GGG Tube Driver

[Mick Bailey]

The grey picture is the bias trimmer.

There is no regulation or filtering before the juice hits the board. The circuit is fed from AC and rectifies and smooths this to provide V+ and V-. This way your 12v AC input becomes roughly 26v DC to give the tube higher voltage (hence headroom) than would otherwise be achieved. If you want to power the LED I would take this from between +V and  ground (NOT -V) and increase the resistor 4.7k resistor somewhat.

[kurtlives]

Alright cool...SO I just connect the 12V from the transformer to V+ and the 0V to the V-....

[Grizz]

Please explain what V+ and V- is.

Thanks,

Grizz

[Mick Bailey]

Alright cool...SO I just connect the 12V from the transformer to V+ and the 0V to the V-....

No, V+ and V- are the output voltages from the PSU section. The AC input is marked "Transformer 12.6v" on the layouts shown previously.

Please explain what V+ and V- is.

V+ is the rectified DC output from the PSU, and with respect to ground (0V) is positive. In this case it will be roughly +12 volts or so.

V- is also the rectified DC output and if measured with respect to ground will show a negative voltage of approx. -12 volts.

The PSU output is therefore roughly +12v/0v/-12v. This also means that you get 24 volts if you measure from V+ to V-. The PSU acts as a voltage doubler.

[kurtlives]

Alright cool...SO I just connect the 12V from the transformer to V+ and the 0V to the V-....

No, V+ and V- are the output voltages from the PSU section. The AC input is marked "Transformer 12.6v" on the layouts shown previously.

Sorry I knew that, brian fart.
Please explain what V+ and V- is.

V+ is the rectified DC output from the PSU, and with respect to ground (0V) is positive. In this case it will be roughly +12 volts or so.

V- is also the rectified DC output and if measured with respect to ground will show a negative voltage of approx. -12 volts.

The PSU output is therefore roughly +12v/0v/-12v. This also means that you get 24 volts if you measure from V+ to V-. The PSU acts as a voltage doubler.

Ok...my 800mA transformer goes to the connections the board. But how from there to the V+ V- does the current get rectified?

[Mick Bailey]

The original schematic shows this - D3 & D4 in the PSU section. the rest of that circuit is smoothing.

http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=83&Itemid=26

[kurtlives]

Thanks a bunch Mick....

I still dont get why I dont need regulation but thats ok.

How important is the 1W 10ohm resistor? I cant get one.

[Mick Bailey]

Regulation would just add unnecessary complexity to the design and I doubt if you would hear much difference. In fact, most classic valve amps are unregulated and use AC supplies for heaters.

The op amp in the design is quite tolerant of voltage variations.

It's when you get into Hi-Fi territory that you see more regulation more with valves - regulated DC heater supplies as well as regulated DC feeds.

The resistor isn't overly critical, but you should be able to make up the value from other values in series or parallel. You could go up on the rating to 2w or 3w, or use something close and get the correct value later. A slightly higher value wouldn't hurt. 

[kurtlives]

Thanks for all that, I understand now!

I was just worried about it being not regulated becuase my 470mF caps are 16V.