MK7 - tube mic project

[ioaudio]

yes, the sct700 is engraved.
one low-noise tube out of four seems reasonbly.

 

[Jonkan]

I guess one can live with the engraving, but you know what theyre all going to say: "What, youre going to use that t.bone mic on my vocals, are you crazy ?"

And then i have to explain, "no see, its a special microphone that sounds a gazillion times better, even though it looks like a cheap chinese knockoff".

I presume these are rebadged oem mics from china. Has anyone found the same mic somewhere else but without the engraving?

Perhaps i shouldnt bother searching, I mean you cant really complain about the price of the thomann mics. Plus the fact that Ioaudio has made it so damn easy for us newbs to make this mic, is also worth alot to me. When i made my g7 body, i slaved for hours and hours just to get the cutout for the grill to my satisfaction. This would save alot of time, since im making 4 of them (2 for me, 2 for a friend).

How in your opinion is the sct700 mic grille and headbasket working for your design Max? Have you tried other body designs?

/J

 

[bradb]

http://www.groupdiy.com/index.php?topic=30742.0

 

[Skylar]

Thanks Max...

If anyone else has found a good solution too, pipe up...

RE: 9-pin tube sockets with 18-19mm mounting holes

This should be skinny enough to work, but you'd have to glue it in.
http://www.tubedepot.com/sk-9pinpc2.html


Part Number S-B9A CWSF on this page should work also:
http://www.evatco.com.au/webcat1p12.htm

 

[waldorfcave]

Hi,

I have some hum problem , the mic works perfect but i have hum, if i switch of my psu
the hum is gone. the mic works for 1 minute with psu switched off.

my build the passive psu, but with stock trafo from thomann. maybe somebody can give a hint where
i have to look ???

i have modified the psu a bit to get exakt the right voltages.
i have put a 50k trimme instead of the 13.3k resistor and trim to 150v.

i also bypassed the two 4.3r resistors after the choke to get the right voltages, because with them in my heater voltage was to low.

thx

lars

 

[ioaudio]

i also bypassed the two 4.3r resistors after the choke to get the right voltages, because with them in my heater voltage was to low.

which is also the reson for your hum. you will need a proper transformer with the specified voltages.

 

[waldorfcave]

ok, i have to buy the right transformer. i thought i could use the chinese trafo.

thx

 

[bradb]

Been stalled on this project for awhile.

Skylar, did you try that smaller 9 pin socket?


Max, any source for the smaller 9 pin sockets?

 

[Gus]

I have sandblasted then filled the engraving with car repair stuff "bondo" with mxlv67 bodies.  You need to let the bondo cure and shrink before matching it to the body.  I installed the body in my lathe with a cone ball bearing device at the tail stock and turned the body round. I then painted the body.  If you don't let the Bondo shrink with enough time after you paint it you can make out the outline of the engraving if the bondo shrinks more under the engraving.

Or you could have metal plates made to glue over the engraving.

 

[Skylar]

Skylar, did you try that smaller 9 pin socket?

No, not yet.

If you look at its specs, the diameter of that socket is 23/32 or 0.71875" or 18.25mm

So, it should fit in ioaudio's PCB.

EDIT: I measured the PCB opening with calipers at 0.7125" or 18.10mm; it'll be a tight fit! Slight reaming may be necessary.

The only thing is that there's no retaining mechanism.
It's a straight cylinder, so you'd have to get creative with gluing or something.

 

[seavote]

Bradb . i have two of the same sockets you have from some previous project. i thought id use them for this. what is the problem with them. do they block the installation of other components? or do they not fit in the mic body the way you have it mounted on the pcb?

 

[bradb]

they are too big to fit thru the hole and if we enlarge the hole I think the structure will be compromised.  The whole shebang is really large and bulky.

un-elegant


b

 

[rodabod]

I'm not building this project with you, but don't compromise - buy the correct size part.

 

[matta]

Hey Guys,

The tube socket that Skylar linked to does indeed fit into the hole on the MK7, beautifully. The only problem is that since it is PCB mount there is no way, other than glueing it to afix it in place.

I did have a bit of a brain wave and thought that maybe someone could design a small PCB that we could solder the socket to, the PCB would then have the mounting hold to attach it holes provided on the MK7 capsule board.. presto, neat, workable solution, far safer than relying on a bit of glue to keep it in place.

Hopefully Max is reading this, or I'll drop him a line to bring it to his attention.

I was also hoping we could work on a PCB layout for his new PSU something that would fit neatly into the PSU enclosure that Skylar has designed, with room for the trafo and choke.

Cheers

Matt

 

[ioaudio]

this one should work, though i didnt test it: http://www.tubeampdoctor.com/product_info.php?cPath=36_92&products_id=1132&language=en
i will additionally look for the original preh sockets.
i would not add another pcb, but if you do so leave pin 9 (the grid) without touching the pcb e.g. make a 3mm hole so this pin does not touch the pcb.

-max

 

[aamicrophones]

Hi Guys, you can buy a 9 pin ceramic socket that bolts in place from New Sensor in NJ.

I can bring in blank sleeves from China but would need to know the diameter and length.

I have blank 460/TCM1100 sleeves on hand and 9 pattern power supplies with a 6 volts filament and Zener regulation that can be easily set from 110v to 150v.

How, would I source a Dale M7 capsule to try in our CM47 microphone?

Is it possible to source more of the full size BV8 type transformers?

I have a nice dual bobbin custom wound low profile BV8 type transformer that is very inexpensive but like to compare it to the larger transformer used in the DIY project.

Cheers, Dave Thomas
www.aamicrophones.com

 

[Jonkan]

Dave, if you can get blank sleeves that fit the thomann mic body, and if theyre not too expensive, id probably be interested in a couple. Have no idea about the measurements yet, as i havent bought any yet, but im sure someone here could provide them.

Or are you talking about complete blank micbodies?

/J

 

[dissonantstring]

hi dave,
you should take a look at the M7 buy thread: http://www.groupdiy.com/index.php?topic=31592.0.
if you have difficulties reaching dale, i have his email address, but he gets a lot of spam so i will not post it.
PM me and i can provide you with dale's email if you'd like to discuss getting a capsule, but dale is pretty responsive to posts on his thread.

are you offering yourself as a source for mic bodies?  would they be the same as the type on your site?  as jonkan mentioned, can you provide detailed measurements?  very interested.

oh, and welcome to the forum!
kind regards,
grant

p.s.  sorry for the OT interest, but this maybe another body option for max's MK7 project which would be nice.

 

[Jonkan]

As mentioned earlier in this thread, the dimensions for the thomann mic is apparently: 58.5 mm x 180mm. Maybe that info helps?
/J

 

[Jonkan]

If anyone is looking for tube sockets that will work with very minor modifications, i ordered these: http://www.banzaieffects.com/Micalex-Socket-Noval-miniature-Chassis-mount-pr-18441.html

I had to file away maybe 1/10 of a millimeter of the hole in the mk7 pcb to get them to fit. Shouldnt affect structural intregrity at all in my estimation.

Ordered four sct700 mics today aswell. Im just to anxious to get started on these to wait for other body options that may arise.
Since this is what Max used, im pretty sure they will sound just great, and thats really what matters the most to me. If any blank sleeves are available in the future, id definately be interested in upgrading though.

And since i have 5 of dales m7 capsules at home, im thinking im going to buy one of those tasty u47 "clone" bodies that skylar and the guys/gals are working on anyway for a future mic building project

/J