SMPS for powering headphone amp?

Hmm, I'm not an audio guy, but I think "tube sound" is mostly the absence of cross over distortion... which I assume modern amps do much better than the first transistorized ones. And soft clipping at the peaks of the signal... you could do the soft clipping with transistors/ diode/ opamps.

I know, I didn't answer your question. You might pospone battery replacements till you hear if you like the sound.

George

Sure that would work, the circyit diagram shows the 3V and the 18V having the negative terminal common, and for that boost regulator that's a requirement.

At $2.33 it's over-priced and at 2A capability massivly over-sized

I'd go with a more compact converter,

it's likely to be more efficient at the low powere level needed for tubes.

this one will need some modification to get 18V change R2 to 470K - that should be close enough.

the real power hog will be the filaments on the tubes and replacing the built-up linear 1.2v regulator (Q1,R10,LED1) with a switching buck regulator will increase battery life by a factor of about 2

unfortunately that one needs 4V or more to run, so 2 lithium cells, or 4 AAs

The running time with good alkaline cells for both batteries is about 100 hours.

With rechargeables and a boost converter, the time is about 3-5 hours

The whole circuit is a PILE OF JUNK.

Forget it.

.... Phil

That amp is insane. The max rated cathode current for those silly little tubes is 500 uA, so they can't usefully drive headphones. Looking at the board, they are probably making a symbolic pass through the tubes into an IC that actually drives the phones.

What do they claim for power output per channel? A schematic would be amusing.

The OPA2134 can deliver 40mA, which is adequate.

.... Phil

OK, it is an IC output stage. So the tube is cosmetic. Cosmetic and ugly at the same time.

I wonder why people think they like distortion. The guys who mastered the music have a zillion dollars worth of gear and hundreds of years of experience. You'd thing that if they wanted distortion, or tube sound, they would put that on the CD.

Seems they were originally made for use in pocket worn hearing aids that employed 22V and 1.5V dry batteries and drove a special in ear transducer that was VERY efficient.

Such tubes competed with Germanium transistors in that job until about the early 60s.

... Phil

I used to buy CK722s from Allied for about $5, a month's alowance. I still have a few.

They were really pretty awful electrically.

Bill Wagner kindly sent me a couple of proximity fuze tubes, super-rugged versions of the hearing-aid tubes.

I still boggle at the idea of firing tube circuits out of cannons at

Well, for less than 30 frog pelts I may find out. Then again maybe not. By the way, my grandfather, William B. Snow, was a sound engineer. He worked for years for Bell Labs. He did pioneering work on binaural sound and sonar. He had a sound lab in his house and when I was a kid I loved going into his lab where he would have me speak into a microphone and show me what my voice looked like on an oscilloscope. He showed me the different frequencies that made up my voice and all sorts of other cool stuff. I sure wish I could speak to him now. Eric

So true. Schematic here:

Note the LED used to regulate the heater supply... The tube gain and input impedance and output drive are all ... underutilized.

It DOES, however, have impressive immunity to input overdrive...

Years ago I read a short article written by an American man who was a soldier during WW2. He was sent to Britain as part of a crew that were manning anti-aircraft guns and shooting American shells. Their success rate was much higher than the British. So the Americans bragged about how they were such good shots and denigrated the British for being such poor shots. The Americans were shooting the new shells with the new and secret proximity fuzes. Of course the Brits were eventually told and got to use the new proximity devices. I had no idea the amp kit I bought uses the consumer version of the same type of tube. Cool. Eric

Good book:

Thanks for the links George. If the little amp makes sound I like I may indeed take advantage of the links you posted. Eric