Been doing a bit of experimenting with the T-wreck circuit topology in the interest of coming up with another small, simple amp with at least most of the tone and response I like to play but at a lower sound pressure level. Lots of load lines drawn, lots of calculations as well as lots learned on the bench. I am a amp doodler but thought I would share what I came up with in hopes that there are one or more of you that might want to mess around with this topology. Feel free to comment or critique as I value your insights.
I built a Liverpool clone several years ago so I understand the Wreck as a compressive, fairly gainy touch sensitive circuit. The trait I like the most about this circuit is that the clipping initially occurs at the finals so it is essentially clean through the preamp section up to the point that clipping initially occurs. It also has the most power to deliver to the load up to that point. As the output clips further, the PI begins to clip and the screen current on the finals pulls the screen and the PI voltage so it can compress and bloom as it comes back. The screen sag limits the plate current enough to reduce output power slightly. The 3rd stage eventually clips as you drive it more but, up to that point, it adds nice array of even order harmonics. At least that is my take on it based on the bench and the gigs.
But a little too loud for most situations I now play and actually too gainy IMHO as built Twreck-proper. So I initially started with a 12AY7 for V1a/b and 2x EL91 with a generic VVR. It had a great edgy--but not harsh--sound and overall pretty good; I gigged with it over a weekend in a small drinking establishment and while it delivered the tone, my 3-4 watts began to get buried by about the hour three. I stepped it up to a 2x 6BM8 PA section. Voltage scaled PI and the finals. It is still suprisingly loud but it retains all of the good tones I like even when you trim down the VVR. Cleans are great with the Strat and OK with humbuckers. No need for pedals--even on La Grange.
So this is what I ended up with. I don't have a legitimate sound clip as of yet. The tone stack is customized but I liked it especially for the Strat. I had a devil of a time getting the PI to clip at the right time and the right bias point without severly overdriving the finals so if the voltages look on the low end, it ended up as it ended up. The RC choice immediately preceeding stage 3 is critical for the lower end roll off and it is really personal preference.
As you were gents. Regards
dennis
Topic: Experimenting with Wreck Topology (Read 4454 times)