|The Dynaco PAS series of tube preamplifier is a good entry level tube preamp. These generally sell for about $200. In stock form the performance is nothing special, but with an upgraded power supply, new caps, and some other mods a PAS preamplifier outfitted with a good set of Mullard, Raytheon, Sylvania or Telefunken 12AX7 tubes, is capable of performing as well as a $2000~$3000 preamplifier.
My PAS2 is used as my computer preamp and yes,the power supply is in need of an upgrade-really is the weak spot.Other areas that need attention are the jack panel,input selector switch (and the tone controls for some though I kept mine in).
A "quickie" power supply mod is to get the neon bulb out of the heater supply and replace it with a low current LED.This bulb is stealing current from an already current impaired heater supply.I also use RCA 5751 tubes in the line section.Lower mu and nice sound
For the really adventurous-resistor and cap upgrades
oh yeah almost forgot !
The phono stage to the tape outputs are where most tap in to use the PAS as a "phono stage only" device.Be aware that both this output and the main outputs are NOT low impedance outputs and should either be followed with a buffer,matching transformer or be only used with high input impedance -100K ohms or better
just adding to the knowledge pool