JRC386 clipping

[g3rmanium]

Hello,

a friend of mine recently dissected a certain boutique distortion that is nothing but a JRC386D running at insane gains. I read in the literature that the gain is 200 if a 10 µF cap is placed between pin 1 and 8. In this design, there's a 47 µF cap.

I looked at the audio specs and they aren't really stellar from what I can tell.

The question is -- why is a 386 used there? Is the clipping in these amps different/better from opamp clipping?

Thanks

[bancika]

It depends on what you like about clipping, to me it's too fuzzy

[g3rmanium]

It depends on what you like about clipping, to me it's too fuzzy

In other words, you think there's nothing special about it?

[petemoore]

  Plenty of 20 minute 386 wiring plans around here, Bobtavia, Smashdrive, New Fuzz, Freak Out Fuzz, Grace, Big Daddy, all quite 'easy'...the 386's take very few connections to wire up, the V_/+ supply can go right to the chip!
  And very easy to mess around with...all you need is a small handful of parts, a chip/socket/and piece of perf or Breadboard to do it on.
  In other words, you think there's nothing special about it?
    http://www.national.com/pf/LM/LM386.html
  LM4887...'more power, 'better' THD'

[g3rmanium]

And very easy to mess around with...all you need is a small handful of parts, a chip/socket/and piece of perf or Breadboard to do it on.
  In other words, you think there's nothing special about it?

I meant the distortion characteristics. In this circuit, the chip is used at very high gains. Is this chip really sounding very different from other opamps or what is the specific reason it's used in so many designs (simplicity aside)?

[bancika]

I generally don't like IC's to do any clipping at all. One of tube's advantage is simplicity. I like having as few (basic) electronic components between pickups and speaker. IC is a mess of zillion components (386 has 10 transistors IIRC)

[dano12]

And very easy to mess around with...all you need is a small handful of parts, a chip/socket/and piece of perf or Breadboard to do it on.
  In other words, you think there's nothing special about it?

I meant the distortion characteristics. In this circuit, the chip is used at very high gains. Is this chip really sounding very different from other opamps or what is the specific reason it's used in so many designs (simplicity aside)?

The clipping can sound quite nice when it is used as a low power amp, as in the Ruby from runoffgroove. I'm building a couple of 386-based distortion circuits, too soon to know if the same type of clipping will occur.

[David]

And very easy to mess around with...all you need is a small handful of parts, a chip/socket/and piece of perf or Breadboard to do it on.
  In other words, you think there's nothing special about it?

I meant the distortion characteristics. In this circuit, the chip is used at very high gains. Is this chip really sounding very different from other opamps or what is the specific reason it's used in so many designs (simplicity aside)?

The 386 and single op-amps like the TL071 are alike in that they are both 8-pin DIP chips.  That's where they part company.  The TL071 is an op-amp.  The 386 most definitely is not.  It is a .5W audio amplifier.  You cannot substitute between the two.

[David]

And very easy to mess around with...all you need is a small handful of parts, a chip/socket/and piece of perf or Breadboard to do it on.
  In other words, you think there's nothing special about it?

I meant the distortion characteristics. In this circuit, the chip is used at very high gains. Is this chip really sounding very different from other opamps or what is the specific reason it's used in so many designs (simplicity aside)?

The beauty of a 386 design IS the simplicity.  You can get screaming high-gain distortion from 9V, one chip and almost no support components.

[kusi]

hi,

i understand the "normal" gain-controlls in the 386er circuits. (minimize the 1,35kR between pin 1 & 8 or bypass it with a capacitor)

but i do not understand the gain-controll in the smash-drive;
the 1,35kR is shorted, and the gain-controll is a voltage-divider. (internal 150Ohm + 5k pot + DC-blocking-cap). now, if i decrease the value of the gain-pot, the amplfied signal goes lower. but why increses the gain of the circuit? 

other question; pin 7, with the "bypass-cap". this capacitor is just for a more stable operation, right? (dc-filtering?)

thanks,
kusi

[petemoore]

other question; pin 7, with the "bypass-cap". this capacitor is just for a more stable operation, right? (dc-filtering?)
  Pin 7 is the power supply input, so a cap from there to ground would filter the DC.
  Smash Drive Schematic...I only saw the layout, it looks like the Drive connects to the gain pins 1 and 8, other side through a stop resistor [100ohm] then 4u7 to ground, so 'some' AC gets shunted to ground through the pot+stop resistor/capacitor to ground, the 4u7 will pass guitar signal frequencies.

[Peter Snowberg]

The JRC386 is a great fuzz building block.  (the LM parts are too, just not quite as great)

[MartyMart]

other question; pin 7, with the "bypass-cap". this capacitor is just for a more stable operation, right? (dc-filtering?)
  Pin 7 is the power supply input, so a cap from there to ground would filter the DC.

No, pin 6 is the power input ! pin 7 is "Bypass" ??

MM

[doug deeper]

what boutique pedal are you speaking of? 

[g3rmanium]

what boutique pedal are you speaking of? 

It doesn't sound very good.