LM380 2.5W Amp (Request)

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LM380 2.5W Amp (Request)

Silver Blues
I stand watching the steam-liners roll by...
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Re: LM380 2.5W Amp (Request)

Heath
Thanks, Silver!  I'll try and verify this as soon as I get some LM380s in (thought I did, but turns out they're LM308s).

Edit:  Just ordered a couple LM380s on Ebay.  I should be able to try this out by Friday.
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Re: LM380 2.5W Amp (Request)

AC_FX
In reply to this post by Silver Blues
This one has me interested - I want to make a little solid-state amp soon.  I'd like to adapt the Noisy Circket with more control over gain and tone - might give that a shot after I get a couple of other pieces of pointless tinkering completed.

Just a thought - the datasheet for the LM380 says it wants a power supply of 10V-22V.
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Re: LM380 2.5W Amp (Request)

Heath
Here's the schematic:


It might be worth trying it with 12v or 18v once I get it verified at 9v.

I was thinking of trying it with this:
http://guitar-fx-layouts.42897.x6.nabble.com/Bax-in-a-box-active-baxandall-tonestack-td7264.html

for a super-gnarly cigar box amp.  

I found a cigar box big enough to mount a 6 inch speaker in, but I'm afraid that this little amp circuit through that speaker might just shatter the cigar box.
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Re: LM380 2.5W Amp (Request)

Silver Blues
Yeah, a bit higher headroom would surely be nice with this considering the supply range it can handle. Easiest way would probably be to charge-pump it up to 18v with this site's pump layout.
I stand watching the steam-liners roll by...
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Re: LM380 2.5W Amp (Request)

Heath
Yep, my thinking too, SB.
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Re: LM380 2.5W Amp (Request)

Heath
Verified @ 9v

It's quite nice!!

All of my 470uf caps are 16v :/

I might see if I can get my hands on some proper caps to handle 18v and try it at that.
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Re: LM380 2.5W Amp (Request)

Silver Blues
Yay, a verification among a string of "bad" layouts!  Cool, glad you enjoy it! How much volume do you actually get out of that? Seems like a fair amount of wattage for a single-chip amp.
I stand watching the steam-liners roll by...
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Re: LM380 2.5W Amp (Request)

Heath
I've got some higher voltage 470uf caps on the way.  For now, as soon as I get home, I'll try it through a proper 12" cab at 9volts.  When I upgrade the caps I'll try it again but at 18volts.

As I mentioned before, I'm looking into building some eccentric little amps and I wanted a circuit that would go quite a bit louder than the Noisy Cricket but still be small, cheap, run off a 9volt battery, and easy to build.  I'm going to mess around with adding some tone controls, headphone out, etc. and see what I can do with this one.
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Re: LM380 2.5W Amp (Request)

Heath
I just tested a Noisy Cricket MkII, a Chime Amp, and the LM380 amp laid out here.

Tested with a pine Esquire with a GFS Memphis Retrotron pickup in the bridge (medium output humbucker) through a 12" Eminence speaker from a Fender Supersonic 22 amp.

Noisy Cricket MkII:
This gets some volume through a 12" speaker, but at it's loudest no one is going to tell you to turn it down.  Also tends to dirty up pretty quickly.  I don't like this amp for getting a good clean sound.  I want to test this one again through a good quality 6" speaker and/or headphones.  Still, it's got a kind of "blah" tone to it.  Not bad but not great.

Chime Amp:
This is a GREAT circuit!  Clean from 1 to 11 with a very pleasant tone.  Turned all the way up it gets loud enough to bother me if I'm right in front of the speaker.  Could potentially bug a neighbor if turned up at night.  The volume is fairly close to the NCMII with the gain turned all the way up, bass boost engaged, and dirt switch turned on.

For comparison, I ran my guitar through a Catalinbread CB-30 and was quite surprised at the amount of volume coming out of this amp.  I didn't even get to the point of turning the volume/level on the pedal all the way up as it was neighbor annoying at about halfway vol on the pedal and full vol on the  amp.

In my opinion the Chime Amp kicks the shit out of the Noisy Cricket.  As with the Cricket, I am anxious to try this amp out through a good quality 6" speaker as I would like to build a little 9v carry-around amp that still sounds good.

LM380 2.5 Watt Amp:

I haven't been able to perform a proper test on this one yet, but I did run it through the 12" cab at 9v and so far, it sounds great.  It's about as loud as the Chime Amp in my limited testing (keep in mind it's being underpowered, though) which is to say I could probably just manage to annoy the neighbors with it.  It starts to dirty up a little bit at about 7-8, but not much.  At 10 it's like a nice mild overdrive.  I expect this to go away when it's powered at 18 volts (but I could be wrong) and I'm anxious to see if it provides more output.

It's pleasant sounding.  Better than the Cricket, maybe slightly less sweet sounding than the Chime, but again, I want to re-compare with proper voltage.

All things being equal I'd say the Chime Amp stands out of the 3... BUT I don't think the LM380 amp has been fairly tested yet.  I've already got replacement 470uf caps on the way and once I get them in I'll charge pump it to 18volts and see what I get.

I'm thinking that for a portable lunchbox-type amp, the Chime might be the perfect circuit.  Even if the LM380 blows me away at 18volts, I'd be concerned about the battery life of the amp compared to the Chime running at 9volts.  

I want to hear the LM380 at 18volts driving a 4x12 :D
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Re: LM380 2.5W Amp (Request)

Heath
I upgraded the 470uf caps to 35v and powered the amp at 18 volts.

It's pretty loud, for sure.  The 18volts REALLY opens it up.. it gets a small but significant volume boost, but what is most pronounced is the tone/color/whatever you want to call it.  It goes from kind of dull sounding at 9v to bright and open at 18v.  I think it has a nice "personality."

However, it's almost impossible to get a clean sound out of it.  At about 3 on Vol it's verging on dirt but is mostly clean.  At about 5-6 it dirties up like a mild overdrive.  It increases from there up to a pretty aggressive OD at 10.  With my testing setup it sounds pretty good, better than some pedals I've heard.

I've got a 6" Gretsch speaker on the way so we'll see how this all sounds through a smaller speaker as well.  

As far as mini amps go, this is more like a Marshall, with it's intended overdrive and the Chime Amp is more like a Fender Amp with it's extended cleans.  

All in all I prefer the Chime Amp with whatever OD/Distortion I want added via pedal.  It just has so much sweet clean sound on tap.  

That said, the LM380 amp is pretty damn ballsy for such a tiny thing.  I'll bet someone smarter than me could tweak that circuit and optimize it for more/better range of clean before it starts dirtying up.  I would be a monster then.  I just don't feel this circuit is taking full advantage of the amp chip.  Then again, what do I know? :p
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Re: LM380 2.5W Amp (Request)

Tesla
In reply to this post by Silver Blues
Any chance of getting a 14 dip version please!   It’s all I have and I really want to avoid the 386 based practice amps
Exodus Effects