Is there a *clean*, tiny, ~1W tube amp build that can be run on a 9V adapter?

[midwayfair]

I've looked around and all the tiny amps I can find are built to get lots of distortion at low volumes (e.g. Firefly). I don't need or want much if any breakup from the amp itself or even much volume, just practice/testing volume that can drive an 8 Ohm speaker while running on a 9v adapter (with an appropriate charge pump or 555 step-up, obviously).

Why a tube? Because I want to do something different. Otherwise I'll just build a Noisey Cricket or something. I don't particularly care what kind of tube, but 12A_7 or would be ideal since I keep lots of those around. Oh -- also, no power tube section! Ideally it's one dual-triode and done.

If it just can't be done with a 9v supply, I do have an extra 12V laptop power supply that I guess I could use instead.

If this doesn't exist and it's possible, just point me in the direction of reading material I'll start working on it ...

[Scruffie]

I'm no tube expert by any means but if you use 9V you'll want high current supplies as wiring the heaters for 6.3V takes 300mA instead of 150mA at 12V so probably 800mA with 2 x 12A_7 tubes and the charge pump.

A MAX1771 charge pump is probably your best bet, I think for cleaner sounds you'll want the most voltage possible plus that supply is more stable than the 555.

With a mini amp you're not gunna find lots of clean headroom though.

No power tube? Then how are you going to get output? Do you want a hybrid amp? You'll want at least 2 tubes for a tube amp with any kind of clean.

You're probably better off with a Ruby or Noisy Cricket from what you're saying, or maybe something like the Tiny Giant.

If you do the Super Fly with standard tubes like I did it'd be the best all tube amp bet probably, it does offer some useable clean headroom. There's already a PCB layout (sadly the tube pads are backwards so you have to wire the sockets by hand) I did for 12AX7 & U7 with the MAX1771 supply in the super fly thread.

[midwayfair]

I'm no tube expert by any means but if you use 9V you'll want high current supplies as wiring the heaters for 6.3V takes 300mA instead of 150mA at 12V so probably 800mA with 2 x 12A_7 tubes and the charge pump.

A MAX1771 charge pump is probably your best bet, I think for cleaner sounds you'll want the most voltage possible plus that supply is more stable than the 555.

With a mini amp you're not gunna find lots of clean headroom though.

No power tube? Then how are you going to get output? Do you want a hybrid amp? You'll want at least 2 tubes for a tube amp with any kind of clean.

You're probably better off with a Ruby or Noisy Cricket from what you're saying, or maybe something like the Tiny Giant.

If you do the Super Fly with standard tubes like I did it'd be the best all tube amp bet probably, it does offer some useable clean headroom. There's already a PCB layout (sadly the tube pads are backwards so you have to wire the sockets by hand) I did for 12AX7 & U7 with the MAX1771 supply in the super fly thread.

Thanks, Scruffie.

>No power tube? Then how are you going to get output?
Erm, not quite what I meant. I want to use what's normally a preamp tube (e.g. 12AY7) as the power tube.

[Scruffie]

I'm no tube expert by any means but if you use 9V you'll want high current supplies as wiring the heaters for 6.3V takes 300mA instead of 150mA at 12V so probably 800mA with 2 x 12A_7 tubes and the charge pump.

A MAX1771 charge pump is probably your best bet, I think for cleaner sounds you'll want the most voltage possible plus that supply is more stable than the 555.

With a mini amp you're not gunna find lots of clean headroom though.

No power tube? Then how are you going to get output? Do you want a hybrid amp? You'll want at least 2 tubes for a tube amp with any kind of clean.

You're probably better off with a Ruby or Noisy Cricket from what you're saying, or maybe something like the Tiny Giant.

If you do the Super Fly with standard tubes like I did it'd be the best all tube amp bet probably, it does offer some useable clean headroom. There's already a PCB layout (sadly the tube pads are backwards so you have to wire the sockets by hand) I did for 12AX7 & U7 with the MAX1771 supply in the super fly thread.

Thanks, Scruffie.

>No power tube? Then how are you going to get output?
Erm, not quite what I meant. I want to use what's normally a preamp tube (e.g. 12AY7) as the power tube.

Ahhh, when you said ideally one dual triode I thought yeah... well there you go, Superfly, 12AU7 output tube.

[markeebee]

I made this a while ago.  Not bad at lower gain, but PRR weighed in with some good advice (as always) to improve the clean performance.  See his last post re transformer ratios.

http://www.diystompboxes.com/smfforum/index.php?topic=96952.0

[midwayfair]

I made this a while ago.  Not bad at lower gain, but PRR weighed in with some good advice (as always) to improve the clean performance.  See his last post re transformer ratios.

http://www.diystompboxes.com/smfforum/index.php?topic=96952.0

Thanks, Mark. Demo sounds pretty good on the clean stuff.

[Kesh]

Putting  a constant current source on the anode is a pretty good way to get clean low voltage tubes to work, however I've never seen it at this low a voltage.

[culturejam]

Have you considered the myriad of integrated chip amps out there? You could tack on a tube preamp and get some decently clean output. There are plenty that are single-supply and can output anywhere from 3w to 30w (or even more). And they are usually really cheap (under $5). Tayda has several.

I don't think you can really do 1) low-voltage, 2) tube, and 3) headroom

Pick any two. 

I had a Vox Lil' Nighttrain, and if you set it just right, you can get clean tones just above conversation level. It was rated at 2W total output. It had a self-split 12AU7 like the FireFly. But alas, it was not low voltage.

[midwayfair]

Have you considered the myriad of integrated chip amps out there? You could tack on a tube preamp and get some decently clean output. There are plenty that are single-supply and can output anywhere from 3w to 30w (or even more). And they are usually really cheap (under $5). Tayda has several.

I don't think you can really do 1) low-voltage, 2) tube, and 3) headroom

Pick any two. 

I had a Vox Lil' Nighttrain, and if you set it just right, you can get clean tones just above conversation level. It was rated at 2W total output. It had a self-split 12AU7 like the FireFly. But alas, it was not low voltage.

on Scruffie's suggestion, I've been checking out the Tiny Giant. I like what I hear -- it's bright enough, which is important (I mean, I use one of the brightest amps on the planet, so I need an accurate test ...), it's clean, and I have multiple laptop supplies around the house.

I'll look into tube preamps ... I was definitely going to skip the giant's TL072 Preamp and go with something different. Have a suggestion in that realm? Something Fenderish would be ideal, or at least something I can add a [Fender] tone stack to.

I should reiterate that I really was looking for basically conversation level cleans. My concern with the Firefly was that there was basically no point on the dial where it was clean.

[culturejam]

It ain't DIY, but Sweetwater is blowing out the Lil Night Trains for $189
http://www.sweetwater.com/store/detail/NightTrain2H

[tca]

You could try something like this: http://meatexz.com/engel-sound/space_charger.html
It uses some low watt tubes for car audio at 12V! I've build the ECH83 preamp and it works great.

Cheers.

[Pyr0]

on Scruffie's suggestion, I've been checking out the Tiny Giant. I like what I hear -- it's bright enough, which is important (I mean, I use one of the brightest amps on the planet, so I need an accurate test ...), it's clean, and I have multiple laptop supplies around the house.

I'll look into tube preamps ... I was definitely going to skip the giant's TL072 Preamp and go with something different. Have a suggestion in that realm? Something Fenderish would be ideal, or at least something I can add a [Fender] tone stack to.

I should reiterate that I really was looking for basically conversation level cleans. My concern with the Firefly was that there was basically no point on the dial where it was clean.

I built a Tiny Giant amp and used a Colorsound Overdriver as the preamp, and I guess you could easily modify the tone stack for a fender one. Worked really well, just turn up the drive knob for some nice distortion. My son uses it for busking.

[garcho]

Highly recommend the Tiny Giant. Get the PCB from Taylor @ musicpcb.com and be done with the whole thing in like, 15 minutes or so. Knowing you, it'd be 5.

[brett]

Hi
the 12U7 is your friend in this adventure. It is designed to run at low voltage (ie in car radios in the 1930s and 1940s).
Just insert it in any circuit that calls for a 12A_7. It is similar to a 12AU7, which for several reasons is probably your second best choice.
With an efficient (very small) output transformer and an efficient speaker you should be able to get reasonable volume.
cheers

[PRR]

> 1W tube amp .... 9V adapter?

Do your math.

Pretend the tube and circuit could be perfect.

1 Watt at 9 Volts means 0.111 Amperes.

9 Volts at 0.111 Amperes is 81 ohms.

We need a tube with internal resistance MUCH less than 81 ohms.

> 12AY7

25,000 ohms. Not remotely close. But looking closer, it can do 1mA at 10V, 10,000 ohms, Still way out of sight. Looks more like 0.001 Watts audio output.

> low watt tubes for car audio at 12V

The best of the bunch is 0.05 Watts and NOT clean.

> 12U7

Is a voltage amp, not a Power amp. 12,500 ohm internal resistance, less than 1mA peak current, much less than 0.01 Watts output. Yes, you can hear this. But this isn't the 1W amp of your dreams.

> ECH83

?? This is a frequency changer. 0.0002 Amps max at 12V.

6080 twin pass-tube is 280 ohms per side. Two bottles gets down to 70 ohms. We could find a quarter-Watt that way. It's more heat, just in the heaters, than a Champ or Junior.

6C33C-B was used to switch Russian radar. Even a pair of these won't make a whole Watt from 12V.


Beach-radio tubes were about as good as it gets. 0.1W-0.2W with 67V-90V supply.

Table-radio tubes were extremely well developed. 1 Watt with 110V supply. 25C5, 60FX5, and others.

_____________________________________

> 12U7 .... designed to run at low voltage (ie in car radios in the 1930s and 1940s).

They knew better in the 1930s. Whole radio was high voltage, 250V.

Also cars were 6V, so a 12U7 would be awkward.

12U7 is a byproduct of *solid-state*. Electrical systems moved to 12V in part because crystal rectifers work better at the higher voltage. The early transistors were not good for radio but OK for audio, but very expensive. You got your big 2 Watts with one transistor; costly, but cheaper than a hi-volt supply. Then you needed tubes to limp along at 12V and do the radio and 1st-audio duties. The date on the preliminary 12U7 data is 1 April 1956, same year as the swelling of 12V alternators and fat-transistor power stages.

[jeffaroo]

www.madbeanpedals.com

its called "lil green watter" guy has a video of one in action
even has a pdf to download to build yur own

http://www.madbeanpedals.com/forum/index.php?topic=6904.0

[midwayfair]

www.madbeanpedals.com

its called "lil green watter" guy has a video of one in action
even has a pdf to download to build yur own

http://www.madbeanpedals.com/forum/index.php?topic=6904.0

Oh hey thanks. I completely forgot Corey's build was a power amp as well. It was actually on my build list!