Sounds great so far , but it's got plenty of gain on tap ... just wondering how to tame the beast ?? ;D
(http://i1085.photobucket.com/albums/j431/onflooraudio/SCHEMATICS/PurplePlexi800_zps31821a0a.gif) (http://s1085.photobucket.com/user/onflooraudio/media/SCHEMATICS/PurplePlexi800_zps31821a0a.gif.html)
Thanks for any help !! ( Sucks being a Noob )
Quotejust wondering how to tame the beast
What do you want to do that the potentiometer controls (gain and volume) don't achieve?
Even with the gain pot at Zero .... it's still got too much .
Feedback biasing. I dont have the knowledge to tell you where or how to do it, though.
if you feel like getting a little crazy, https://www.youtube.com/watch?v=piHi9o5Q4vc
it's basically A -B = C, so you could reduce the gain with a differential amplifier add-on. It may also help you understand how to feedback bias an op-amps pins to get gain where you want (which would be the simpler route). I just find the concepts in the video are relatively illuminating for re-imagining how opamps work.
R4 is in parallel with the gain pot, that changes your 1K gain pot to ~300 Ohm pot. If you remove R4 you'll change your gain pot back to 1k giving you more low range in your gain control but will make it a little more touchy at high gains.
Please let me know how this works out, I'm interested in making one of these smashdrive/PP.
There might be "beast" in the DNA of the 386 you'll never get rid of.
If you cut the trace between pins 1 and 8 it would clean right up. Maybe you could splice a pot in between those two pins for some sort of pre-gain?
I have to agree with jeremy. That's also a real good idea.
I thought the exact same thing of this circuit but seeing as it cleans up awesomely with the guitars volume, I wasn't going to bother altering it.
I am however, going to build another and try the 'pot between pins 1 & 8' idea of Jeremy's. Sounds cool!
How about a dual concentric pot between the cut tracks of pin 1 and 8 and the rest? Maybe you could get a larger sweep of gain range.
Hi
Did this work?
I've got the same problem with a DIY purple plexi, but a pub circuit from Pedal Parts.
I never tryed it to be honest ... but i might try it on this build !!
I'm doing another one , and trying to remember how to tighten up the low end now , i find this circuit to be
very loose & tubby on the bottom end imo .
Quote from: rousejeremy on June 07, 2013, 12:04:32 PM
If you cut the trace between pins 1 and 8 it would clean right up. Maybe you could splice a pot in between those two pins for some sort of pre-gain?
Do you mean cut the vero board trace under the 386 op amp between 1 - 8 pin ??
Yup. Or you could try out some of the "typical applications" here. http://www.ti.com/lit/ds/symlink/lm386.pdf
A 10uF cap between pins 1 and 8 lowers the gain, and a 10uF cap in series with a 1.2K resistor lowers it even more.
Well I finally got around to messing with the circuit and thought I'd report some findings.
I found that a pot between pins 1 & 8 (as described above) really helps tame the gain and make it much more usable. And if you disconnect the cap & pot to ground it becomes more of a high gain overdrive in a pretty nice way.
One of my issues with this circuit has been squeeling and/or some non-appealing artifacts in the signal - I think alot of people have had this problem. I found that adding a little resistance (100 Ohm) between pins 1&8 helps resolve this.
Instead of a resistor between 1 & 8, I've tried a cap with/without a resistor but didn't care for it, a pure resistor sounded much butter.
I'm thinking my final incarnation will include the pin 1&8 pot, then have a switch to enable the cap and pot to ground for higher gain.
Standby to see if the next Lovepedal includes this pot.