crazy ideas for a tube amp with many watts!

[ELS122]

so I read about the fender 400ps and how it outputs a decent 435w RMS, so I then wanted to know. how much power can I get out of a tube amp before it starts to get really stupid, and yes I know 8 power tubes probably are stupid already,
anyway, I heard Carlson talk about power tubes oscillating when there are many of them connected together in his "six-pack repair" video and how some amps put resistors in series with the plates to fix that.
would this be a problem with 8 6550A tubes? and how would I fix that? I tried to find something about this on google but didn't find anything.
also, are there more powerful audio output pentodes?
also, I find many really cheap power and modulator tubes that have a plate dissipation of several hundred or even thousand watts, are there any that type of tube that can be used in an audio circuit or is that a dumb idea?
also, I know I will have to get some custom output transformer that can withstand all that current.

[woodchips]

Try valves like the 6080, lots around as used in Tek etc scope PSUs. Run them as cathode followers, at your power levels probably won't need an output transformer? A variac can make a good output transformer, adjustable too.

[ELS122]

at your power levels probably won't need an output transformer? A variac can make a good output transformer, adjustable too.

that made me laugh but I guess it's true, you can use a variac probably.
but could I use any modulator tube or are they just not at all suitable for audio?

on second thought... I don't see how you could use a variac for this, only if you wind another coil on top of that one maybe but I mean you couldn't use it cause it only has one winding.

[T3sl4co1l]

They made tubes up to 1.5 MW, watts are not a problem.  Now, if you expect it to be compatible with a 120V 15A circuit, or 240V 7A circuit, don't expect more than about 800W real output (even for a solid state linear amp), more likely 400 or thereabouts (or about double that from a 240V 13 or 15A circuit, etc.).  Probably the Fender example is such a case.

What tubes to use?  Doesn't much matter.  6L6s and the like (more or less including the families up to KT88s and such) are preferred for audio to begin with, and are cheap (relatively speaking) and plentiful in current production.  6080/6AS7 is hard to drive, more expensive(?), has lower plate dissipation, shorter load line (triodes have less power output than tetrodes), and consumes far more heater power.  Sweep tubes are generally expensive, and offer high plate efficiency but only modest overall efficiency (again, heater power).

Sweeps are generally quite powerful, especially when driven hard, as befits their original application.  One could construct a class D tube amp, doing probably over 800W (from a 1800 VA circuit), with just a quad of, say, 6LF6 or 6LV6 or EL519 (or any of their series-heater brethren).  The power density easily offsets the cost of obtaining these tubes.  One might (rightfully?) question whether such an amp would be worthwhile, i.e. create "That Tube Sound", in the presence of so much distortion (PWM modulation is essentially "100%" distorting a signal plus carrier).  Note, you still need an output transformer rated for the full signal bandwidth -- you don't get to save any transformer size with just PWM alone, not without a lot of extra work (see Dave Berning's DC transformer / chop-amp designs for example).

Tube cost isn't a huge motivation, anyway; it is a maintenance cost, but the rest of the amp will easily cost upwards of $1000 to build or buy, too.  The capital/operating cost tradeoff is a worthwhile concern here.  One could go with NOS industrial or PQ types, derated modestly, to obtain a likely 10khr+ lifetime, versus cheap Chinese 6L6s that will wheeze out in a tenth of that time.  Derating requires considering this in the design -- you might only need 8 x 6L6s if you're beating the shit out of them, but 10 or 12 might be needed to give adequate derating.

Protection circuitry is a good idea regardless, as that beefy output transformer won't be something you want to melt from an errant sparking tube.  Adequate fusing and/or supply limiting, and maybe bias servo control, are simple enough precautions.

The power transformer doesn't need to be expensive, fortunately.  A switching supply is very reasonable at this power level; of course, making one that operates safely and reliably without belching out EMI, may be best left to the professionals...

Tim

[unitedatoms]

Tubes have limits, but one can go full forward with transformers using magnetic amplifiers. They are used in electrical locomotion, transoceanic transmitters, and WW2 cruise missiles. Also used to amplify music in most artful form, where just pure copper and iron do the work.

http://www.auditorium-23.de/MagAmp/MagAmp.pdf



I'd replace diodes with mechanical synchronous rectifiers and input tubes with smaller magnetic amplifier. Thus making multikilowatt amplifier with only copper and iron and nothing else.

Edit: Also for speakers at bass, the highest acoustic power density can be reached by using rotating fans. Imagine steampunk civilization without vacuum or semiconductors or chemistry. Only metallurgy, magnets and silk fabric as dielectric. With only pure Electrical Engineers (zero electronics) the life and entertainment is still possible.

[ELS122]

Ok well all of this is really involved for me.
I found a tread about using a lot of tubes together in an amp and one guy commented that it’s just easier to use triodes cause of many reasons, I just can’t seem to find that tread anymore.
Anyway, certain big (in power) Russian tubes are REALLY cheap, like I found Gi-70bT triode for 8eur. And it looks like it could deliver some serius power.
Anyway, I quite like the idea of using 6080 tubes as cathode followers. Might try that since it wouldn’t dim the lights in the whole city.
Anyway, would there be any problems using those tubes in pushpull amp as cathode followers?

[unitedatoms]

the Gi7bt datasheet says it is only 30W continuous output power. Or 11kW for 10useconds with 9kV at anode. So for musical performance longer than 10useconds at 1000W there should be 33 tubes involved, with forced air and 1.2kV anode at 150mA each. So 6kW of quiescent power.

Considering power requirement at DC, the AC side should accommodate ripple current, so transformer is 10kW. I think this is a transformer size which is larger than common distribution transformer immersed in oil and placed on telegraph poles. It possibly will require small concrete foundation when placed stationary and will require building permit and fence and lock.

 

[David Hess]

so I read about the fender 400ps and how it outputs a decent 435w RMS, so I then wanted to know. how much power can I get out of a tube amp before it starts to get really stupid, and yes I know 8 power tubes probably are stupid already,

Power costs money, how much do you want?  It also costs a lot of weight and volume.

anyway, I heard Carlson talk about power tubes oscillating when there are many of them connected together in his "six-pack repair" video and how some amps put resistors in series with the plates to fix that.
would this be a problem with 8 6550A tubes? and how would I fix that? I tried to find something about this on google but didn't find anything.

The same thing can happen with transistors.  Each tube plate sees the other plates as loads and the plate loads include reactive components.  The parasitic elements from the physical construction do not help.

Dampening the reactive components can be done by adding series or parallel resistance.  Notice that a tube amplifier can sometimes oscillate, perhaps destructively, if no loudspeaker load is connected.  Adding series resistances to the grids could also suppress oscillation and is commonly done with tetrodes to suppress snivets where their operating point creates a negative resistance, aka tetrode kink, which is prone to oscillation.

[Moshly]

You should sub to 'ElPaso TubeAmps'

[Alex Eisenhut]

[ELS122]

Power costs money, how much do you want?  It also costs a lot of weight and volume.

well, I wanted to see how much power can you stuff in a tube amp before it gets really unreasonable. not really to put it into practice, although some of the things I learned could be really useful in an amp with reasonable output.

Considering power requirement at DC, the AC side should accommodate ripple current, so transformer is 10kW. I think this is a transformer size which is larger than common distribution transformer immersed in oil and placed on telegraph poles. It possibly will require small concrete foundation when placed stationary and will require building permit and fence and lock.

I'll just build another power station to run it.

[unitedatoms]

I think the densiest power wise tube is 6C33C with very low anode voltage and 60W continuous power.
Some amplifiers run it without output transformer. It can be more expensive, but less dangerous voltage wise.


6C33C is may be even worthy to use in AC motor drives

[T3sl4co1l]

There are forced air ceramic tubes doing 5kW in the same size as a 6S33S* and water cooled tubes doing >10x more than that...

*Give or take how you like to transliterate; it's a Cyrillic 'C' which looks like a Latin 'C' but is actually 'S'.  I see people writing things either way, so, just to make light of that.

Tim

[floobydust]

One big problem when you increase power by increasing voltage, is the output transformer's windings need very high voltage insulation. With 6550's it's maybe 1,200V but once you need say 5kV then the windings get too fat. Costs for everything go up.
So the usual approach is to instead increase current by paralleling tubes, instead of using a big high voltage, high impedance tube.
Hammond 1650W goes up to 280W ($330 28lbs) by going low impedance 1,900 ohms as if for 6-8 parallel tubes, like the Ampeg SVT approach.
Another advantage staying with paralleling smaller tubes is the grid drive voltage does not need to be so large. Generating a clean 50Vpp signal for grid drive and 6550's is not that difficult but Eimac 4-400A is around 200V drive.

The last thing to look at is speakers - if you have say a 1kW amplifier, then it gets complicated because loudspeakers don't really operate at this power level. Your typical 15" speaker maybe 500W tops. You remember what happens to Marty in Back to the Future at volume past 11...

[Yansi]

Whats the point of having a guitar amplifier larger than 50W?  Whats the purpose? Making the FOH/sound engineers pissed & angry?

I have never understood this. It is the job of the sound crew to make things loud.

[ELS122]

Whats the point of having a guitar amplifier larger than 50W?  Whats the purpose? Making the FOH/sound engineers pissed & angry?

I have never understood this. It is the job of the sound crew to make things loud.

well, there are many uses for high power amps, maybe if you are playing in a small place 50w most likely will be enough, but if you play in some big place you either need to mic up your amp which changes the tone (which might be either good or bad), you can get more amps or you can get a more powerful amp.
saying why does anyone need more than 50w is like saying why does anyone need more than a few 60w light bulbs to light up a place.
also, there will always be someone who needs more power.

also, I now found out that there were really powerful tube amps made. I don't know why I thought there weren't 
so I'll just try to find some really powerful tube amp for sale somewhere rather than try to build one myself. also, all the parts I couldn't easily get like the transformers would also make it more expensive than sourcing an old tube amp probably.

[langwadt]

Whats the point of having a guitar amplifier larger than 50W?  Whats the purpose? Making the FOH/sound engineers pissed & angry?

I have never understood this. It is the job of the sound crew to make things loud.

well, there are many uses for high power amps, maybe if you are playing in a small place 50w most likely will be enough, but if you play in some big place you either need to mic up your amp which changes the tone (which might be either good or bad),

it's not the 1950's, being loud on stage just makes it harder to get good sound

[unitedatoms]

Whats the point of having a guitar amplifier larger than 50W?  Whats the purpose? Making the FOH/sound engineers pissed & angry?

I have never understood this. It is the job of the sound crew to make things loud.

well, there are many uses for high power amps, maybe if you are playing in a small place 50w most likely will be enough, but if you play in some big place you either need to mic up your amp which changes the tone (which might be either good or bad),

it's not the 1950's, being loud on stage just makes it harder to get good sound

You need to get louder, or else the audience will not hear you. Everyone in audience has a hearing damage loss from music being too loud, so you need to go louder.

[langwadt]

Whats the point of having a guitar amplifier larger than 50W?  Whats the purpose? Making the FOH/sound engineers pissed & angry?

I have never understood this. It is the job of the sound crew to make things loud.

well, there are many uses for high power amps, maybe if you are playing in a small place 50w most likely will be enough, but if you play in some big place you either need to mic up your amp which changes the tone (which might be either good or bad),

it's not the 1950's, being loud on stage just makes it harder to get good sound

You need to get louder, or else the audience will not hear you. Everyone in audience has a hearing damage loss from music being too loud, so you need to go louder.

that's what FOH is for, and around here all the live venues have voluntarily agreed to a max 103dBa 15 minutes at the mixer

[woodchips]

The point about using cathode followers is that the signal is ground referenced. With a normal type amplifier the output is at the anode, and as has been mentioned is hundreds of volts up. So an isolating transformer is needed.

The Variac is ground referenced, just adjust the tapping point to get the speaker impedance you want. I have seen 25V 6A Variacs, and at very high outputs a 110V one might do.

Another possibility is the E12. All these valves designed as series voltage regulators have low anode cathode voltage, but lots of current.

Experiment!

[ELS122]

Whats the point of having a guitar amplifier larger than 50W?  Whats the purpose? Making the FOH/sound engineers pissed & angry?

I have never understood this. It is the job of the sound crew to make things loud.

well, there are many uses for high power amps, maybe if you are playing in a small place 50w most likely will be enough, but if you play in some big place you either need to mic up your amp which changes the tone (which might be either good or bad),

it's not the 1950's, being loud on stage just makes it harder to get good sounding

Well it’s probably only me but I can’t stand being silent.
And yes, I kinda live in the past.

[ELS122]

Whats the point of having a guitar amplifier larger than 50W?  Whats the purpose? Making the FOH/sound engineers pissed & angry?

I have never understood this. It is the job of the sound crew to make things loud.

well, there are many uses for high power amps, maybe if you are playing in a small place 50w most likely will be enough, but if you play in some big place you either need to mic up your amp which changes the tone (which might be either good or bad),

it's not the 1950's, being loud on stage just makes it harder to get good sound

You need to get louder, or else the audience will not hear you. Everyone in audience has a hearing damage loss from music being too loud, so you need to go louder.

that's what FOH is for, and around here all the live venues have voluntarily agreed to a max 103dBa 15 minutes at the mixer

Also you couldn’t have a cheering crowd of like multiple thousand people and have them all hear you while you are using like a 50w Marshall. Although I play in a crowd of about 100 people so it’s not really a problem for me, but some big rock band will need a lot of amps just to get all people to hear you, it’s not just preference for loud noises.

[ELS122]

Whats the point of having a guitar amplifier larger than 50W?  Whats the purpose? Making the FOH/sound engineers pissed & angry?

I have never understood this. It is the job of the sound crew to make things loud.

saying why does anyone need more than 50w is like saying why does anyone need more than a few 60w light bulbs to light up a place.

Like I said, your not gonna light up a stadium with a few 60w bulbs, but you also wouldn’t use  stadium lights as a desk lamp.

[Yansi]

Nothing personal, but then you are the typical dumb guitarist, that is a pain in the ass to work with on stage.

It is the job of the sound engineers / FoH to makes things loud and to set you up your monitor, so you can hear yourself.  You use only such volume, so you can hear yourself on the stage. You absolutely do NOT want your amp to interfere with the main PA or pass excessive sound levels in front of the stage.

Excessive volume on stage also annoys your band mates, that due to your stupidly loud amp stack can't hear themselves.

If one can't hear himself on stage, the correct way to do it is to lower the level of OTHERS, not to add more volume to yourself.

It is the classic "trash in - trash out".

[ELS122]

Nothing personal, but then you are the typical dumb guitarist, that is a pain in the ass to work with on stage.

It is the job of the sound engineers / FoH to makes things loud and to set you up your monitor, so you can hear yourself.  You use only such volume, so you can hear yourself on the stage. You absolutely do NOT want your amp to interfere with the main PA or pass excessive sound levels in front of the stage.

Excessive volume on stage also annoys your band mates, that due to your stupidly loud amp stack can't hear themselves.

If one can't hear himself on stage, the correct way to do it is to lower the level of OTHERS, not to add more volume to yourself.

It is the classic "trash in - trash out".

oh, here comes the typical dumb sound engineer, that doesn't get the point of live shows.
it's not a studio dude, no live show has to be perfect if it is it's a bad show since humans don't like things that are 100% perfect.
what's the point of a live show if it sounds exactly like a studio recording.
and also you aren't the one playing in the show. it's the guitarists or whatever you're talking about, choice on how loud they are.
you are not meant to teach the performers on how to play music, people like you have too much power nowadays and don't really know what they're doing at all.

so stop shitposting about how stuck up you are.