Re: inexpensive small true mic preamps

[Douglas Baldwin <coyotelk@optonline.net>]

> Rick Walker wrote:
> > I want to get either a mono or a stereo, tube mic preamplifier
> > that has a small footprint and also is a true tube mic pre.
> >
> > If memory serves me correctly,  there was thread here where
> > someone said that the inexpensive tube mic pres, like the Art
> > where not true tube pres,  sending only a small amount of the signal
> > through the actual tube.

Let me preface this by saying that I have found very little need for a tube
pre in either recording or live applications so far. I don't own another
dedicated mic pre besides the ART Tube MP.

I own two ART Tube MPs - the ones Musician Friend has been blowing out at
$30 each, with the little analog VU meter on the face. A couple of months
ago I had my studio assistant test one of them for "tube coloration." I 
gave
her a box of 12AX7s, 12AT7s, 12AU7s, etc.; one of those MXL 990 series
microphones; and a pair of Grado headphones. (So we're talking lowest of 
the
low budget stuff. Bear with me.) She opened up the Tube MP, popped in a
tube, and talked into the mic while listening with the Grados. Then she
wrote down some comments on the sound. She went through over 40 tubes this
way. The range of results was huge. Everything from "dull, muddy" to "warm,
reserved" to "neutral" to ""bright" to "aggressive" to "edgy, raspy at high
gain" to... you get the picture.

Is this or is this not a "true tube pre?" I ask this somewhat innocently. I
think that the ART Tube MP is running on a "starved plate" circuit, because
I think that a 12A-7-type tube requires some heavy voltage to run in its
normal range and of course the ART Tube MP is running on a little 12V wall
wart. But so what? My assistant (whose ears are very trustworthy, and whose
verbal skills are excellent) could hear and communicate significant
differences between different tubes in this preamp. This little sucker also
has a very pleasant compressor/limiter circuit, and many budget-minded
engineers have called it their "Swiss Army knife" of audio signal
manipulation. At $30, and with a few 12A-7 tubes, you could have a field
day.

One warning: the ribbon of wires that connects the base of the tube socket
to the circuit board is VERY FRAGILE. As she was finishing up the testing,
my assistant thought that the last couple of tubes didn't work. Then we saw
that the ribbon had broken. Oh well, it was worth $30. I'm gonna buy a
couple more.

Discuss "true tube preamps" all you want, but I will pay closest attention
to those who speak directly from experience. Has anyone done some tube
swapping with the ART Tube MP and compared it to other tube pres?

Douglas Baldwin, coyote-at-large
www.thecoyote.org
coyotelk@optonline.net

"The volume knob on your telepathy is your morality."
- Stephen Gaskin, The Farm