Yo,
Long time no speak...
We had quite a few conversations back and forth regarding Risson (and a little bit of Plush) back when I was still living in St. Louis...I forget which year it was but I think you had just picked up the Plush Super 450...2008? 2009? I forget now.
If you ever need any guidance on the Plush, I can help.
Regarding it being old...yep, that it is. Crappy? Well, judging on the use and abuse that may be the case but that circuit is 98% pure Fender AB763 and the Northlake Iron bolted to the heavy duty steel chassis was made by Northlake and is considerably higher quality than anything Fender ever originally installed. In other words, the potential of one of these amps is at least that of a Blackface era Showman or Twin...but with the superior iron, if you get the amp fully healthy, you've got yourself a phenomenal amplifier.
Depending on what year your 450 is...it may have some really nice, heavy duty fiberglass tag boards...a very nice upgrade over the Vulcanized Fiber that Fender, Traynor, Risson and others utilized back then. 40 years later, the Forbon is warped causing all sorts of fun and mysterious issues...the HD Fiberglass Plush used? nice and flat. If it is a 1972 model it will likely have PCB's...but one never knows, the beauty of Plush, you have to look and see...their mantra was that of inconsistency. The filter cap's will be Sprague or Mallory, the 1/2 watt, 1 watt and 2 watt resistors Allen Bradley, The pots either CTS or Centralab. Any higher wattage resistors will be Ohmmite. The switches will be Carling. Tube sockets are Cinch brand...all of this as good as it got back in the day.
The B+ will be right around 450 VDC and the screens a smidgeon less...just like a Fender. The bias network will likely need some tweaking in order for the grids to see the proper negative voltage. There are some very obvious lead dress issues in all of these amps that require revisions...if you know what you are doing, you can get these amps to be dead quiet.
You do not need a footswitch for the reverb and vibrato to function...they should function when plugged into either two inputs on channel 2. The reverb can be transformer/tube driven like an AB763 or it might be tube/transistor driven...probably the latter. Depending on the reverb circuit depends on which reverb pan is used. Plush used a 13", 2-spring unit...could be Hammond or Gibbs stamped on the housing...doesn't matter, they are the same basic unit...only the transducers used varies depending on the impedances required. The vibrato is easy to fix if broken...not much to the circuit really. Both sound great when healthy.
One thing you'll need to fix for sure are the midrange controls. Plush used a pair of 100K pots with a resistor in parallel to approximate the function of a 10K pot. What you get is a useless midrange control...it only works on the extreme ends of the pot travel. Yank them and slap in a pair of 10K's and you'll be treated to functional midrange controls. These are important because the midrange setting really dictate how much growl you can get out of the amp.
You'll note that the way V1 & V2 are wired up is different when compared to an AB763. This is good because it gives you more options on pre-amp tube selection and how it impacts the voice of the amp...resist the urge to use 12AX7's in all 9-pin sockets...unless you want to kill the clean headroom.
Regarding the output...
Plush claimed 110 watts RMS...that was a lie. In a healthy state of tune they are good for between 80-90 watts RMS...no problems if pumping into 8 ohms off the 8 ohm tap. The 4 ohm tap into a 4 ohm load is going to be more like 75 watts. Of course, you never know which tap Plush wired your amp with...you'll need to investigate. Most 450's have both a 4 ohm and 8 ohm taps on the OT. The output jacks may be wired straight parallel or set up for auto impedance switching...I always recommend switching to the auto impedance switching setup which requires a proper switching output jack along with a standard jack.
For power tubes...look no further than JJ's. The price is right and they sound better than any of the Russian or Chinese 6L6GC variants with this circuit. You can bias them hot or cold...but the amp will sound basically the same...so I always go cold. You might want to install a bias trim pot...as these amps otherwise used discrete components to set the grid voltage.
The drivers in the crappy void-filled plywood cabinet were originally either CTS or Eminence parts. They were junk when new and are only junkier at this point in the game. Depending on what you are after sonically, there are many better options. Personally, I don't like cone break-up...I like efficiency so I'm all about the EV's, JBL's, Altec's (Now Great Plains Audio), Cerwin Vega's and Gauss drivers. The only issue with this is that they make an already heavy combo that much heavier.
Personally, I love these amps...most folks don't know what they are and/or confuse them with Earth amps (which used lesser quality iron) or even Kustom's which obviously were solid-state. You can acquire them for a pittance and with a modest investment, you have yourself an amp equal to or better than what some regard as the finest vintage tube amps ever produced. Like a Showman or Twin, they respond well to OD pedals...or really, any pedals for that matter. A great warm and sparkling clean tone is a great place to start with any amp...
And that's what these amps deliver in spades, if you take the time, skill and patience to get them healthy.
