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In Reply to: RE: Maxing Out my 2A3 amp's Power Transformer posted by Al Noakes on November 26, 2014 at 06:37:18
Hiah Al,
Lets do it one by one :
What gauge is the wire inside the fuse ?
A: Very small.
All of Jeff's most recent personally-built DIY amps use TWO AC switches, The second AC switch is a fuse and / or thermistor "bypass" or short-out switch, so I don't need to have them in the circuit when I am in the room with my amps, and I am doing serious listening.
What gauge is the wire inside the fuse ?
A: See above.
What gauge of wire is used inside the transformer ?
A: Lowest gauge possible.
Its an large core 18 pound device. It sports an under 9 Ohm "ultra hi fi DCR " high voltage winding secondary, from either end of the winding to the center tap. The 125 VAC primary, the entire winding, is "about" half of one Ohm. The wire I use is 950 mA. continuous capable, what is yours ??
What gauge is the wire inside your tubes ? What difference does a tiny fraction of an ohm make ?
A. The tube design is fixed, we work with it as thoughtfully as we can.
ps Why didn't you use black wire ?
A: With the new wire, having a low AWG rating, high silver content, and wide bandwidth, its likely good enough performance wise to use black insulation colors, and be better than anything else " I " have used previously.
Now you know what I am doing. What are you up to in the UK these days? Have a great day.
Jeff Medwin
Follow Ups:
I can understand bypassing the thermistor . I use a delay timer to bypass the thermistor in my hybrid amp . A simple test is to measure the AC across these things under load usually shows slight volt-drop . The rest of what you are doing seems pointless . The fuse bypass is downright dangerous !!!! I have plenty of huge transformers and chokes that will probably put what you have used to shame (ever seen a 3H 1A choke ?) but I rarely use the large items apart from in breadboards . I currently run 100VA 300V 45 ohm transformers for HT with 2A3 monos which are more than adequate and run cool in operation . Wire I use is 1/0.6 for small signal (23AWG) , 19/0.2 for HT and heaters (20AWG) , 19/0.25 (18AWG) for filaments/mains wiring and 19/0.3 (16AWG) for the output transformer secondary (all silver plated copper/PTFE) . I hold stocks of silver plated copper/PTFE all the way down from 26AWG (1/0.1) to 10AWG (37/0.4) but don't feel the need to use anything this thick inside a valve amp
Al
Hi Al,Nice post and explanation. Use what you want. I am not here to dictate what you must use !! I have A-Bed almost all of what I write about, so I have tried all I discuss. I am most happy using wire, similar to yours, but lower in AWG. YMMV, fine !! One size does not fit all.
Regarding chokes, a large size and weight I do not seek. Recall, I want low stored energy, so my choke of choice will weigh 2 pounds or less, easy to fit below deck, and I prefer 10 Ohms or less DCR.
As long as we are HAPPY in our hobby, that is what counts in the end to my way of thinking. Hi to Andy. Cheers.
Jeff Medwin
Edits: 11/26/14 11/26/14
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