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Replace LM386 with LM358?

5 years 2 months ago - 5 years 2 months ago #1713 by stuffmattdoes
Hi folks!

I have been pretty excited about the 1Wamp and decided I would try and assemble it myself to learn more about electronics. I have everything except for the required LM386 chip. Instead, I've got a few LM358s. I just can't figure out how to reconfigure the power amp stage!

Here's what I have so far

It seems the main difference between the two op-amps is that the 386 has pins dedicated to gain, while the 358 does not (I suspect that is because it's dual and restricts each op-amp to only 4 pins). So I designed an inverting configuration that depends on the feedback between the output and inverted input. I use a voltage splitter to bias my input voltage up to half my supply because this is a single power supply setup. I left out the aux input and power supply sections here, but they will exist in my final build.

I think my problem is the coupling capacitors - why is the output still biased after the capacitor?

Before this project I knew very little about electronics and how electricity actually flows, or even how capacitors worked. I'm looking to understand more so I appreciate any advice.


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5 years 1 month ago #1716 by Ray
Replied by Ray on topic Replace LM386 with LM358?
Hi, I was not aware of the www.falstad.com/circuit/ simulator, it looks pretty cool.
So basically, you cannot replace the 386 with a 358

The LM358 is an op-amp, its maximum output current is around 40mA, not bad but not enough to drive speakers.
The lm386 is an integrated audio amplifier (not an op-amp), its maximum output current is around 300mA (e2e.ti.com/support/audio/f/6/p/360550/1267040#)

If you cannot find the LM386, you can try to use higher output current op-amps (like the JRC4556 that gives 70mA) and place them in parallel.
I never tried that myself, but there are some headphone amps like the O2 that use op-amps as a power amplifier (nwavguy.blogspot.com/2011/08/o2-details.html) or the A47 (www.head-fi.org/threads/i-need-an-update...p-parts-list.544829/)

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5 years 1 month ago #1745 by synesthesia
There's no way. Do not just consider similar part numbers. LM358 is a BJT based op-amp as Ray mentioned, with mirror current drivers so it can run on double power supplies (+Vcc and -Vee) while LM386 is only single supply. By the way chip architects is not the same (LM358 contains two opamps through pins 1(out) 2(-in) 3(+in) and for 5,6,7 as posterior) so basically you need to change PCB and routes. That's a nightmare, believe me.

Desperate electronics enginner | Passionate audio hobbyist.
The following user(s) said Thank You: Ray

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3 years 2 months ago #2512 by AsaGong
Replied by AsaGong on topic Replace LM386 with LM358?
Hi....on the off chance that you need current upper than 80ma you should utilize a corresponding intensifier As rl and put your RL at out put of reciprocal enhancer. Voltage gain of this circuit is determined :650 with this circuit you can get (my circuit with correlative) 28 watts with the 4 ohm load.(actual watt) on the off chance that you decline ohm of your heap force will increment.

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3 years 3 weeks ago - 3 years 3 weeks ago #2658 by Anthony120
A belated Answer... LM358 can be used as transducer amplifier, DC gain block etc. It has large dc voltage gain of 100dB. This IC can be operated on wide range of power supply from 3V to 32V for single power supply or from ±1.5V to ±16V for dual power supply and it also support large output voltage swing. To go further, you can check the LM358 Datasheet and Applications. Knowing more about LM358 ICs and their applications never go out of date ;)

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3 years 1 day ago #2718 by jillianmontague3
Choosing a suitable online game, what did you choose? Join the build royale and enjoy the 2D space.

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2 years 7 months ago #3332 by henryjones147
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