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Re: Overdriving Power Transformers

5/4/2000 4:33 PM
Re: Overdriving Power Transformers
Isn't the amount of B+ a big factor in determining how  
much power the two EL34's will put out? If so, say the B+  
were somewhere around 350Vdc, a 30W rated OT might  
work well. If the B+ were more like 450-480Vdc, then  
that 30W OT might suffer. Does this make sense or am I  
toatally off track here?
5/4/2000 4:47 PM
Don Symes

If you don't re-bais for the higher B+, you now have a higher-powered amp, so, right track, but the tubes would melt before the OT starts to smoke.
5/4/2000 5:51 PM

" but the tubes would melt before the OT starts to smoke."
In a lot of cases, the delta time between the melting tubes and the smoking tranny would be quite small *lauhg*
5/4/2000 7:10 PM

Right. So, if you bias correctly, your 30W OT will be happy. This theory leads to the fact that the OT should be selected according to the size (B+) of the PT as well as the type of output tubes (Z) you are planning on using.
5/4/2000 7:30 PM
Chris Harden

So, if I understand you all, providing I don't take the output transformer too far over it's rated power, and the tubes are baised correctly for that tranny, I should be allright. Thats good, because the price difference between a 30W and a 50 W Hammond OT is quite a lot, especially when I have to add the cost of shipping the extra weight to the UK.  
5/5/2000 12:16 PM
Stephen Conner
why not buy in UK?
Hey Chris,  
Hammond aren't the only transformer makers in the world ;) Why not buy your OT from Sowter Transformers in England:  
They have a great selection of PTs and OTs for tube amps, and if you want something really weird they can custom build it for you.  
Steve C.
5/5/2000 12:53 PM
Paul Stansfield

I've heard a couple of people whinging about Sowter's pricing - although I haven't seen any, so I can't vouch for their quality. Have you used any?  

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