Don’t know if this thread is still alive or died on the vine.
Bottom line up front: if you have access to an amp, I imagine it shouln’t be too overwhelming. .But if you’ve never physically seen or been in one, this project will be a major time suck. you peel away layer after layer of “WTF”?
I have been working on recreating a Tbird Twin 30 for a friend. The critters are scarce, he only had it in his studio on loan for a short time but really was intrigued by its tone and uniqueness. I thought it would be nice to get one built so we could tweak based on that. Having never seen one in person, and with only a couple demos out there to hear the amp, it’s I didn’t have a ton to go on. And no voltages or other useful tidbits.
As it turns out the schematic has a number of non-trivial errors. I think one version was scanned, and the way the original paper was folded, wiring didn’t get scanned, so there are section of the amp apparently going to nowhere. I also have issues with the way the LFO is supposed to interact with the 6BR8 pentode section (output varies screen voltage, which sounds clever except I couldn’t get it to work in LTSpice no matter how many tweaks I made. It does work if you mix the LFO signal into the grid of the pentode, but the pentode design is so squirrelly something has to be off (like the data sheets I have are from the wrong planet.
This project has taken oodles more time than I ever could have imagined (and I have a good imagination). Bottom line here at the end of the post? Unless you have tons of time, experience, and know what you are after (ie have one or access to one) , trying to build one is not for the faint of heart.
I’ve identified most of the sketchy wiring and finally have the whole amp up and running in LTSpice, but it has felt like creating a baby dinosaur out of and old chicken
Egg.
On top of that, spec’ing Trannies and various chokes based on guesses is hard on the wallet.
Nonetheless, sometime in the next few months I’ll be excited to have this beast up and running so I never have to do anything remotely similar again.
The last speed bump was a bad power tranny from Hammond )I’ve had two this month, plus one from Merc, lucky me)
On the plus side I’ve drilled down into the circuit in Spice, have modeled it every which was from Tuesday, and all its little eccentric bits are working. I my build is in a BFSR chassis, which is a bit snug and not neat, but hey? No porn here!
Topic: Selmer Thunderbird Twin 30 transformers (Read 3891 times)