Going to do a tube mic project

Heres my plan..... money is a bit tight, I have a broken solid tube that I will repair then sell, but 1st I will borrow its capsule, found some EF86s in the shed I robbed them from old reel to reel recorders, ordered some 1 gig reistors from farnell {service mount tho im hopin I can adapt them wont be pretty} found a OEP transformer, im going to make Jakobs G7 circuit birds nest style from bits I have laying around, found some wall wart transformers I hope to use for PSU, im going to throw this lot together if all works ok I will get Pesulo capsule C12 type, a MXL V67 to use case and grill and neuman style china capsule for later experiments then think about a nice transformer.

the aim is to end up with a nice better than solid tube sounding mic, anyone thoughts will be most welcombe.

Thanx..........................Gary O.

read the metas there are answers

You will have a hard time fitting a ef86 in a MXL V67

cheers Gus the V67 was off top my head will find cheap mic with nice size case and decent grill plus any experimental parts would be bonus...bin reading thru the metas learnt some stuff but so much to wade thru end up going round in circles a lot of the time so I thought id get fiddling.


Cheers ...................Gary O.

4 years later update haha .....didnt buy the MXL didnt have a capsule to play with at the time......the G7 guts sat in my junk draw all this time.....parts robbed from it for other projects.....but because of snowed in I had time to play with the G7 ...Im glad I did works great cardiod only with my Violet Vin 67 lollipop!!.....Thanks Jakob !

Havent managed to get it working with a Oktava MK101 capsule tho .....

gary o said:

Havent managed to get it working with a Oktava MK101 capsule tho .....

Click to expand...

It could be that Oktava capsule is designed for lower bias voltage and the membrane stucks to backplate with higher voltage?

Maybe would i be able to see if i watch capsule.....and will it hurt my capsule.....hope not ....I tried lower B+ voltages first of all dont no if that will lower the capsule voltage .....but no sound........

Thanks

gary o said:

...and will it hurt my capsule.....hope not ....

Click to expand...

Propably not.

You better adjust the voltage divider in the mic than the B+.

So that would be the 2x470K I guess.....I cant measure voltage at mo but I wrote on my own schematic I had 63V at that node...as I say I have various B+ voltages to play with lower than 160+.....perhaps I can put a pot in place of the 470K resistos...

So 63V at that node implies 126V B+. For about 40V polarization voltage change the bottom 470k to about 220k. Interested to hear how the Oktava capsule sounds in this circuit!