12AX7 Micpreamp

[supro66]

PreSonus Tubepre Single-Channel Vacuum Tube Mic Pre
I got one and it works good

http://www.amazon.com/gp/product/B0002D0KG4/ref=oh_details_o05_s00_i00

How can this work on only 1-amp 12 volt wallwart
and power the 12AX7 tube filament and the 100 volt pluse plate voltage

[sluckey]

Filament is easy. 12AX7 requires 12VAC @ 150ma to properly heat it. The plates only need 2 to 4ma current so B+ can be developed in several different ways. Another stepup transformer and rectifier, or voltage multiplier rectifier, or ss multivibrator driving a small hi-freq stepup transformer, are just a few easy ways to develop 100VDC.

Open it up and show us some pics and we'll make some guesses.

[drgonzonm]

I am going to say this a little more complicated than the average bear.  With XLR input, 48V phantom power, instrument input, and DI capabilities, I would venture to guess, highly PCB, and lots of SS. 

I am curious, as I am looking for a DI for my bass, and this unit might do the job. 

[PRR]

Not the same, but similar: PaIa TubeHead.

[supro66]

Filament is easy. 12AX7 requires 12VAC @ 150ma to properly heat it. The plates only need 2 to 4ma current so B+ can be developed in several different ways. Another stepup transformer and rectifier, or voltage multiplier rectifier, or ss multivibrator driving a small hi-freq stepup transformer, are just a few easy ways to develop 100VDC.

Open it up and show us some pics and we'll make some guesses.

open it up

Let me use it first
I would like to do some voltage test
This amp reminds me of a joke

The thermos bottle keeps hot water hot and cold water cold

How does it know

[bakerlite]

i have what seems an identical stereo version of this.

I forget the figure exactly but it required an equally puny wall wart.

I was very unimpressed by the noise floor and and the effect on tone was also noticeable.

I used it a few times but gave up - I wouldn't even have the heart to sell it on.