Another Tube Driver Question

[hendrix2489]

i used the search and came up with some mixed results.  I am going to build the GGG Tube Driver and i already have all the parts minus the Power supply.  It says that you need a 12VAC power supply. But when i searched i saw people using 9vac with high amount of mili-amps.  My question is what would be the exact Power supply that i would need.  i have some ac power supplys i think i have two 24vac with 300-500ma.  I also have two 9vac  300-700ma.  i do not know if i need a certain amount of ma or volts.  I know that the heaters need 6.3v but thats about it. 

Any help would be great.

[DougH]

Look up the datasheet on a 12ax7. That will tell you how much current its heater will draw. Add a few more mA for the signal part of the circuit and for safety margin. The heater will draw more current than anything else. The heaters on a 12ax7 can be wired for 6 or 12 volts. The datasheet has the details. It's best to use the 12VAC pwr supply specified on the schematic. They are not expensive at Mouser.

[hendrix2489]

from what i see, it looks like i could either use a 12vac 150ma or a 6vac  300ma power supply

[the_random_hero]

from what i see, it looks like i could either use a 12vac 150ma or a 6vac  300ma power supply

That's the heater voltage alone. You wouldn't get very good results using 6V to run the SS part of the circuit. I'd be going with 12VAC into a rectifier, then using a 12V regulator with a silicon diode forward biased to ground to get around 12.6VDC to the heaters, which will draw 150mA when they are connected in series (+V to pin 4 and ground to pin 5).

[shredgd]

Mine draws about 160mA, so you need a 12VAC power supply rated for at least 200mA. Go with 12VAC, don't bother experimenting with less...

Giulio

[hendrix2489]

thanks for all the help guys, by the way Giulio your layout for the tube driver, is it more compact or the same size, just wondering

[shredgd]

I think my layout is a bit smaller than GGG's.
Most of all, that layout is reported to have noise problems (however I never tried it, I directly built my pedal using my layout, so I can't confirm).

Giulio

[hendrix2489]

i just looked at it and it looks awesome,  just one question, is there a red led in the bottom right corner if so what is the orientation.  If not what is it.

[shredgd]

Sorry for my layout being not 100% clear... Rled stands for "resistor (current limiting) for the led": as you can see it is connected to the led+ pad. Here you will solder the wire from the + side of your led; instead the - side of the led goes to your 3PDT switch, where you will do the wiring in order to have the led on only when the overdrive is on. You just need another wire from the switch to ground to do this. (Obviously if you don't use a 3PDT switch you will need another strategy to activate your led, for example the millenium bypass).

Giulio

[hendrix2489]

thanks, i just read what you said and used the wiring diagram from ggg for some direction and i get what you are doing.  Great idea.  I hated when the + side of the led was connected to the dc jack. i am going to start building this, this week.