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Old 10th October 2003, 03:09 AM   #1
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Default help me out if you can

Sooooo......Here I am third year in EET at a Purdue University Campus. Wanna get into actually building things that have a use..........tube amps would be nice.......sold state would be OK......Who's got some tips? Or maybe some books I should buy.......It seems they don't teach tubes these days......something about them being old tech? Anything would be helpful......I have been told they work somewaht like mosfets by a prof or two.....any truth to that??
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Old 10th October 2003, 09:08 AM   #2
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Tube Stuff

Hardcopy;

*Radiotron Designers Handbook 4th Ed
F. Langford Smith

*MIT Radiation Labs Series, Vol 18 Vacuum Tube Amplifiers, edited by Valley and Wallman

Vacuum Tube Amplifiers; Morgan Jones (I think edition 6 is the latest)

Online:
www.tubecad.com especially the latest article, Grounded Cathode Amplifiers, but also check out the other articles. John Broskie knows his stuff and tackles it all from a technical point of view, but also listens.

http://w3.mit.edu/cheever/www/cheever_thesis.pdf

http://www.aikenamps.com/TechInfo_2.htm

http://www.aloha-audio.com/library/index.html
Lots of articlulate and informative articles on tube amps, esp the third, fourth, fifth, sixth and eigth. Read the rest too.

*These you might be able to find in a Uni with a good engineering library and they show up on ebay and at hamfests regularly
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Old 10th October 2003, 01:02 PM   #3
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http://w1.859.telia.com/~u85920178/begin/tube0.htm

theres some pretty basic info there, showing common types of application, and how various tubes function. missing some things i guess, but a good starting point.

a triode is kind of like a MOSFET in some ways.. i dont know too much about FETs though, so my explaining might be wrong though.. depletion mode.

Gate - Grid
source - cathode
drain - anode

it depends on a tube's characteristics, but typically it works like this.

with a negative bias on the gate, some drain-source current flows (the amount depends on how negative the gate is. if the gate is very negative, you can effectively cut-off all D-S current.)

when the gate is held negative, no gate - source current flows (well some, but it is negligible.. in the microampres range.. depending on tube again)

now, if the gate goes positive, D-S current increases moreso (the higher voltage the gate is held at the more current) - but now there is also gate - source current.. which is usually a bad thing in signal stages.. it can be acceptable with some power tubes though, they have tougher grids designed to dissipate some heat..


hopefully i made sense of that.

oh yeah - theres no P-channel tubes
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Old 10th October 2003, 02:29 PM   #4
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Tubes are definately "old tech" but they are extremely hard to beat for audio. For $500 you can build a tube amp as good if not better than a $2500 SS amp. Depending on which one you build you may have to buy or build a pair of high efficiency speakers though. I can recommend a pair of full rangers using Fostex drivers as a good place to start. Let me know.

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Old 14th October 2003, 06:27 AM   #5
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Default muchas gracias

Thanx for the helpful info guys......learning more reading this stuff than 2 yrs in EET it seems. Later
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