Sunn T50C - sounds great

[lowell]

I just got a T50C on my bench and I've never seen or heard a Sunn before today. Boy, I do have to say that this amp sounds incredible. It really nails that SRV sound, which can be a great sound if that's what you're looking for. Tight bass but not overwhelming like most CBS Fenders. The breakup on the clean channel is just right too for that little bit 'o dirt playing rhythm. The lead channel has a similar tone but adds this really nice crisp sizzliness to the top end so bending notes the thing really sings. Again, it really reminds of SRV's tone on the Sky Is Crying album to a 'T'. Just wanted to see what people think of Sunn amps or if someone has any interesting thoughts here. I'm really just writing to say these (or this one) are great sounding amps. I have reviewed the schematic and it seems pretty stock Fender however I discovered some differences:

Input stage has a whopping 47uf for a cathode bypass cap. There is a cathode-follower for tone stack after a second gain stage in clean channel. The second gain stage also has the "tweed" cathode circuit (820R) w/ a .68uf bypass cap. The tone stack has some .022uf caps for bass and mid versus the .1uf in typical Fender. There are also 2 more stages before the PI - a cathode follower and common cathode stage. I see a series filter (resistor and cap in parallel) in series b/t cathode follower and grid of final gain stage before PI. .047uf PI coupling caps to power tube grids. Plates of output are at 457VDC and are fixed bias. There is a small amount of NFB via a 4.7nf/150k network.

I'm thinking this amp sounds great because of the output transformer qualities, the frequency responses of the individual preamp stages (namely the 47uf bypass cap of first stage and the .68uf bypass on second gain stage). Also the high end is tamed a bit throughout preamp due to 10k grid stopper resistors. I'd be interested to hear any thoughts one might have on this circuit and/or Sunn amps.

[crosseyedjack]

I bought a T50C a couple of years ago on ebay. I always wanted one when they came out in 2000, but couldn't afford it. They're sort of rare now. I'll never sell mine. Aside from the way it sounds, I like the send/rcv controls and the external tube bias adjustments. The only comment about the tone is that it's very bright. More so than any other amp I've known. But it does cut through the mix in a live performance. I've gotten several comments from people on it's sound, even several months after they've heard it. It's built very well, kind of a Cadillac of the Fender line. It's a heavy amp but thankfully it comes with wheels. I'm still looking for the original cover and the footswitch. If anyone knows of one, drop me a line.

- Randy