Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fossilshark on November 13, 2016, 08:44:57 pm

Title: Amps with 2 output transformers
Post by: fossilshark on November 13, 2016, 08:44:57 pm
Why do some amps have 2 output transformers. Its for 2 seperate channels right? Kind of a dumb question sorry.
Title: Re: Amps with 2 output transformers
Post by: sluckey on November 13, 2016, 08:49:23 pm
That amp only has one output transformer.
Title: Re: Amps with 2 output transformers
Post by: fossilshark on November 13, 2016, 10:50:51 pm
I am sensing i have made a fool of mysef. The big transformer on the right is the output transformer and the two on the left are power transformers?
Title: Re: Amps with 2 output transformers
Post by: sluckey on November 13, 2016, 11:02:31 pm
Right is PT. Left front is choke. Left rear is OT.
Title: Re: Amps with 2 output transformers
Post by: Willabe on November 13, 2016, 11:21:00 pm
Your being too hard on your self, your learning that's all.   :icon_biggrin:
Title: Re: Amps with 2 output transformers
Post by: kagliostro on November 14, 2016, 08:21:44 am
Quote
Why do some amps have 2 output transformers.

There are (very) few guitar amps with two output transformers

One of those was build by Marshall (but I'm not able to find a schematic, sometime ago I've find one, but I've it no more on my archive)

the JTM 45/100 Dual Output (if I remember correctly)

(http://i.imgur.com/zUiQGKq.jpg)

one other amp with that tipology was by ELK

(http://www.drtube.com/schematics/elk/vkb-100.gif)

and this weren't the only, but, as told, only few had this feature

Reasons for that ...... money, may be they had a stock of small (all is relative) OT and want to build a bigger amp, so ....

A different case was the Corland (an old italian guitar amp that a friend of mine restored with me), it was a PP amp but it has on it 2 x SE OT, we were able to contact the old (more than 80 years old) brand owner, and he told us that, at that time, they purcased the transformers from others, and they had under hands only that SE, he told us that a that time was difficult to find OT suppliers (here in Italy) so, after a short  period, they started to build also transformers

Ciao

Franco
Title: Re: Amps with 2 output transformers
Post by: jjasilli on November 14, 2016, 08:39:00 am
Quote from: fossilshark on November 13, 2016, 08:44:57 pm
Why do some amps have 2 output transformers. Its for 2 seperate channels right?


Yes, for stereo -- but then there's two (sets of) output tubes feeding each OT.
Title: Re: Amps with 2 output transformers
Post by: shooter on November 14, 2016, 09:55:05 am
fwiw, my last build has 2 OTs, boiled down to economics 101, had them, met the design criteria, walla!  I wouldn't want to do that on say a PSE KT88 though!, well, I guess I did on a stereo KT! :think1:
Title: Re: Amps with 2 output transformers
Post by: kagliostro on November 14, 2016, 10:07:29 am
No stereo, look to the schematic .........


(BTW, don't be confused by the Transformer PI, consider it like a Tube PI)


Franco