Are tube PA systems still being made?

[George Kimery]

I have become a "tube guy" within the last year. I am wondering if there are tube PA systems still being made. I don't intend for this post to venture off course and become a tubes vs. solid state discussion. Just play along for the moment and assume that a tube amp sounds better than a solid state amp. So, why or why not, are PA tube systems being made?

Also, if your tube rig is miced and run through a solid state PA board, isn't it going to compromise your tube sound out front?

[Tim Marcus]

I'll make you one

[Matt Bush]

I'd venture to guess that fully tube PAs would be far too heavy to be practical. The PA that my band uses regularly is about 2000w. That's a lot of tubes!

[Ross Shafer]

I'll make you one

I wanna see that!

[Steve Collins]

A PA requires much higher wattage than would practical with tube amplification for starters. A PA is also responsible for reproducing a much wider frequency range than your typical tube guitar amp. Your statement that 'tubes sound better than solid state' is highly subjective. A more accurate way of saying it would be 'tubes distort sound differently than does solid state'. To many ears a guitar sounds good through tubes because of the distortion the tubes impart. A vocalist run through the same type of distortion might sound bloody awful. A PA needs to be more linear, therefor more flexible for a variety of input signals.

[Stephen Cowell]

Tubes are still king for megawatt-output amplifiers... they're just more expensive, is all. The audience certainly can't tell the difference... so the cheaper technology gets the job.

Still, I'd love to hear a ceramic-tube power amp at least once...

http://www.cpii.com/docs/datasheets/78/3CX3000A7.pdf

... keep in mind it'll take some hundreds of watts to *drive* this thing... and it runs at 4000voltsDC. These are mostly used at radio frequencies... but I'm pretty sure they'd work at audio too. Ever seen a 3000watt output transformer? How about a 1/4acre electrostatic array instead!

Big tube amps are scary, that's for sure.

[Robert Parent]

Besides the cost mentioned is the huge weight difference... (I also love my Music Man tube amps but a class D amp is sure easier to haul around.) A 1000w tube amp will weigh 10x compared to a class D power amp of the same wattage.

Overall reliability for portable equipment will also be greater for a solid state amp which does not play into demand for a high power tube amp these days.

Robert

[David Mason]

You used to quite often see old silverface Fender PA's for sale, being re-purposed as guitar amps. They were basically the 135w Twin Reverb power section, with four inputs of various matchups. However, they may well have been mostly picked off by now, as the "second-lowest hanging fruit."

Also, if your tube rig is miced and run through a solid state PA board, isn't it going to compromise your tube sound out front?

You have never really "heard" a tube amp, except your own, for a long time now. You do know you have never heard anything real on your computer at all, right? The actual value of a handmade scatterwound point-to-point tube computer motherboard would be almost... inestimable. Maybe Tim will make you one of those too!

[Steven Husting]

The actual value of a handmade scatterwound point-to-point tube computer motherboard would be almost... inestimable. Maybe Tim will make you one of those too!

That's been done - it looks like this -

http://s7.computerhistory.org/is/image/ ... $re-medium$

[George Redmon]

Here's a tube power amp that looks interesting. With adjustable Bias.

http://www.carvinguitars.com/products/TS100

[b0b]

I used to build bass amps at Mesa/Boogie. With six 6L6 output tubes, they put out enough power for a club PA, no problem. The mixer section would be a lot of work, but I'm sure it's nothing that Tim Marcus couldn't handle. An inductor coil master EQ would be really cool.

I had a Mesa 50/50 power amp and used it for PA power once with a Mackie mixer. No problems or surprises.

[Bob Hoffnar]

VHT 2/90/2's would sound awesome pushing a PA.

[Len Amaral]

I have a Fender PA 100 and PA 135. These heads are basically a Fender Twin without the tone stack and have 4 channels with 1/4 inch jacks and no XLR inputs.

Have not tried these units with a mic they are very clean. I use the PA 100 with a Mesa 5 band EQ in my studio for steel and it sounds very nice. Too heavy for me to carry around but a sleeper rig for you younger guys.

[Brad Sarno]

A PA requires much higher wattage than would practical with tube amplification for starters. A PA is also responsible for reproducing a much wider frequency range than your typical tube guitar amp. Your statement that 'tubes sound better than solid state' is highly subjective. A more accurate way of saying it would be 'tubes distort sound differently than does solid state'. To many ears a guitar sounds good through tubes because of the distortion the tubes impart. A vocalist run through the same type of distortion might sound bloody awful. A PA needs to be more linear, therefor more flexible for a variety of input signals.

I think there may be some confusion here equating "tubes" to "guitar amps". Tubes are still king in the audiophile and pro-recording world. Tubes have extremely broad frequency response, just like transistors. It all depends on the circuit. In a guitar amp, that's a lo-fi circuit with a guitar-type EQ and a limited range speaker. But tubes used in full-range hi-fi gear run dead-clean are still hailed as the greatest sound. People spend tens of thousands on tube based ultra-high-end audiophile gear that is as clean as a whistle, but it's warmer, sweeter, nicer, more musical sounding.

Many of the microphones we hear on the radio and on the albums we love are often tube microphones. Many of the mic-preamps that were used in the recording process were tubed. Many of the compressors and much of the gear in the mastering process is tube. Even a guy I know of that was involved with very high end PA sound development in the 70s and 80s had a mid-sized PA system out in the Santa Barbara area that was arguably the most pristine, audiophile, high-end PA system ever devised and could reach a crowd of 2000 people outdoors had the entire tweeter/horn array powered by tubes because of the much nicer tone quality. And that was dead clean, ultra high fidelity.

Just sayin, tubes are absolutely viable devices for the ultimate in clean performance when implemented for that purpose. The problem is that for power amplifiers, it's impractical as it takes a LOT of iron/transformers and a LOT of tubes and is very heavy and gets real hot.

I'd like to see a PA rig that used tubes in the mic-preamps and line driver stages and the mixing stages, and then on to light weight Class-D for power driving the speakers. That would be sweet.

B

[b0b]

I'd like to see a PA rig that used tubes in the mic-preamps and line driver stages and the mixing stages, and then on to light weight Class-D for power driving the speakers. That would be sweet.

I think that's the ticket. In these days of carbon sensitivity, the power requirements of massive tube amps are unnecessary. And the weight! I've become a big fan of class D amps in the past 2 years, first with the GK MB-200 and now with the Milkman Half & Half.

I like the clarity and responsiveness of tubes for manipulating sound in the preamp, but my ears tell me there's no good reason for tubes in the power amp.

[Les Cargill]

I'd like to see a PA rig that used tubes in the mic-preamps and line driver stages and the mixing stages, and then on to light weight Class-D for power driving the speakers. That would be sweet.

I think that's the ticket. In these days of carbon sensitivity, the power requirements of massive tube amps are unnecessary. And the weight! I've become a big fan of class D amps in the past 2 years, first with the GK MB-200 and now with the Milkman Half & Half.

I like the clarity and responsiveness of tubes for manipulating sound in the preamp, but my ears tell me there's no good reason for tubes in the power amp.

On the bass newsgroup, one of the stalwarts there ( who is playing large enough stages ) actually traded in a full 8X10 Ampeg SVT rig for a Markbass combo for a while. He went back the SVT but he's a rabid SVT fan with decades with one, and it shows the Markbass got close.

[Craig Baker]

There have been several articles and kits available that use 833 triode transmitting tubes. Personally, I've worked with 833s, but never attempted to build an amp with one. RCA developed them years ago, and for decades they were used in many 1000 watt AM stations. Two in the final RF stage driving the antenna and another pair in the modulator. (audio power amp) Here are two links regarding using the 833 triode in an audio amplifier.

(A pair can produce 800 watts pure sine wave. At $200.00 each, make sure you aim a fan at them.)

http://www.knipschild.net/projekt833c1.htm


http://www.parts-express.com/project-ga ... triode-amp


http://en.wikipedia.org/wiki/833A

Best regards,
Craig Baker 706-485-8792

cmbakerelectronics@gmail.com

C.M. Baker Electronics
P.O. Box 3965
Eatonton, GA 31024

[Paul Honeycutt]

I once answered an ad for some Altec tube amplifiers. They were in a theater in Oakland. As I recall there were two amps mounted in a six foot rack with tubes as long as icicles. They were probably used to power a couple of Voice of the Theater cabs. Needless to say, I didn't buy them.

Now if I had a theater with an installed PA...

No, a self powered line array still would be my choice.

[Dave Grafe]

There are several reasons why these are not being manufactured commercially:

The old reliable guitar-amp 12AX7 has a bandwidth of only about 6kHz, great for guitar, lousy for PA. There are other tubes that have the bandwidth but not the gain, but it's not as simple as converting a guitar amp circuit.

The power and output transformers alone for a tube system with 20 or more preamps and a couple channels of 300 watt power would weigh more than one person could handle, and the heat generated would be ridiculous.

And as has been mentioned here already, if you went to the trouble of putting one together very few if any listeners could tell the difference in a live performance environment. If you put one into a studio you will have to upgrade your air conditioning for certain.

[Craig Baker]

Dave is correct in his assessment of very high power tube amps. They worked well in AM broadcasting. In fact, many stations still use the transmitter exhaust to heat the building, but they were installed one time. . . you didn't carry them around on Friday and Saturday nights.

The 833 triodes, mentioned in the earlier link each require 10 volts at 10 amps just to light the filament. Each tube is equal to a 100 watt light bulb. The filament transformer is heavy. Then you need a power supply with transformers AND large iron-core filter chokes. (possibly a high-voltage switching supply would save a few pounds here.)

We're almost finished, here is 500 watt audio transformer. Look Ma, it's 14" wide and only weighs 150 lbs.

If you look closely, you can see the spark gaps, intended to protect the windings from excess peak voltages.



No wonder Peavey sells so many 112s

Best regards,
Craig Baker 706-485-8792

cmbakerelectronics@gmail.com

C.M. Baker Electronics
P.O. Box 3965
Eatonton, GA 31024

[b0b]

Here's a timely question. I need to bring a PA to an art gallery concert on Thursday, a lively space with maybe 50 people in attendance. The PA is for miking an acoustic lap guitar (my Stella) and vocals. I have a Mackie mixer and I can borrow a pair of nice speakers on stands, but my only power amp is a Mesa/Boogie 20/20 tube amp.

My question: do you think I'll have any problems? The 20/20 was always plenty loud and clean when I used it for steel. Seems to me it should work. I could borrow a big rack with 500 watt power amps, 31-band EQ, etc. but that seems like overkill for the venue.

You guys keep talking about these big power amps. I'm just wondering if 20 watts of tube power per side will do the job for a small concert. What do you think?

[Lane Gray]

In the absence of bass, drums and other loud thumpy crashy things, that will be PLENTY for Vox and rhythm guitar. Hell, 50 people is almost adequate with nothing.

[Craig Baker]

Hi b0b,
No doubt your Mesa Boogie 20/20 will have plenty of power to cover the room. Several times I've loaned my Nashville 400 and an SM58 to someone needing a PA system. It was probably many times the power needed, but it was all I had available.

The only people who would take notice are other musicians or sound guys.

Trust me. . . the audience will simply sit and enjoy the performance, and love it.

Play well.

Sincerely,
Craig

[Brad Sarno]

There are several reasons why these are not being manufactured commercially:

The old reliable guitar-amp 12AX7 has a bandwidth of only about 6kHz, great for guitar, lousy for PA. There are other tubes that have the bandwidth but not the gain, but it's not as simple as converting a guitar amp circuit.

Hey Dave. I'm not sure where this idea of limited bandwidth of a 12AX7 came from, but that's simply not the case. A 12AX7 can easily amplify way and well beyond 100kHz, Much higher than the highest audible audio frequencies. They are very flat-response audio devices when the circuit allows. Although in a Fender amp circuit, true that the nature of that circuit is bandwidth limited to something more like 16kHz or so, and when thru a guitar speaker, that audio output bandwidth drops to about 6 or 7kHz. But the 12AX7 tube is a truly full range device that very easily goes way on up there in frequency response. Even my Black Box will pass audio way beyond 50kHz. It's not a guitar tube, it's a small audio signal amplifier.

12AX7's are often implemented into high bandwidth mic preamps and expensive audiophile preamplification with frequency response dead flat beyond 30kHz. It's a VERY high-fidelity device when designed to be so. No reason at all why it couldn't be spectacular in a PA system mixer stage.


Brad

[Brad Sarno]

For example, here's a preamp that is using 12AX7's that is flat to 30kHz, and then is only -3dB down at 250kHz under certain conditions.

Extreme fidelity

http://www.arcdb.ws/SP6/SP6.html


B