A top-notch quality attenuator, transparent tube power amp and fx-loop in a compact case that fits into 2U height (rackmount kit is sold separately) or on top of a guitar head. Mine comes with matched Sovtek 6550WE power tubes and Ruby 12AX7C5 HG driver & phase inverter tube. According to manual, KT88 tubes can be also fitted without biasing.
I use it with home-built 100W 1959 SuperLead (no built-in fx-loop, no built-in line-out). I needed to solve master volume, post-amp fx-loop, and solo boost. Before I discovered this device, I had to reamp it, which included a load-box for the first speaker out jack (Palmer PDI-06-16), line-out box for the second speaker out jack (served as post-amp fx-loop), and finally solid-state amp to amplify the signal. This was a little bit complicated setup.
I recommend you to set the input and output impedance to match the settings as your amp was connected straight to the speakers, because it is easy to switch the bypass button and you might get into trouble with mismatched impedances between your amp and speakers.
Pros:
+ reactive load. you would hardly hear the tonal difference between bypass and attenuated mode, very transparent
+ adjustable volume from silent recording across bedroom level to full 100W power
+ two channels with individual volume, presence and depth settings, switchable either by front panel button or footswitch (not part of the package). suitable for lead and rythm
+ silent recording option via line-out (balanced or unbalanced), even without powering the device
+ no-load protection (internaly switched speaker jack to a dummy load)
+ separate 2/4, 8, 16 impedance selection for amp in and speaker out
+ bypass the whole thing by a flick of a switch
+ post-amp fx-loop with level settings
+ line-in for connecting any device; e.g., pre-amp, phone, etc.
+ no need to bias
+ ground lift
Cons (very very slight):
- single speaker output. in comparison to PS-2, the second speaker output has been replaced by a footswitch jack for TRS cable to control the FX-loop and channel selection. if you want to connect a full stack (e.g. two 4x12" cabinets), you have to use Y speaker cable or Palmer CAB M Merger
- fx-loop can be switched on/off remotely only; e.g. with a footswitch pedal
- rack mount kit not included
If you have a non-master volume non-fx-loop amp you love to play and you play in a band with other guitarist, this is a must have. You will love it. Period.