Search found 9 matches

by Boiss
Wed Jun 21, 2023 8:21 am
Forum: Speakers
Topic: DIY High Z Speaker.
Replies: 4
Views: 9352

Re: DIY High Z Speaker.

I ran a few tests with different loads yesterday and it is definitely better with speakers etc over 2k. The secondary resistance of the O/P transformer is just under 1K. Setting up the regen to howl the Audio output V peaks at around a 3.5K load so I reckon 2k is probably where the most power is ...
by Boiss
Fri Jun 16, 2023 12:06 am
Forum: Speakers
Topic: DIY High Z Speaker.
Replies: 4
Views: 9352

Re: DIY High Z Speaker.

Thanks Steve,
Here the Z is 2K plus, there is not a lot of power to play with. The DC resistance of the O/P transformer appears to step up towards the speaker. Running the phones 2K and touching the terminals you get quite a tingle. I will read up on Philips 800 ohm speakers and see what the ...
by Boiss
Thu Jun 15, 2023 9:12 am
Forum: Speakers
Topic: DIY High Z Speaker.
Replies: 4
Views: 9352

Re: DIY High Z Speaker.

Just been looking at Audio exciters, If the coil no longer moves because it is attached to the sound surface and is the magnet assy that is moving then this opens up a whole load of possibilities.
by Boiss
Wed Jun 14, 2023 11:42 pm
Forum: Speakers
Topic: DIY High Z Speaker.
Replies: 4
Views: 9352

DIY High Z Speaker.

I have a Philips 2514 radio Which has finally been brought to life. I have a 1925 BTH horn Speaker which apart from its size sounds pretty bad. The radio on Hi Z phones is OK, well it's just acceptable I was wondering how I might make a Hi Z speaker. The Present O/P transformer is High in High out ...
by Boiss
Wed Jun 14, 2023 11:09 pm
Forum: Valves
Topic: Is this a Valve of some kind?
Replies: 12
Views: 20713

Re: Is this a Valve of some kind?

Probably is an early Xray tube, Is that a sort of mirror on the RH side, inside the envelope. Otherwise Does it have mercury in it?
by Boiss
Wed Jun 14, 2023 5:17 pm
Forum: Everyones Projects
Topic: 833A (GU-48) Amp
Replies: 1255
Views: 575155

Re: 833A (GU-48) Amp


This is an old picture from years ago when I built the first iteration, but it shows what the GU48 looks like lit up. :)

https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcQvjoxIcZul2K_CpUSwM6OklcJ8mySa7OYiGA&usqp=CAU


Mine mounted on a Teflon Base with movable solid brass sections to ...
by Boiss
Tue Jun 13, 2023 11:00 am
Forum: Valves
Topic: Tube geekery to pass the time.
Replies: 28
Views: 32676

Re: Tube geekery to pass the time.

If it sounds OK and YOU are happy who cares. There are many things you can do with Tubes apart from water and liquids although some tubes correctly treated and modified could become a small acquarium! From illumination and heating to miniature amps and Tesla Megavolt generators the imagination is ...
by Boiss
Tue Jun 13, 2023 10:32 am
Forum: New Users
Topic: Big Hi to everyone
Replies: 2
Views: 13244

Re: Big Hi to everyone

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 ...
by Boiss
Mon Jun 12, 2023 11:53 pm
Forum: New Users
Topic: Big Hi to everyone
Replies: 2
Views: 13244

Big Hi to everyone

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 ...