Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: goangling on October 31, 2020, 09:03:40 pm
-
Hope you guys can help me out here. Building a Multivox Premier 50, this one is circa 1959 with 6X4, 12AX7, 6L6GB - I have pretty much everything but the output transformer. - Any recommendations ? I've got an 8ohm speaker - but don't mind having multiple taps. Looking at 6l6GB tube data sheet - I'm thinking about a 5000 ohm OT like https://www.mercurymagnetics.com/2018/wp-content/uploads/shop/specsheets/SE-5K-M.pdf Am I in the right ballpark? Which is a better brand? Mercury magnetics, Classic tone, Hammond....
Thanks!
-
The couple designs im seeing are 5k primary, 15W operation for a single ended 6L6. IDK if id pay that mercury magnetics price.. especially with no power ratings. Give them a shout about power output. Weber WSE15 and Classictone 40-18031 would work.
-
Some people like those big Hammond SE OTs...
https://www.hammfg.com/electronics/transformers/audio/1627-1642?referer=968
-
Multivox would never have paid for those big Hammond SE OTs. They are maybe 4X the size/weight/cost a small (open back!) guitar amp needs.
I don't even see the OT.
http://myvintagetubeamp.com/2018/01/26/vintage-1950s-multivox-premier-model-50-tube-guitar-harp-amp/
Hammond 125ESE is more than enough. 125DSE may be ample. 125CSE *might* be what a factory would spec.
http://www.hammondmfg.com/125SE.htm
Plausible circuit:
http://www.dougcircuits.com/premier50circuit.html
The 305V/62mA operating point is 4.7k, trim down 10% because it looks better on paper, that's 4.2k for all practical purpose. Of course without the Multivox PT you may be at some other op-point.
If you end up a little high on voltage (and a little lower on current), then the 5K connection of the 125?SE iron is spot-on.
-
Thanks - Here is the schematic I'm working off of... I'll price out the classic tone - and the 125DSE - I do like the Hammond 125DSE you pointed out though, seems more versatile with all those taps https://www.hammfg.com/files/parts/pdf/125DSE.pdf. You guys are great thanks! I'm sure I'll have more questions as I move forward. -
-
I kind of like the military look of these bad boys... wonder if the audio output would make everything sound like GI-Joe? :l2:
5Kohm primary and 8ohm secondary-
-
> military look of these bad boys...
"Power level 400mW" says less than a half-Watt of audio.
On the 5k side is maybe 44V of audio; a poor fit to 300V tubes.
The "MAX WV 50V" would mean no part should average over 50V, which suggests a 48VDC supply, but is improbable (not impossible) for tubes.
Some military iron has considerable reserve beyond spec, but this one has a 10,000 FT rating. While you can drive an army over 10,000' altitude a few places (my dad did some cold-studies high in Colorado for the Korean action), this is almost certainly older (piston) aircraft. Which can't spare any excess ounce.
So a fancy telephone/intercom transformer, not a guitar amp.