Inspiration I've been a long-time Ampeg fan; I've owned VT-40s, Reverb Rocket 2s, Geminis, GU12, Mercury, Reverb-o-Jet, etc, etc....but never an early, tube-rectified Reverb Rocket. I tried one a few months ago and really dug it. It had a very nice, musical voicing overall...not too dark, not to bright...really rich midrangey sound that octal preamp tube seems to produce. Notes stay nice and firm, no mush and very little ghosting (there's plenty of filtering in this circuit). The reverb was great as was the tremolo. After a couple months looking, I couldn't find one in decent shape at an acceptable price so I decided to just build one. I figured I've probably built 20 amps at this point, so it shouldn't be an issue. Getting Started So I set about collecting the parts and developing a layout. The challenge began when I got really got into the layout. I've grown to like the idea of keeping the filter caps grounded with the portions of the circuit that they supply...so that's been one of my design goals. This was a challenge as was the complexity of the circuit in general...the reverb circuit alone uses 3 triodes...then you have the tremolo and a somewhat "parts-rich" phase inverter and 6 filter sections. I did eventually come up with a layout that seemed to be a good compromise between my various goals. I'm not sure I couldn't do better if I worked at it a bit more...but this did work out really well overall in terms of the amp performing well and the amp having a low noise threshold. Parts I've been really happy with the transformers I've used from Magnetic Components so I decided to use them again. I found two that while not Ampeg replacements per se, seemed to be a pretty good match, though I eventually decided to use a Zener diode to lower the high voltage winding by about 15V. My OT is tapped at 8ohm and 4ohm which is nice because I do love playing through a 4 ohm cab I built with a couple of old Jensens in it as well as a lot of 1x12 or 1x15 cabs with 8 ohm speakers. I really like the sound of PS series Orange Drop caps, particularly in "American-voiced" amps so I decided to use them pretty much throughout. I may putz with these a bit more...but I'm really happy with the result...so, maybe I'll just leave well enough alone too. Design Alterations I did decide to part ways with the original design in a few respects. First I opted to use 7591s rather than 6V6s. Why? Well...I like them and I have a decent number of some really nice old Sylvanias and others. Plus I already have gobs of 6v6 amps and only one other 7591 amp. Plus, I know my PT is putting out a bit more power than the original...and I know 7591s can handle more than 6V6s. Next, I figured...why do I need two open inputs? I'm not going to be plugging two guitars and a microphone . So I went with one open (47k) input and the "mic" input (47k) with the 470k short to ground. That gives you high and low "input sensitivity" options. I also wanted my amp's reverb and tremolo to work without footswitches plugged in. Ampeg used to just hardwire the footswitch in place, but I opted to use 1/4" jacks instead...but you have to use a shorting jack for the tremolo and a non-shorting jack for the reverb if you want them to work w/o footswitches plugged in. Problems After initially finishing the chassis, I ran into a couple of problems. First, I couldn't get the heaters working on all the tubes. I thought something was wrong with my wiring...but it turned out to be the damned tube sockets! Damned modern, ceramic sockets--they all needed some serious re-tensioning to work with my old stock octal tubes. I couldn't get good connections on all of them and wound up just replacing one of them. Man...PITA!!! Lesson learned--try the sockets with your tubes first. Then...while everything was working, I was getting this bad oscillation if I cranked the amp...but only if the reverb was engaged. I tested, re-tested voltages, ground connections...got out the scope and tried to pin it down...it was clearly in the reverb circuit somewhere. I tried letting more signal bleed to ground before feeding signal to the PI. Then it dawned on me...didn't Ampeg typically use shielded cable to wire the reverb send and return? ...and a few other spots? I didn't have access to an original to verify this but I wrote Gear Pager Slider13 who I know is also an Ampeg enthusiast and very familiar with these amps. He was kind enough to check out one of his RR and sure enough, he confirmed that the r/s and r/r are done with shielded cable. I rewired the r/s and return, input to grid and one other long "grid run" with shielded cable. Boom...oscillation gone. Tweaks I've been testing / playing the amp through other cabs for a week now and I'm really digging it. I decided to switch the tremolo pots from log to linear and I like the "throw" on them better now. I've also putz with the caps in the oscillator...but decided the stock values are fine (and safe). I may try to slow the trem down a little though so there may be some more tweaking there. I also decided that I like having the option of goosing the very-high end a wee bit. So I added a bright switch so I can go stock or get just a scootch more brightness Finally, after a bit of experimenataion, I went with a slightly larger cap in the first filter section, 33uA, and a 150k NF resistor based on recommendations from Slider13. Tones and Performance Well, I've not settled on a particular cab/speaker combo yet...but the octal preamp tubes tend to be very microphonic so I may wind up going in the direction of head + cab. I really dig the sound of the amp through big old Jensens. The best sound I've heard was plugging it into the big 1x15 cab of my National Professional which features an old P15N. Man...killer sound. I've also really dug the sound through a reconned C15P and a Celestion G1265. I'm going to try a Greenback too. I'll get some vids up soon and will add more pics when I build the cab(s). But I've got to say, the amp really meets or exceeds my expectations based on the old RR I played a few months ago. It's got that same "soft-edged" firmness and bouncy response. The low-end remains clear and distinct...no tweedy mush here! The overdrive is just wicked...I'd say it's the most "valco-sounding" Ampeg type circuit I've ever played though there is a bigger low-end response here than on your typical Valco-made amp. I really like the interactivity of the Tone and Volume knobs. You really get more mid-range and overdrive as you crank the tone so you play with the tone and volume knobs together to get the right ratio of overdrive / brightness volume. Just use your ears (rather than eyes) and it's a pleasure to work with...not a bad tone in there. One note about the reverb...boy...I love this reverb circuit!! Ampeg sure knew how to make great sounding spring reverb, if you ask me. Capacitor driven. The sound is very subtle, almost echo-like. Not nearly as sproingy/boingy as your typical Fender. It's a matter of personal taste, but I find this style of reverb greatly preferable. It not only works well on clean sounds, but it works surprisingly well with the amp heavily overdriven as well. My hat's off to Jess Oliver or whoever designed that circuit! The amp just loves pedals too. I like it best with my Timmy, which I set for a transparent boost. With a little extra voltage and 7591s, the amp is plenty loud for any gig I'll be doing. Mike - thanks very much for your opinion and input!