Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: supro66 on June 03, 2012, 10:34:04 am
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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 (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
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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.
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Not the same, but similar: PaIa TubeHead (http://www.paia.com/manuals/docs/9305-tubehead-schematic.pdf).
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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 :w2:
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
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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.