Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Quickie => Topic started by: balancedtriode on June 28, 2012, 12:46:26 PM
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I was thinking of making a completely DC powered system for my klipsch's.
if i put a passive RIAA EQ Between 2 quickie gain stages, do you guys this would work?
just one of those ideas I have in the shower or in some cases crossing a busy street ;)
-coltrane
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not enough gain and too noisy
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Several battery-powered phonostage options are available out there, mostly in kit form. A little searching will net you some good choices.
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I tried to work this out a while back, when we were first working on the Quickie. The main problem is getting enough gain; I can't see it with less than three stages. (Using Quickie stages, you'd need about five of them...) The Quickie circuit could possibly be the third stage, with a volume control in front of it - it would rely on having the RIAA stage(s) physically together with the preamp, since a suitable gain stage would have a high output impedance and couldn't drive cable capacitance comfortably. A secondary problem is that the higher-gain tubes usually don't work that well at 36 volts; then want 50-100 volts.
One upshot is twice as many filament batteries, and possibly more than twice as many high-voltage batteries. At that point, you have to ask "how much battery budget is practical for a product?" One approach there would be an inverter to get high voltage from a single D-cell. We're planning to explore that, but it introduces an internal AC power that kills the purity of DC power.
If there's enough interest within these restrictions, I'll look at it again - I have always thought it would be a cool thing. Some people have DC brushless motors for their turntables ...
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I would have a great interest in a battey powered tube phono stage Kit
I think It would be amazing!
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This doesn't sound feasible without a goodly investment in SLA batteries and a charger. A good cheap charger is under $40. Those that sell for under $10 will just create smoke.
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Most of the commercially available battery powered phonostages are solid state based designs, a little easier to implement than a tube based unit. I have heard the Nova Phonema, sounds great when used in battery mode. I remember seeing a kit recently that uses the tiny Raytheon tubes with flying leads, but I did not read the article in depth.
Cheers,
Shawn
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Shawn, that's a good idea - I forgot, there are some hearing-aid tubes that have much smaller current drain and might work if a Quickie output stage is used. I'll look into it - I also think it would be pretty cool!
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I remember the tube now, Raytheon JAN6418. I am not sure what the military used them for, but I remember that Audio Technia still builds a microphone with this tube. Hearing aid tubes? My father has a cochlear implant, I should tell him I could have saved him money by building him something with tubes!
Cheers,
Shawn
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Are Nuvistors in this class of tube?
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Hey Grainger, are you referring to the "Nuvistors"? If so, i believe they are all small signal tubes. The Raytheon is a conventional glass tube with flying leads. Looks like an oversize Christmas tree light. I don't know about the hearing aid tubes, but my guess is that the Nuvistors might have worked for that application.
Cheers,
Shawn
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Shawn,
Yes, my typo is corrected. The ones I am familiar with are metal encased and smaller than an acorn. And a yes to small signal tubes. I have two, can't remember where from or why. It has been that long ago.
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Grainger, I make typos so often that Typoist was added to my title at work. The Nuvistors are the metal and ceramic ones correct? I read something about them a while ago, it said that they had to be manufactured in a vacuum chamber by robots.
Cheers,
Shawn
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This is the Nuvistor, out of focus, next to a standard PCB mount 9 pin miniature socket.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi244.photobucket.com%2Falbums%2Fgg7%2FGrainger49%2FFor%2520Posts%2520Private%2FNuvistor.jpg%3Ft%3D1341081432&hash=a3bc551b6a860200ac012c9c26b0186596fcc6f3)
The outer shell is metal and the leads fit into a tiny, tiny socket.
If manufactured by robots they were early. This tube was old by the 80s (early robots). I knew of them in the 70s.
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Cool, thanks for the picture Grainger. Went and found the article I read. You're right, developed by RCA in 1959. It said 'robotic devices', which I assume were motorized arms or something similar manipulated by a human. I guess there was no way to evacuate a metal envelope.
Cheers,
Shawn
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Metal octal tubes had been made for a long time by 1959-maybe very early forties?
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I think the potential issue is that nuvistors were not created with the idea of low current draw for use with batteries. I haven't checked specs, but I think they may draw more current than "battery specific" tubes.
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Here's a link to a data sheet if anyone is interested, http://frank.yueksel.org/other/RCA/RCA_Nuvistor_Tubes.pdf , nope, doesn't look like they are suitable for this purpose. Oh, almost forgot, Paul there is a portable headphone amp kit based on the Raytheon tubes available, I remember reading some reviews, seems the tube is a little too microphonic for a portable device but the opinions on the sound of the tube were favorable. All heresay of course, never heard it myself.
Cheers,
Shawn
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Those little "Christmas tree light" tubes are unbelievably microphonic. I have a bunch in my junkbox and have played around with them on a breadboard to learn about how tubes work, try various operating points, etc. The filament only draws something like 10mA and is the thickness of a hair, and if even so much as wind goes by the tube, it rings like a bell. The ringing lasts for at least 30 seconds. I was going to use these in a Quickie to make a headphone amp for my guitar (using a few of the little tubes for gain and tone duties, then taking the output to the pair of 3S4 tubes wired in push-pull), but never found a good way to damp them. In between the ringing, they do sound good, however. I've only wired them as triodes.
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Bummer about the microphonics - that's a killer for a phono preamp! I'll keep looking though, there may be a better candidate. If they made hearing aids there must be a mic preamp tube. There is the 1U5 in regular 7-pin form which was intended for mic preamps, but it's drawing 50mA heater and we'd need two per channel, minimum.
That 6418 is a beam power tube, capable of a full 0.002 watts output ! :^) I just read the data sheet.
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Is there anything in the battery tube (7-pin) world that even comes close to a normal hi-mu triode like a 12AT7 or 12AX7 when used in pentode configuration? The problem I've found with the battery tubes is that they all seem to have rather low amplification factors. This appears to preclude their use in things like phono or guitar amps without using a bunch of stages....
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Yes, that's the problem. Tiny cathodes need little heater power but can't muster very many electrons. So you need either very high impedance loads, or you settle for low gain.
Example: 1LH4, mu is 65 but rp is 240K. That's nearly 100 times higher than the 6922 used in Seduction!
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Steve Bench has done a bunch of work with the pencil tubes (including a phono stage using 6088 tubes) using battery power. Check this out: http://www.jacmusic.com/techcorner/SBENCH-PAGES/sbench/6088pre2.html
He's no slouch, either. Check his no R no C amps. Fun!
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Steve is a very smart and very nice guy. I "licensed" a hum cancellation circuit from him years ago, for our long since retired Parabee amp (I think I traded a kit to him). It worked for me, but for some reason it didn't work too well in the field. So I would simply suggest that one might do their own due diligence when trying his very intriguing ideas. They are often tantalizingly off the wall. Could very well be that we had some other issues in our designs that didn't allow his circuit to work. I think that he is one of the most cutting edge guys out there.