freestompboxes.org

Hi Guys,

For R13, which is supposed to be a 180k-1W resistor, can I substitute either a:

180k - 1/2W

or

220k - 1W

with the least amount of damage to tone, safety, whatever.

Thanks in advance

Stick with 1W, it's a dropping resistors, many people would use a 2W there. I don't see any designation for wattage on the Jack Orman schematic for the original R13 (10k), which would imply a 1/2-watt resistor, but if ANYONE specs a 1W or 2W or whatever...there is a reason.

You can safely use the 220K, to quote Lone Wolf themselves...

The plate voltages will be lowered to 130V by replacing R13 with a 180k resistor (a 200k is ok).

As for whether you like it...YMMV. It'll lower the plate voltage of that first gain stage a little more, but you are already more than halving it. Of course, you possibly don't know f you'll like the mod anyway.

Thanks a lot!!!

Well according to the schematic that resistor is dropping 149 volts (321-172=149). If you use Ohms law (I=V/R), that means there is only 828uA flowing through it. That means (V^2/R) 149^2=22201/180=123.339 milliwatts of power. If you double that for safety you still have less that a 1/4 watt. I would think you would be safe with a resistor of 180K of between 1/4 and 1/2 watt. Each of the preamp tube are only pulling 414uA through the 100k plate resistors. Assuming the voltage reading on the schematic are correct.

Thanks for calculating that for me Groovenut!! So many helpful dudes here. So appreciative.

You could use your 1W 220k and put a 1/4W 1M in parallel with it.

Probably best not to go with 1/8W due to the voltage across it.

Thanks Deltafred!