Hi,
My significant other had an old radio(1950ish) I disassembled and found these 3 tubes and I'm thinking about reusing them for some sort of bluetooth speaker inside of the old radio enclosure.
First off, I haven't dabble with tubes previously but started reading up about it to a basic level.
My question simply put: I imagine i should be able to use on of the UCH21 and make a monospeaker, but should i try to replace the UBL21 for something else and make stereo speaker?
2x UCH21: UCH 21, Tube UCH21; Rohre UCH 21 ID285, Triode-Heptode
UBL21: UBL 21, Tube UBL21; Rohre UBL 21 ID287, Double Diode-Pentode
there was also a YU1N(UY 1N, Tube UY1N; Rohre UY 1N ID288, Half-Wave Vacuum Rectif) in the radio but i assume was for rectifying AC, so I would not reuse that one.
Thanks!
My significant other had an old radio(1950ish) I disassembled and found these 3 tubes and I'm thinking about reusing them for some sort of bluetooth speaker inside of the old radio enclosure.
First off, I haven't dabble with tubes previously but started reading up about it to a basic level.
My question simply put: I imagine i should be able to use on of the UCH21 and make a monospeaker, but should i try to replace the UBL21 for something else and make stereo speaker?
2x UCH21: UCH 21, Tube UCH21; Rohre UCH 21 ID285, Triode-Heptode
UBL21: UBL 21, Tube UBL21; Rohre UBL 21 ID287, Double Diode-Pentode
there was also a YU1N(UY 1N, Tube UY1N; Rohre UY 1N ID288, Half-Wave Vacuum Rectif) in the radio but i assume was for rectifying AC, so I would not reuse that one.
Thanks!
You are aware that these U-tubes require 100mA current heating?
Which is provided directly from mains voltage inserting a series power resistor?
It will be hard to find some alternative tubes for a stereo setup, as U-series a rare now.
So I would take the mono power stage as is and modify the triode as pre amp.
And be extremely careful with these radios when connected to mains!
Which is provided directly from mains voltage inserting a series power resistor?
It will be hard to find some alternative tubes for a stereo setup, as U-series a rare now.
So I would take the mono power stage as is and modify the triode as pre amp.
And be extremely careful with these radios when connected to mains!
That was almost certainly a live chassis set. You must rebuild the power supply to use a proper mains transformer or use an isolating transformer. If not, the Mods on this forum will close the thread.
UCH21 is a frequency changer. You won't get much audio output from it, and as it is probably a variable gain valve you will get some distortion. UBL21 was the output valve.
This is not a suitable set for a newbie to be playing with.
UCH21 is a frequency changer. You won't get much audio output from it, and as it is probably a variable gain valve you will get some distortion. UBL21 was the output valve.
This is not a suitable set for a newbie to be playing with.
The tubes you recovered from the radio are the worst possible candidates for the upcycling you have in mind, but it could be done. Be aware that the circuit you need to build will work at dangerous voltages.
If you want to build a stereo amplifier, you may reuse the two UCH21 triode sections as tube buffers. It will give a nice "tube sound". Pair them with a stereo chip amp to drive the speakers. You need a beefy 24V power supply for the chip amp and the tube heaters. UCH21 tube filament needs 20V: you must add a 39 ohm 1W dropping resistor in series to each tube filament. Download the UCH21 Philips datasheet and go near the end, at the table listed with the name "operating characteristics of the triode section as low frequency amplifier with resistance coupling". Select a row according to your high voltage power supply and required distortion. The first row looks promising. Build the circuit according to this standard schematic and add the required 200V DC power supply. You cannot reuse the original high voltage power supply of your radio because it is a dangerous live chassis that is now banned.
If this is your first tube project, this path has a big advantage: the tube part is not essential to use the upcycled radio as a bluetooth speaker. You may still use the solid state amplifier directly, while you debug the tube buffer section. It is not a trivial project and I would not recomend it to a beginner, unless you have experience with audio electronic builds.
If you need a mono amplifier and 1W output power with noticeable distortion is ok, you may use both UCH21 and the UBL21 tubes, and two 48V DC power supplies with the outputs stacked togheter to get 96V. You may also get this voltage with a traditional transformer and rectifier. Connect all 3 filament in series, and turn them on with the 96V supply. Reuse the original audio frequency circuit of the radio; you will use only one UCH21, the other tube is there only to drop the filament string voltage.
If you want to build a stereo amplifier, you may reuse the two UCH21 triode sections as tube buffers. It will give a nice "tube sound". Pair them with a stereo chip amp to drive the speakers. You need a beefy 24V power supply for the chip amp and the tube heaters. UCH21 tube filament needs 20V: you must add a 39 ohm 1W dropping resistor in series to each tube filament. Download the UCH21 Philips datasheet and go near the end, at the table listed with the name "operating characteristics of the triode section as low frequency amplifier with resistance coupling". Select a row according to your high voltage power supply and required distortion. The first row looks promising. Build the circuit according to this standard schematic and add the required 200V DC power supply. You cannot reuse the original high voltage power supply of your radio because it is a dangerous live chassis that is now banned.
If this is your first tube project, this path has a big advantage: the tube part is not essential to use the upcycled radio as a bluetooth speaker. You may still use the solid state amplifier directly, while you debug the tube buffer section. It is not a trivial project and I would not recomend it to a beginner, unless you have experience with audio electronic builds.
If you need a mono amplifier and 1W output power with noticeable distortion is ok, you may use both UCH21 and the UBL21 tubes, and two 48V DC power supplies with the outputs stacked togheter to get 96V. You may also get this voltage with a traditional transformer and rectifier. Connect all 3 filament in series, and turn them on with the 96V supply. Reuse the original audio frequency circuit of the radio; you will use only one UCH21, the other tube is there only to drop the filament string voltage.
Thank you for the replies, to clarify: I’ve stripped the radio of all components and I do not intend to use the old circuitry - only the tubes and their sockets. I also don’t have any way to determine if the tubes even work...
It sound as these tubes are both a bad starting place for a newbie, and the result wont be great. I think I’ll gut thetubes and fake the illumination of the heating with LEDs just for funsies. 🙂
Thanks!
It sound as these tubes are both a bad starting place for a newbie, and the result wont be great. I think I’ll gut thetubes and fake the illumination of the heating with LEDs just for funsies. 🙂
Thanks!
Those tubes aren't even the best candidate to fake illumination, because the spigot at the base is metallic and you can't put a LED under the base. It is actually the 9th contact (cathode) on this weird tube. And if you try to apply excess force to the glass to free it, it will shatter immediately. If you want to see those tubes glowing, the best approach is to supply the heater with 24VDC trough a 39 ohm 1W resistor, or 19V DC directly. You will need this power supply anyway for the solid state amplifier. Loctal tubes like this one are uncommon and they look good.
Personally I think valves underlit by LEDs look astonishingly naff. Either use valves or don't use them; don't pretend to use them like some silly art installation.
Sell the valves to someone who has an old radio to repair or restore. These valves will never be made again.
Sell the valves to someone who has an old radio to repair or restore. These valves will never be made again.
This was a quasi-standard European live chassis radio from the 1940ies, see the attached schematic as an example.
For a monophonic audio amplifier You could copy the AF section around the 2nd UCH21's triode and the UBL21.
With a second UBL21 yor would have been able to build a stereo version (two channels) - or a push-pull mono amplifier. Philips (I think) has an application for the latter with two ECH21's and EBL21's, which are rather similar to your tubes.
And don't do any live chassis experiments with audio amplifiers! Never ever!!
Best regards!
For a monophonic audio amplifier You could copy the AF section around the 2nd UCH21's triode and the UBL21.
With a second UBL21 yor would have been able to build a stereo version (two channels) - or a push-pull mono amplifier. Philips (I think) has an application for the latter with two ECH21's and EBL21's, which are rather similar to your tubes.
And don't do any live chassis experiments with audio amplifiers! Never ever!!
Best regards!
- Status
- Not open for further replies.