In a nutshell:
I am extremely happy with the PA-250 and recommend it based on the details provided below:
This unit was suggested to me by the Thomann staff. I needed something because I was sick of looking at my favourite amp and not being able to use it to record or play. I don't do gigs much anymore.
For reference, here is the gear I used:
I have a Marshall JCM2000 DSL100 head. I have recently biased it and changed the power tubes to JJs. This goes into a 4x12 1960B cabinet with greenbacks. I use a Jackson soloist with Duncan Seymour JBs and Hot Rail passive pickups. I sometimes use a tube screamer. Not much of a pedal guy. For microphones, I use a SM57 and e906 combo to record my cabinet.
I have never been able to crank my amplifier above 3.5. Even when I did gigs with it at large venues, it is an insanely loud amplifier. It's a Marshall; more balls than brains. I cranked the poweramp and turned on the attenuator. I had to use the highest settings of attenuation, but it really brings it down to what I would call 'loud conversation level'. I could still have a conversation while playing.
The load box functionality and line out work very well too. I can now record a cranked JCM2000 at 2AM in the morning and everyone around me can sleep peacefully. This is a huge factor for me.
Regarding how it affects tone, in my opinion it does suck a bit of the highs away. So all I did was adjust my amp's EQ slightly and the problem was solved. I recorded the attenuated cabinet and was extremely pleased with the results. The recordings still had that 'oomf' that you get from recording a cabinet. But the volume was loud conversation level. The cranked poweramp section afforded great tones.
I tried layering the miced cab with the line out recordings (and IR-loading cabinet plugin). Once I factored in phase, the results were monstrous. I think I may prefer this to just recording the cabinet. I got a rich and powerful tone that needed very little in the way of EQ. Obviously, results here will vary wildly depending on the skill of the recording engineer.
The unit gets warm, but in my experience not hot. This is great. The fan is audible but not annoying and not loud at all. When you're recording the noise of the fan is a none-issue. If you need total silence to record something else, then you probably shouldn't have your amplifier on in the first place.
The unit requires a power supply and this is not provided. I didn't know I needed this and was only able to have it working out of the box because I have spares. I don't think it's good enough that this detail is omitted. I have deducted a star from features for this reason. The documentation is extremely basic - but accurate. It can be relied on.
This unit has increased my quality of work and has enabled me to do something I thought was impossible. This has given me a ton of freedom and a lot of confidence.
A bedroom player would not be able to use this very late at night if they wanted to play through the cab. But during the day and evening, it's probably fine - just check your local laws and your family/neighbours' situation. This does lead me to think that the PA-250 would be great for attenuating an amp for smaller venues in case you are a gigging musician.
I am extremely happy with this product and recommend it based on the details provided within the review.