On page #1, on the top of page, in the middle.
R49 is a 330k resistor at the volume pot. Does this just add series resistance, and attenuate the signal a bit.? If that were just a wire, would the amp OD too much.?
Maybe I have this all wrong, I do not know. But why not just use a 1M pot then.?
Guess what I am really asking is for an explanation of what R49 does.......
Thank You
Schematic help
Moderators: pompeiisneaks, Colossal
Schematic help
You do not have the required permissions to view the files attached to this post.
-
martin manning
- Posts: 14308
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: Schematic help
R39 limits the max signal out of the pot wiper to about 60% of what's available 500/(330+500) = 0.60. Presumably it prevents overdriving whatever is downstream, that being an op-amp.
Re: Schematic help
R49 is there to keep C12 from totally shorting out (when switch is closed)so there will still be some distinguishable highs perceived as volume pot is dimed.
-
vibratoking
- Posts: 2640
- Joined: Tue Nov 10, 2009 9:55 pm
- Location: Colorado Springs, CO
Re: Schematic help
To be clear. martin and Masco are both correct.
The cap is called a bright cap, which is normally used to retain some highs as the volume is reduced. The cap shunts high frequencies around the voltage divider formed by R49 and the pot so that the highs are not attenuated as much. This is normally done to compensate for the Fletcher-Munson characteristic of human hearing.
R49 and the variable resistance at the top of the pot combined with the cap form a single pole filter with an approximate -3dB point as follows:
2.2kHz at max volume
822Hz at min volume
There are less highs at max volume and more highs at min volume.
The cap is called a bright cap, which is normally used to retain some highs as the volume is reduced. The cap shunts high frequencies around the voltage divider formed by R49 and the pot so that the highs are not attenuated as much. This is normally done to compensate for the Fletcher-Munson characteristic of human hearing.
R49 and the variable resistance at the top of the pot combined with the cap form a single pole filter with an approximate -3dB point as follows:
2.2kHz at max volume
822Hz at min volume
There are less highs at max volume and more highs at min volume.
Re: Schematic help
Once again.....Thank You.....all of you.
I was recalling one of the old Lyle Caldwell mods where he suggested removing R49 and just bridging it, that is to say replace it with a straight wire.
As pointed out previously, there is an Op Amp after the volume pot, but maybe that is no big deal. Not sure Lyle would suggest the removal of R49 if it would be problematic.
But maybe it would be.?
Thanks
I was recalling one of the old Lyle Caldwell mods where he suggested removing R49 and just bridging it, that is to say replace it with a straight wire.
As pointed out previously, there is an Op Amp after the volume pot, but maybe that is no big deal. Not sure Lyle would suggest the removal of R49 if it would be problematic.
But maybe it would be.?
Thanks