Couple lm386 questions

[Locrian99]

Hey guys,

I was thinking of trying out building the power section of the 1w amp from electrosmash, and the power amplifier stage.   And use a clone of the eqd tone job circuit as the "pre amp".   I have this circuit built and boxed however I havent been using it on my pedal board since I now have a 6 band EQ I prefer.   






Remove the volume pot, the aux input and R11.   Would I still need to leave the input cap, I also noticed in this circuit the gain pot is huge compared to the ruby, is this because of the input stage?   And would I most likely want to use a similar value with the above schematic as a "pre amp".   Anyways I'm just trying to figure out if this idea would work before I build the 386 stage (I'd breadboard it first but every time I try to breadboard anything related to the 386 I always get some awful noise in the mix, and I won't know if its from the bread board or the idea.   Thanks.

[FiveseveN]

Remove [...] R11.

You probably shouldn't.

Would I still need to leave the input cap

There is no "input cap", '386 inputs are ground-referenced. C4 is there to remove DC from Q2's output. Does the Tone Job already have one that does the same thing? (Yes)

the gain pot is huge

What is 50K in parallel with 1K (R16)?

Since the Tone Job already has a volume control (LEVEL) you can also skip POT2.
Have you looked at the "typical application" circuits in a '386 datasheet? Do you understand them?

[Locrian99]

Remove [...] R11.

You probably shouldn't.

Would I still need to leave the input cap

There is no "input cap", '386 inputs are ground-referenced. C4 is there to remove DC from Q2's output. Does the Tone Job already have one that does the same thing? (Yes)

the gain pot is huge

What is 50K in parallel with 1K (R16)?

Since the Tone Job already has a volume control (LEVEL) you can also skip POT2.
Have you looked at the "typical application" circuits in a '386 datasheet? Do you understand them?

I haven't gone over the typical application circuits in great detail.   I went through the electrosmash article on the 1wamp to get an idea on what was going on, I'm still pretty green at this mostly solder by numbers but trying to understand what's going on in the time I have to mess around with this stuff.   Anyways...

Little confused as to why I shouldn't remove r11, electrosmash article states that r11 is there for the aux input so there is always a load there if the volume pot is at turned all the way down.   So just figured I didn't need it since I wouldn't have the aux input. 

On the "input cap" that makes sense and that is what I assumed which is why I asked the question.  There's been plenty of times in my short time playing around with this stuff that I think I'm understanding something and I'm wrong,  electrosmash refers to c4 as the input cap which is why I did so here. 

That makes sense on the 50k pot, no idea why I didn't get the parallel thing, I just saw the 50k and thought thats way bigger than the ruby, I do wonder why you wouldn't just use a 1k pot there like the ruby, it doesn't specify taper in the schematic, and I believe the parallel would change the taper only reason I see for it unless theres something I don't know that would cause the 980 to be better than 1k....

Thank you for answering my questions, sounds like I can use the tone job as the pre amp part then.   

[FiveseveN]

Little confused as to why I shouldn't remove r11

Personal preference I suppose. In my own dealings I've found the '386 to be too "saggy" for lack of a better term at large input signals without some series resistance.

[Locrian99]

Little confused as to why I shouldn't remove r11

Personal preference I suppose. In my own dealings I've found the '386 to be too "saggy" for lack of a better term at large input signals without some series resistance.

Ah ok, that is good to know

[merlinb]

I also noticed in this circuit the gain pot is huge compared to the ruby, is this because of the input stage?

It's because a 50k pot was already used for volume, simpler for some people to buy two pots the same value. You could use a 1k pot for gain if you prefer (instead of R16).

And would I most likely want to use a similar value with the above schematic as a "pre amp".

If you want fixed gain then use a 1k trimpot and dial in the volume that works for you. You could then measure the trim and replace it with a fixed resistor. Or just leave the trim, whatever.