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by Mike H
Mon Feb 05, 2024 5:53 pm
Forum: Everyones Projects
Topic: Fg810 - A Working Title
Replies: 43
Views: 20275

Re: Fg810 - A Working Title

Revised schematic .....

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Fg810 amplifier version 7.png
Fg810 amplifier version 7.png (91.99 KiB) Viewed 1175 times
by Mike H
Mon Feb 05, 2024 5:49 pm
Forum: Everyones Projects
Topic: Fg810 - A Working Title
Replies: 43
Views: 20275

Re: Fg810 - A Working Title

Back onto the main event - I wasn't overly convinced by the double-diode temperature compensation for the bias, (read as, 'not good enough'), for example it would have helped if the diodes were closer to the heatsink end maybe? :oops: So I changed the design slightly, and opted for the adjustable te...
by Mike H
Mon Feb 05, 2024 5:21 pm
Forum: Everyones Projects
Topic: Side Projects
Replies: 108
Views: 50996

Re: Side Projects

Had to recalibrate the Voltmeter. For the 10V scale this is done by adding a low value resistor in series. I don't know where I got the idea from that it should be 20 Ω. :oops: More like 100 Ω. Actually, it IS 100 Ω. That being done, the 50V scale was reset (twiddle preset), and readings are a lot m...
by Mike H
Mon Feb 05, 2024 5:10 pm
Forum: Everyones Projects
Topic: 6550 SE Amplifier
Replies: 110
Views: 9421

Re: 6550 SE Amplifier

That will be the the result of inselbildung, or the island effect, where the field from the grid gets to a large enough size to reach the cathode and crate "shadows" on the cathode reducing its effective size, so breaking away from the 3/2 law that normally governs triodes. http://livingi...
by Mike H
Sun Feb 04, 2024 9:36 pm
Forum: Everyones Projects
Topic: 6550 SE Amplifier
Replies: 110
Views: 9421

Re: 6550 SE Amplifier

Paul Barker wrote: Sun Feb 04, 2024 3:56 pm No left, but Ive just realised its pinched up whin it transitions positive. So its a non issue as it wont need to go positive.
Gotcha. :thumbleft:

As you were .....
:D
by Mike H
Sun Feb 04, 2024 9:34 pm
Forum: Assorted Stuff
Topic: The Quackery Thread
Replies: 360
Views: 190362

Re: The Quackery Thread

Sounds like them. Some had like a lightning bolt symbol printed on, I remember. :D
by Mike H
Sun Feb 04, 2024 9:33 pm
Forum: Everyones Projects
Topic: Pass Sony VFET Project
Replies: 21
Views: 3099

Re: Pass Sony VFET Project

Ta muchly. I was curious what the 6-legged thing is, now we know. :D
by Mike H
Sun Feb 04, 2024 2:20 pm
Forum: Assorted Stuff
Topic: The Quackery Thread
Replies: 360
Views: 190362

Re: The Quackery Thread

Anyone remember the conductive straps you could hang from your car? Dangled down behind the rear wheels or something like that. It was a 'thing' quite a few years ago.
by Mike H
Sun Feb 04, 2024 2:15 pm
Forum: Jokes
Topic: A little light humour
Replies: 2698
Views: 1171924

Re: A little light humour

:lol: :thumbleft:







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For your safety.jpg
For your safety.jpg (34.34 KiB) Viewed 4928 times
by Mike H
Sun Feb 04, 2024 2:05 pm
Forum: Everyones Projects
Topic: 6550 SE Amplifier
Replies: 110
Views: 9421

Re: 6550 SE Amplifier

I cant get my head round the way from -5 to 0 the grid line spacing is smaller. So introducing 2nd distortion which wont mitigate the high 2nd distortion of the 6550. Do you mean at the righthand end of the graph? This might be on purpose to reduce gain at large negative grid - ergo, AGC may be app...
by Mike H
Sun Feb 04, 2024 1:49 pm
Forum: Everyones Projects
Topic: Pass Sony VFET Project
Replies: 21
Views: 3099

Re: Pass Sony VFET Project

Any chance of a schematic or is it copyright? Just curious.

Tried a Google but so many confusing variations or things with the same name, apparently! :shock:
by Mike H
Sat Feb 03, 2024 9:27 pm
Forum: Assorted Stuff
Topic: The Quackery Thread
Replies: 360
Views: 190362

Re: The Quackery Thread

Image
by Mike H
Sat Feb 03, 2024 9:25 pm
Forum: Everyones Projects
Topic: 6550 SE Amplifier
Replies: 110
Views: 9421

Re: 6550 SE Amplifier

You might have misunderstood me - it's not the cascode operation aspect that's the possible issue, it's that ECC88 is a radio valve and may want to ocillate at RF. To be honest I've never used it for audio, as I can remember, but I have for radio.

:D
by Mike H
Fri Feb 02, 2024 12:40 am
Forum: Everyones Projects
Topic: 6550 SE Amplifier
Replies: 110
Views: 9421

Re: 6550 SE Amplifier

In case you weren't already aware - "The ECC88 is a VHF double triode with separate cathodes. The ECC88 was designed for service as a cascode amplifier in the front ends of VHF radio receivers. One triode acted as the local oscillator and the other as the mixer (frequency changer)." - (The...
by Mike H
Tue Jan 30, 2024 8:29 pm
Forum: Valves
Topic: Valve amplifier service
Replies: 176
Views: 84442

Re: Valve amplifier service

Well, there you go. (Weren't the words I actually used...)
:lol: