Hi,
here is the schematic of a cool sounding 2Watt Amp! ;)
I built it, and its fantastic for practising at home!
Schematic:
http://rebel.massberg.org/source/schematic.pdf (http://rebel.massberg.org/source/schematic.pdf)
Layout:
http://rebel.massberg.org/source/layout.pdf (http://rebel.massberg.org/source/layout.pdf)
Interesting using a TL072 as a preamp chip for the LM386. Oddly enough I'm messing around with the LM386 as a preamp chip haha. Looks like a cool amp. Do you have any sound clips? Or pictures of the build?
The "Little Rebel" site http://rebel.massberg.org has some clips.
My own built little Rebel sound much better than the soundclips on rebel.massberg.org.
At the moment i dont have a microphon, so i cant record my amp.
(sorry for my english! ::))
I will post some pictures here later!
hey what happened to the pictures? :)
How does it sound clean?
Quote from: obelix on September 09, 2007, 10:16:56 AM
hey what happened to the pictures? :)
I'm not sure if I know what you mean, they seem to all be there.
Quote from: joecool85 on September 09, 2007, 04:00:43 PM
Quote from: obelix on September 09, 2007, 10:16:56 AM
hey what happened to the pictures? :)
I'm not sure if I know what you mean, they seem to all be there.
Where is there? I don't see any pictures either.
Quote from: LJ King on September 09, 2007, 08:15:19 PM
Where is there? I don't see any pictures either.
Aren't you guys refering to the pics on the website: http://rebel.massberg.org/ ?
All six of them load fine, click on them and they get bigger. The links for the layout and schematic also load fine.
If you were refering to pics within the thread here, I don't think there ever were any.
**edit**
I just realized you guys were refering to DrBoogey's post when he said he would post some pics of his build. He never did as far as I know.
Ok, so i want to build this amp but on the schematic it calls for a TL082 and on the layout it says TL072 so which one is, it what did you use? and does the LM386 have o be a LM386-N3 or can i use a LM386-N1?
The reason i ask is because i can get the Lm386-N1 and TL072 locally but i would have to order the other parts.
And YAY my first post.
TL082 and TL072 are both FET input dual opamps with identical pinout. It doesn't matter which one you use.
What comes to LM386 I really can't say for sure. How many different models of this IC they plan to make anyway..? The datasheet lists 5 different LM386 chips and then we have the copies from other manufacturers. :grr
Anyway, the datasheet indicates that both LM386-N1 and N3 would work with the same supply voltage range. The quoted output power of N1 is lower than of N3 but those have been quoted with Vsupply of 6V and 9V respectively so comparison is quite meaningless. Perhaps some one else can shed light into this. I suggest you use the N3 version.
hi, i'd like to build this amp but it seems that the original website has been taken down. does anyone by chance have the schematics and pcb image for this?
sorry for the dredge, but I'm starting to build this (btw, project file is attached.. if that is a problem, my apologies to the mods.. I"m new here :tu:).
what I don't know is the resistors need to be a certain wattage or not.
I started building it with 1/4W resistors, but the legs don't fit to the holes 'quite right' which got me wondering if I should have been using 1/2W ones (it looks like they would fit better).
the only resistor I can see which IDs a resistor wattage is the 10R from pin5 of the 2nd 386 chip.
also worth noting that the project file PCB needs reversing.. I found that after I etched mine ::)
It won't make much difference 1/4 or 1/2 Watt.
Just build with what you have.
Except of course the obvious 1Watt. :tu:
Re printing backwards,,, been there before myself. :-[
I recently etched an onboard pot backwards. :lmao: Makes you mad ay? :grr
Phil.
thought/hoped that was the case.. thanks :dbtu:
and yup.. everything else about the project seemed so "right" so I just assumed it'd be the right way round.. might do my own layout for it later on anyway and correct it there.
oh.. one more thing.. am I right in assuming that the 1W 10R is effectively just a sort of dummy load? I don't have (and neither does my local electronics store) a 10R 1W, but they had 8R2 1W.. so if it's a dummy load then that should do, right?..
also guessing I could stick an 8 ohm speaker in there?
It's not a dummy load but part of a "Zobel" stabilizing network.
8.2 ohms will be fine.
Also 1W isn't needed; 1/2 (and even 1/4W) will be fine.
And no, you can't use a speaker there, it needs to be pure resistive.
ha ha.. so result correct, but assumption wrong... thanks very much :tu:
alright.. so pretty much a copy and paste from FSB (am a member there too) but thought it may be useful here, and also someone here may be able to help too..
I built this using the original (reversed) file, so turned my ICs inside out ( >:( ) and got nothing, but the lm386 got warm
so I scored some more lm386 and started again with my own layout... built it and got nothing.. no sound at all..
I made the preamp and power amp modular.. easier to troubleshoot, and if I want I can swap the power amp out for something bigger maybe
the lm386 in the power amp are both getting pretty hot.. not melting yet, but I've not left it on very long cos I think they will if I leave it too long..
so, I disconnected the power amp and put the preamp into my ruby. I got a farty sound and only on full gain..
audio trace got it to the first opamp with good signal as far as pin6
as of pin 7 it was the awful farty sound.. kind of like a badly biased fet.. so I pulled out the LEDs and boom.. works awesome..
so a) do I need the LEDs in there (remembering I have zero theory knowledge so if they're vital, then .. um.. :blackeye )
and b) why would the LEDs cause an issue?
I noted that whilst they're both 3mm red LED, one is physically slightly larger than the other (maybe 0.5mm? but still nowhere near a 5mm LED).
thanks in advance
oh.. and layout and PCB are attached if anyone wants it, but bear in mind the power amp is as yet unverified and the preamp sounds like poop with the LEDs I had in there
Hello Rocklander,
Note on Leds,
They clamp the the AC swing (the sound you hear) so the amp will be louder and clearer without them.
Maybe this is confusing the outcome?
Hold up the LEDS to strong light and you can see the two ends inside.
Note the small bit is positive and the bigger bit is Negative.
These need to be mounted *opposite or reversed to each other* otherwise it will only clamp one side of the AC swing.
It's debatable as to whether such a small Amp even needs diode clippers or not as being so small in the wattage department it will be easy to get distortion without diodes at a low volume.
As to the heating of the Power stage you might have messed up the PCB,,, which is easy to do.
As a wise teck once said;
Turn the schematic up side down and start again LOL
This will (by design) force your brain to look at at it all from a different perspective and you may find you made a mistake.
Having done exactly that I've learned that it is indeed true. Winky.
Phil.
thanks Phil.. pretty sure I oriented the LEDs correctly as the both light up, and I also tested them with a 9V battery (and a 3K9 resistor) to get the polarity correct.
the power section seems pretty simple, but you're right in that I may well have goofed.. think I'll grab the datasheet and ensure I've got things within spec.
A quick glance at the poweramp section tells me you have Chip A and B reversed.
But I might be mistaken?
Whether that will mess up the result I don't know? Better minds will tell more I'm sure 8|
Phil.
hmm.. not sure, but should that matter? they're both the same chip.
and since the 47n and 10r are in series, does it matter which chip each goes to?
Both amps are "reversed" so they end up being out of phase.
Notice that the speaker does not have one end grounded but goes from output to output.
It ends up being a bridged amplifier.
The implementation is horrible, but happens to work on LM386 (I guess nowhere else)