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IFixAudio 8th February 2012 06:38 PM

SVT output iron as single ended
 
Hi,
Any thoughts on whether a 6550 powered SVT output transformer with an open Blue wire primary tap could be used in a single ended output application.
Schematic here:
Ampeg SVT (1969) Amplifier Schematic
I have one that burned a tap internally after a tube short and had thought of scrapping it when the aforementioned idea came to mind.
I will not entertain the idea of rewinding it... an SVT power transformer, yea right...

Thanks

Jim

radiostar 8th February 2012 06:57 PM

No air gap for SE ...

tubelab.com 8th February 2012 07:45 PM

It is not gapped for SE use, but it will work for low powered use. As a guitar amp you might get 20 to 40 watts through it before saturation sets in.

Another possibility is to open it up and see if the open is right where the windings connect to the lead wires. it is a common place for a failure to occur.

IFixAudio 8th February 2012 08:25 PM

Thanks for elaborating!
It doesn't sound like it's worth the trouble.
It's off to the scrap pile.

astouffer 9th February 2012 01:04 AM

You might want to hold off on scrapping. There is an old Glass Audio article from 1995 called "Single Ended Glory for under $100" where I believe PP output transformers are used with some 45s.

Thatch_Ear 9th February 2012 02:44 PM

If the section of lams on the bottom of an OPT can be removed and put back in is it possible to gap a PP OPT? I am looking at an Eico ST-70 that look like they could easily have an end lifted out. They are 90* off from the Sansui PP EL-34 OPTs that were gapped for my 300B. Unfortunately I didn't inquire just how the guy who built this did it. I can't remember his name, though I think his 1st is ED and he lives in Oregon. I bought this thing about 10 years ago and the only thing I don't like about it is that it is SS rectified (there is a socket and it was delivered with a 5V4 which was in the photo which did nothing but make noise. No 5V taps for tubes either, so I guess he changed power supplies and or it was in the Sansui which could have been SS rectified) or another amp was on this great chassis.
My thought for the Eico was to run some stat tweeters that will top some horns I have been drawing up, but I could rebuild some Amperex PP 6V6 mono blocks to do that and save a lot of space in my rack.
The specs on the Eico at low wattage are downright great (9 Hz to 60 Khz at 1 watt. +-.5db at 35 watts and 18 Hz - 43Khz) so I was thinking about 6A3s or 6B4Gs if they could be gapped.
Not being able to is no great loss, but I do like SE.

Thatch


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