What tubes to use

For that kind of power you will find it difficult, if not impossible, to achieve your goals. All kinds of things will be unobtainable at the extreem high power you are talking about..

**output transformers.... for sure ... if you could get them they would weigh several hundred pounds each. **power transformers and power supply ... several amps at 800 - 1200 volts or more ! ! expensive and hard to do. **output tubes... even with push pull- parrallel ( 4 tubes) you will have trouble getting anything close to 1000 watts with audiophile tubes. You would probably have to use really expensive RF power tubes which in all likely-hood will not be power pentodes and will require serious drive power which at your desired power level would be a problem for even "normal" high power audio output tubes.... then, where would you get the high power interstage transformers.

All of these things will be most likely an exercise in futility. My advice to you is to stick with solid state for you desired very high power requirements.... there are several brands of readymade

1000 watt plus (many units can be bridged to increase power) professional solid state amplifiers available that would be hard to beat the price even if you built it yourself. electricitym

The main interest in valves these days is with SET (single ended transformer) designs which are the best for that 'valve sound'. And by nature low powered so need sensitive speakers.

However, all is not lost. Simply use one of those driving a suitable inductive load then feeding a decent high power solid state design. The valve amp will give you all the distortion of the type you crave and the SS one amplify it.

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    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Is this a joke? 1KW from a tube amp? What do you plan on using for output transformers? Hope you have a forklift to move them around and a very large electrical service to power it all. It would eliminate the need for central heating in your house as well.

It used to be done all the time. While in college, I babysat an RCA BTA-50F1 (almost the last of the plate-modulated 50 kilowatt AM transmitters). The modulator delivered a cool 25,000 watts of tolerably clean audio. The transmitter was on the second floor; the entire first floor was the plenum for the blowers.

I suggest you look for a couple of old AM broadcast transmitters, and extract the modulation transformers and audio circuits, for a good starting place.

Then, I suggest that you learn exactly what the performance differences are between tube and solid state amplifiers. Pay special attention to what those output transformers do to the frequency and phase response.

Prepare to rewire your listening room, too, because if you don't, there's no way you're getting a kilowatt -- much less a stereo pair of kilowatts -- of output from a tube amp connected to a normal outlet. With a switchmode solid-state job and special attention to efficiency, maybe.

Isaac

No, not a joke. I have wanted all my life to build a stereo that handles the same power levels as a live concert. I'm now retired and want to finally do it. Back when I was in my 20's I built my rather crude system which consisted of 3 separate amplifiers, each putting out 120Watts RMS, with 4 6L6 tubes in PPP. (The 3rd amp was a "center" or combined channel that drove a bank of woofers). My huge speaker towers that I built with one inch thick plywood, held guitar amp speakers and horns. The power was amazing, but not quite as clean as I wanted it, and that feedback thru the tubes was always a problem. Once, when I was rather messed up (I'll skip the details), I cranked it wide open and blew all the windows out of my apartment (the landlord was NOT pleased). I attribute the window shattering to low end distortion, (in a much too small apartment).

Now, I live on a farm and I want to fill the whole farm with "live-like" sound. I guess you could call it my personal "Woodstock" (ya, I'm showing my age). Actually handling hundred (or more) pound transformers/amps would not be a problem, since I actually DO have tractors and such to move them. but getting the xformers probably is. I have 400AMP service at my panel, so I got enough power too.

However, I will consider using solid state amps if I can achieve the right sound. I would imagine I could get some ready made PA system amps. I used to know a guy that worked for a sound company that did all the sound for major rock concerts. I know for fact that they had the capability to run 10,000 watts total, and in most places used the full amount at outdoor concerts. So, myself wanting to run at least

2000watts total is not too much to ask.

I'm curious why you think this is a joke? I'm asking because there was a time when everything was tube. What did they use back then for large concerts and auditoriums for the main system? Ya, I know that the concerts back in those days were not as large as they have been since the late 60's. I'm curious what they used at Woodstock, since that was more or less the first concert of it's size, and that was during the transition from tube to semi-conductors, and I know that semi-con... power amps back in those days were prone to failure.

There seems to be a lot of historical information about Woodstock and other major concerts back in the 60's and 70's, but finding details such as the type of power amps used to supply the main system just is not documented.

Mark

I'm not real familiar with this. Is there a website with details and possibly schematics or at least detailed drawings? This might be just what I am looking for.

Thanks

Mark

People get so caught up in watts these days, there's a lot more to audio than watts. Large concerts use(d) stacks of amplifiers to achieve the total power, you need a lot of power coupled to high efficiency speakers to fill an auditorium or outdoor area with high volume sound, but in your house? How much space do you have? I have an amp that produces a solid 120W RMS per channel connected to a pair of moderate efficiency speakers and it's capable of far higher volume than I would ever wish to listen to. You can get speakers that will produce enough sound to damage your hearing at 50W, or you can get them that will require 500W to produce the same volume, look at those first.

100W is very large for a tube amp, 1KW is outlandish. If you still wish to proceed, you're asking the wrong group.

No, they haven't. A crappy tube system sounds as bad as a crappy solid state system.

I suggest that you first go to a transformer manufacturer and get quotes on the output trans.

A better idea is to build an amp. for each speaker.

Bill K7NOM

Utter nonsense. First off you're got that sodding great lump of steel in the output transfomer which corrupts everything.

Lateral Mosfets are the best by far.

Graham

You mean the ones with the highest distortion !

Graham

Yes. You can get SR (sound re-inforcement as it tends to be called these days rather than PA) amps with power rating up to about 10kW in a single unit these days.

They aren't designed to be ultra-hi-fi though. Their specs are good but the main criteria for SR use is power and light weight.

You can however get very good studio monitor type amps of the 1kW / channel rating.

Graham

Worse usually in fact.

Graham

That and poor damping factor.

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*A backward poet writes inverse.*

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

That give that 'better' sound - LOL !

Graham

Dear Mark,

This topic comes up every so often. Today the cost is so prohibitive. Can you spend $20.00 per watt for parts? If not, better try solid state. Tubes are simply not available on demand and you will pay market price for what you can find. Assuming you can spend the money, take a serious look at the OTL designs of Futterman. They scale well and do not require an output transformer. Consider wiring your speakers in series or use custom voice coils so the load is 16 ohms or more. Eliminate all passive crossovers. Consider multiple amplifiers per frequency range. Reconsider the choice of speakers. Set an SPL goal-not a watts goal and work backwards.

VTL labs made a 500 watt tube amp based on 6550s. The Mac MC3500 did

500 watts midband on 6LF6s. You could strap 2 for a 1000 watt single channel.

On the solid state front, a strapped Bryston 4b sounds fine. BGW has several offerings. Often, using solid state below 1khz and tube above is a better answer. There are real issues with power handling at high frequencies. Few drivers can take the power. Still fewer are worth listening to. If you use multiple drivers, just use multiple amps. There are real issues associated with the design of wideband, high power output transformers. I want to build a tube power amp for my stereo. Tubes have always had

The reason to use valves is to get that valve 'sound'. Eliminating some of the causes of the distortions so beloved of valve enthusiasts defeats the purpose.

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    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in news: snipped-for-privacy@davenoise.co.uk:

Once you have a good amp, without distortion, it is relatively easy to modify the signal at a low level, to produce any kind of distortion you might want.

Analogue to Digital(A-D) --> computer --> D-A --> AMP would allow you to produce a signal with almost any imaginable and certainly any 'real amp' characteristics that one might desire.

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You'd need to package it inside some large heavy box that glowed in the dark, though. Don't underestimate the power of the eyes over the ears.

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    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.