Tube boost + overdrive running off a 9 volt battery

[Renegadrian]

VERY NICE INDEED!!!  LOOKS GREAT...
GOOD WORK ON THOSE CUTOUTS!

[MikeH]

This has most likely been covered in this thread (I didn't feel like browsing the 30-some pages to see) but after being fed up with the lackluster sound of my valve caster (I had tried numerous different types of tubes, mods, input cap values, etc...), I decided to wire up two 9 volts and  try running mine at 18 volts.  Holy crap- it sounds.... thousands of times better.  It sounds awesome!  Highly recommended.

[frequencycentral]

This has most likely been covered in this thread (I didn't feel like browsing the 30-some pages to see) but after being fed up with the lackluster sound of my valve caster (I had tried numerous different types of tubes, mods, input cap values, etc...), I decided to wire up two 9 volts and  try running mine at 18 volts.  Holy crap- it sounds.... thousands of times better.  It sounds awesome!  Highly recommended.

Yeah, I think so too. I've been playing about with 6111 submini tubes and switched capacitor voltage convertors to get the plate voltage up to 44 volts. I think this helps with the linearity/symmetry of the waveforms. Apparently tubes like higher voltages!

This is an experiment I did recently, the input waveform was a triangular wave, I decided that 30 volts was really good enough for my purposes, there's not much difference once you get above that. The law of diminishing returns:

[MikeH]

Maybe I'll try four 9 volts... 

[frequencycentral]

Maybe I'll try four 9 volts... 

Or just one 9 volt, a MAX1044 and some caps n diodes...........

[kurtlives]

Can the heaters take 18V?

[frequencycentral]

Can the heaters take 18V?

No - 12.6 maximum. But the heaters are powered seperately. At least that's how i do it.

[kurtlives]

Cool thats what I figured...

I bought a 12V DC 300mA adapter today...is 300mA enough?

[frequencycentral]

Cool thats what I figured...

I bought a 12V DC 300mA adapter today...is 300mA enough?

Yup thats good enough, each 12#7 consumes 150ma @ 12 volts. Is it regulated? If not you may want to use a 7812. Also, always a good idea to use a decoupling cap across the power rails. I use 10uf.

[MikeH]

Correct me if I'm wrong, but in this design powering up the heaters would be just for aesthetics, would it not?  Not that there's anything wrong with doing something just for aesthetics; I'm a big fan of doing just that. 

But is there any "sonic" advantage to it?

Again I'm sure it's been covered somewhere in the previous 30 pages, just... you know... lazy!

[MusicAudio]

Correct me if I'm wrong, but in this design powering up the heaters would be just for aesthetics, would it not?

The heaters are essential for operating a vacuum tube. Without the heaters there would be no electrons for the anode/grid/cathode to play with.

I hope that's what you're asking.

Putting an LED behind the tube would be the kind of thing you'd want to do for aesthetics.

[MikeH]

Yes, for high voltage vacum tube operation, but at 9V the heaters aren't necessary, right?.  Don't the heaters get voltage from pin 9?  Which is left disconnected in the original design.  I could be totally mistaken.

Edit:  Okay, pin 9 is for the heater centertap.  Pins 4 and 5 are for the heaters for each triode. 

[frequencycentral]

Yes, for high voltage vacum tube operation, but at 9V the heaters aren't necessary, right?.  Don't the heaters get voltage from pin 9?  Which is left disconnected in the original design.  I could be totally mistaken.

Yes MusicAudio is right, without heaters the electron won't get 'excited' enough to do anything. The tube won't. work.

Pin 9 is left unconnected in this (and many other tube circuits using 12#7) because it is the 'centre tap' for the filament - using the centre tap and pin 4 you can power the heater at 6.3 volts/300ma. Using pin 4 and 5 you can power the heater at 12.6 volts/150ma.

EDIT: OK you got it, I was typing as you were editing!

[kurtlives]

Cool thats what I figured...

I bought a 12V DC 300mA adapter today...is 300mA enough?

Yup thats good enough, each 12#7 consumes 150ma @ 12 volts. Is it regulated? If not you may want to use a 7812. Also, always a good idea to use a decoupling cap across the power rails. I use 10uf.

Its not regulated but I am adding a little regulating board. Add 0.1mF at the start and a 100mF cap after the regulator.

[kurtlives]

Having a bit of an issue with my Valve Caster I just finished...

It doesn't make any sound when engaged...
I get sound though at lug two of the volume pot (output) when I audio probe it. It is much louder than when I probe the inout cap. It is so faint there I can barely hear it. As I go along the circuit it gets louder so that must be good I think.

I get sound also on pin 5, it is very odd... Pin 5 is a heater that is directly connected to B+... This seems like an issue.

Also when all voltages on the pins are super low compared to Rick's postings before (his were like 12V on some spots where as mine were 0.124V)... Btw my readings were with a tube installed...

Its a stock build besides a 4.7mF in parallel with the gain pot to boost gain and a little variable B+ circuit I made.

Help please...

[frequencycentral]

Chris, post your voltages and any changes you have made. Best set that variable B+ to 12 volts for your voltage readings (and remove the 4.7mF in parallel with the gain pot), that way the circuit should be similar to mine. You're not varying the voltage to the heater (pin 5) are you? Pin 5 needs to be an unvarying 12 volts.

[kurtlives]

Chris, post your voltages and any changes you have made. Best set that variable B+ to 12 volts for your voltage readings (and remove the 4.7mF in parallel with the gain pot), that way the circuit should be similar to mine. You're not varying the voltage to the heater (pin 5) are you? Pin 5 needs to be an unvarying 12 volts.

I am using an unregulated 12V DC power supply...It can shoot upwards of 16.5V DC.

With my variable B+ design the overall voltage gets adjusted, I cant set the heaters independently. From my understanding the heaters can work if they recieve too much or too little voltage, it just affects tube life.

All test so far have had the B+ at 13.7V...

Ill readjust and get voltages...

[kurtlives]

B+ 12.58V DC

1. 0.2V
2. 0V
3. 0V
4. 0V
5. 0.2V
6. 0.2V
7. 0V
8. 0V
9. 0.1V

Btw without a tube in the voltage seem reasonable considering the circumstances.

[frequencycentral]

B+ 12.58V DC

1. 0.2V
2. 0V
3. 0V
4. 0V
5. 0.2V
6. 0.2V
7. 0V
8. 0V
9. 0.1V

Btw without a tube in the voltage seem reasonable considering the circumstances.

Here's mine again:

Pin 1: 3.02v
Pin 2: -0.518v
Pin 3: 0.00v
Pin 4: 0.00v
Pin 5: 11.97v
Pin 6: 8.21v
Pin 7: -1.285v
Pin 8: 0.00v
Pin 9: 5.91v

Your voltages are extraordinary. They were taken with the tube in, yes?

The first thing I would say is that I think giving the heaters anymore than 12.6 volts is bad - giving them less would shorten the life - but giving them more will probably burn them out - like a lightbulb thats rated at a certain voltage if you give it too much. You need to set the heater independently at 12 volts. Maybe you should consider a 7812 voltage regulator for that.

Is the heater glowing?

I just did a quick test on a tube that I know to work. Not in a circuit, just the tube. The resistance between pins 4 and 5 reads 10 ohms. The resistance between pins 4 and 9 (the heater centre tap) reads 5 ohms. Thats a healthy heater. Take your tube out and do this test, post your results.

I've noticed that this circuit doesn't like some power supplys - my brother tried one which seemed appropriate but all he got was hum, we plugged it into my power supply and it worked fine. You should run it from a (new) 9 volt battery, then we can concentrate on if the problem is just the circuit or the power supply.

It occurs to me that nearly all you voltages are 0 volts - I don't know what happens if you blow a tube heater - but maybe it shorts out the whole tube, and therefore the entire circuit - which would explain your short circuit. If you circuit shorts, it may cause your power supply to fail and/or shut down. Pins 1, 5 and 6 should be reading at least some reasonable positive voltage, as they are closest to the power supply. If there's nothing at pin 5 the heater isnt powering up, the electrons wont get excited! they won't do their thing.

[kurtlives]

Yes I had a tube in... Ill try that test you suggested.

The heater does not glow at all.

I have another 12AU7 and more power supplies (and a battery) that I can try.

My power supply is 300mA...is that enough..what does your draw? Earlier in the thread someone said 500mA is the minimmum.