Lovepedal - Purple Plexi 800 [goop-alarm] [traced]

[compuwade]

I built this with a JRC386 and it sounds fantastic! I had none of the issues I have seen described by some others here. However, the max gain is bunched up at the very end of the gain pot's rotation but, I don't really use that much gain anyway. The only thing I would like to change is to lower the gain at the lowest pot setting. Where is a good place to start to address this? The 470R resistor?

If im not mistaken you can disconnect pin 8 from 1 and lower the gain considerbly. I'm not sure how this will alter the sound, but thats how its done with the noisy cricket and the other circuits using the lm386.

[highway jones]

I built this with a JRC386 and it sounds fantastic! I had none of the issues I have seen described by some others here. However, the max gain is bunched up at the very end of the gain pot's rotation but, I don't really use that much gain anyway. The only thing I would like to change is to lower the gain at the lowest pot setting. Where is a good place to start to address this? The 470R resistor?

If im not mistaken you can disconnect pin 8 from 1 and lower the gain considerbly. I'm not sure how this will alter the sound, but thats how its done with the noisy cricket and the other circuits using the lm386.

Thanks,

I routed the pin 1 -> 8 connection on a switch so that I can remove the gain part all together as you mentioned. The difference isn't huge but, closer to what I was after at minimum gain. I have been through quite a few Marshall-in-a-box circuits but, this may be my all time favorite. The tone control really gives it its versatility.

[compuwade]

I built this with a JRC386 and it sounds fantastic! I had none of the issues I have seen described by some others here. However, the max gain is bunched up at the very end of the gain pot's rotation but, I don't really use that much gain anyway. The only thing I would like to change is to lower the gain at the lowest pot setting. Where is a good place to start to address this? The 470R resistor?

If im not mistaken you can disconnect pin 8 from 1 and lower the gain considerbly. I'm not sure how this will alter the sound, but thats how its done with the noisy cricket and the other circuits using the lm386.

Thanks,

I routed the pin 1 -> 8 connection on a switch so that I can remove the gain part all together as you mentioned. The difference isn't huge but, closer to what I was after at minimum gain. I have been through quite a few Marshall-in-a-box circuits but, this may be my all time favorite. The tone control really gives it its versatility.

I'm glad that worked for you. I'm sure there is a better way to lower the gain even further but I haven't messed with the circuit yet.
My favorite Marshall in a box is the BSIAB2. But it can be quite noisy, and my bridge pickup doesn't help the issue much. This circuit on the other hand, is very quite for the amount of gain it has. Which makes it more pleasurable to play. So for as simple as this circuit is, it's definatly one of the better ones I've built. It has a home on my pedal board for sure.

[Renegadrian]

I built a PP800 following Torchy's vero, only used 4.7n where he declares 22n (all the other schems/layouts have 4.7n) - this beast has got a good amount of gain and a great sound, also it has a lot of volume! I have to keep the volume pot at half or even less to get unity!!! it definitely screams! But hell it whistles like creaze with the gain at max and the volume a little above unity...maybe I should try another 386...Hints anyone?!

[ansil]

which one do you have. if you are using the jrc386 rumor has it you should be fine. if you are using the lm386n-1 then good luck chuck.

try the n-3 and n-4 those are my two favorites. i still have yet to try toe jrc one but am working on it.

[Renegadrian]

LM386L is on and got a couple ofLM386N-1 to try.
Saw a mod a couple of pages before but I didn't get how to put it in the vero I already assembled...

[ansil]

based off datasheet the l is just lead free and nothing more. so more than likely it is a n-1 which works best on a 6v supply. the others work better at 9v

the n1 max output is aprox 325mw where as the 2-3 is 700mw n-4 is 1000mw

the three and four seem to be the most stable in my experience with them over the last million years lol

btw here is one of the many datasheets for the 386. http://www.national.com/ds/LM/LM386.pdf

when i was a member over at arons there was a link posted to another really cool datasheet of things to do with a 386 but i dont' see it now. but i will tell you that bass boost really helps out.

you can also tailor the freq response you want to dump back into the feedback loop there i liked to drive the high end a bit more and drive reduction on the low end. then you can use a stomp switch to jack the bass end back up real nice stuff.

[Renegadrian]

Got a jrc 386 now, still hisses and whistles at max gain. Now what?!

[ansil]

ok now i am cornfused will have to look at the schematic again when i get off work.

ed

[ansil]

i am not sure what to tell you here my friend. this is bizarre since it only has 1.5k of high end available according to the schematic. are you using the updated one from sandmannn69. with the 4700pf behind the 4.7k if so that explains it your are getting a freq response of 7.2khz

previous one had high end of 1.5k based off the .022uf cap

[Renegadrian]

As I wrote before, I used Torchy layout, strangely he didn't use 4.7n but another value (22n If memory serves well...)

[ansil]

didn't see that sorry it was late when i got home and only had a few minutes. well then short of parasitic capacitance between leads i dont' know what to tell you.

[ansil]

ah i went looking for torchys layout and it was a dead link you got it i will look up for you

[Renegadrian]

ah i went looking for torchys layout and it was a dead link you got it i will look up for you

thank you ansil - this is torchy's
download/file.php?id=960
As you see, two 22n caps, while other schems call for 4.7n, so I went that way...

[ansil]

well one of the things i would try is the 100pf vs the 370pf on the input. torchys says 100pf where as original says 370. something to try also is a 10uf on the 7th pin to ground. it is rumored to help with th stability of the circuit. it has fixed some issues for me in th past and is recommended by national semi. other than that. run it through a freq analyzer and find the annoying freq and use a simple rc filter to remove it.

[Renegadrian]

Ansil, thank you for your advices - Actually I built two of them, and both have that whistling hell.
100pF-330pF no difference in whistle.
LM386L-JRC386D no difference in whistle.
10uf on the 7th pin to ground no difference in whistle.
no freq. analyzer but damn it whistles!!!

[ansil]

the only thing i can think of right now is perhaps a simple low pass filter on the output. or perhaps since its only at max gain use a dual gain pot so that it winds down the high end as you crank the gain. such as the marshall guvnor. look at that.

[Renegadrian]

I think I am gonna throw them outta the window - My patience is not so high these days, and those MF bored me...No worries...

[equinox]

did anyone build these up with stripboard or the pcb in the thread?? how did they sound??

i'm also a little sonfused because i have a purple plexi stompbox and 1. it is not SMD and also the schematic and components are different?!?!?!? I wonder if it is an early development model. it's also handwired with a small pcb and all throughhole components.

let me know your thought.

equinox

[distortion_gfx1]

Does Anybody got a real deal with the Schem..????

i really dont know what to use?..