• 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.

heavy duty valve amps.... for PA use....?

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Valve power amp, rackmountable, 2- channel, approx 500-800wpc

Do such units exist? and where can you get em. (ive searched all over the web)

the closest ones i can find are the marshall ones, 100wpc, 200 bridged, not sure thats enough for my uses.

Can anyone point me in the right direction? regards jc808
 
1900w? ouch :)

the reason i was thinking about such a powerful option was i was thinking about doing a few parties, and wanted something powerful, with a little 'headroom' to avoid clipping (which is not such an issue with valve amps, but...)

a custom-made 833a system would be roughly how impactive on the wallet?
and fairly large, one would presume..?

youd also need a three-phase inlet with a 3000v draw, surely :-s

cheers for all the answers so far guys (and gals?), youve been a great help :)

fyi the size of room i would be playing in would be no larger than 50ftx 40ft, max
 
On eBay about a year ago there was a pair of massive PPP KT88 amps with about 16 KT88 per channel... They were used by some Sound System for jungle/rave parties in London apparently!

They looked pretty tired, but who knows? I remember they had massive transformers and the ad stated that the tubes glowed in time with the music... glowing plates perhaps?
 
1900w? ouch

The largest tube-amp I have seen so far was a 3 kW one (mono only). It wasn't rack mountable - it was consisting of a whole rack! :xeye:

When you talk about PA, I assume it is for FOH and not for a single instrument, is it ?
A large tube amp for that purpose was the Dynacord "Gigant" (German for giant) with 200 Watts. Maybe they can be obtained 2nd hand. But you will need two of them since they are also monaural.

Regards

Charles
 
jc808 said:
1900w? ouch :)

a custom-made 833a system would be roughly how impactive on the wallet?
and fairly large, one would presume..?

I guess it would be very expensive. The circuit can be very simple (look at some of the old WE or Altec amps - a couple of transformers and four tubes). But all parts made for high voltages are very expensive and hard to get. I don't think anybody makes output transformers with 3000V isolation. A 1000-1200V amp. would probably be possible, but still very expensive. But I wouldn't make an amp like that - it's bloody dangerous!

You would need a lot of expertise to take on a project like that...

I would think you should look for a more sane/normal amp - perhaps 100-150W. And if that's not loud enough it's probably because your speakers are too ineffective.

Best regards,

Mikkel C. Simonsen
 
You could probably use a pair of 833 tubes and operate them at a reduced plate voltage of 1,000 to 1,200 volts.
As for an output transformer, you would need to use a power transformer. The center tapped high voltage windings would act as the primary and the 240 volt winding (the original primary) would become the secondary.
I've seen this done. The amplifier wasn't the best I've heard but it did produce a massive amount of power and sounded "good".
 
Scrap the idea of using tube amps for your sound reinforcement and stick to SS amps. You can easily pick up used Altec Lansing 9444's or EV 2600's on Ebay for peanuts. These will run 300watts per channel into a 4ohm load, 200watts into an 8ohm load, or bridge to a comfortable 600watts.
They can also be converted to voltages other than U.S. in minutes.

These would be overkill for your sized room.

J
 
Granted I am still shaking from having to use the SS word. However, there is something that should be said in terms of practicality,cost, availability and so on. In this application tubes aren't the way to go. I suggest saving those precious tubes for the gentleness of the livingroom system along with a good bottle of wine and a fine woman.

J
 
Big tube amp

Hello all,

I'm a bassplayer, and I've got an Trace Elliott 350Watt tube power amp. It's got 6x 6550 GE tubes in it. I have also seen versions of this amp with 8x 6550 pumping out about 400Watts. Maybe you can try to find these amps, although perhaps it is tough because I don't think very many were made. It is essentially aimed at bass players, but, as bass guitar is a rather "hifi" instrument, will do for PA use as well.

Regards,

Jarno.
 

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thanks for all your help, guys, it is really appreciated.

owing to the fact that valve amps sound 'louder' than ss amps at the same rated watt output, and overdrive in a more pleasant fashion, i think two bridged 100+100W (200W) amps from Marshall would do the trick. Anyone had any experience with these amps?
 
For a decent approximation of your power requirement, a valve amp is going to eat a large hole in your fund sack. You will be an order of magnitude better off, both price and performance, if you get high efficiency loudspeakers, and moderate size valve amps to bi or tri-amplify. Tri-amped with 60 watts per, will set you back for six amps and crossovers.

Remember that a 3 dB increase in the 1W-1m spl is equivalent to doubling the amp power at the lower sensitivity. From 1kW with 92 dB 1W-1m, you get 500 watts with 93dB, 250 watts for 98 dB, and 125 for the easilly atainable 101 dB sensitivity. 62.5 for 104 dB....get the picture yet?

Careful arrangement fo the speaker aray can further increase the efficiency, and that is just the beginning. Get good speakers, and seperate amps for each frequency band and you will have no need for high power exotics.
regards,
Douglas
 
At the risk of making a rather lethally high-current suggestion:

Use the topology of the Son of Zen from the Pass Labs forum..

Replace the gain resistor (1 ohm horizontal one) with the load, then switch the semiconductors for 20 paralelled 6C33C-B tubes for 1 ohm output impedance, more if you want less output impedance. Remove the top resistors, unless you want to do something with anode feedback (at great expense in efficiency), and lastly exchange the low resistors for constant current sources, or at least a current mirror.

Add a BZLS with valves (e.g. 6N1P or 6N30P) to drive it.

Operate the valves at up to 90% of their rated dissipation if you want.

This should give you about 1200W peak.

The 6C33C-B's can idle at as much as half an ampere, as long as you stay within their dissipation limit.

In case it was not obvious from the description, this is an output transformerless solution.

HTH.
 
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