Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: hesamadman on July 18, 2013, 06:40:04 am
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First, thank you everyone who have been helping me through my post after post of questions.
Ok, so I have my black and orange wires here. 2 need to go to pilot light and then 2 to preamp tubes and 9,5,4 of preamp tubes. The schematic just says, to all X filaments and the tube sockets are just marked with an X. But what im unsure of is which wire do i send to these locations. Black or orange. Do I put half the locations on black and the other half on orange? :(
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That is actually a very reasonable and important question (not "dumb" at all).
There is a wealth of great information in the Hoffman Library of Information including an excellent diagram on heater wire hook up. Just scroll down to "heater hookup".
http://www.el34world.com/charts/CommonHookups.htm (http://www.el34world.com/charts/CommonHookups.htm)
With respect, Tubenit
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That is actually a very reasonable and important question (not "dumb" at all).
There is a wealth of great information in the Hoffman Library of Information including an excellent diagram on heater wire hook up. Just scroll down to "heater hookup".
http://www.el34world.com/charts/CommonHookups.htm (http://www.el34world.com/charts/CommonHookups.htm)
With respect, Tubenit
thank you so much
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In truth, a large amount of this is "lore" and tradition. Many British amps have the heater wires run simply in parallel, untwisted, though close to the chassis. When building amps we really just want to place all the odds on our side. Fenders, of course, have the traditional "up in the air" twisted pair; yet with no regard to the phasing of the wires. I say "no regard" because both wires are green...and if you think that in Fullerton, CA, Consuela holding 100 feet of doubled-over green pushback wire while Fernando held the other end in the drill chuck in Leo's shop...they took care to produce coherent phasing all down the heater line....I think you'd be wrong. There are four components to trying to reduce heater-induced hum. 1: Center tap, real or synthetic. 2: Close to chassis, 3: twisted pair, and 4: phasing. If you do all four, you've done pretty much all you can (short of creating a DC heater supply) to reduce hum. The center tap is for the most part, mandatory. The choice of "up in the air" is, IMHO, more related to whether you solder the heater wires BEFORE everything else or AFTER everything else. My suspicion is that Fender wired up the heaters AFTER everything else, but I have no way of knowing that for a fact. If BEFORE, and you use different colors, then you can do 2: close to chassis 3: twist 4: phase; all at almost no extra effort. Experience has shown that the more of these you got going, the better. And that's about all there is to it. You want to use sufficient gauge wire to a pile of power tubes. It's just a "best practice" thing. Do it right, or as right as you can, and then you can pretty much stop thinking about it.
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also, speaking of heaters, there is the practice of elevating the center tap (real or artificial) to the power tube cathode(s). I do this on all cathode biased amps that I build or resuscitate.
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> less current
More voltage.
Is your hum from current or voltage?
Both.
I think in average guitar-amp work, the voltage is more of a problem.
Also note that AC heaters were lower voltage, often 2.5V, in the old days, and probably to conserve hum. The notion of using 6V happened only in the Car Radio fad.
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That is actually a very reasonable and important question (not "dumb" at all).
There is a wealth of great information in the Hoffman Library of Information including an excellent diagram on heater wire hook up. Just scroll down to "heater hookup".
http://www.el34world.com/charts/CommonHookups.htm (http://www.el34world.com/charts/CommonHookups.htm)
With respect, Tubenit
thank you so much
Ok this all makes so much sense now. The leads are actually 3.15 volts. Which is why one lead goes to pin 4 and 5 of the preamp tube and the second lead goes to the center tap heater filament of the tube. The 2 legs of 3.15 giving you 6.3
:icon_biggrin: