Page 1 of 1

#1 Big Hi to everyone

Posted: Mon Jun 12, 2023 11:53 pm
by Boiss
A big Hi to everyone,
I have been playing with valves off and on for 60 odd years, and often go OTT with my bottles.
Present amp is an all mains toroid job, with EL34s in triode and Antitriode, Long tailed pairs with
individual CCSs to balance I in the 350W mains toroids. Presently restoring a Philips 2514 with some
Mosfets in the positions where the valves are as rare as rocking horse poop. I have a cunning plan for a
GU48 after I've got the filament supply sorted, (Modded Ex computer SMPS)
Watching the 833A Amp project which is how I found myself here.
Thanks for taking me in and good luck to everyone with their projects.

#2 Re: Big Hi to everyone

Posted: Tue Jun 13, 2023 8:46 am
by pre65
Hi and welcome.

Nice to see a GU48 (833) fan onboard, perhaps I'll get some enthusiasm to finish mine.

Just out of interest, whereabouts are you situated ?

#3 Re: Big Hi to everyone

Posted: Tue Jun 13, 2023 10:32 am
by Boiss
Hi pre65, I am Near Alicante in Spain.
I have an old EL84 class A amp with an HT of 250V. Just for a few tests about 5 years ago, I connected An 813 (RCA) Emission a bit down but OK in place of of one of the EL84s Obviously with a 10V DC filament supply, no other changes apart from the long wires going to the 813. It worked quite well with about 1W O/P. Ia was quite a bit lower if I remember correctly. I then tried the GU48 (New) as above, It worked but the audio O/P was well down, not distorted just low and Ia was very low too, maybe a bit of positive bias or shorting the cathode R/C comps might have changed it.
I did wind a biggish toroid for PP 813s but never got round to trying it.
It was good to see you using the GU48s, It was what drew me here. They look great lit up too.
Looks like I've got a lot to read.
Good luck with the project, keep it going.