I was making a PCB for the BrontoBoost, and I noticed on the schematic that lugs 3 and 2 of the Volume pot were connected together. It seems like if those two were connected, the signal would just bypass the pot all together and go straight to the output. Should those two lugs be connected?
Phillip
>>>Link?<<<
From what I understand from your description, it looks like the pot is configured as a rheostat. To be used for volume control, this would probably have to be part of a voltage divider (???)... no... well... maybe just ignore this post and i'll take a look at the schematic.
>>>Okay I can't find the schematic, and the link seems to broken. Anyways, to answer your question:
When 2 lugs of a pot are connected, it is configured as a rheostat. Technically speaking, this is the truest form of variable resistor. In essence, it has 2 terminals. When the wiper is turned to the end of the pot that is furthest from the two connected lugs, resistance is at it's maximum (whatever the pots rated value is, +/- tolerance). When the wiper is turned to the other end of the pot, all three terminals are internally connected directly, and thus, no resistance.
As far as I know, this is not a common configuration for a volume control. The majority of what I've seen is basically: "top" lug (1) connected to output from previous stage... "bottom" lug (3) connected to ground... wiper lug (2) connected to input of next stage. It may work as it is in the schematic, but again, I'd like to take a look at it before I say anything definate.
Good luck! Take care!!!
Here it is:
http://www.ampage.org/sounds/files/BRONTOschemV3.0.gif
Check out the way the volume pot at the end of the circuit is hooked up.
Phillip
Looks like the 'bottom' of the Volume Pot goes through a switch sometimes?
the Wiper goes to the BP switch....?
The wiper should go to the switch...through the switch then to the output jack. I'm not quite sure why the "hot" lug is connected directly to the wiper arm. It seems like if those two were shorted, then the signal is going to completely bypass the volume pot and go straight to the switch.
Phillip
Yeah that is strange...
Not to Discredit Joe G. at all (sorry!!!), I'd have to say it's a possible error in the schematic. It would work just fine if the short between the hot lug and the wiper just wasn't there.
in my eyes, it looks as if he intentionally wants to "load" the diodes, when vol is set low to mid, so that they only come into the game at higher vol settings
(in contrast to: just taking off a certain amount of sheer volume from an otherwise "finished", all-the-time-being-clipped signal) ?
Joe probably *did* do this to get a certain response.
That said, no, the signal doesn't bypass the pot: the pot is wired as a rheostat - a variable resistor - to ground. Lower it's value and you shunt more signal away to ground, plus you load the circuit differently. It will work just fine.
If you don't like or trust it, wire it like a regular volume control and compare. It's just one wire ;)
oops, I am not sure why this schematic was drawn like this, but it is definitely an error. It is wired like any standard vol pot. Sorry for the confusion.
The diodes don't kick in until the pedal is crankin pretty hard. But not because of some 'new' way to wire a vol pot!
I don't know how to log in to the 'new ' ampage sounds to post a corrected schem.
I have a new one ready to load. I will email tboy to ask for a way in to the matrix.
Thanks for the help, Joe! Did you get my email?
Phillip