Quickie phonostage Idea, will it work?

[balancedtriode]

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

 

[grufti]

not enough gain and too noisy

 

[jmv]

Several battery-powered phonostage options are available out there, mostly in kit form.  A little searching will net you some good choices.

 

[Paul Joppa]

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 ...  

 

[balancedtriode]

I would have a great interest in a battey powered tube phono stage Kit
I think It would be amazing!

 

[Grainger49]

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.

 

[Noskipallwd]

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

 

[Paul Joppa]

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!

 

[Noskipallwd]

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

 

[Grainger49]

Are Nuvistors in this class of tube?

 

[Noskipallwd]

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

 

[Grainger49]

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.

 

[Noskipallwd]

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

 

[Grainger49]

This is the Nuvistor, out of focus, next to a standard PCB mount 9 pin miniature socket.

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.

 

[Noskipallwd]

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

 

[Paul Joppa]

Metal octal tubes had been made for a long time by 1959-maybe very early forties?

 

[Doc B]

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.

 

[Noskipallwd]

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

 

[Dr. Toobz]

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.

 

[Paul Joppa]

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.