is there a dual diode tube that runs off a 9v battery? - anyone?

[HTH]

I'm arsing round with using tube diodes as the clipping diodes in a SD-1, but the heaters in the tube diodes I have require 300mA at 6.3v (ac or dc).

This isn't a problem when using a wall wart, but it would be cool if there was an old dual diode tube that ran from a battery - there must be such a thing from back in the day.

Anyone?

[guitician]

There may be military surplus tubes from field radios that have low current draw heaters. But if you think about it, heat is power, and it hard to produce without current/voltage.

Here are some......
http://pw2.netcom.com/~wa2ise/radios/penciltubes.html

It looks like there are some that will run on a 9V.....

[guitician]

A couple of these CK5676 may work.......
CK5676 5676 Submini Triode Tube DHT for WD-11 Rebuild - eBay (item 200393838279 end time Apr-10-10 13:22:19 PDT)

Data on the CK5676 shows that it's heater uses 1.25v@.12A

http://frank.pocnet.net/sheets/138/5/5676.pdf

A pair connected as diodes, with the grid shorted to the plate, will draw 300mw.

An alkaline 9V has a rating of 450mah. So, your looking at almost two hours before the battery is drained, not very long is it.

[HTH]

Thanks for your post and help. I think you've confirmed what I've found in my own tests - tubes won't work with a 9v battery either at all, or for very long.

I've been messing with some 5726 dual diode tubes tonight and managed to get 9vdc padded down to around 6.5vdc by stringing three 1N4007s in series with the +'ve lead of the power supply.

The glass envelope gets quite hot though - gonna need some serious ventilation in the side of this SD-1 to get rid of the heat in the battery cavity.

Will post some clips of the valve diode in action compared to the silicon diodes that the SD-1 uses for clipping in the opamp loop.

[HTH]

well, I tried it and the tube diode didn't work out - don't think there is enough signal to get the diodes working. oh well.

[defaced]

What about using them as diode clippers in an amp?

[Steve Conner]

The 6AL5 is the most popular dual diode tube I can think of.

If you wanted to make a tube pedal, you would get tubes with 1.5v heaters and run them off a D size battery. An alkaline D cell gives about 10 amp-hours.

[guitician]

Looks like you would need more p-p voltage than a SD-1 could put out, which is limited to a little under 9V DC.

What about using them as diode clippers in an amp?

Yeah, maybe on the PP plates?

[imaradiostar]

12au7 is pretty happy running on lowish voltages. Maybe a low voltage pedal ala tube driver using a 12au7 (cascaded) into a 6al5 would sound good. I'd imagine you could get a blend of the triode distortion and the diode distortion depending on how you set it up. You can get around 32 volts from a 12vac wall wart connected to a voltage doubler and run the tubes from the wall wart too. You'd just have to either use a 12 volt diode or an appropriate voltage dropping resistor for the 6al5.

jamie

[Enzo]

6AL5 would be most common, but one of my all time favorite tubes - not electrically, just for coolness - is the 6H6 dual diode. It is a metal octal tube, but the thing is only 3/4 inch tall.


And another favorite tube of mine is the 1B3, just for styling elegance. A couple of those would make dandy clippers. Well they'd look good on the chassis anyway.

[HTH]

Firstly, thanks for all the responses and suggestions. I was concerned that the SD-1 wouldn't have enough peak-peak voltage to drive the tube diodes, but you gotta try these things.

Does anyone know what P-P voltage the 5726/6AL5 wants to see (i.e. turn on voltage) in order to work. In other words, a typical silicon diode will break over at 0.6vdc - what voltage would I need for the 6AL5 to start clipping?

I'm happy to mod the pedal to the point where I'm running the voltages necessary to make this work. Of course, the 4558 opamp would need to go and be replaced with something that can run above 18v (and the 'lytic caps would likely need replacing too with higher voltage types).

The datasheet on the NE5534 says it can output up to 32v P-P, would that be enough to get the 6AL5 clipping?

[Steve Conner]

The 6AL5 datasheet is linked from this page:
6AL5 @ The National Valve Museum

The V-I characteristic looks worryingly linear.

With vacuum tube diodes, the conduction voltage varies between about -1 and +1 volt, both between different tubes, and over the life of a single tube.

The softest clipper I've ever found is a 2.7 or 3.3 volt zener diode. When I tried connecting the plate and grid of a triode together to use it as a diode, the clipping was remarkably hard.

[guitician]

2v p-p is not that far from the stock 1.4v p-p of the original diodes. It could be that the heaters were pulling down the B+ limiting the max. p-p output.

[HTH]

The 6AL5 datasheet is linked from this page:
6AL5 @ The National Valve Museum

The V-I characteristic looks worryingly linear.

With vacuum tube diodes, the conduction voltage varies between about -1 and +1 volt, both between different tubes, and over the life of a single tube.

The softest clipper I've ever found is a 2.7 or 3.3 volt zener diode. When I tried connecting the plate and grid of a triode together to use it as a diode, the clipping was remarkably hard.

hmm, could mix/match the valve diode clipping with silicon diodes in series - that would give a higher clipping threshold. thats IF I can get this to work.

gonna mess round with this again and post back with a diagram of how I'm connecting it up if this doesn't work since you've got this to work and other people claim to be able to get this working too.

its gone past whether it sounds good or not - now its a case of just getting it working to satisfy my curiosity AND I don't like being beaten by this stuff.

[HTH]

2v p-p is not that far from the stock 1.4v p-p of the original diodes. It could be that the heaters were pulling down the B+ limiting the max. p-p output.

The heaters shouldn't be pulling down B+, but I'll hook up a DMM when I mess with this tomorrow. I'm using a 1200mA regulated DC supply, so there should be no problem supplying 300mA to the 12AX7's heaters and power to a SD-1.

[paggerman]

Hi Defaced, I pulled apart a Nippergram radio/record player the other day and in it was a 6X4. This is a full wave rectifier, which in my dangerously under-educated mind means two diodes. From the datasheet: 'For use in compact ac or auto receivers where the average current is not in excess of 70ma'.

[guitician]

6x4 is a common cathode dual diode.

HTH... I was thinking your still using battery power.

And while I was into clipper circuits I found that to simulate "Gain", your ratio of diode threshold to peak input should be as great as possible. This allows the signal to remain clipped longer as the note decays.

[HTH]

well, it works now, but sounds shit - HARD clipping like Steve O'Connor reported in his experiments.

more work needed on this one I think.

[J M Fahey]

Yes, hard clipping. Fact is , "tube sound/clipping" which we want to emulate, does not come from any diode action within the tube per se, but from a very complex interaction of plate-approaching-cathode-voltage + gate-cathode diode conduction + screen voltage going down (if we have a screen) + gain compression because of transconductance shifting + internal resistance shifting + probably a host other factors I fail to see but which are doubtlessly there.
Compared to that, diode clipping is boring (no news around here) and tube diodes are not much more than funky diodes, certainly with different threshold and curve slopes, but nothing to write home about.
Of course, slamming an orange glowing filament within an otherwise SS amplifier doubles or triples its marketability.
F*nd*r had the chutzpah enough to slam a dual diode connected (grids tied to plates) 12AX7 into the Performer and Rock-something series and call them "Tube Preamps".
Funny things is they used so-called "black tubes", 12AX7 shrink-wrapped, soldered to PCB pads (no sockets). They were "eternal" for all practical purposes and obviously it was a way to somehow use microphonic/hissy/way out of spec "junk" tubes. Oh well.