DIY tube microphone preamp

[Thebrain]

i've been googling forever trying to find a site or some kind of thread
telling you where you can get a full tube microphone preamp kit.
(and a good one!)
all i find is threads and sites giving you instruction what to buy and how to make your pcb.it is just too much of a hassle
if someone here can help with a link or something i would be really really happy

[mississippi]

Here a schematic diagram of a mic_amp with the EF86.

[Moke]

hamptone:
http://www.hamptone.com/

very highly regarded, and, available in kit form.

edit:
click the www link below my signature line. Its a link to a recording forum where we discuss mics / preamps / recording, endlessly, 24/7/365. You can get some good info, and probably some good leads there, as well.

[Thebrain]

Originally posted by mississippi
Here a schematic diagram of a mic_amp with the EF86.

thanks man this one looks really really simple does it work?

im pretty noobish at this stuff what power supply should i use for this
one?

[mississippi]

You will need a transformer with the right mains winding (120 or 230V)
Then sec. 6,3 V 200mA or more.
And a sec voltage of 145 V 5 mA or more.
Then you need a rectifier bridge with can stand 400V or more, a few elco's (2 x 50uF 250V) and some resistor to bring the voltage at 200V.

[Thebrain]

sweet thanks!

[kevinkr]

Better design here:
http://www.frontiernet.net/~jff/pult...onePreamp.html

and here: http://www.recording.org/users/kev/G9_tube_micpre.htm

[Hugh]

Mississippi
wouldnt that unloaded mic transformer create a peaky audio response?? 10M load on the EF86 grid to me should be more like 50K to load the transformer properly, presuming a 200 ohm to 50k typical transformer.
...Hugh

[mississippi]

Without micr. transformer you use a micr of 5 mV and 1Mohm impedance.
There are 2 transformers for this design.
the EL6805/01 50/25000 ohm
the EL6807/00 500/500 ohm.

[Hugh]

The circuit above must be not quite complete. Whatever transformer 500 Ohm or 25k secondary to me should have that as a load impedance, not 10M as shown on circuit. Circuit would be fine for HiZ mics & no Tx.

Whatever.

Hugh