Hi all, I wanted to share with you guys my first tube project, a scratch built battery powered pre-amp based on the Bottlehead Quickie design. It uses 2 triode strapped 3S4 tubes, 4 9v batteries to provide 36v to the plates, and 2 D cells to power the filaments. I tried to use relatively high quality parts like an ALPS pot, low noise resistors, and polypropylene output caps. It sounds really good, definitely improved the sound of my system. Now it just needs a dedicated power amp to go along with it! (Unfortunately a solid state amp most likely, due to my rather inefficient speakers)
Yeah that'll be the next thing. I think the NiMH batteries are the way to go. They're pricey, but the only rechargeable batteries that actually supply at least 9v.
It's a bit messy hahaha, but it works! I used point to point wiring for the negative side of the circuit too, which was probably overkill. A ground buss would've been sufficient.
Last edited:
This is awesome! Nicely done!
Now someone will add opinions of the "sound" of the batteries. Some people preferring Energizer, others Duracell.
I'm weird as it seems, I still prefer carbon cells for grid bias. Longer shelf life with no current draw. I've serviced 50 year old equipment where the original Eveready battery was still bang on 1.5V!
Now someone will add opinions of the "sound" of the batteries. Some people preferring Energizer, others Duracell.
I'm weird as it seems, I still prefer carbon cells for grid bias. Longer shelf life with no current draw. I've serviced 50 year old equipment where the original Eveready battery was still bang on 1.5V!
Last edited:
Make certain that you purchase 7 cell assemblies. "Rayovac" definitely made them and may still do so. Don't forget the matching charger.
I say use 18650. 🙂 Or a 12V SLA and a boost converter for B+ and buck converter for heaters. Then again I like to use modern tech and tubes both for what they are good at.
HAHAHA! That's probably true, but I don't listen to hip-hop much!
Powerex Low Self-Discharge Precharged 9V(9.6V) Rechargeable NiMH Batteries (MHR9VP): Amazon.ca: Gateway
I like these 9v because they put out slightly higher voltage, but they're probably the most expensive 9v you can buy.
Might try the Rayovac Zinc Carbon D cells, as most rechargeable D cells are AA batteries in disguise. I also haven't found any rechargeable D cells that put out a solid 1.5v.
For the 3S4 and similar small battery tubes, designed for carbon-zinc cells originally, the 1.2 volts from NiCd or NIMH is just fine for the filaments. Rated voltage range is usually 1.0 to 1.5v.
Full-size rechargeable D cells do exist; usually rated 10-11 amp-hr.
I got a laugh when I saw your chassis - it's the same one I used for the original prototype Quickie circuit.
Full-size rechargeable D cells do exist; usually rated 10-11 amp-hr.
I got a laugh when I saw your chassis - it's the same one I used for the original prototype Quickie circuit.
Oh good to know! I was going off this data sheet that specifies 1.4v for a parallel filament: https://frank.pocnet.net/sheets/127/3/3S4.pdf
I did see some rechargeable D cells rated at 1000mah and 1.25v so those might just be the trick.
That chassis is the perfect size, not too big, not too small!
Nickel Zinc cells are 1.6V... close enough?
Amazon.com : PKCELL NiZn AA 2500mWh 1.6V Rechargeable Battery for Cameras 4 Pack : Camera & Photo
I can't share the schematic because it's not public domain. I bought the assembly manual from Bottlehead to build mine.
I worked on a similar, hotter, plan, and was not too distressed by battery consumption.
We know it is two 3S4. At 67V-90V these eat 7-8mA plate current. Resistor loaded from 36V it will probably be 1/2 to 1/4 of that- maybe 2mA per bottle. A 4mA load on a 9V tranny radio battery lasts a long time. (Pocket radios drew 10mA and up.)
The logical heater IS a primary D-cell; that is what the tubes were designed for (C or D). D-cell is 8,000mAh, tube is 100mA, 80 hours. Even at full retail battery price it is $0.05/hour, which is cheap fun.
Rectangular 9V batteries are really crappy, with six tiny series cells. I'd go six AA batteries
instead. For most purposes, now I use these Panasonic Eneloop rechargeable batteries.
They're great for intermittent use too, and won't fail you. Eneloop - Wikipedia
Bear in mind the 9v batteries are wired in series to provide 36v to the plates. The Eneloop AA batteries are rated at 1.2v, so in my case that is 30 batteries wired in series to provide the necessary 36 volts.
They would be usable for the filaments though, as mentioned earlier 1.2 volts would be sufficient. Since they're rechargeable, AA would be fine since they can be recharged whenever. D cells are best for utmost longevity.
Technically, the Quickie is my design, and I retain the rights to it. I licensed it to Bottlehead.
Now that the product has been retired, I don't mind anyone making one of these for themselves, as long as you give me credit for the design, and as long as you don't sell it.
The circuit is very simple. Triode-wired 3S4 because it has pretty linear curves. Cathode resistor 1K bypassed, plate load 4K, 36v batteries. The filaments are powered by two D-cells, one per tube. The tricky bit is that the negative of the D cell goes to pin 5, the filament centertap; pins 1 and 7 go to the positive D cell terminal. The cathode resistor attaches to pin 5. Output cap was 2.2uF, with a 470K from output RCA to ground; input is a pot, wiper to the grid. That's the entire circuit!
The original idea was to make something really affordable, hence the user-supplied power supply. It was just meant to be something fun to play with.
- Status
- Not open for further replies.