I bought a box of old valves, some new in box and I want to build some projects

[hofnergalaxie]

Hi there, I hope the title introduced this thread well.

Here is a list, most have been never used and are in boxes.
6SQ7-GT - TOSHIBA
6CM5 - AWA
IB3GT - BRIMAR
6DT6 - HITACHI
?????A - MULLARD
?IT4 - AWV
6EM5 - PHILLIPS MINIWATT
6JW8 - AWV
12BE6 - HITACHI
6CG8A - PHILLIPS MINIWATT
6J6 - TOSHIBA
6AL3 - MULLARD
N78 - AWV
IR5 - PHILLIPS MINIWATT
6U9 - MULLARD
6CM5 - AWV
ECL85 - MULLARD
6CU6 - AWV
6EA8 - PHILLIPS MINIWATT
6X4 - HITACHI
6SN7GT - TOSHIBA
6AQ5 - AWV
6BL8 - AWV
6X5GT - TOSHIBA
6BL8 - PHILLIPS MINIWATT
6CS6 - AWV
6AN7A - MULLARD
IS5 - AWV (DATED 28/03/1951)
6N8 - PHILLIPS MINIWATT
6CS6 - PHILLIPS MINIWATT
6C4 - HITACHI
6AJ8 - HITACHI
6CS6 - PHILLIPS MINIWATT
12AV6 - HITACHI
6AM8A - HITACHI
5U4GB - HITACHI
6BX6 - PHILLIPS MINIWATT
6EW6 - PHILLIPS MINIWATT
6EA8 - AWV
6AL3 - PHILLIPS MINIWATT
6AX4GT - AWV
6BD7 - AWV
6AR7GT - AWV (HAS WEIRD METAL TAPE AROUND SOME OF IT)
12AT7 - HITACHI
3V4 - AWV
XC81 - AWV
B7L - MULLARD
6EM7 - AWV(BROKEN PIN)
6X9 - MULLARD
6U9 - PHILLIPS MINIWATT
6BQ5 - HITACHI
6SH5 - PHILLIPS MINIWATT
6CG8 - HITACHI
6EJ7 - PHILLIPS MINIWATT
6V6 - RCA
Z729/EF86 - MULLARD
2A17 - PHILLIPS MINIWATT

There are also have about 20 others that have had their labels rubbed off and other questionable looking ones with black burn marks. They aren't including in the list.

I am interested in building small amps for playing music and guitar amps.
Many of the tubes are small so I was thinking I could use them with 9-12v supply, perhaps using a joule thief/booster circuit. I heard them being used.

I just wanted to put the list as there could be some tube combinations there you will recognise and point me to a schematic or something.

Thanks in advance,
HG

 

[gingertube]

HG,
Just a quick breeze thru' your list.

preamp Tubes:
6SQ7
6SN7
12AV6
6BD7
12AT7

Rectifier
5U4

Power Output
6CM5 (EL36)
6EM7 - great for flea power Single Ended Amp, triode + output triode
ECL85 (6GV8) triode + output pentode
6AQ5
6V6

Phase Splitters for push pull output
6BL8
6N8
12AT7

For Power Amp Section around 40 Watts use push pull 6CM5. Look at some old Ampeg circuits using 6AN8 as the phase splitter /driver and use 6BL8 instead.

12AV6 is a high gain triode equaivalent to half of a 12AX7.
12AT7 is twin triode useful for preamps.
6BD7 is also a twin triode which may be handy.
6SN7 is low gain twin triode good for Jazz or Blues preamp.

For low power single ended amp (studio or bedroom amp)
6V6
6AQ5 (is a 6V6 in a 7 pin small package)
6EM7 is a high gain signal triode (same as half a 6SL7) and an output power triode simililar to 2A3 - should make a stunning little amp
ECL85 (6GV8) is a triode (equivalent to 1/2 a 12AT7) + an output pentode equivalent to a 6M5 (EL80).

The short amswer is that I can't think of a circuit which uses a particular combination of the tubes you list but many which could be adapted to use those tubes.

What would you want to build?
For small amps to play music the 6EM7 is probably "the go", search for "spud" amps (spud meaning single "tuber").

6V6 are one of the highest regarded tubes for guitar amps, about 3.5 watts from just one tube in single ended, about 12 to 14 Watts in push pull.

Any published guitar amp preamp circuit can use the 12AT7 triodes and the 12AV6 triode in place of a 12AX7 triode with no changes to component values.
Cheers,
Ian

 

[chrispenycate]

Somebody else having talked about the tubes themselves. I'm going to talk about transformers, and power supplies.

Valves are inherently high voltage, low current devices. As loudspeakers aren't you need a transformer to match their outputs to their loads. These transformers come in a variety of powers and ratios, and the sound of an amplifier depends a lot on their quality. If you were building a preamplifier to get the vacuum state sound with a solid state power stage, you might be able to avoid them, but otherwise you're looking into output transformers – and they're quite heavy, and expensive.

Even if you do go for a preamplifier as a first project, you're not going to be able to run it off a wall wart power supply. Preamp valves are rarely run below a hundred volts, typically quite a bit higher, and I can't think of a power amp circuit that runs below 250VDC. Voltages which bite you if you are not careful with them. Additionally, because the cathode must be hot to emit electrons, valve mains transformers have one or several "heater" windings on them, to run the internal filament heaters. Typically 6.3 volts AC, though you can rectify it and use DC heaters if you like. Old television valves (which I'm happy to see you don't seem to have any of) ran their heaters in series, with a fixed current rather than a fixed voltage, which made everything very complicated.

So the very first stage in your project is to build a power supply, probably solid state rectifiers and no smoothing choke, at least to start with. If you can arrange it so the transformer can be rotated, so its magnetic leakage fields can be directed away from the sensitive grid regions of your valves, so much the better (since the electrons are actually traversing space they are vulnerable to both electromagnetic and electrostatic fields. Those screening cans (who sells screening cans nowadays, by the way?) are aluminium; they're good for the electrostatic, but don't do much for the magnetic hum fields. When you've worked out the positioning of the transformers, punch the holes for the valve sockets, and mains connector and drill for connectors, pots, fuse holders and the stand off for the tag board. Punch for one or two extra valveholders; an empty one isn't too ugly and it's easier now than when you decide later to add…

I assume you know that valves plug into sockets, they are not soldered to directly, which not only means you need to find a source of octal and b9a sockets (either chassis mounting or PC, depending on how you're intending to construct. Personally, for prototyping, I'd go for chassis mounts and tag board. Not only does it look splendidly vintage, you can modify endlessly, and try things out. Besides, with the higher voltages, greater spacing is advised than with most PC layouts. But (he says, coming back to his poor, deserted sentence, you will need tools to make fairly large round holes in chassis. Even I'm not sure I've got chassis punches for valve sockets any more, just XLRs, and I don't think you'd get an octal socket through that. And you'll need chassis to make holes in. These used to be universally available, but it seems plastic boxes have taken over.

The valves with black marks on; are those sort of metallic reflective black? If so, there might be nothing wrong with them at all; when emptying the air out of the envelope they used to (probably still do) put a little metal vapour into the glass envelope to chase out the last molecules of air. When this condensed on the cooling glass, it often left those spots.

And remember, whenever you're working with valves, you're playing with voltages that can kill you.

 

[hofnergalaxie]

HG,
Just a quick breeze thru' your list.

preamp Tubes:
6SQ7
6SN7
12AV6
6BD7
12AT7

Rectifier
5U4

Power Output
6CM5 (EL36)
6EM7 - great for flea power Single Ended Amp, triode + output triode
ECL85 (6GV8) triode + output pentode
6AQ5
6V6

Phase Splitters for push pull output
6BL8
6N8
12AT7

For Power Amp Section around 40 Watts use push pull 6CM5. Look at some old Ampeg circuits using 6AN8 as the phase splitter /driver and use 6BL8 instead.

12AV6 is a high gain triode equaivalent to half of a 12AX7.
12AT7 is twin triode useful for preamps.
6BD7 is also a twin triode which may be handy.
6SN7 is low gain twin triode good for Jazz or Blues preamp.

For low power single ended amp (studio or bedroom amp)
6V6
6AQ5 (is a 6V6 in a 7 pin small package)
6EM7 is a high gain signal triode (same as half a 6SL7) and an output power triode simililar to 2A3 - should make a stunning little amp
ECL85 (6GV8) is a triode (equivalent to 1/2 a 12AT7) + an output pentode equivalent to a 6M5 (EL80).

The short amswer is that I can't think of a circuit which uses a particular combination of the tubes you list but many which could be adapted to use those tubes.

What would you want to build?
For small amps to play music the 6EM7 is probably "the go", search for "spud" amps (spud meaning single "tuber").

6V6 are one of the highest regarded tubes for guitar amps, about 3.5 watts from just one tube in single ended, about 12 to 14 Watts in push pull.

Any published guitar amp preamp circuit can use the 12AT7 triodes and the 12AV6 triode in place of a 12AX7 triode with no changes to component values.
Cheers,
Ian

Thanks for your helpful & thoughtful reply gingertube. Breaking the tubes up into lists is a huge help.

I have limited experience and expertise in electronics but have been building 0-9v battery circuits for about 4 years. I've made many fuzz face/distortion circuits and have recently built a mono 2.5 LM380 amp with built in switchable overdrive circuit running off 2x9v batteries.

I have never made anything that runs off of ac mains supply and understand the seriousness of knowing what you're doing if you want yourself and others to live. I will read as much as possible about building tube amps and the safety measures required before beginning - just wanted to clarify that.

There are 3. things I want to build.

1. A small simple (class a) guitar amp that I can crank in my small bedroom studio. I want some nice tube breakup distortion.

2. A small simple mono amplifier that will have rca and 3.5mm input. Just for plugging tablet, laptop, phone into. I'll look into trying to repair that broken pin on the 6EM7 for that spud project perhaps?

3. A battery powered single or dual tube amp. I want to try and look into using a joule thief type circuit to conserve battery power. I'd want to use 2 rechargeable 9v batteries(solar panels!) or something.

So using the 6aq5 and the 6v6 together could be a good option? Or I could make two!

Thanks again gingertube, you're sending me in the right track.

 

[hofnergalaxie]

Thanks so much Chris, the information is very valuable and thank you for taking the time to help me out. I'll study these posts more.
My electronics shop has the power valve sockets (8 pin) and the smaller 9 pin ones. I have alot of 7 pin valves I have to source sockets for.

I have a few furniture piece organs from the 60s/70s. A Lowrey Magic Genie 33 I think, which I've stripped for wire so far - would those transformers be suitable I wonder? The other one is a Lowrey but it's too cool to rip apart as it does Baba O'Reiley on it. Another is a 60s Farfisa one, it has a few buggered keys but sounds really nice. What I'm thinking is - I don't really have the room for them and if the parts are worth getting - I'd do it. Also got a small Peavey bandit amp that doesn't work anymore. What about 70's/80s tuners/hifi amps?
Thanks again.

Somebody else having talked about the tubes themselves. I'm going to talk about transformers, and power supplies.

Valves are inherently high voltage, low current devices. As loudspeakers aren't you need a transformer to match their outputs to their loads. These transformers come in a variety of powers and ratios, and the sound of an amplifier depends a lot on their quality. If you were building a preamplifier to get the vacuum state sound with a solid state power stage, you might be able to avoid them, but otherwise you're looking into output transformers – and they're quite heavy, and expensive.

Even if you do go for a preamplifier as a first project, you're not going to be able to run it off a wall wart power supply. Preamp valves are rarely run below a hundred volts, typically quite a bit higher, and I can't think of a power amp circuit that runs below 250VDC. Voltages which bite you if you are not careful with them. Additionally, because the cathode must be hot to emit electrons, valve mains transformers have one or several "heater" windings on them, to run the internal filament heaters. Typically 6.3 volts AC, though you can rectify it and use DC heaters if you like. Old television valves (which I'm happy to see you don't seem to have any of) ran their heaters in series, with a fixed current rather than a fixed voltage, which made everything very complicated.

So the very first stage in your project is to build a power supply, probably solid state rectifiers and no smoothing choke, at least to start with. If you can arrange it so the transformer can be rotated, so its magnetic leakage fields can be directed away from the sensitive grid regions of your valves, so much the better (since the electrons are actually traversing space they are vulnerable to both electromagnetic and electrostatic fields. Those screening cans (who sells screening cans nowadays, by the way?) are aluminium; they're good for the electrostatic, but don't do much for the magnetic hum fields. When you've worked out the positioning of the transformers, punch the holes for the valve sockets, and mains connector and drill for connectors, pots, fuse holders and the stand off for the tag board. Punch for one or two extra valveholders; an empty one isn't too ugly and it's easier now than when you decide later to add…

I assume you know that valves plug into sockets, they are not soldered to directly, which not only means you need to find a source of octal and b9a sockets (either chassis mounting or PC, depending on how you're intending to construct. Personally, for prototyping, I'd go for chassis mounts and tag board. Not only does it look splendidly vintage, you can modify endlessly, and try things out. Besides, with the higher voltages, greater spacing is advised than with most PC layouts. But (he says, coming back to his poor, deserted sentence, you will need tools to make fairly large round holes in chassis. Even I'm not sure I've got chassis punches for valve sockets any more, just XLRs, and I don't think you'd get an octal socket through that. And you'll need chassis to make holes in. These used to be universally available, but it seems plastic boxes have taken over.

The valves with black marks on; are those sort of metallic reflective black? If so, there might be nothing wrong with them at all; when emptying the air out of the envelope they used to (probably still do) put a little metal vapour into the glass envelope to chase out the last molecules of air. When this condensed on the cooling glass, it often left those spots.

And remember, whenever you're working with valves, you're playing with voltages that can kill you.

 

[chrispenycate]

The battery one is going to be a pig. No, I'm not saying don't do it, but it's going to involve lots of power supply work. My portable radio when I was a kid had a 90 volt HT battery, and a four and a half volt flat for heaters (it was eight times the size of anyone's transistor portables, but it sounded at least eight times as good. Transistors back then had numbers like OC171, meaning a triode with no heater volts, and nobody had worked out how to get quality out of them yet.) You don't want ten seriesed 9 volt batteries, which means a switch mode power supply to get up to HT, and I don't know if there's one conveniently commercially available (48 volts for phantom supplies, yes; perhaps two of those in series?), then there's the heaters, running all the time on six volts…*I think you might end up on C cells, or even D rather than nine volt and yes, I know about the weight, remember that radio?

Organs, apart from tone wheel organs, went transistor quite early; you've been stripping the wire out, were there valve bases in there or bakelite PCs? Even if the tone generation was solid state the amplification might have been valves, which would give us a mains transformer (apologies to our transatlantic cousins that might be reading this; I am using "valve", short for "thermionic valve" everywhere, and "mains" is power – a mains lead would be a power cord, OK?) with a reasonable secondary voltage and heater wiring. And, by the seventies, most HiFi had gone transistor; you'd need sixties gear, from the period when you could heat your room listening to a symphony.

The Peavey bandit appears to be solid state, so the transformer's useless for us. For these projects, anyway. Valve televisions are useless in that, in general they didn't use transformers, just rectified the mains.

So, a little lateral thinking. We could use two mains transformers, one for the heaters - and obtaining 6 volts isn't too hard – and one for the HT. For preamp circuits, an isolating 230/115 volt transformer would rectify up to a usable 150 volts (note that "isolation" – not an autotransformer. Perhaps one of those bathroom transformers "for electric razors only" things. For low power amps, a 230/230 isolation transformer, then we need an output transformer, a lot of 100 volt line building installation speakers have audio matching transformers of about the right ratio (and valves, when not required to give ultimate fidelity are very forgiving). Of course we could find sources to buy in the iron directly, as we're going to have to do for the 350 volt electrolytics and rectifiers, but Henry's on Edgeware road is no longer there with its selection of transformers of all shapes and voltages (and weights, as I remember it).

 

[hofnergalaxie]

Fair enough I see. I'll have to check the amp in the organ to see if it has valves. I am hoping not to have to buy iron but at last resort I will. There is a good recovery yard in my town that often has pretty old record players/hifis.

Thinking about something a bit like the Fender Champ 5F1 http://www.sophtamps.ca/images/champ/champ_5f1_schem.gif

 

[hofnergalaxie]

Ha that sounded like a cool setup - did you build it yourself? I might put the battery one aside for now then and concentrate on my little mains recording amp. Thinking of a 5F1 Champ or something like that - http://www.sophtamps.ca/images/champ/champ_5f1_schem.gif
I'll check the organ's amp to see if it is not solid state & also check my local recovery yard for old gear for cheap. I've got alot to learn about transformers I'll need, how to test them.etc.
Thanks a lot.

 

[chrispenycate]

Transformers are difficult to burn out, even with stupidity (yes, all right, I admit I've managed a few, but…) Maybe a fifties radiogram, or – no they're already on antiques roadshow worth their weight in gold.

Yes, the Champ looks like a good first project, but you will notice they give no details of HT voltages (though the 450 volt electrolytics give us a clue) or the ratio of the output transformer. I don't know the 6V6 as well as I know eg. the EL84, and I'm in process of moving, so my "Radio Valve Data Book" is sealed into a cardboard box.

I'd still use solid state rectifiers; you'll notice the valve rectifier requires a separate heater winding and, apart from a slower warmup time (which is good for the life expectancy of the capacitors), has no major advantages.

If you punched the holes for an extra valve base (and left space on the faceplate for some extra pots) you could later add a tone control, of overdrive, or even a vibrato or reverb spring.

 

[hofnergalaxie]

That's good to know- means I may be able to salvage them. Can you think of any odd applications transformers would be used in excluding an amp?

Ok I'll keep on looking for a schematic with that information - and one with a ss rectifier,

As for chassis - I've never made one before, nor punched holes. I could get them made at a sheetmetal shop and punch them myself. What tools will I need?

I like the idea of having the option to modify in the future.

 

[djgibson51]

2x 6BL8's,
12v wall wart
240v/12v transformer
5 watt 100v line transformer.

See schematic on Page 140 of 100 buck amp challenge.
See picture on Page 133 ditto.

Have fun, don't touch the wires.

Cheers
JimG

 

[chrispenycate]

For the schematic - you just take out the rectifier valve, the 5Y3GT on the diagram (which needs a 5 volt heater winding anyway) and replace it with a pair of 1N4007 diodes (or whatever the modern equivalent is) with the white-striped end toward the reservoir capacitor, the other end to the transformer windings. That's it; no other mod required. They cost about a cent each, if you buy twenty.

Before going to the sheet metal shop, check that chassis are not available somewhere ready bent (as they always used to be) – surely not everything goes into plastic boxes? A quick google brought up mainly ridiculously expensive units in the USA (where are you, by the way? helps for suggestions.) but that wasn't conclusive. If you do go to a sheet metal place, check whether they've got a fly press (or modern equivalent), and can do the round holes for you. Just involves planning and drawing out in advance, and then you drill the holes for mounting screwa, tag board or tag strip, fuse holders… those latter are frequently difficult to do well. I used to have Qmax chassis punches for all standard holes (Octal, b9a, b7g) and I think my 19mm for male switchcraft XLRs would probably do b9a) but I haven't been involved with this for some time, and I get the impression that prices have gone silly. If you're using aluminium chassis, you can use a hole saw, or buy a conical drill bit (nasty, but it works) - you'll need a decent drill, anyway, for pot, switch and jack holes.

Fifties and early sixties everything electronic had valves – but there just wasn't that much domestic electronics. And the most prevalent, the television, cut weight and cost (and any slight hope of safety) by not using mains transformers. I've salvaged ex medical gear, devices from university experiments, office intercoms and valve pape recorders, but by now most of that backlog has gone. And not all of them were suitable for power amplification, anyway; not only because they didn't always have enough current, but if they were designed for preamp style work they didn't have enough voltage. You really need at least 400 volts, and you'll find circuits on this forum exceeding 1000 volts (but the UHT winding of an old cathode ray tube oscilloscope is useless, because of its negligible current rating).

 

[Nigel Goodwin]

For the schematic - you just take out the rectifier valve, the 5Y3GT on the diagram (which needs a 5 volt heater winding anyway) and replace it with a pair of 1N4007 diodes (or whatever the modern equivalent is) with the white-striped end toward the reservoir capacitor, the other end to the transformer windings. That's it; no other mod required.

I would suggest you should place a wirewound resistor between the diodes and the reservoir capacitor, this simulates the 'highish' impedance of the valve rectifier and will keep the HT rail at a similar level.

Otherwise the amp runs at a higher voltage, and doesn't have the PSU 'sag' which is common with valve rectifiers.

 

[hofnergalaxie]

Awesome, thanks for all the replies - they are prompting me to do some research. I will re read until I completely understand what's going on. Thanks again