Hi, I want to build a really clean LM386 based amplifier.
I'm planning to have a tube preamp section (Subcaster which I've already built) at the front end, so I don't want the amp to have a distortion feature.
Any suggestions?
Try looking at the datasheet; there are some designs in there. The LM386 isn't really a good quality chip though.
Quote from: sfx1999 on May 18, 2008, 12:28:28 PM
Try looking at the datasheet; there are some designs in there. The LM386 isn't really a good quality chip though.
Why is it not a good chip? Almost all the little DIY amps I have seen use em.
Some things that may help with your design.
1. Supply it with 12 volts instead of 9. Get the higher rated LM386 chip. The N1 through N3 versions will go to 12 volts and the N4 will handle up to 18 volts. The NJM/JRC386 will go to 12 volts, and in my opinion, sounds better and is a bit more stable.
2. On the output of the subcaster, use a b100k pot as a voltage divider to attenuate the signal before going into the 386. You may want to find the max volume that you like, and use another fixed resistor to set a limit.
When I was designing the Tube Cricket, I had poor luck with the LM386 and went with the JRC part instead. It may work better for you.
Hope that helps.
Quote from: dano12 on May 18, 2008, 03:54:59 PM
Some things that may help with your design.
1. Supply it with 12 volts instead of 9. Get the higher rated LM386 chip. The N1 through N3 versions will go to 12 volts and the N4 will handle up to 18 volts. The NJM/JRC386 will go to 12 volts, and in my opinion, sounds better and is a bit more stable.
2. On the output of the subcaster, use a b100k pot as a voltage divider to attenuate the signal before going into the 386. You may want to find the max volume that you like, and use another fixed resistor to set a limit.
When I was designing the Tube Cricket, I had poor luck with the LM386 and went with the JRC part instead. It may work better for you.
Hope that helps.
Thanks Dano. The chip I'm playing about with is an N1. I was planning to use 12 volts anyway as the Subcaster has that power requirement. Good idea to attenuate the volume into the 386.
Try this one: http://www.headwize.com/projects/guitar_prj.htm
Quote from: kurtlives on May 18, 2008, 02:29:38 PM
Quote from: sfx1999 on May 18, 2008, 12:28:28 PM
Try looking at the datasheet; there are some designs in there. The LM386 isn't really a good quality chip though.
Why is it not a good chip? Almost all the little DIY amps I have seen use em.
I think what sfx1999 meant was that it is not a really good audio chip, which is something all those DIY amps--which are designed to be easily overdriven, and to drive various speaker loads--take advantage of. If you want really clean, you will want headroom and lower distortion. Any number of chip amps (TDA xxxx) will do you better there, although the builds may be larger and more complicated due to higher power supply requirements and heatsinking.
Quote from: frequencycentral on May 18, 2008, 04:04:23 PM
Thanks Dano. The chip I'm playing about with is an N1. I was planning to use 12 volts anyway as the Subcaster has that power requirement. Good idea to attenuate the volume into the 386.
The N1 only puts out 325 Mw @ 8Ohm max and is the lowest power version, meaning it will also distort at lower volume levels then
the N3/N4 version. Get at least the N3 and preferably the N4 if you intend to get maximum clean volume.
(N3= approx 700Mw @ 8Ohm, N4= approx 1000Mw @ 8Ohm)
Cheers
Quote from: Ben N on May 18, 2008, 07:08:16 PM
Quote from: kurtlives on May 18, 2008, 02:29:38 PM
Quote from: sfx1999 on May 18, 2008, 12:28:28 PM
Try looking at the datasheet; there are some designs in there. The LM386 isn't really a good quality chip though.
Why is it not a good chip? Almost all the little DIY amps I have seen use em.
I think what sfx1999 meant was that it is not a really good audio chip, which is something all those DIY amps--which are designed to be easily overdriven, and to drive various speaker loads--take advantage of. If you want really clean, you will want headroom and lower distortion. Any number of chip amps (TDA xxxx) will do you better there, although the builds may be larger and more complicated due to higher power supply requirements and heatsinking.
Yeah I wasn't referring to their reliability I was referring to their signal quality.
Quote from: any on May 19, 2008, 01:57:16 AM
Quote from: frequencycentral on May 18, 2008, 04:04:23 PM
Thanks Dano. The chip I'm playing about with is an N1. I was planning to use 12 volts anyway as the Subcaster has that power requirement. Good idea to attenuate the volume into the 386.
The N1 only puts out 325 Mw @ 8Ohm max and is the lowest power version, meaning it will also distort at lower volume levels then
the N3/N4 version. Get at least the N3 and preferably the N4 if you intend to get maximum clean volume.
(N3= approx 700Mw @ 8Ohm, N4= approx 1000Mw @ 8Ohm)
Cheers
Thats what I love about this forum - I didn't know there were different versions of this chip when I started this thread.
I quite like the schematic Mark Hammer suggested. I will build that one and order an N4 version of the chip in the meantime, and swap it out with my N1 when it arrives.
Thanks everyone!
What about this?
(http://www.febat.com/Elettronica/Elettronica_ampli_finale_LM386.gif)
R1= 50 k log
R2= 1,5 k
R3= 10 r
C1= 10 uF
C2= 47 uF
C3= 100 nF
C4= 10 uF
C5= 10 uF
C6= 47 nF
C7= 220 u
what about lm384? It gives 5w output...anybody used it?
Ok, I built this http://www.headwize.com/projects/guitar_prj.htm onto my Subcaster board. It's the schematic Mark suggested.
It's worked out pretty good. I didn't use C5, C6 and R5 from the schematic, wanting the distortion to happen in the tube not the chip. Also didn't use C3 - didn't seem nessesary. I changed the Subcaster 50k gain pot for a 100k, which I thought would enable a cleaner sound at lower gain - it seem to work. With the gain cranked up its nice and dirty! I've still only got an N1, but it's loud enough for home through the speaker in my VJ clone. I'll pick up an N4 when I can. Just for fun I took it to band practice tonight, played it through a Crate 4x12, then a Marshall 2x15. Obviously it didn't fill the room, but the tone was excellent. Its not even boxed yet - my band think I'm nuts but they were fascinated! Tried it driven by my LPB-1 - more intense tone.
So now I have to decide - head or combo? And build an LPB-1 in for drive maybe? Also thinking of an effects loop between the Subcaster and the 386......hmm?
It's been christened 'Doctor Analogue's Nasty Little B@$t@rd!'
You could try the Omega (http://www.runoffgroove.com/omega.html) from ROG as a booster. You could also try one of the amp simulating projects, like The English Channel (AC-30 brilliant channel), Thor (Plexi), Professor Tweed (Tweed Princeton), Eighteen (18W). Another option would be to combine the Omega with the Thor.
Also, what about TDA2005 (http://www.hobby-hour.com/electronics/tda2005-power-audio.php) and TDA2003 (http://www.hobby-hour.com/electronics/tda2003-power-audio.php)?
I believe they would be clean, they are used in small car systems if I ain't wrong...and use 9-12V
Seem quite easy to build one...
Quote from: Renegadrian on May 22, 2008, 07:16:51 PM
Also, what about TDA2005 (http://www.hobby-hour.com/electronics/tda2005-power-audio.php) and TDA2003 (http://www.hobby-hour.com/electronics/tda2003-power-audio.php)?
I believe they would be clean, they are used in small car systems if I ain't wrong...and use 9-12V
Seem quite easy to build one...
Nice ideas Adriano, but this was a 'use up spare parts/circuits' project. I originally built the Subcaster for a pedal - but it works out that it makes more sense to use a 12au7 as it's half the current draw of a 6111. So I thought 'what shall I do with the Subcaster board?' Answer - use it as a preamp in a little amp, as I had a spare 386 knocking about that seemed be the logical way to go.
The TDA2003/TDA2005 idea is tempting - But now I have four guitar amps: Roland Bolt 60 (80's - their only tube amp), Harley Benton GA5 (Thomann VJ clone), Vox Pathfinder 15R (Used mostly with my Rhodes piano at home - the onboard tremolo and spring reverb suit it down to the ground) - and now my new Doctor Analogue Nasty Little B@$t@rd.
Can a man have too many guitar amps? I have a sh*tload of keyboards too, including a grand piano - you have to stop somewhere!
Double post - sorry! :icon_redface:
I think I'll try the TDA2005 in stereo to connect my ZOOMs (I love them...) or to connect my mp3 player for my mum while she's ironing... :icon_razz:
Made a small 386 ckt - N1 - it distorts yeah...gotta try a N4...
I used THIS LAYOUT HERE (http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=43996&g2_serialNumber=1)
edit
nah it distorts badly even with a N4 - no clean amp here...
Let's do some thinking here.
The LM386 is a solid state amp with a decent feedback factor. When it is fed a signal that does not drive it beyond its power supply limits, it does not distort in a gross fashion. What distortions is has under these conditions are the small distortions of any Class AB amp - crossover and very low THD. The datasheet says it will be under 0.2%.
What makes an LM386 distort is feeding it a signal large enough to drive its output beyond its power supply limits. If you have an LM386 powered from 9V, It cannot swing its output more than 0V to 9V. In fact, it can't go that far; it can only get to 6V peak to peak with a 9V power supply and an 8 ohm speaker load. If you load it down with a 4 ohm load, it can only get to about 3.5V peak to peak before distorting.
The LM386 has a variable gain, set by the impedance between pins 1 and 8. If you leave 1 and 8 open, the gain is 20. If you bypass 1 to 8 with a capacitor, the gain goes up to 200. You can set any value between there with a resistor in series with the capacitor.
Here's how you make it not distort, as mentioned in an earlier post: don't feed it an input signal so big that it's driven to distortion, considering its gain. If you have it powering an 8 ohm speaker and running from 9V, it can't swing more than 6V peak to peak, 3V peak or 2.12V rms. The lowest gain you can make it have is 20, so the biggest input it can take without distorting is 2.12V/20 = 0.1Vrms.
That's about the output of a single coil pickup. You can't have *any* gain before the LM386 and have it not distort with this power supply and loading. Putting a 4 ohm speaker on it would require you to pad a raw guitar output down to keep it from distorting.
This gets better (a little) when using higher power supplies. Even better when you change to a different chip to get much bigger power supplies.
No amp will be clean if you feed it an input signal bigger than its maximum output swing divided by the gain it has. Period.
THX Mr. RG for your precious reply as always!
As you can see from the layout I used, pins 1 and 8 are tied together with nothing in between swe gain should be 20. I just plug the guitar in, straight. I tried both a fresh 9V battery and a 12V unregulated WW (so it gets +-13V)
ACK! NO! OPEN pins 1 and 8 to get the gain down. No connection at all.
Uh, I just used that layout which states CLEAN amp...There is no line break at pins 1 and 8...I'll do it in a second!
edit
ok now it works like it's supposed...L O U D!!!
Just a tad of distortion (with N1) when the 47k pot is maxed. but it's ok!!!
Swapped it with a 386 L - less loudness but it's CLEAN as it can be. and it takes so well my Zoom!
Nice, Adriano! I think I could be trying it soon. :icon_biggrin:
That's very good info, R.G., Thank you!
I have messed with the 386 a lot. Honestly, if you are going through the trouble of building a tube pre-amp, use a different chip that will get you more clean headroom. You can not give the 386 much before it distorts.
I built a TDA2005 guitar amp (dual 10W) from the datasheet that gives much more clean headroom. I designed my own solid state preamp for it to give it good tone shaping for guitar. It isn't that much more difficult to build a more substantial chip amp, again especially if you are going through the trouble of building a tube preamp.
Maybe take a look at Taylor's forum amp thread. There's lots of car audio 12V amp chips that can be built very simply.
car audio ckts should be the solution...Let the valve preamp section be the only "to blame" for the sound and just add the cleanest power amp after that...
> different versions of this chip
The '386 has a special problem: you use it when you just do not care.
The last place I noticed a '386 in a non-DIY project, it was the squawker in a dialup modem. That's not "quality audio".
And from comments and measurements I have seen, some '386 makers have got real sloppy. Letting the process tolerances run wide and wild, so power stage bias current vanishes and low-level (in this case, anything below max) linearity vanishes.
NJM/JRC has a rich tradition in good cheap audio. They are probably holding the tolerances better than the shops making RS232 and relay drivers in the same vats with their '386s.
Before this quality-slide: the '386 is very respectable for how simple it is. When well made, its faults are fairly inoffensive (both in audio output and in throwing stray garbage back into the radio it might be built into). But it is at heart a cheap chip.
And not real powerful. And raising the voltage only goes so far. It only handles so much current and heat. It's really optimum for 9V and 8 or 16 ohms.
If you want an accurate expression of whatever tube color you find, there are better chips.
> what about lm384?
Can you actually buy one today? Whoah! You can!
LM384, like '386, is a variant LM380 (grandfather to them all). It's still a cheap chip, not a precision audio amp. Just bigger than 386. It won't go near 5W out unless you solder a couple square inches of copper directly on the center pins (see datasheet).
TDA2002/TDA2003/TDA2006 family is the classic better small mono power amp. CanaKits has TDA2003 amp-kits at unbeatable price. (One blurb says TBA810.... that's wrong.)
http://www.canakit.com/5w-audio-amplifier-kit-ck153-uk153.html
http://www.canakit.com/10w-audio-amplifier-kit-ck003-uk003.html
LM1875 is a fine audio amp but needs near 18V to wake-up good. LM675 is nearly the same thing, but organized to run good from 12V. Either will do 20 Watts with 35V total supply, but closer to 1 Watt at 12V supply.
> What distortions is has under these conditions are the small distortions of any Class AB amp - crossover and very low THD. The datasheet says it will be under 0.2%.
I suspect the current crop may not meet datasheet. Although that would be easy, I hear too much badmouth about recent '386 builds to believe it's all just bad builds.
BUT: you MUST use the 10 ohms and 0.1uFd across the output!! (Check these values.) I see these omitted on a LOT of plans. '386 is barely stable without them, at idle, but when pushed it just goes nuts.
> nah it distorts badly
Of course ANY part-Watt amp is sure to distort if pushed. As R.G. says, a '386 is very easy to slam. And a slammed '386 hardly annoys the neighbors. In musical terms, it is like raking leaves with a table-fork. Some big acoustic guitars may play louder than a '386 on a small speaker. (Will be louder through your eight-10" full stack.)
is this amplifier use for headphone?
Quote from: Renegadrian on November 25, 2010, 10:03:22 AM
Made a small 386 ckt - N1 - it distorts yeah...gotta try a N4...
I used THIS LAYOUT HERE (http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=43996&g2_serialNumber=1)
edit
nah it distorts badly even with a N4 - no clean amp here...
hi adriano, just a note : i made this in a box for a friend to boost his acoustic that had a pickup installed ...it works fine for him..
he was getting low levels going into his laptop/soundcard, its fine for that..and very clean i found. with a n4 too..hmmm..... ???
Quote from: deadastronaut on November 26, 2010, 11:41:56 AM
he was getting low levels going into his laptop/soundcard, its fine for that..and very clean i found. with a n4 too..hmmm..... ???
That'll be the Zobel network ;-)
Seriously though - I'd much rather put the LM386 face up on a rotund female colleague's chair & use a TDA7052 in a circuit instead.....4x the power 'like for like' vs an LM386, no chunky output cap needed. If you really must use an LM386, be sure to wear massive flairs & sing "Everybody was Kung Fu fighting" as you solder up your circuit.....else you'll not get the right vibe coming out of it when you come to fire it up
hi gurner..not that bloody zobel again,.... :icon_mrgreen:
yeah ive got my flares on too lol... :icon_wink:
i remember you saying about another chip which was clean, i cant remember the number though...4025 or something?..
but it looked good from what i remember...
@adriano..yeah the 1 - 8 pins unconnected...whoops.. :icon_redface:
Why not simple amps like this?
http://www.redcircuits.com/Page80.htm
Look in older transistor books 60's, 70's for more amp circuits
I've built that Red circuits amp and it's very nice. Needs a big heatsink on the output transistors but it's a simple build.
Quote from: deadastronaut on November 26, 2010, 12:11:38 PM
@adriano..yeah the 1 - 8 pins unconnected...whoops.. :icon_redface:
Yes Robert, it's something that some like PRR didn't get - I wasn't talking about a verified ckt, I just built yours with 1 and 8 connected and it was terrible - it distorted badly because the ckt was wrong - but as suggested by the mighty RG they need to be apart - just a twist to break the line and it works flawlessly, as it should be according to the data sheet...
yep thats how i built mine with the cut, just forgot the cut under 1-8 on the layout...i will amend it on my layouts page..... :icon_wink:
Check out the TDA2822... [url+http://www.taydaelectronics.com/servlet/the-773/Amplifiers--dsh--Audio-DUAL/Detail]Tayda carries them[/url]
I found one of these in a cheap computer speaker setup that I tore apart for another project. They are stereo, like 1W per channel at 9V, and operate off of supplies similar to the 386. I've been digging on them. You can run a mono speaker, and with the right switching, you can plug in headphones and take advantage of stereo effects if you really wanted to go that far, or just have 2 separate amps on a single chip.
http://www.electro-dan.co.uk/electronics/TDA2822.html (http://www.electro-dan.co.uk/electronics/TDA2822.html)
http://www.electronica.ro/audio/TDA2822.shtml (http://www.electronica.ro/audio/TDA2822.shtml)
Actually, check out the LM3886. The LM3886 works down to +/-10V. Power that from a 24Vdc wall wart. It can run from a single supply, in which case the heat sink tab can be tied to a grounded chassis, as it is at V-. According to the datasheet, at +/- 10V, it will put out 10W into 4 ohms, 5W into 8 ohms. It'll be a bit more with a 24Vdc supply.
My 386 chips are a few years old and the NJM version.
So I can't comment on the quality being bad,actually I love these little chip amps.
But I can testify that with a 12V supply and an effecient 12" spkr my wife was having trouble listening to the T.V. at the other end of our house.
A couple of my friends swore it was my Valve Jr I was using and not that little chip on the breadboard.
(A) I really think for best results you need to leave pins 1 and 8 open like RG said.
(B) Also you need a 12V supply.
(C) You need an efficient guitar spkr, 12" is optimum.
I think alot of the bad build reports on 386's come from...
(A) Too much gain from not utilizing pins 1 and 8 properly.
(B) Slamming the input too hard or not hard enough/impedence mis matching.
(C) Using a little 1"-4" spkr that was salvaged from a toy or radio,ect with a really low spl rating like under 90 db. (I use spkrs rated 96 db or higher)
I also agree about the TDA 20** line being excellent,and easy to use.
Same for what RG said about the LM3886,they sound good and can be really loud.
Bryan, I used the layout Robert made (link on the previous page) - it is indeed quite clean (not hi fi for sure, but clean as it can be) - pins 1 and 8 MUST BE DISCONNECTED. I left therm connected and a horrible noise came out.
I use an old salvaged speaker (more or less 4") but it sounds quite good. Guess it would be even better an a serious cab/speaker.
I just bought some 2822, gotta try them out...
btw...IT'S FUN TO BUILD THOSE "AMPS"!!!
Quote from: PRR on November 26, 2010, 02:09:10 AM
BUT: you MUST use the 10 ohms and 0.1uFd across the output!! (Check these values.) I see these omitted on a LOT of plans. '386 is barely stable without them, at idle, but when pushed it just goes nuts.
I built a distortion pedal with a 386 based on the Smash Drive. Good tone, but notes die off with an irritating buzz or fizz at the end. I didn't use the 0.05uf and 10 ohm cap and resistor to ground from pin 5. Would those components have anything to do with how notes die off?
Maybe an even better question would be, "What is meant by
stability in the context of the 386?"
(Hope I'm not hijacking this thread.)
TDA2822M clean amp - louder than 386! Quite simple ckt but it SCREAMS!!! Used a 8" speaker (kind of you put on the ceiling) which is 8 ohm. YEAAAAAH
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=44174&g2_serialNumber=1)