So, a friend gave me a few tubes he pulled from some random equipment in a dumpster outside the EE building at my university. There are two 12ax7, two 6u8a, two 6x8, one iv2, and one 6aq5a.
I know very little about actual tube numbers (I know how they work in theory, and I have a grasp of tranistors from some classes, but nobody teaches vacuum tubes in EE classes anymore). I know the 12ax7 tubes are pretty common in preamps; can I use these tubes to make either a power amp or a phono preamplifier?
I know very little about actual tube numbers (I know how they work in theory, and I have a grasp of tranistors from some classes, but nobody teaches vacuum tubes in EE classes anymore). I know the 12ax7 tubes are pretty common in preamps; can I use these tubes to make either a power amp or a phono preamplifier?
6AQ5 is a low power audio output Pentode, good for say 2W.
6U8 is a combination Triode and Pentode good for small signal amplification
6X8 rectifier
1V2 I don't know
You can build a single channel single ended output amp with them.
If the dumpster isn't dumped yet, get the chassis for it's transformer(s).
6U8 is a combination Triode and Pentode good for small signal amplification
6X8 rectifier
1V2 I don't know
You can build a single channel single ended output amp with them.
If the dumpster isn't dumped yet, get the chassis for it's transformer(s).
The 1v2 is a low current high voltage rectifier used for focus voltage in older color television service. The 6X8 is not a rectifier, but a triode-pentode once used as an oscillator-mixer in old black & white TV tuners. The 12AX7s are really the only useful audio amplifier tubes. The 6U8 could be pressed into service if desired.
Apparently these came from an old oscilloscope-y thing. And my friend did scavenge the transformers...and then tore them apart to figure out how they worked >.<
Anyway, I guess the next step for me is to figure out how turntable preamps work and which of these tubes I can use in the design. Obviously the 12AX7s, and probably the rectifier too.
Anyway, I guess the next step for me is to figure out how turntable preamps work and which of these tubes I can use in the design. Obviously the 12AX7s, and probably the rectifier too.
Nope, not that 1V2. It's only rated for perhaps a milliamp or two at most and the voltage drop is over 100 volts. (The tube manual says a max of 10mA, but it's never used for that much. Typically ½ milliamp)
Eli: Fantastic; I'll take a look at that. I may very well build a power amp too, then; 30 WPC should be enough to drive my bookshelf speakers. Do you happen to have a link to stuff about that amp style?
HollowState: My bad; I forgot the 6U8s aren't rectifiers. Anything that 1v2 would be good for?
HollowState: My bad; I forgot the 6U8s aren't rectifiers. Anything that 1v2 would be good for?
The Scott 299D uses a 6U8 and 2X 7591s in the power section of each channel. Just look at the right hand side of the linked schematic to see the power section. We'll talk PSU, if you think this sort of stuff is within your capability. Remember tubes run at deadly dangerous voltages and reading the "nube" safety "sticky" is important.
The Dyna ST70 was an incredibly popular item, back in the day. The linked schematic shows a 7199, but substituting the 6U8 is not a big deal. Perhaps some passive parts value changes will be necessary.
The basic theme of both designs is a pentode voltage amplifier DC coupled to a "concertina" phase splitter and on to PP "finals". Please notice the global NFB loop in both setups.
The Dyna ST70 was an incredibly popular item, back in the day. The linked schematic shows a 7199, but substituting the 6U8 is not a big deal. Perhaps some passive parts value changes will be necessary.
The basic theme of both designs is a pentode voltage amplifier DC coupled to a "concertina" phase splitter and on to PP "finals". Please notice the global NFB loop in both setups.
I've been reading through the stickied threads in this forum, especially the safety one.
I'm pretty sure I could take something like this on, but I think I'll plan out and build the preamp first, to get some experience. I can follow a schematic pretty well, and I am starting to be able to see what particular parts of the schematic are for, but troubleshooting might be a different situation.
I'm pretty sure I could take something like this on, but I think I'll plan out and build the preamp first, to get some experience. I can follow a schematic pretty well, and I am starting to be able to see what particular parts of the schematic are for, but troubleshooting might be a different situation.
Get an RCA Receiving Tube Manual, it has descriptions and specs for each type, lots of schematics in the back, and I think some short theory stuff in the front. The last was marked RC-30, published in 1975.
BookFinder.com: Search for New & Used Books, Textbooks, Out-of-Print and Rare Books
Looks like the RC-30 is kinda pricey. Earlier editions are cheaper and contain most of the same stuff.
Or just put each type number into Google, and you're sure to find hits with data sheets and schematics using that type.
Just so you know, a 30WPC tube amp will have big, heavy and expensive transformers. The pic at the bottom of the ST-70 link only shows the big and heavy part.
BookFinder.com: Search for New & Used Books, Textbooks, Out-of-Print and Rare Books
Looks like the RC-30 is kinda pricey. Earlier editions are cheaper and contain most of the same stuff.
Or just put each type number into Google, and you're sure to find hits with data sheets and schematics using that type.
Just so you know, a 30WPC tube amp will have big, heavy and expensive transformers. The pic at the bottom of the ST-70 link only shows the big and heavy part.
Hmm, Amazon has some RC-30s for really cheap, but I'm suspicious they may be older versions instead of the RC-30. Either way, I'll get my hands on some version of the book; it looks fantastic.
Ouch, I didn't realize transformers were that expensive, but I guess that makes sense given the amount of metal in there. I'll definitely need three, right? One for power, and two to decouple the left and right output channels.
Ouch, I didn't realize transformers were that expensive, but I guess that makes sense given the amount of metal in there. I'll definitely need three, right? One for power, and two to decouple the left and right output channels.
Nothing cheaper than free: Technical Books Online. There are a lot of other RCA manuals and other books, all free.
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