Tube boost + overdrive running off a 9 volt battery

[zambo]

I think it does matter....let me see what i can find...   here we go   http://tdsl.duncanamps.com/show.php?des=12AU7     this place rules for tube info. Looks like 4 and 5 are hot and 9 is ground for both. Duncan amp pages has been a life saver for me. Read tubes for dummies on the home page of this sight as well. Awsome info and very helpfull.

[lowend]

This one I presume http://www.diystompboxes.com/pedals/tubedummy.html ta.

Thinking about it some more, it can't matter as in one scheme 4 is hot and the other it's the ground, quid pro quo it doesn't matter. Cool. Maybe I'll get to build a real amp one day.

I had another look at my wall wart and it's obviously not using a typical lump of coils transformer because it weighs hardly anything. I figure it must be some fancy electronic deal, regulated and filtered so I'm probably good without the mystery capacitor off the side. But for the extra 20c it would be good to throw one onto my order if someone can help out.

[served]

Well there is a problem with impulse adaptors. Their output is not flat enough. There are only very few models that suit for the purpose. But if you try it and it will pass, you are the lucky one.

As for the pins. Then there is no difference between the pins. Heater acts like a lightbulb. It has only repressive effect (like a resistor). No matter which way the current flows.
If using AC for heaters then there is no different also, but you could avoid some disturbance if you try to change the wires.

[lowend]

Google isn't picking up "impulse adaptor" so I'm stuck on that. It's similar to this one but 1A: http://www.sparkfun.com/commerce/product_info.php?products_id=298

[served]

The phrase might be wrong, I am not sure, its not my native language.

EDIT: The correct phrase is "switching battery eliminator" I think.

I have tried sever of thouse, they were cheap for me and I had resources to try a lot of different models, but no luck for me.
Oscope showed impulses for most of them. So I was suggested to stay to transformer based adaptors.

Its very offtopic, but I hope you don't mind.

[lowend]

Mind? Not at all. I must have missed the part where it said you can't run a valvecaster on a switching supply. Did yours have the cylinder doofer wired into the lead like mine? I wonder if that is there to clean up the power.

EDIT, reading around the "1spot" seems popular and it's a switching supply so I'm thinking this is a case of ymmv.

[served]

Well actually in my experience, I have not tried it with valvecaster, you can be the first one, it doesn't work in audio circuits.
I have tried to smooth it up and filter it and so on, but without any success. Have tried various pedals, amps, op-amps and so on. But hey! Try it out, there is nothing to loose only to gain some knowledge!

[jcgss77]

Just for knowledge purposes, if you power the heaters to pin 4 or 5, it doesn't matter.  If you ground pin 9, it will only power the heater that has the power connected, then complete the circuit to ground, leaving the other heater unpowered. 

I am pretty sure that I read somewhere on this thread that someone uses laptop psu's, and I am pretty sure that most, if not all, are switching.  So I would believe that if you have good filtering and/or regulation, it should be ok.

[lowend]

use a regulated dc power supply. I use a 1 spot 9 volt. You can run 9 volts to pin 5 and ground pin 4. Works great.

not the first to use a "1 spot", maybe the first to use 6.3V parallel but I really doubt it.

An extra cap and 7812 on the dc jack make it quieter. Renegadrian has the cool vero layouts that are tried and true...

Just wondering if you think it necessary for the extra bits? I'll have to revisit that 7812, I thought it needed extra volts to power it.

[lowend]

Yep, needs extra volts. I'm gonna assume my switching 9V power supply is already regulatated and go with a simple capacitor filter to take out any hiss it may or may not make. I know it's simple because I can't find an explanation for one in a good half hour of searching

I found a bunch of threads that got no further than some resident posting the link to the Rolls Royce DIY powersupply of bliss, not gonna happen. I have read in passing about using a cap and a resistor, or just a cap but I'm short of specifics. Somebody please help so I can order the sucker with the rest and know where to put it.

My 9v is going to 4 and 5 and I'll ground 9 with a resistor as I posted earlier for 6.3 V parallel heater operation (patent applied)

[served]

Just put Electrolyte cap there. - to minus and + to plus and that's the deal. (if this was what you were asking)

[lowend]

Thanks for that, I did some more digging and have ended up plunking for a 220 and a 470uF to try out in the absence of anything more specific.

My cunning plan,
RE EDIT Ok, 300mA at 6.3V makes for 6.3/0.3 = 21 0hm from the parallel pair of heaters. 9v @.3 amp needs 30 ohm so I need to put a 9 ohm resistor soaker into the heater circuit to deliver 6.3V.  Did I get that right?

btw The power supply has a doofer in the line about an inch long and thick as a finger. I'm guessing that's there to regulate and/or stop hum?

I have struck a hitch in my cunning plan so it makes me wonder if i got the maths right.

putting .3A thru 9 ohm at 2.7V makes I^2*R = .09x2.7 = 0.243W which is right on the 1/4W limit of the resistors commonly sold. Seems a bit underengineered! All good?

Anyone know much about those inline doofers? The exact same style of doofer on a similar supply here at Godlyke http://www.godlyke.com/power-all-digital-power-supplies (mine's not Godlyke)

[Govmnt_Lacky]

Ok. I have spent the last 2-3 hours combing through this thread and I still cannot find any layout/wiring info for a 12AX7 tube! All of the posts I read allude to 12AU7 and 12AT7. Even some soviet tubes but NO 12AX7s!
Can someone point me in the right direction? Did I miss some info in this thread about using the AXs?

[R.G.]

Ok. I have spent the last 2-3 hours combing through this thread and I still cannot find any layout/wiring info for a 12AX7 tube! All of the posts I read allude to 12AU7 and 12AT7. Even some soviet tubes but NO 12AX7s!
Can someone point me in the right direction? Did I miss some info in this thread about using the AXs?

All the 12a?7 tubes have the same pinout.

[Govmnt_Lacky]

All the 12a?7 tubes have the same pinout.

I agree however, they do not all have the same gain value nor do they all work well from 9V. I do remember reading about that in this thread.

What I did not see was any solution to the higher voltage requirement or a solution for the proper usage of the increased gain.

Basically, I am throwing this out there to see if this has been discussed already or whether it needs further exploration.

Ideas??

[jcgss77]

What has been stated about the 12ax7 is that it doesn't sound good in this low-voltage circuit.  There are better designs out there for those.  This circuit is intended for a boost and light overdrive, which is what you get.  Actually, I am very pleased and surprised with the distortion you get from a 12at7, which I use.  Throw it on your breadboard and see.  If you need more gain, do a 2 tube version.

[R.G.]

I agree however, they do not all have the same gain value nor do they all work well from 9V. I do remember reading about that in this thread.
What I did not see was any solution to the higher voltage requirement or a solution for the proper usage of the increased gain.

Sorry. I misunderstood your question from the "wiring and layout" thing.

12AU7: amplification factor 20
12AT7: amplification factor 60
12AV7: amplification factor 41
12AY7: amplification factor 40
12AX7: amplification factor 100
12AZ7: amplification factor 60
There are also many other tubes which have the "9A" dual triode pinout.
All of these were designed for running with 100V upwards on the plates. They can all be run at lower voltages, but the consensus I've heard is that there is a starved or grainy quality to the sound from doing that.

There exist (or existed) tubes designed to run from significantly lower voltages, usually for portable or car radios.

Basically, I am throwing this out there to see if this has been discussed already or whether it needs further exploration.

It's been discussed a lot, although I don't think much of that discussion was here.

The bottom line is that to get a lot of gain with a tube you can actually buy replacements for, you're kinda stuck with the 12A?7. They can work at voltages in the 30-50V range, but there is a characteristic sound to that which some people like and some people don't.

[lowend]

Thanks for that, I did some more digging and have ended up plunking for a 220 and a 470uF to try out in the absence of anything more specific.

My cunning plan,
RE EDIT Ok, 300mA at 6.3V makes for 6.3/0.3 = 21 0hm from the parallel pair of heaters. 9v @.3 amp needs 30 ohm so I need to put a 9 ohm resistor soaker into the heater circuit to deliver 6.3V.  Did I get that right?

btw The power supply has a doofer in the line about an inch long and thick as a finger. I'm guessing that's there to regulate and/or stop hum?

I have struck a hitch in my cunning plan so it makes me wonder if i got the maths right.

putting .3A thru 9 ohm at 2.7V makes I^2*R = .09x2.7 = 0.243W which is right on the 1/4W limit of the resistors commonly sold. Seems a bit underengineered! All good?

Anyone know much about those inline doofers? The exact same style of doofer on a similar supply here at Godlyke http://www.godlyke.com/power-all-digital-power-supplies (mine's not Godlyke)

I'm surprised nobody spotted my mistake, perhaps they were distracted. I was bored at work and rehashed it and got a fright. Good thing I have yet to order the bits.

power= I^2 * R = 0.3A * 0.3A * 9ohm = 0.81W far too much for a single 1/4W resistor methinks. Being that they don't stock any gruntier ones I guess I'm stuck with 4 of them paralleled on the vero.

What's the current limit on vero at 9V anyway?

[served]

Put some solder on the lines and you will be fine!


I have one questin. How much voltage this kind of schematic will hold?
Can I just put 200V on anode without changing anything (except caps)?

[Rg505bk]

Almost forgot about this thread. I never finished the twincaster and when I came back there's allready a tri-caster

So naturally I want to build that now. Here's the casing, it's mahogany with the metal part made out of an old propane tank warning sign. The Shell - logo

is still on the inside of the case. Kinda quick and dirty, looks like something out of an old sci-fi movie. Think I'll just shine some and start building the thing