I love 50 watters, not just for the more useable volume (cough, cough, this is a loud mofo!!), but there is something special about the way they interact vs. 100 watters with their imposing tone.
The circuit I’ve selected is bone stock 68 specs. As you guys know, this was somewhat of a transitional era and the 1st gain stage did alternate between 2.7k and 820r, both with 0.68uf bypass cap. I like the later, which is a bit warmer but I am going to try the more classic late 60s / 70s 2.7k spec at some point.
I’ve used mustard and Sozo larger value caps throughout, and since the photo below the output PI couplers have been replaced with mustards also and the PI input cap 22nf. The only exception is the Polysytrene 1st bright coupler, which I love for the clarity. I am getting pressure to deck this out with a full set of mustards (!), so I will be keeping an eye on the market for some in the 2.2n and 22n values.
The only significant departure from the stock specs is the use of a better (electrically) grounding scheme (thanks Larry!), as the originals can be noisy and use less than ideal grounding.
Finally, for the lower values I have elected to use a combination of Polysytrene, Polyester and Paper in Oil caps as opposed to the original ceramic caps. To me, they sound a little clearer and smoother, but still retaining that classic Plexi kerrang.
The Power Transformer and Choke are Marstrans and hit the voltage mark perfectly. I wanted something in the low 430vdc range and this is 432vdc - exactly what Brian said. The Output Transformer is a Mercury Magnetics. I was a little torn by this, as I had a Heyboer Drake clone, but I’ve heard this particular Merc OT in action and loved the upper mid range clarity and punch. I was not disappointed. Mercury make benchmark quality iron (and charge for it too!). I would have no reservations using anything of theirs in the future.
The chassis is also one of Brian's from Marstrans and the most of the other components are from ValveStorm, with the exception of the headshell which is Mojotone who produce the best cabinetry out there IMO.
A big shout out to Mike Hausler (page 361), who sold me the headshell and rear panel, but was kind enough to allow me to drop ship the ValveStorm order for me to save on shipping costs. Being in Australia, the tyranny of distance means shipping is hideous!
It sounds exactly like a good Plexi should: fat, punchy and that familiar upper mid range grind. Set clean (at around 1-2 on the dial), it’s a punchy and clear tone that cuts through. Cranking from 2-3 and you get that classic edge of breakup tone which is spectacular with a Strat. Cranking further and you have the rock sweet spot between 4-7. Playing with the guitar’s volume knob and using a good booster, and the tones are incredibly versatile. Pushing beyond 7 and it’s entering bouncy compressed EVH territory.
A great setting I’ve found which many Plexi lovers in the know use is to dime the Middle and Treble, roll back the Presence to just under half, set the bass between 2-4 and have the Volume to taste - I love that 4-7 range here.
There is something to be said for the simplicity of 2 gain stages and no channel switching, toggle switches etc. Clear, open and punchy. I love it!
She’s decked out with a full set of NOS preamp tubes. Older =C= power tubes didn't last long, and it's the 4th set that have died on me. Not doing that anymore. The Svet EL34s in there now sound great. The photos were taken with 6CA7s as the testing tubes. The preamp has a Telefunken in V1 and V3, and a Tungstram in V2. These NOS preamp tubes have a touch less gain than their modern counterparts, but so much more clarity and openness.
Overall, I’m very happy. Still getting to know her and relish every tone opportunity to crank it un-attenuated.
