Tube boost + overdrive running off a 9 volt battery

[Faber]

Yeah, I do know that except for the tube lighting up it would be useless...

I am not 100% on the rectifier calculations so that's useful information!!!

So if the heaters are running off of AC, then don't rectify the heater voltage that you need and rectify what you do need...

It's a ridiculous idea, I know...

[machineman]

I've built one of these...It's awsome!!! Very very warm.  I put it infront of my effects chain...And I love it!!!

[petemoore]

  Would the heater filament not prefer ~6.3v for longest life?

[Zben3129]

Depends on wiring.

If you go straight off the 9vbattery, yes you are declining tube life no matter what. For best tube life you need 6.3v or 12.6v. 6 or 12 is close enough, b9 is obviously nowhere near either. You either want 6.3 volts across pins 4+5 and 9, or 12.6v between 4 and 5.

Zach

[bancika]

I don't think that lower heater voltage (like 9V for both heaters) would lower tube life. It would just sound different that it's supposed to.

[Caferacernoc]

"I don't think that lower heater voltage (like 9V for both heaters) would lower tube life. It would just sound different that it's supposed to."

Lower heater voltage is actually worse. From the Tone Lizard,

Look about halfway down the page of this link to see the chart:

http://www.tone-lizard.com/Marshall_Myths.htm


"I would like you to study the diagram below carefully. It is from the book Audio Cyclopedia, by Howard M. Tremaine. It deals with the prospect of running the filament voltage on any tube at other than 100% rated value. The illustration shows that tubes will fail prematurely if the filament voltage is either higher or lower. For maximum tube life, the voltage must be 'right'."

"From the chart above, you should be able to determine that if a tube has a usable life of approximately 6,000 hours with its filament operated at 100% of the rated voltage, the tube's life expectancy is reduced to 1,000 hours just by lowering the filament voltage by 10%. This translates to a 6.3VAC tube being run at approximately 5.67VAC, or the input voltage lowered from 120VAC to approximately 108VAC. Ask your local tube guru if they have read Audio Cyclopedia. However, even 'experts' can disagree on anything and everything. GE published data confirming tube life is decreased substantially by raising the filament voltage, although tube life can be increased by lowering the filament voltage very slightly. The performance of the tube was purported to be more 'even' over its useful life. However, it should be pointed out that the slightly lowered filament voltage GE 'recommends' proportioned to the plate voltage (via your VariacTM) won't make a difference to our ears. People who set their VariacTM to 100VAC are only asking to replace tubes every other month. The GE report also stated that the transconductance of the tube was reduced dramatically, and an audible deterioration in performance was noted when reduced filament voltages were employed. So why bother?"

[mojo_hand]

There are a lot of different figures on tube life and heater voltage, in part because different tubes respond differently.  Those with thoriated heaters, for example, do well when run at rated voltage for their first 200 hours, then dropped to 95% of full voltage until they approach end of life. http://www.cpii.com/docs/related/22/AB18.pdf  Dropping to 90% of rated voltage after the initial 200 hours may increase filament life to the point that heater failure will be eliminated as a cause of (thoriated) tube failure. http://www.burle.com/cgi-bin/byteserver.pl/pdf/tp202.pdf  Tubes with oxide-based heaters are different.  Power tubes can have their life shortened by running at lower heater voltages, but others often benefit from slightly lower voltages: at 10% above rated voltage, life will be cut by half, at 5%-10% below rated voltage, tube life will be significantly enhanced at the cost of slightly worse performance in various other regards. http://www.pmillett.com/Books/Tomer_1960_Getting_the_Most_Out_of_Vacuum_Tubes.pdf  I suspect that the author cited by the earlier poster was thinking of power tubes when he condemned running tubes at reduced heater voltages, since it is very true with those.

My recommendation would be to never run power tubes at anything but their rated voltage, and to rectify, filter, and regulate that voltage if you're using expensive tubes.  For other types of tubes, if high longevity matters more to you than squeezing every last bit of performance out of it, rectification and filtering are also good, but the target voltage should be 5%-10% below rated value.  Anything lower than 90% of rated value will cause worse performance without enhancing tube life, and may actually shorten life.  Using tube coolers and/or cooling fans will also increase life, often doubling it.

Using 9v in place of 12.6 for heaters is not a great idea from any perspective, in this schematic it has to be considered a matter of convenience rather than good design.

[petemoore]

  If you're playing in Timbuktu, carry a spare tenbuck Tube.

[brett]

Why do backflips in order to avoid using a 12V DC wall wart ?

[mojo_hand]

Why do backflips in order to avoid using a 12V DC wall wart ?

I agree, 12v would be a lot better, no idea why the original design didn't use that (can't read Japanese).

[andrew_k]

Why do backflips in order to avoid using a 12V DC wall wart ?

I agree, 12v would be a lot better, no idea why the original design didn't use that (can't read Japanese).

I'll see if I can do some samples of this circuit at 9v vs. 12v tonight, so long as I can get ProTools 7.4 and OSX 10.4.11 to play friendly. 

<noob> Perhaps as well as being better for the valve it also will provide a cleaner boost? </noob>

[Zben3129]

Sounds good, hope you get it working!

I'd say maybe more clean headroom. I can't really hear any discernable difference between 9v and 12v, but my wallet sees the difference between 9v bat and 12v ww. Trust me, go wallwart guys.

Just my $.02 (or if you use 9v batteries, $10/week)


Zach

[MasaRGR]

Going back and reading Matsumin's notes, he mentioned that there are lots of schematics and designs for 12v, so he wasn't interested in making another 12v version.

His original goal was to make a simple tube booster that anyone could easily build and if possible, make it 9v, and this was the result. He doesn't know lots of the theory and concepts involved with using vacuum tubes in these type of circuits and that this was an experiment to see if he could just make it work.

He said that on breadboard, he got a more cleaner sound with higher voltages like 12v and 15v and that for people seeking more clean headroom to try higher voltage power supplies.

He got some nice sounds with the 12AT7 tube, but preferred the 12AU7 in this circuit. He tried a 12AX7 but said that it didn't work well at all with this design.

He mentioned that he designed this for single coil pickups and that his humbucker equipped guitars were too boomy.

Hope this helps.

Masa

[Krinor]

He mentioned that he designed this for single coil pickups and that his humbucker equipped guitars were too boomy.

Hope this helps.

Masa

Now that makes sense. Maybe it sounds okay with single coils at 9v, but needs 12v to sound good with humbuckers ? I have only used mine with a rather dark sounding SG and a 12v supply. Sounds nice to me.

Thanks for the translations. Could I be so bold as to ask you to please translate the whole article and post it for the benefit of the DIY community ? I know a lot of people would be very gratefull. 

[andrew_k]

He mentioned that he designed this for single coil pickups and that his humbucker equipped guitars were too boomy.

Interesting. To me, it has more of a light OD jangle when I set the 'buckers on my carvin to split (single coil), but the sound when being driven by the full humbucker is still good; a lot more crunch to my ears and I prefer it over the single coil sound. It does do wonders for funk rhythms on my strat though, so long as I keep the gain low 

Regarding 12V operation -- does anyone else notice a defined hum when switching to 12v? I know it's not the power supply as I'm using a BBE supacharger and just flicking the 9v/12v DIP switch for that output. My gut feeling is that it's a bias issue... and my n00b guess is that R3 (100k between pin 6 and V+) is responsible for bias?

I dig the sound of this circuit, but I'll wait until someone confirms or denies my guesses regarding 12v hum and bias before replacing the resistor with a pot. 

[Krinor]

He mentioned that he designed this for single coil pickups and that his humbucker equipped guitars were too boomy.

Regarding 12V operation -- does anyone else notice a defined hum when switching to 12v? I know it's not the power supply as I'm using a BBE supacharger and just flicking the 9v/12v DIP switch for that output. My gut feeling is that it's a bias issue... and my n00b guess is that R3 (100k between pin 6 and V+) is responsible for bias?

I'm using a regulated ac/dc adaptor capable of 500mA. It's switchable between 9 and 12 v. I tried it with everything maxed on the valve caster and the amp turned up loud. There is a subtle hiss at these extreme settings. Switching between 9 and 12 volts does not alter that rather faint hiss in my case. All in all I was actualy surprised at how quiet this circuit was.

[jakenold]

Regarding 12V operation -- does anyone else notice a defined hum when switching to 12v? I know it's not the power supply as I'm using a BBE supacharger and just flicking the 9v/12v DIP switch for that output. My gut feeling is that it's a bias issue... and my n00b guess is that R3 (100k between pin 6 and V+) is responsible for bias?

I dig the sound of this circuit, but I'll wait until someone confirms or denies my guesses regarding 12v hum and bias before replacing the resistor with a pot. 

Now you have rewired the heaters for 12V operation, right? If you're running them in parallel (6,3V operation) at 12V, that can't be good.

Jake

[MasaRGR]

Thanks for the translations. Could I be so bold as to ask you to please translate the whole article and post it for the benefit of the DIY community ? I know a lot of people would be very gratefull. 

You're very welcome.

As for translating the rest, most of it isn't of much use as he makes lots of references to some obscure Japanese magazines and texts, and the rest is just some "shoulda/woulda" kind of brainstorming.

A few things that may be of interest - he said that he bought a tube socket with pcb pins - but the pins weren't sized for his board holes so he had to do a lot of bending and twisting to get the socket mounted. One thought he had was to just use a regular tube socket and attach the components directly to the base of the socket (ala DanO) or use a small turret board or lag board. He used some vintage ceramic caps in C1 and C4 as well as an oil capacitor for some extra "mojo". He did say that his layout wasn't too well thought out as he would have to remove knobs and unscrew the pots to get access to the tube 

He did give big props to Bancika's DIY layout creator and mentioned how much he appreciated the upgraded version.

[DryRoasted]

Built mine!  Will only work with 12V though (I'm using a 12AT7, may or may not have anything to do with it).  Sounds very very good.  just for jollys, turn the vol and gain up full and crank out the riff to Smoke on the water! 

I tried an AX7 that I had lying around and that sounds different still, not too bad, quite useable in fact but just not as clean as the other.

[andrew_k]

I'm using a regulated ac/dc adaptor capable of 500mA. It's switchable between 9 and 12 v. I tried it with everything maxed on the valve caster and the amp turned up loud. There is a subtle hiss at these extreme settings. Switching between 9 and 12 volts does not alter that rather faint hiss in my case. All in all I was actualy surprised at how quiet this circuit was.

Damn. Exactly the same power situation as me, but yours doesn't make the odd noise.

Now you have rewired the heaters for 12V operation, right? If you're running them in parallel (6,3V operation) at 12V, that can't be good.

If I had half a clue what that means, I'd respond appropriately...