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Author Topic: First real build. LM386.  (Read 1151 times)

flester

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First real build. LM386.
« on: December 20, 2017, 04:11:47 AM »

I mentioned this in other posts but heres a rundown as a novice on my LM386 build. I call it the Bearskin amp. Its a veroboard project very similar to the Little Gem , Ruby, and Smokey amps. No internal speaker. 1K gain pot plus a IK volume control on the output side.
Overall very pleased with this build. The only issue is the volume pot. It is linear slope but still seems more loggy if u know what I mean. Admittedly the quality of the pot is not great but maybe I need a different resistance or slope?

Sent from my SM-G935F using Tapatalk

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flester

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Re: First real build. LM386.
« Reply #1 on: December 20, 2017, 04:19:50 AM »

Since taking these photos I glued sheets of pickguard inside to provide support for the pots and jacks as the walls are rather thin. Also sub mini toggle switch in between the pots.

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Katoda

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Re: First real build. LM386.
« Reply #2 on: December 20, 2017, 11:30:15 AM »

Cool, congrats!

The gain and volume pots are supposed to be logarithmic, if yours are linear, then they probably have an exponential curve effect to the ear, as we percieve the power vs volume logarithmically. You can simulate the log response by putting a resistor from the wiper to tje ground, but then you need a bigger pot or to decrease the impedance going into the pot.

Glad to see it works, cheers.
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flester

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Re: First real build. LM386.
« Reply #3 on: December 21, 2017, 09:47:39 AM »

Cool, congrats!

The gain and volume pots are supposed to be logarithmic, if yours are linear, then they probably have an exponential curve effect to the ear, as we percieve the power vs volume logarithmically. You can simulate the log response by putting a resistor from the wiper to tje ground, but then you need a bigger pot or to decrease the impedance going into the pot.

Glad to see it works, cheers.
Thanks I might try that. Just used the pots I had so I knew they might not be right. 1k lin was recommended for the gain but the vol specified 25ohm. (Ruby Amp project on generalguitargadgets.com). Certainly getting great enjoyment from the project and looking forward to playing it

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flester

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Re: First real build. LM386.
« Reply #4 on: December 31, 2017, 09:21:57 AM »

Cool, congrats!

The gain and volume pots are supposed to be logarithmic, if yours are linear, then they probably have an exponential curve effect to the ear, as we percieve the power vs volume logarithmically. You can simulate the log response by putting a resistor from the wiper to tje ground, but then you need a bigger pot or to decrease the impedance going into the pot.

Glad to see it works, cheers.
Thanks I might try that. Just used the pots I had so I knew they might not be right. 1k lin was recommended for the gain but the vol specified 25ohm. (Ruby Amp project on generalguitargadgets.com). Certainly getting great enjoyment from the project and looking forward to playing it

Sent from my SM-G935F using Tapatalk
I tried making a few changes and basically all the 1k pots disintegrated from too much soldering and de soldering. So ended up with 10k linear for gain and no vol pot. Gain does nothing from 0 to 9 then it all happens between 9 and 10 so look likes i need a log pot. Any good suppliers or brands i should look for?


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Katoda

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Re: First real build. LM386.
« Reply #5 on: December 31, 2017, 11:26:24 AM »

Doesn't really matter what brand you use. But before you order a new pot, you might want to try soldering a 1.5k resistor from wiper to ground, which will somewhat simulate the log curve.
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flester

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Re: First real build. LM386.
« Reply #6 on: January 02, 2018, 07:29:40 AM »

Doesn't really matter what brand you use. But before you order a new pot, you might want to try soldering a 1.5k resistor from wiper to ground, which will somewhat simulate the log curve.
Onlt asking about brands as the ones I got were trash. I think 10k is too much for the gain as its in parallel to a 1.35k res within thw chip. It works more like a high/low gain switch than a pot

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Katoda

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Re: First real build. LM386.
« Reply #7 on: January 02, 2018, 08:37:37 AM »

Oh right, sorry, I wasn't looking at the schematic, didn't see that the gain control was actually feedback control. For that configuration you might need an anti-log pot. Also, datasheet specifies you should use a capacitor in series with the pot, but that's not really the problem.
For the pots - I usually use Alpha brand, they're cheap and of all-right quality.

Sorry I couldn't be of more help, good luck.
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flester

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Re: First real build. LM386.
« Reply #8 on: January 03, 2018, 04:32:52 PM »

Oh right, sorry, I wasn't looking at the schematic, didn't see that the gain control was actually feedback control. For that configuration you might need an anti-log pot. Also, datasheet specifies you should use a capacitor in series with the pot, but that's not really the problem.
For the pots - I usually use Alpha brand, they're cheap and of all-right quality.

Sorry I couldn't be of more help, good luck.
Today i added a DC jack to use a 12v supply or the 9v battery. 12v fattens and cleans up the sound nicely at minimum gain. Also  screwed the board in place and used hot glue here and there so nothing moves that shouldnt.

Im guessing any 1k pot would be an improvement but will try antilog and also linear.

Now planning MkII. Will post final schematic and sound samples in due course


Sent from my SM-G935F using Tapatalk

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flester

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Re: First real build. LM386.
« Reply #9 on: January 11, 2018, 03:27:12 PM »

Oh right, sorry, I wasn't looking at the schematic, didn't see that the gain control was actually feedback control. For that configuration you might need an anti-log pot. Also, datasheet specifies you should use a capacitor in series with the pot, but that's not really the problem.
For the pots - I usually use Alpha brand, they're cheap and of all-right quality.

Sorry I couldn't be of more help, good luck.
Today i added a DC jack to use a 12v supply or the 9v battery. 12v fattens and cleans up the sound nicely at minimum gain. Also  screwed the board in place and used hot glue here and there so nothing moves that shouldnt.

Im guessing any 1k pot would be an improvement but will try antilog and also linear.

Now planning MkII. Will post final schematic and sound samples in due course


Sent from my SM-G935F using Tapatalk
Heres a video with my lap steel
https://flic.kr/p/23otDrP

Sent from my SM-G935F using Tapatalk

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phatt

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Re: First real build. LM386.
« Reply #10 on: January 12, 2018, 08:14:07 AM »

Hey some nice blues riff there :tu:
BTW, looks like you are driving a hifi type speaker box,, if so then be aware they are woofers and generally have a low SPL,, a real guitar speaker will give a much bigger sound,, louder per watt of input.
Phil.
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flester

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Re: First real build. LM386.
« Reply #11 on: January 16, 2018, 02:10:25 PM »

Hey some nice blues riff there :tu:
BTW, looks like you are driving a hifi type speaker box,, if so then be aware they are woofers and generally have a low SPL,, a real guitar speaker will give a much bigger sound,, louder per watt of input.
Phil.
A friend has a 12" guitar speaker I can use. Time for a bit of joinery I think


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flester

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Re: First real build. LM386.
« Reply #12 on: January 23, 2018, 06:24:42 AM »

Hey some nice blues riff there :tu:
BTW, looks like you are driving a hifi type speaker box,, if so then be aware they are woofers and generally have a low SPL,, a real guitar speaker will give a much bigger sound,, louder per watt of input.
Phil.
A friend has a 12" guitar speaker I can use. Time for a bit of joinery I think


Sent from my SM-G935F using Tapatalk
Works as a harmonica amp too. I made the mic using a headphone speaker. The black box on the right contains a Kemo preamp module, needed to overdrive the amp. A Danelectro overdrive pedal works too. https://flic.kr/p/22mhiVv

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flester

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Re: First real build. LM386.
« Reply #13 on: January 31, 2018, 07:28:17 AM »

Thinking about the speaker, I want to use a combo as a cab. Very useful for testing all kinds of amp projects. What type of jack will disconnect the internal amp when an input is plugged in. Been searching 'switched jack' but that doesnt seem to cover what I want.

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Katoda

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Re: First real build. LM386.
« Reply #14 on: January 31, 2018, 09:26:57 AM »



A jack like this one, but a mono version. Or stereo, doesn't matter. Plastic 6.3 mm jack
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