| Alastair E |
Has anyone else tried various valves at say, only 12V +B....
Not the special 'Space-Charge' types, but common ones like the 6DJ8
I have done some low-voltage experiments all based on 12V +B, and was very surprised what can be done with ordinary valves....:bigeyes: |
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| owen |
Then you'll be even more suprised what valves designed for car radios can do ;)
Owen |
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| Alastair E |
| quote: | Originally posted by owen
Then you'll be even more suprised what valves designed for car radios can do ;)
Owen |
I can imagine...
Heaters, 12V....
+B, regulated 6V...:eek: |
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| Nordic |
I'm jst putting the last few touches to it, but I am basicaly just finished with one... will post in the morning, little tired now...
But it basicaly runs of 9V B+ and 9V cell on cathode.... ecc88/6dj8/e188cc/6922 with opamp as output stage... |
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| Alastair E |
| Have you seen this, I posted it under a different thread while trying to help out a guy with a baulky Tubalizer device.... |
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| aletheian |
| quote: | Originally posted by Alastair E
Has anyone else tried various valves at say, only 12V +B....
Not the special 'Space-Charge' types, but common ones like the 6DJ8
I have done some low-voltage experiments all based on 12V +B, and was very surprised what can be done with ordinary valves....:bigeyes: |
I have chimed in on eht other threads, so maybe this is redundant, but I'll expand on what I have tinkered with.
in terms of linear audio amplification, i have had good luck with the 6922 family as low voltage impedance buffers in front of solid state circuits, running off the SS PSU. I have built up a couple preamps and buffers for my SS power amp, and my computer soundcard that run on very low voltages, and in front of some chipamps and they worked out quite well. They were not clinically clean, but the harder sounding 6922's hit you with enough 3H that the increased 2H is not too mucky... in other words... distortion specs aside, it SOUNDS good to me. I have also used the same circuits with an output transformer for a balanced output.
For purposely trying to "tube up" the sound to approaching smarta$$ levels, I have run ecc82 a low volts, which gives horrendeous distortion figures, but sound really 'fat'. I used that for signal processing in a DAW, not hi-fi, so the nonlinearity was the point. Ecc81 worked as well, but not ecc83... at all.
I have also built up a few musical instrument amps with voltages that low. that is fun to tinker with. The voltage swing is the biggest limiting factor. since hot guitar pickups and bass pickups can hit around 9v peak or more just by themselves. |
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| Eli Duttman |
The 6GM8/ECC86 is a close relative of the 6DJ8/ECC88 intended for low voltage service.
6GM8 data sheet here.
While it definitely will work with 12 V. B+, you can't swing much of an audio signal. With B+ of about 25 V., you can do some good things. |
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| aletheian |
| quote: | Originally posted by Eli Duttman
The 6GM8/ECC86 is a close relative of the 6DJ8/ECC88 intended for low voltage service.
6GM8 data sheet here.
While it definitely will work with 12 V. B+, you can't swing much of an audio signal. With B+ of about 25 V., you can do some good things. |
I just ordered a pile of those things. You can find them cheap at online surplus places. |
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| Wavebourn |
| Collins R-392 receiver works from 28V and uses particularly 6AK5 and 12AX7 tubes. |
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| HDaudio |
| quote: | Originally posted by Alastair E
Has anyone else tried various valves at say, only 12V +B....
Not the special 'Space-Charge' types, but common ones like the 6DJ8
I have done some low-voltage experiments all based on 12V +B, and was very surprised what can be done with ordinary valves....:bigeyes: |
Hi Alastair E !
I undesrtand you have power stranfomer out with 12VAC, if you have 12 - 0 - 12 vac,and now we have 24 - 0, then put two diot and we have 24vac x 1*4 *2 = nearly 60 vdc , remember dont forget capacitor and do C-R-C about 50VDC, we have B+ verygood for 6922, and 182cc,.6C4..v use IV for DAC, preampli. v.v.
For heater we do R+R+R and x+x+x= number VDC from X ( R) go down from B+.
Same here :
Goodluck ! |
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| andrew_whitham |
Alastair E
If voltage doubling is an option, ie you have AC voltage to use, look around the forum for the Musical fidelity X-series, X-Can, X10-D etc they fairly sucessfully get +/- 60v from a single 12vac source. And use the 6922 /ECC88 as standard
Its an alternative to the fancier types of tube I guess - a fancier PSU
Also take a look at headwize.com they have a section on tube headphone amps. If I recall one uses low voltages.
what experiments did you do? I'd personally be interested to know if you got consistency with the 6dj8 at lowwww voltages?
Andy |
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| Alastair E |
I was experimenting at 12V as I didnt want inverters etc or voltage-doublers as its to be used in the car., direct off the usual 12-14V supply...
Ive found great results with various valves in the scheme Ive posted, as there is huge amounts of local Neg FB at the expense of gain. I was looking for a small pre-amp to run between a MP3 and a class T in the car. The Class T and MP3 combo dont quite get the job done and a little extra gain is needed I didnt really fancy messing round with the class T input stages as the print on the TA2020 E.B development kit I have is pretty cruddy....
Ive tried various valves in the scheme, such as the 6SN7, 5687 , 6/30L1, 6DJ8 family and the 7586 Nuvistor valves- All work pretty well.
There is very little difference sonically between 12V and 24V +B, apart from a slight increase in gain at the higher voltage. Current through the valves however gets above 1mA into more 'Normal' ranges!
The Higher Mu types like the 6CW4 and 6SL7 'ECC83 worked' but sounded pretty hideous, I guess this could be improved by altering bias/local neg FB but I havent explored that yet..
I quite like the challenge of restricting myself below 15V just to see what can be done with the common audio valve types like above, rather than the special Car-Radio tubes made specially for 12V.....(I havent actually got any of those 'specials' 12V valves at the moment either!)
:bawling: |
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| poynton |
Hi.
I messed around with low B+ when I was developing a tube output stage for the CD63.
ECC88 worked ok to +12v as did the following wire ended minature tubes - 6021, 6BF7W
Andy |
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| 316a |
Hi ,
Don't discount the directly heated types at low voltages , around 40-50V . Battery valves such as trioded 1S4 and type 49 work well , as does the 958A acorn . I built a battery operated linestage with 1S4 last year with six PP3 batteries clipped together and a D cell for each filament with dropper resistor . The whole thing fitted in the palm of my hand and sounded quite good for a junk project ;) There are also various wire ended electrometer valves which can run off 12V but no idea about how linear these are . Also the wire ended types (was it CV1/2/3 or 4?) designed to be used as proximity fuses in artillery shells may be of use , no idea of the linespan of these :LOL:
cheers
316a |
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| Nordic |
Here is my 9V headphone amp
E188cc with round getter + NE2322 opamp
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| lousymusician |
I've got a Scott Nixon TubeDAC that uses a 6DJ8 cathode follower at 24V (voltage doubled from the 12 VAC input) as the output buffer. I have no measurements for it, but it sounds pretty good to me.
What would it take to swap in a 6GM8, just for the heck of it? |
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| andrew_whitham |
| quote: | Originally posted by Alastair E
I was experimenting at 12V as I didnt want inverters etc or voltage-doublers as its to be used in the car., direct off the usual 12-14V supply... |
I see :bigeyes: clever stuff,
You do have an alternative though, for the currents needed in a preamp a dc/dc converter might be useful, (you can get 12v to 100's of volts in a 10mm cube - not too car unfriendly?)
I've used them before to get 200v from 24vdc (PICO 28A200S) but they tend to blow up if you connect them in reverse :smash: or attempt to pull more than the rated power... sheesh silicon can be SOOO picky sometimes :cannotbe:
But I appreciate what you're doing is maybe a more elegant solution.
However I also got some ECC86's for a half thought about head amp. It just seemed easier ;)
I take it you've seen Steve Bench's page on AOL he has tube curves for the 6SN7 at low voltages?
http://members.aol.com/sbench101/
Andy |
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| aletheian |
| quote: | Originally posted by andrew_whitham
I've used them before to get 200v from 24vdc (PICO 28A200S) but they tend to blow up if you connect them in reverse :smash: or attempt to pull more than the rated power... sheesh silicon can be SOOO picky sometimes :cannotbe: |
Whoa... good catch on that one. I have been looking for converters over 90v for a while. how much $ did they run you? Did you have any noise problems? |
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| andrew_whitham |
I cant remember what I paid - not much of ebay. But I just checked, they are supposed to be WAY more than that. :rolleyes: You can get a 12v to 150 volt version, that might be more appropriate for the ECC88 etc, But thats maybe a BIT lucky..
Have a look on ebay for Nixie related stuff, they do come up. (there was a guy did a kit too) In this case I also used it to drive a Nixie, so I dont know about audio noise. Realistically these (the PICO ones) state 20Khz min switching frequency so I'd think it be OK.
I dont think anyone will argue that the best way to run tubes is with big volts and big current (?) but thats not always possible. So its a compromise either way. At least thats what 'they' say.
To be honest if you can run normal tubes down this low (12v) and they work acceptably, then a converter might be a moot point anyway, just a thought...
Andy |
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| Alastair E |
Been experimenting adding a dry battery of 9V from the cathode-circuits to deck-- neg end of batt to the cathode ccts and plus to deck....
It could be made a semi-perminent part of the circuit if done correctly, as the current drain is just 2.5mA heaters on, and zero heaters off....
A good low ESR low-leak cap accross the batt may be an advantage, I havent explored the effects of that yet though...
Ive got 22 odd volts accross the valves, no inverters or switching-silicon and Still have a straight 12-14V supply for '+B'.....
It doesnt seem to alter anything in the sound, but dramatically extends the headroom!:devilr:
Not sure how long a standard 9V 'PP3/6F23' type batt would last here, but guess it would be a good few months of say an hour or two a day use, based on my commuting in the car....
Guess with some cunning work with a relay I could use a re-chargeable 9V, and re-charge while the ignition is off...Just a wacky idea:bigeyes: |
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| Alastair E |
| shameless bump...Sorry!:smash: |
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| Shepster |
You may remember the old vibrator power supplies, used in old car radios. These were used specifically for B+. The more modern equivalent is to use a 555 timer to drive a MOSFET. I don't understand your desire to run a [non 12V] tube at this low voltages. :confused: DC-DC conversion allows you to have the optimum B+ for whatever design you choose...Of course if your wish is to see if it can be done, you sound like you are already well on your way!
Good Luck!! |
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| Sonusthree |
| quote: | Originally posted by Alastair E
I was experimenting at 12V as I didnt want inverters etc or voltage-doublers as its to be used in the car., direct off the usual 12-14V supply
...........
I quite like the challenge of restricting myself below 15V just to see what can be done with the common audio valve types like above, rather than the special Car-Radio tubes made specially for 12V.....(I havent actually got any of those 'specials' 12V valves at the moment either!)
:bawling: |
Yeah, I guess he likes the challenge.
I have built his posted schematic and it works with a 6SN7.
6SL7 is not so good though. The 6SL7 seems to struggle a little on 24V.
I have to say that this low B+ concept has opened my eyes to the possibility of diy tube circuits.
Just wish I'd known more before spending £80 on a 'Tubalizer'. :bawling:
Cheers,
Martin. |
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| aletheian |
| quote: | Originally posted by Alastair E
shameless bump...Sorry!:smash: |
Are you bumping about the battery life? The typical 9v is made up of six AAAA 1.5v cells, which have a 625mAh lifespan for alkaline... twice that for lithium. NiMH rechargables are actually 1.2v cells, so you get 7.3-8.4v at 250mAh. if you are going rechargable, you may want to consider a Li-ion flat pack like in a cell phone or MP3 player. They are 3.6v cells, so you can get them in 10.8-11.1v for around $20. A lot of them will shut off below a certain voltage though.
AA batteries are probably a better choice if you have the room... or even AAA. AA Alkalines are 2800mAh, and AAA are 1,200mAh, which is 2-4 times better than a 9v. |
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