be the most perfect donor ever

Click to expand...

What do you mean? It's a piece of cake to add a multi-pattern switch in there! I thought this was a DIY forum.

This kit is also sold as SCT800 by thomann. It's a perfect donor to all tube mic projects ever presented here.

That 130 bucks is a steal for the brass body and grill and PSU casing alone. I wish this was available 5 years a go when I got that t bone. Now I have to repaint it and scratch that stupid OEM logo.

There is a picture of the schematics in the link but it´s in poor quality. If it´s the same ass the 460 i´ll just stick with the 1/2 c24 mod.

Click to expand...

yes...agreed.....documentation was a bit average (to say the least)- hence my build thread on their forum...

I experimented with other 12 series tubes and mod'ed the circuit - but as I said, the existing capsule is the biggest limitation, so I have been really happy with the "better" sounding one with a Telefunken 12ax7 in it...lower gain and more mellow somehow..

I would love to upgrade capsules but, the nearest one is about three times the cost of whole unit!.....maybe next year.......maybe after I finish those four comps and 6 channels of mic pre's that are currently on my bench.... :

Mac

I just got an email from them by paypal:

- Refund for overcharge in shipping. 22$

pretty honest!!!!

115€ with shipping to France for this mic...

Are you sure the G7 and MK7 PCB will fit in it? It seems pretty slim and short from what i see,  ??? I think i've asked a guy who had actually the same mic from T.bone, and the dimensions were not ok i think don't remember more tought, but here is the link to Thomann for you to have a look, anyway nothing is impossible...

http://www.thomann.de/fr/the_tbone_sct800_tube_mic.htm

Oh i found the dimensions that the guy gave me, it seem to be ok, the max length without the chinese transformer is 124mm, and the PCB given with it has a 40mm width, is this correct?