Rather than using four 9-volt batteries, would this power supply work well? Qualtek QPDF-320-36 Switching Power Supply 36 VDC 8.8A 320W Single Output, Parts Express part number 129-148
No, that would be a poor choice. That power supply is very likely to be quite noisy (notice that it's shielded inside a metal box), and the Quickie doesn't need nearly 8A of current. A lot of these supplies aren't particularly happy when they aren't loaded down. When looking at the supply closer, the specified noise is less than 200mA, and that's really pretty terrible. For a reference, my test equipment will measure noise down around 0.070mV and I can't really see much of anything coming off a 9V battery.
Also, can the filament voltage be run off a 5-volt DC supply, such as a USB charger?
The filament voltage for the 3S4 as designed in the Quickie is 1.5V. USB chargers are also generally very noisy devices and the filament will be very sensitive to a poor quality filament supply.
$20 will buy you 20 alkaline 9V batteries (never buy "heavy duty" batteries), and that will get you five sets of batteries, or 500 hours of listening time.
Alkaline D-cell batteries are about $1.50 if you are willing to buy 10-12 at a time.
If you need a tube preamp with a power cord, the Smash fits the bill nicely and has a linear filament supply with a voltage/current regulator specifically setup for the 4P1L tube.
-PB
« Last Edit: September 16, 2017, 10:33:49 AM by Caucasian Blackplate »
Paul "PB" Birkeland
Bottlehead Grunt & The Repro Man
