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In Reply to: Re: BATTERY for filament heating posted by dave slagle on October 26, 2001 at 13:57:35:
yes "dumb" but I am doing it, each valve is adjusted accordingly in my amp, that is to say the bias controlled through the driver is altered to get a satisfactory average for each tube the only thing you can't alter unless you monoblock is the B+ to each channel, but working with the bias alone you can get both tubes even.Now I have Anrej's 6a5g's in place though I'm going to try ac heating and this will no longer be a problem. Though I love the sound of lead acid batteries they are an inconvenience. It's all that charging and disconnecting from charger for playing beloney that wears you down in the end, and the fact that only the electrically competent can use the amp. In a house where the 4 year old son has to show the 43 year old mother how to get sound out of the video this is an issue.
Regards
I'll keep chipping away for "dumb" ideas!
Paul Barker
Follow Ups:
well we have to remember at some point not to long ago a group of folks shunned SET's as dumb for PP pentodes... then those PP pentodes got dumped into the dumb category for solid state...its funny how the whole "dumb" concept is brought to life by engineers, and then the marketing division gets ahold of it and they get their cut and the only people who suffer are those convinced by someone else that everything they spent on their sysrem was right.
some fool once said... two wrongs do not a right make... well i have more than two wrongs and guess what... i think my sound is pretty right...
someday those marketers will realize that three lefts actualy make a right, and that means they can sell 3X the stuff... which will of course require 3X the engineers and everyone will be happy.
oh yeah... i don't care how far apart my tubes are operating... as long as they are not totally screwing up and the sound is good... why worry...
on the 6A5G... i would love to see the whole story on that tube... i have heard autopsy reports that many are just plain old DHT's and the books are wrong... who knows maybe the relabel of the 6B4 was just a marketing ploy to keep the tube base diagram drawers happy :-)
dave
Well Dave,they have the V shaped filament (ok I should call it heater but like I say looks and glows same amount as PX4 V filaments). The cathode is connected at the midpoint and they sound pretty good!!! Whether that cathode connection makes them the same characteristics as a dht but with an equal tap I don't know.
I haven't heard any other idht output valves except the 6EM7 power stage. The 6EM7 is far more clinical, and gets distorted at high output, as a look at the curves would tell (know you don't bother much about curves but they do guide and in practice yes though I prefer 6EM7 to multi grids hooked up as triodes it ain't a dht.) I would like to get hold of some R120's they would be an inetersting listen compared to the 2a3 type and these 6a5g's.
Regards
Paul
when you say the cathode is connected in the center of the VV it is just a CT DHT filament with the CT labeled cathode... the tube is still directly heated, it just has a cathode tap...or thats how i see it.. the tube drawing shows the filament CT connected to a cathode, but i have yet to see the cathode element in any of the tubes... has anyone else???for it to be an IDT like most people call it it would need a cathode sleeve... i suspect you could ignore the cathode connection altogether and wire it with a traditional hum-balance or DC and the tube would function the same... but given that the CT is there you would be foolish not to use it!
dave
That makes sense to me, as I said it sure looks like a filament. I see the centre tap as a gain, though an inconvenienceas it means it's not a plug in replacement for 6B4G. Having said that not a problem to guys like us, I very much like the sound of these so I'll use them until destruction.
RegardsPaul Barker
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