386 op amp

[TimWaldvogel]

So i have a shit tone of single and dual op amps, but none of the pinouts match the 386 op amp, however I wanna build a krank distortus Maximus, I know it would affect tone slightly, but what can I substitute forthis op amp?

[TimWaldvogel]

I have never seen a pinout like the 386 before

[aron]

You need the lm386. I got em in the store.

[geertjacobs]

If you check the data sheet for the LM386, you'll see that it's not a simple opamp.
It's a complete low voltage audio power amplifier.
That's why you can't subsitute it with a simple opamp.

[deadastronaut]

the lm386n is my fave chip...

it comes as lm386n-1
 
                lm386n-3

                lm386n-4

all are slighty more miiliwatt than the previous model...great op amps...get em off aron!........

[Mark Hammer]

The -1, -3, -4 suffix only matters if you plan to use it AS the power amp it was ntended to be.  The suffix indicates how much wattage it can safely handle (and how much heat it can dissipate/tolerate) before it goes poof.  The higher the suffix, the greater the power handling.  For the purposes of fuzzboxes, though, the wattage capacity means nothing.

[soggybag]

This is a pretty interesting chip. I really like the fact it doesn't need a bias voltage on the input. This makes for some very interesting possibilities. You can switch the phase with a single switch. Tim E. used both to create an octave effect, I think it was called the Rambler.

[TimWaldvogel]

Does anybody have schematics/perf layouts for anything besides the krank d m ? Tell me how the gain stages work, I notice two of he pins are labeled gain

[soggybag]

Placing a small value, 1K to 10K pot across pins 1 and 8 will create a gain control. This should produce gains of 20 to 200.

You can also a pot to ground on pin 1 to ground to create a gain control that goes above 200. See the Smash Drive for an example.

I posted some examples of different types of gain controls for the 386 on my site here: http://www.super-freq.com/?p=209

[John Lyons]

Thanks Mitchell.
That's a handy reference.

[TimWaldvogel]

So after bookmarking that page I gotta ask, how to you measure gain on a number scale, what would the max, min gain on a tube screamer be? And is the 386 soft or hard clipping

[soggybag]

Hard to say how you would measure the gain. The app notes say the gain is 20 when pin 1 an 8 are not connected and 200 when they are connected.

The path between pins 1 and 8 is a feeback loop. Shunting pin 1 to ground cuts the feedback more increasing the gain. I'm not knowledgeable enough to figure the value.

[TimWaldvogel]

I just don't know what to compare the numbers as ya know?

[Electron Tornado]

I built a pedal with the 386 based on the Smash Drive and the Grace Overdrive. A 1k or 2k pot is adequate for the drive pot. There seems to be very little range for controlling the amount of drive, however.

When using the chip close to a gain of 200 what you'll find is that notes, especially low freq ones, will fade out with an annoying buzz, which then ends abruptly. I haven't figured out how to cure that, or if it can be. The attack and middle of notes, however, have a nice crunchy, slightly fuzzy overdrive sound to my ears.

Here are a couple of circuits from Runoff Groove that use the 386:

http://runoffgroove.com/grace.html 

Here are a couple of other pages discussing the 386:

http://www.intio.or.jp/jf10zl/LM386.htm

http://www.qslnet.de/member/la3za/dokumenter/Unleash386-SPRAT03.pdf

[TimWaldvogel]

I think the 386 is so cool and I stumbled across the big daddy at runoffgrove upon following the grace overdrive link, it looks great, just needs tone controls, baxandall?

[PRR]

> what would the max, min gain on a tube screamer be?

I don't know, but:

In an existing working system, adding gain of "1" is no change at all, adding gain of 10 is a LOT of gain. I see boosters with gain of 4 to 40. Sometimes a stage gain over 100, but then a lot of padding-down.

http://www.national.com/ds/LM/LM386.pdf

The '386 is sort an opamp, but the input voltage range is restricted to near ground (not 1/2 Vcc as in single-supply circuits using standard opamps) and the DC biasing and AC gain resistors are onboard. Just as it stands, it IS a dandy low-volt single-supply booster and power amplifier. Really a different function than more flexible but wimpier '741 TL072 opamps.

You should get some. It is a $0.35 part if you buy a ship-load. Aron and DigiKey ask a buck a chip for just one. Radio Shed charges $1.50, if you can find them beyond the flat-TVs and cellphone salesmen.

BTW, the '386 is a tiny+cheep LM380, and many '380 notes apply to the '386.
http://www.national.com/ds/LM/LM380.pdf
http://www.national.com/an/AN/AN-69.pdf
Wow.... 1972!

[TimWaldvogel]

I suck at getting things right on breadboard lol, I wanna try the distortus Maximus or the rog big daddy

[Electron Tornado]

In an existing working system, adding gain of "1" is no change at all, adding gain of 10 is a LOT of gain. I see boosters with gain of 4 to 40. Sometimes a stage gain over 100, but then a lot of padding-down.

What is "padding-down"? Do you mean that after a high gain stage, the signal level is then reduced, or there is some filtering, or both?

[TimWaldvogel]

I 2nd that above movie

[TimWaldvogel]

I meant "I second that question" dang corrective texting lol