Amazing Battery Life!

[Dr. Toobz]

I thought I'd post my findings regarding battery life on my headphone-adapted Quickie. I first turned it on the evening of October 8, 2009 and have used it an average of 2-3 hours a night, every day since then while at my iMac. Batteries are standard Energizer alkalines. As of tonight, my filament cells are at 1.28V each, and the B+ is at 27.94V. Not bad for over a month's use! At this rate, I should easily have enough juice to go for another couple of weeks!

Just more evidence that this new product is fast destined to become a classic! Kudos to the Bottlehead team for a great design.

[Paul Joppa]

If you believe the numbers from the battery makers, lifetime should be about 200 hours for both D-cells and the 9-v batteries.

Back in the day when most farms had no electricity and used battery radios (twenties into the forties I think) there were giant cells, the size of 845 tubes. I remember using them to fire the glo-plugs on model airplane engines. They still exist, but only as old-fashioned zinc-MgO2 cells; they were never adapted to alkaline chemistry as far as I can discover. I don't think they have all that much more potential life than a good alkaline D-cell, and they certainly fade with age even if they are not in use. So the D cell is still the biggest practical filament battery available.

[Dr. Toobz]

As of 1/10/10, I still have the same cells in the Quickie, though they are probably going to croak any day now. B+ voltage is down to 19.5V, and the heater cells are around .95V. I don't hear any obvious distortion or problems at this low voltage, surprisingly, though I'm now using the Quickie as a linestage, not to drive headphones. There's still a ton of gain when used between a DAC and the S.E.X. amp, so much that the Quickie is usually turned up 2/3 of the way (any more and the S.E.X. gets too loud, too quickly).

What's the lowest voltage the B+ could go and not get totally distorted sound from the tubes? How about the heaters - would .5V still put enough electrons "out there" to keep things conducting?

[Paul Joppa]

IMHO, batteries are "dead" at 2/3 the rated voltage - 1.0v for the D cells, 24v for the HV pack. Lower voltage puts the 3S4 at risk, though the low HV means the ion energy is limited so they can't do too much damage to the cathode. And 3S4s are cheap still ...

[Dr. Toobz]

What happens, exactly, when tubes are starved of voltage? I would imagine that when battery tubes were popular (20's-50's) people must have run the cells down to the point of not getting any (intelligible) sound at all. Does that wear the tubes out prematurely?

[Len]

I think you'd probably get some cathode poisoning/stripping if the filament lit less than the plate.

Maybe my terminology is wrong. I mean them thar electrons would be goin' the wrong way and stickin' where they ain't supposed to.

[Dr. Toobz]

I think you'd probably get some cathode poisoning/stripping if the filament lit less than the plate.

Maybe my terminology is wrong. I mean them thar electrons would be goin' the wrong way and stickin' where they ain't supposed to.

Ha! Very funny. I did figure it had something to do with the cathode being stripped, though. In the long run, the cheapest/best thing to do (for both the tubes and one's battery budget) would probably be to buy a set of NiMH cells and charge them before they dropped below 1.0V/each for the heaters and 6.0V/each for the B+.

[Paul Joppa]

When the filament cathode gets too cold, the electron cloud that surrounds it becomes small. This cloud protects the cathode from positive ions, which are much more massive than electrons. Tohose ions are accelerated towards the cathode by the plate-cathode voltage, and when they crash into the cathode they will damage the electron-emitting surface and even dislodge small pieces. That's how cathode poisoniing works, as I understand it.

In these little battery tubes, the cathode is designed to function over a wider range of voltages than usual. In the Quickie, the actual current is much lower than the design maximum, giving a bit more margin. And the plate voltage is quite low, so the ions won't build up so much speed. All this should make the 3S4 in the Quickie pretty tolerant of run-down batteries, compared to non-battery tubes.

[jbraveman]

Will the batteries run down if the unit is left on, but not playing any music?

[Len]

Yes.

IIRC, somewhere between 100 and 200 hours and all batteries will be dead.

[Dr. Toobz]

Coincidentally, the batteries finally took a dive today, and the sound quickly became really disgusting and distorted. B+ was at 19V. I'd estimate I got about 200+ hours from the original set of Energizers I put in the Quickie way back on 10/8/09!

Who would have thought this level of performance could be had for so little? 200+ hour battery life and exotic DHT sound from a pair of lowly battery pentodes? Another hit product for Bottlehead!

[Wanderer]

I get amazing battery life too. Unfortunatly some of that life trickles away while I have forgotten to shut the thing off. Nobodies fault but mine.

Is there some way to hang an LED pilot light on the Quickie so this dumb user can reduce his carbon foot print?   

[Paul Joppa]

...
Is there some way to hang an LED pilot light on the Quickie so this dumb user can reduce his carbon foot print?   

Yes - just put an LED in between the 9-v battery stack and the rest of the circuit. Look for a high-efficiency LED since the actual current is quite small!