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The One Watt Open Hardware Guitar Amplifier.

TOPIC: Replace LM386 with LM358?

Replace LM386 with LM358? 2 years 7 months ago #1713

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.

Thanks!
Matt
Last Edit: 2 years 7 months ago by stuffmattdoes.
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Replace LM386 with LM358? 2 years 7 months ago #1716

  • Ray
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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

Why?
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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Replace LM386 with LM358? 2 years 6 months ago #1745

  • synesthesia
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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.
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Replace LM386 with LM358? 7 months 3 weeks ago #2512

  • AsaGong
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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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Replace LM386 with LM358? 5 months 4 weeks ago #2658

Hi,
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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Last Edit: 5 months 4 weeks ago by Anthony120.
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Replace LM386 with LM358? 5 months 4 days ago #2718

Choosing a suitable online game, what did you choose? Join the build royale and enjoy the 2D space.
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Replace LM386 with LM358? 3 days 3 hours ago #3332

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