vibroverb63RI bigger tranny help needed.

[ballynally]

You said that you wanted to upgrade the OT, that's exactly what I suggest above. I never said anything about converting to 4x6L6, your PT can't take it anyway. I suggested the Showman style OT (100W, 1.9K:8ohms) because it will work with 2x6L6 & your speaker wired for 16ohms (~3.8K:16ohms - Google "Output transformer turns ratio"). Otherwise you would need a 100W OT with a 2ohm output to work as intended with 2x6L6 and a 4ohm load...and you don't see many 100" 2Ohm OTs.

Yes, sorry. didn't read it right. But, what's wrong with the Bassman option? Is there an advantage to your Showman/Twin option? I'm slightly confused about the Ohmage side. All i need is the 4Ohm output/230v (i'm in Ireland), if i'm running 2 8 Ohm speakers, is it not?

[MWJB]

There isn't anything wrong with the bassman option...other than you are replacing a 40W OT with a 50W OT, better but there is room to move, you can go bigger if you need to.

"All i need is the 4Ohm output/230v (i'm in Ireland), if i'm running 2 8 Ohm speakers, is it not?" the wall AC does not have any impact on the output transformer,only the power transformer. The OT in your amp is in the region of 4000ohms (this is what the 2x6l6 see) into 4ohms (2x 8ohm speakers in parallel). Because a 100W OT typically expects to see 4x6L6 (2 on each side of the OT primary) the primary impedance that the tubes operate into is halved (which is where I got the 1.9K from, approx half of 4K).

Most common options for you are the Twin OT (1.9K:4ohms) or a Showman style/Multitap Twin OT with an 8ohm speaker load. Because you are now operating the OT with just one 6L6 at each of the primary, rather than 2, impedances are doubled. So the Twin OT goes from 1.9K:4ohms up to 3.8K:8ohms, and the Showman OT goes from 1.9K:8ohms up to 3.8K:16ohms.

You have 2x8ohm speakers, these can only be wired as 4ohms in parallel, or 16ohms in series, not as 8ohms total. This rules out the Twin OT (unless you replace the 2x10" 4ohm speakers & baffle with a single 8ohm speaker, say a 15" which is a fairly common mod) & makes the Showman (NOT dual Showman - this is the same as the Twin) operating into 16ohms (rewire your speakers in series) the logical choice if using the speakers that you have.

You should know this stuff if you intend to fit a multitap OT, OTs often come without legends, or with wrong legends, or with wire colours that do not conform to what you already have installed. Like I said, google "output transformer turns ratios".

[ballynally]

Thanks for the info.

[olddawg]

Seems like an awful lot of trouble. Have you simply tried using a boost pedal and a compressor. The noise floor will go up, but live who cares? Btw, I have an 18 watt Marshall clone that has a giant old Zenith OT in it. I have no idea what it came out of, but everyone ask me about the the tone and volume of that amp.