• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Anyone know of some ridiculously powerful triodes for class A useage?

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kenpeter

Member
Joined 2007
And soft, but slightly unequal clipping the other...

What musical information is contained in a flat line? None.
At the very rails. Thats what you got.

Try not to crush a signal so hard against either rail the
finer details are completely lost.

And an amp with a 2nd order harmonic offset from GND
(equal areas under the curves) will clip far more on the
skinny peak than the wider one. And spend less time in
flatland, where all information is lost.

The error will be more Harmonic of the root, Less IMD
with the other frequencies.
 
Jeb-D.

Jeb-D.

Member
Joined 2005
diyaudio.com/forums/swap-meet/157276-garage-sale.html#post2023179
I DO want even order harmonics present and some mentioned they can still be reproduced A/B but I thought even orders got cancelled out by the split driver phasing
Click to expand...

If the signal contains even-harmonics before it was split, it will contain them when joined back together. So use a single ended input stage if you desire even order distortion.
 
Tubelab_com

Tubelab_com

Member
Joined 2005
tubelab.com
All harmonics, even or odd are musically related to the root.
Click to expand...

The 5th harmonic is dissonant and sounds particularly nasty. It takes a small amount of 5H to be noticible. The 2nd is an octave above the fundamental and adds "warmth".

Assume the fundamental is a pure tone at the "A" above middle "C". This is known as A4 and is 440 Hz. The 2nd harmonic is 880 Hz which is also an "A" (A5). The 3rd harmonic is 1320 Hz, close enough to 1318 which is an "E" (E6). These 3 notes when played together form a plesant sounding "chord". The 4th harmonic is again an "A" which will not destroy the harmony. The 5th harmonic is 2200 Hz which is not close to any note in the scale, and sounds bad when added to the mix. The 6th harmonic is again close to an "E". The 7th is again not close to any note in the scale. The 8th is again an "A". The 9th is 3960Hz which is reasonable close to B7 at 3951 Hz, which is a note in the scale, however B and A together with E do not form a major chord.

From this exercise it can be concluded that the 5th and 7th harmonics are to be minimized, and the "evens" can be tolerated, and even used to add "warmth" to the sound. This is the major forms of harmonic distortion. ALL IMD is dissonant and should be avoided.

The even harmonics in the output stage do theoretically cancel if the tubes, bias currents, and output transformer are perfectly balanced. This is rarely the case. The even harmonics generated in prior stages are amplified anong with the signal in the output stage. So a push pull amplifier will have some second harmonic content. This can be increased by purposely upsetting the AC balance.

At any rate a high powered tube amplifier is not a project for an inexperienced builder. There are just too many things that can, and will go wrong. Aside from the safety issues related to some seriously lethal amounts of electricity, the probability of success is low and the build costs are high. Spending big bucks on parts and watching things fry on initial power up is a sure fire way to ruin your enthusiasm for the hobby. Trust me, I know. I have blown up a whole bunch of parts over the years. I now know to use cheap parts and get the concept working on a small scale first, then build a bigger version. It might soung like more work, but it isn't in the long run.
 
rdf

rdf

Member
Joined 2004
Look through the Eimac stuff for metal triodes used in AM modulators. 3CX1000 family might be a good start. In you application loud cooling fans won't be an issue. Consider some of the smaller metal tubes like the 100 for a driver, many metal industrial tubes are available for voltage gain stages. I believe tungsten filaments grow brittle with use so carry spares. Broadcast will keep these tubes in production for a while still. Good luck and don't let anyone put beers on this one.
 
D

DrewP

Member
Joined 2002
Anyone ever used V20 Micropups with forced air cooling for audio yet?

Tiny little thing with a finned copper anode, a grid connection at the topcap and two pigtails for the DH cathode.

The WW2 radar station we have at work uses V20's as the output tube with 833's as the drivers...
 
Richard Ellis

Richard Ellis

Member
Joined 2006
An approximate 500 Watts SE?? Yeah right! I have heard of transmitting tubes for multiple Megawatt radio stations that resemble large circular fishtanks (6ft diameter?). Never seen a photo of such things so..
What of the power requirements in the field? Will he be lugging around a hundred foot three phase 440V powerline to these gigs??
And a forklift to transport the whole thing. The cost creating this monstrosity will get you a nice house.....Completely a non starter...even for the most highly experienced builder.
_____________________________________Rick..........
 
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