| Re: rectifier valves... [message #30052 is a reply to message #30050] |
Sun, 26 December 2004 16:55   |
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Wayne Parham
Messages: 18792
Registered: January 2001
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Illuminati (33rd Degree) |
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Sweeeeeet. I was just thinkin' about putting together a bill of materials to build at least the amplifier circuit. Looks like we're getting closer to a finished design, so maybe I'll be able to purchase everythnig I need all at at once. I'm pretty pinched for time right now, bu I think I can assemble this preamp fairly quickly and I think it'll be fun. Thanks for your input on this project, and to everyone else participating too!
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| Damper diodes [message #30055 is a reply to message #30054] |
Sun, 26 December 2004 20:27 |
PakProtector
Messages: 935
Registered: May 2009
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Illuminati (2nd Degree) |
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Hey-Hey!!!,
Part of the restriction we are designing to is expense. The filament requirements of a full bridge worth of damper diodes is ~4A of 6.3 at a minimum. For the 6AU4 it is more like 7A. The hybrid bridge using a 6CA4 and two 1N4007-style SS diodes gives vacuum tube performance w/o big expensive filament TX's. The 6CA4 is one tough little valve too. If we look at the size of the filter capacitance the valve can stand working into, it is right up there with a 5U4 and 5AR4/GZ34, these rectifier tubes are all good for a meduim sized stereo amp, let alone a linestage... For a twin diode rectifier tube there are many options at the 2A/6.3 volt limit imposed by selection of the 261G6 Hammond. 6BY5 is an octal dual diode. On the smaller side, 6X5 is an octal version of the 7-pin 6X4. 6BW4 is another, lying about in the middle between 6CA4 and 6X5 capabilities. It is a bit of a challenge to make something small, light and simple after becomming used to very overbuilt and complex-as-desired circuitry.
regards,
Douglas
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| there's lots of choices... [message #30072 is a reply to message #30058] |
Wed, 29 December 2004 18:37 |
PakProtector
Messages: 935
Registered: May 2009
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Illuminati (2nd Degree) |
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given a 2A/6.3V winding, there are a bunch of nice choices. the beefy EZ81/6CA4 is going to require about an amp. The octal 6BY5 is going to take about an amp and six-tenths. 6X4 and 6X5 are going to take less, and also contribute a bit more voltage drop. A 6AX5 will fit, but a 6AX6 won't. The WE412 is another neat little 9-pin, and the 6754 Bendix Hy-G-300 will also give a ~45 second warm up for the rest of the circuit due to its wonderful cermanic heater sleeve. The Bendix is also graced with a heater-cathode voltage rating exceeding its plate rating. I would go with the 6CA4 as a first choice. 6AX5 a close second, tied with the 6BY5, also an octal.
regards,
Douglas
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