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Old 25th July 2002, 03:20 AM   #1
SHiFTY is offline SHiFTY  New Zealand
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Question Tube subwoofer amp

Hi all,

Well after getting my 6V6 PP stereo amp sounding real nice, (check my other threads) I am looking for a new project.

I have a 10"sub in a box sitting around, and access to a variety of big *** tubes (some smaller transmitting triodes and stuff) which I can get for free. I am wondering about using a single-ended triode amp with negative feedback, using one of these tubes. My question is: what kind of power/output transformers would I need?

I was thinking I would need a reasonable power tranny, however the amp would probably only have 2 tubes: an octal triode like the 6SN7 as a preamp (heck, maybe even a 6V6 as a preamp!) and a big coke bottle power tube. So maybe I could get away with a scrounged tranny from a big console radio... Maybe?

I am thinking around 30W RMS would be good enough for a fair bit of bass, could I use a toroidal power transformer as an opt? I only need a freq range of 20-120 Hz, and I am using NFB, so would that be good enough?

Any other crazy person thought about this (or done it )

~~H~~
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Old 25th July 2002, 05:21 AM   #2
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Default Re: Tube subwoofer amp

You will need a monster of an OPT... SE amps aren't renowned for their low bass.

dave
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Old 9th August 2002, 12:56 PM   #3
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Default Tube sub amp

Why do you want to use a tube amp for the sub. A large tube amp capable of 20 Hz at full output must be very large and expensive.
On the other hand you could use a Hybrid amp with tube front end and transistor ( bipolar or Mosfet) output stage. This way you can go into the x100 watt range. They will also have better damping ( lower output impedance ) at the critical bass frequencies and have better low frequency response.
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Old 12th August 2002, 11:40 PM   #4
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Shifty,
I like your ambition. This sub in a box.........speaker cabinet shaped like a box.........cardboard box, what are we looking at here?
As far as a reasonable amp for the sub the easiest and cheapest thing to do would to be getting your hands on an old piece of integrated SS gear and strapping it into mono.
For what your talking about which is a volume adjustable amp it would take a lot of work. For amps of that ilk what I have seen is a dual triode driving a power tube driving a transmitting tube. That much work deserves much more that subwoofer duty.

But I still want you to do it so we can find out about it! OK?
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Old 13th August 2002, 01:50 AM   #5
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Unless you have some real horn subs, and can get the output iron would and optimised for low frequency performance, get a nice big SS unit. You'll be happier and have a fuller wallet.

Sure, if you want to build a big-mutha tube amp for your sub, look no further than the <a href="http://bulk.pearl-hifi.com/Misc_Downloads/Altec_260A_Instr.pdf">Altec 260A</a> , a 260W/ch beast. Only requires 2 x 6AU6 and 2 x 813 per channel (+rectifiers), and good Russian 813s are about $US12 each. A pair of 813's lit up at full power produces the most amazing light show, heat and creates almost a forcefield in the air around them. Very impressive for the neighbours and friends.

I have no idea where to get the parts like iron and PSU caps, but I would caution you to keep one hand behind your back at all times when building and working on it. It has a B+ of 1800V and the 813s have anode caps. I'd rather our DIYers didn't become charcoal prematurely, and I'd <i>strongly</i> advise not using it around children or pets you care about.

Seriously folks, unless you really know what you're doing, amps voltages this high should not be attempted unless you are <b>very</b> well versed in all the safety requirements. Even thinking about it should absolve diyaudio, Pearl and me from any liability. Link provided for educational and entertainment purposes only.

Cheers
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Old 13th August 2002, 10:15 AM   #6
SHiFTY is offline SHiFTY  New Zealand
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Well, the project is on hold for a while due to lack of suitable transformers at a low enough price... but its gonna happen one of these days!
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Old 14th August 2002, 07:21 AM   #7
dice45 is offline dice45  Germany
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ShiFtY,
(being mean now )
did you consider and 845 PP? (or maybe 211 PP?)
You would need 1200V of B+ however but you would get 100W if you drive the babies a little bit into class-B.

Gintaras (ebay: kwtubes) sells the Russian equivalent to the 845, having 20V of heater voltage instead of 10 but else pretty much the same as the 845. Maybe he also has an idea where to get decent PP trannies?
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Old 7th April 2012, 12:43 PM   #8
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wonder whatever happened here....
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Old 7th April 2012, 03:06 PM   #9
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Quote:
Originally Posted by Tony View Post
wonder whatever happened here....
Probably a disappointment per money and effort went in and result that came out especially when SS sub amps are so cheap and perform well these days.
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