As tube technology gets old I thought it might be a idea to produce a Hi-Fi tube amplifier using components and technologies that were available 100 years ago.
Maybe a competition, the prize, the glory of doing it.
The rules, let us all make them up.
My ideas:
Capacitors, resistors, transformers were all about 100 years ago so they may be used.
The UX250 audio power triode was introduced in 1928 so it may be used in a build for 2028.
The UX245 was available in 1929 so any type 45 even a modern production could be used in a 2029 build.
The UX201 was introduced in 1925 so any 01A type could be used in a 2025 build.
The 6L6 was introduced in 1936 so it could be used in a 2036 build.
The speakers are not part of the amplifier.
The power supply is not part of the amplifier as batteries were about.
Spice sims allowed in the simulation class.
I personally have some 45's and 01A's so the best I could do is a 92 year old build, maybe I could scrape a year or two off it.
Spice sims allowed in the simulation class.
Ken Kranz
Australia
Maybe a competition, the prize, the glory of doing it.
The rules, let us all make them up.
My ideas:
Capacitors, resistors, transformers were all about 100 years ago so they may be used.
The UX250 audio power triode was introduced in 1928 so it may be used in a build for 2028.
The UX245 was available in 1929 so any type 45 even a modern production could be used in a 2029 build.
The UX201 was introduced in 1925 so any 01A type could be used in a 2025 build.
The 6L6 was introduced in 1936 so it could be used in a 2036 build.
The speakers are not part of the amplifier.
The power supply is not part of the amplifier as batteries were about.
Spice sims allowed in the simulation class.
I personally have some 45's and 01A's so the best I could do is a 92 year old build, maybe I could scrape a year or two off it.
Spice sims allowed in the simulation class.
Ken Kranz
Australia
Alan Turing mentioned circuit simulations as a possible application in his 1945 system design proposal for the ACE computers, but that is decades too late, and it was just a wild idea anyway (and the pilot-ACE only ran its first program in 1950, the Manchester Baby in 1948). So I'd say:
-Circuit simulations strictly forbidden until 2048, after that allowed if you write your own program and run it on a home-built valve computer
-Slide rule calculations allowed
-Circuit simulations strictly forbidden until 2048, after that allowed if you write your own program and run it on a home-built valve computer
-Slide rule calculations allowed
100 year old amp for this year would be a 1:3 interstage transformer-coupled two-stage design with RCA UA-201 tubes driving Western Electric electromagnetic headphones. Parts will be assembled on a piece of board using thumb nut connectors (no soldering). Power will be from A (filament), B (plate), and C (bias) batteries.
A hi-fi version with permalloy core transformers (available from a number of manufacturers in 1920s, e.g. Varley, Brandeis, or Formo) would sound quite impressive with top line Grado, Sennheiser, or AKG phones.
A hi-fi version with permalloy core transformers (available from a number of manufacturers in 1920s, e.g. Varley, Brandeis, or Formo) would sound quite impressive with top line Grado, Sennheiser, or AKG phones.
"using components 100 years old " ?----- have you seen the prices for original radio parts and original amplifier parts -eg- PX4 (original ).
Energized magnet speakers ( usually from the HT supply (plate ) and even earlier 1920,s non voice coil types.
I have WW bound volumes from 1915 to 1947 and there are plenty of unusual designs .
Energized magnet speakers ( usually from the HT supply (plate ) and even earlier 1920,s non voice coil types.
I have WW bound volumes from 1915 to 1947 and there are plenty of unusual designs .
I have a working 1934 hi-fi kit amplifier made with just introduced 56 and 47 tubes. It has 1:2 80% nickel input transformer, 500k wirewound (!) volume control pot, 56 driver, 1:3 Ferranti AF-3 interstage, and 4x47s arranged in parallel push-pull. No feedback of any kind. Power supply is on separate chassis.
I have been gathering parts for a guitar amp with a similar, but slightly different goal. The first Fender guitar amps appeared in the late 1940's with simple circuits, often taken from the RCA tube manuals and tweaked for guitar use. As with most electronics today, cost was the biggest design driver. They were obviously quite successful.
What could Leo Fender have built if he tried to make the ultimate amp? I set an arbitrary year, 1952, the year I was born, and set out to build an amp with parts that were available in 1952. Modern equivalent parts are OK, and long as they were available in or before 1952. IE, a modern 20 uF 400 volt capacitor is OK, but a 1000 uF 450 volt cap is not, as you couldn't get one in 1952.
Electromechinical relays did exist in 1952, but good working examples from 1952 may be hard to find, so modern relays are OK. I have found that CDS photoresistors did exist, so they will be used. Still looking into low voltage rectifiers. I would hate to use selenium.....I burnt too many of those in my childhood....stinky stuff.
Just to be different, this will be the MetallicAmp, all tube, no glass. The metal cased 6L6 first appeared in 1936, and metal cased vacuum tubes were made into the late 50's, so they will be used.
What could Leo Fender have built if he tried to make the ultimate amp? I set an arbitrary year, 1952, the year I was born, and set out to build an amp with parts that were available in 1952. Modern equivalent parts are OK, and long as they were available in or before 1952. IE, a modern 20 uF 400 volt capacitor is OK, but a 1000 uF 450 volt cap is not, as you couldn't get one in 1952.
Electromechinical relays did exist in 1952, but good working examples from 1952 may be hard to find, so modern relays are OK. I have found that CDS photoresistors did exist, so they will be used. Still looking into low voltage rectifiers. I would hate to use selenium.....I burnt too many of those in my childhood....stinky stuff.
Just to be different, this will be the MetallicAmp, all tube, no glass. The metal cased 6L6 first appeared in 1936, and metal cased vacuum tubes were made into the late 50's, so they will be used.
Leo Fender DID build the 'ultimate amp' for HIS application. If you want perfection from that time, I would look to a RadioCraftsman triode amp or a Marantz model 2. They would sound lousy as guitar amps, but great for hi fi, even today, within their operating range. When I design amps today, I strive to sound as good as a Marantz model 9 tube power amp. I still can't beat the very best tube power amps ever made at any price. Tubes rule! But solid state is more practical. '-)
Hundred years ago it was shortly before the beginning of the talkie movies so the first Western Electric horn systems were developed in the 1920s.
Very low power amps with transformer coupling and a frequency limited response somewhere in the region of a phone line (for some reason those first WE amps and LOUDspeakers were called "Loudspeaking Telephone". There was no audio or hifi in existence. The goal was to reproduce speech for an auditorium in the big cinema halls. No radio was invented although Marconi was already successfull with its telegraphic demonstrations and that was heavily used by mostly military industry in WW1.
Maybe ten years later, one could say there is a very early audio industry which has managed to some extend to let orchestra, music and speech be reproduced with good quality. But even this is, by modern standards, just a freq. response up to max. 10K cycles, maybe 7K max. only.
You will have a hard time to find the parts for this project. Tubes are not so problematic, as they were of stupendous quality even without gettering materials being used those times. Vaccuum welding and the whole process of producing tubes was already known very well and had good quality. Even today those tubes from the 1920s are being used because they were build so well. Look at WE 101D etc.
Very low power amps with transformer coupling and a frequency limited response somewhere in the region of a phone line (for some reason those first WE amps and LOUDspeakers were called "Loudspeaking Telephone". There was no audio or hifi in existence. The goal was to reproduce speech for an auditorium in the big cinema halls. No radio was invented although Marconi was already successfull with its telegraphic demonstrations and that was heavily used by mostly military industry in WW1.
Maybe ten years later, one could say there is a very early audio industry which has managed to some extend to let orchestra, music and speech be reproduced with good quality. But even this is, by modern standards, just a freq. response up to max. 10K cycles, maybe 7K max. only.
You will have a hard time to find the parts for this project. Tubes are not so problematic, as they were of stupendous quality even without gettering materials being used those times. Vaccuum welding and the whole process of producing tubes was already known very well and had good quality. Even today those tubes from the 1920s are being used because they were build so well. Look at WE 101D etc.
Which was making money.
Around 1960 a ham radio guy showed me a schematic of a 5C1 Champ that he had reverse engineered. I made a paper and pencil copy of that schematic and set out to build one. It was a crude device made on a piece of pine board with parts taken from old radios, but it worked....and the seeds of Tubelab were planted. I would spend much of my time in the 60's making and selling guitar amps made from parts salvaged from old TV sets.
One of my current TSE amps uses a pair of NX-483 tubes that I pulled from a scrap Sparton radio. The stickers on the tubes bear an install date in 1929. Those 90+ year old tubes are still going strong.
Some wonderful knowledgeable replies to this thread, as Schmitz pointed out some excellent tubes were made in the 1920's, duncan2 rightfully pointed out the cost of components is a limiting factor to most of us.
The spice idea was to see just how good one could make an amplifier work using 100 year old technology if we could actually afford the components. Unfortunately the only actual build that I could afford to make would use 45's as output tubes. The working amplifier built from kit produced in 1934 that is owned by sser2 sounds excellent, nothing wrong with 56's and 47's maybe a photo of the amplifier could be posted at some stage.
The spice idea was to see just how good one could make an amplifier work using 100 year old technology if we could actually afford the components. Unfortunately the only actual build that I could afford to make would use 45's as output tubes. The working amplifier built from kit produced in 1934 that is owned by sser2 sounds excellent, nothing wrong with 56's and 47's maybe a photo of the amplifier could be posted at some stage.
That shows that the general fear for failing tubes is almost the last part in an amp thats going to weaken its performance. From the 1970's onwards people throw their tube based radio and TV sets as garbage out of the streets. It became old fashioned with the nice wood enclusures. Obsolete technology told the marketing staff to the customers. Exchange it for better transistor gear.
The tubes, if they were quality brands, were mostly intact.
The tubes, if they were quality brands, were mostly intact.
Last edited:
At least here in the US, that practice started in the early 60's. "Old" tube desk radios in their nice wood cabinets were exchanged for "modern" plastic solid state units, HiFi consoles were tossed in favor of stereo consoles, which were eventually tossed for component sets. B&W TV's began to get traded for color, or smaller sets. Not to mention the huge vacuum tube organs of the 50's being upgraded to "transistorized" models. Where else can you get 36 vintage 6SN7's in one spot? An old Baldwin organ got me a box full. 12AU7's were also common organ tubes.
This mass disposal of vacuum tube electronics provided me with a limitless supply of free parts until I was old enough to afford buying some.
There were all sorts of amplifiers for microphone, accordion, dobro and other types of guitars long before Fender and Gibson made the more popular amps.
Somewhere around age 7 my parents gave me an electric guitar, but no amp as they thought it made enough "noise" without one. Somewhere around age 8 my father was one of the people who discarded his Magnavox HiFi for a Silvertone stereo console. I was given the Maggie, and.....it took me about 13 seconds to cut a guitar cord in half and connect its wires to the wires in the Maggie's tone arm....The kid had "made" his first DIY guitar amp.
A couple years later I was playing this creation with some friends when one brought over a Fender Champ.....I plugged into it, and suddenly the Maggie wasn't cool any more.
Another friend from elementary school had an older brother who was a ham radio guy, and played guitar. That's where the Champ schematic came from....
Given different circumstances, I could be building anything, but this was the early 60's. The Beatles were not even a thing yet, and surf music was still king, at least where I was, just a few miles from the Atlantic ocean.
In 1967 I was given a pair of early 1940's Stromberg Carlson PA amps that ran 4 X 6L6GA's. They made awesome and LOUD guitar amps. I have an identical unit here, awaiting a rebuild.
National Dobro Amplifier
Recognize picture at top its -Mad Mag -Alfred .E. Neuman
read a lot of them in the ,50,s
The RCA company was ahead of you on this project. In 1926 they introduced Loudspeaker 104, which was based on the newly-invented moving-coil loudspeaker (just like what we use today) and an amplifier using a UX-210 triode, UV-874 gaseous voltage regulator, and UV-886 current regulator tube. The output from most radios of the time was enough to drive the UX-210. Even in 1926 there was a lot of music programming on the radio and a demand for a quality, living-room level loudspeaker. I have a couple of these awaiting restoration and I’m eager to see how they sound. Probably a little tinny by our standards but potentially pretty good.
How about a magnetic amplifier using two big ferrite cores and a tube oscillator. Or one could use a big stepper motor as the HF generator, driven by a motor. With the multiple HF phases available from a stepper motor, one could overlap conduction from multiple magnetic amplifiers, avoiding the need to filter out HF from the output.
"By 1916 Alexanderson added a magnetic amplifier to control the (audio) transmission of these rotary alternators for transoceanic radio communication."
Since the Galena "coherer" was performing solid state rectification even before tubes, we should allow SS silicon rectifiers for any "Ancient" builds. Selenium for rectification is too toxic, un-available, and poor performing.
"By 1916 Alexanderson added a magnetic amplifier to control the (audio) transmission of these rotary alternators for transoceanic radio communication."
Since the Galena "coherer" was performing solid state rectification even before tubes, we should allow SS silicon rectifiers for any "Ancient" builds. Selenium for rectification is too toxic, un-available, and poor performing.
Last edited:
Slide Rule
Like this? Very cool to show off to the youngsters how it should be done - though I last used this back in 1985
Like this? Very cool to show off to the youngsters how it should be done - though I last used this back in 1985
Attachments
The first commercial amplifier tube mass produced was probably the RCA UV201 actually made by General Electric. It was available in 1920. The UV200 was a "detector" tube. Both were gas filled!!
Cunnigham produced a triode tube in 1915. They were not glass bulb tubes but rather a glass tube with the leads coming out both ends. I suspect one could rather easily make a similar tube today. Of course he was ripping off the patented work of others.
If you want to really build an oldish amplifier I would suggest the 71A tube. Still around at modest prices!
Cunnigham produced a triode tube in 1915. They were not glass bulb tubes but rather a glass tube with the leads coming out both ends. I suspect one could rather easily make a similar tube today. Of course he was ripping off the patented work of others.
If you want to really build an oldish amplifier I would suggest the 71A tube. Still around at modest prices!
A excellent source about early tube technology is the book "Saga of the vacuum tube" by Gerald F.J. Tyne, published in 1977 and reprinted by Antique Electronic Supply. This thread reminds me that I still have two french Métal TM tubes (see page 195 of the book) with good filament that I wanted to incorporate in a preamplifier few years ago, but I never dared to try. Maybe I should, they were manufactured at the end of the first world war but they aren't so incredibly rare and my specimens have cosmetical flaws, so a loss would not be a big deal. I also have a Marconi V24 (page 223) wich was built before 1921; someone in the past soldered wires directly over the terminals, maybe out of desperation because the sockets are even rarer than the tube. I see specimens of this tube sold at reasonable price on UK ebay site every few months, so I guess that it it's not even that rare, and a 100-year-old amplifier could be built without excessive risk or expense. The first problem I encountered is that there is no technical data about early tubes. At least the filament and anode voltage of TM and V24 tubes is known, but I've found no data beyond that, and no radio schematics. I suspect that the manufacturing process has not been refined enough to have consistent results, so the manufacturer has not specified them.
The RCA UV200 and UV201 are probably the earliest tubes with enough published data and consistent parameters. I was able to find a pair of brass base tipped UV201A with emission from a seller in the United States, but they got lost in the mail. At that point I was a little demoralized and I put the project aside. The 100-year-old amplifier would be a much simpler project at the end of this decade.
The RCA UV200 and UV201 are probably the earliest tubes with enough published data and consistent parameters. I was able to find a pair of brass base tipped UV201A with emission from a seller in the United States, but they got lost in the mail. At that point I was a little demoralized and I put the project aside. The 100-year-old amplifier would be a much simpler project at the end of this decade.