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Loud Community designed 9v battery powered amplifier.

Started by No6h, June 18, 2015, 02:46:19 AM

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J M Fahey

That TL084 based preamp and EQ will work  better with +12V or higher (up to +36V), in fact it's a miracle it works at all with just meager +6V .
And you can chop the LM386 off and use a TDA2003 there (LM383 disappeared from shop shelves many years ago) .
In fact, even TDA2003 is somewhat hard to find,but don't worry, any car radio amp will work very well, and all datasheets suggest a practical example.

No6h


J M Fahey

#32
Of course.

Or, to be more precise, it will put out the real power stated in the datasheet; claimed power at reduced voltage is ... ummmm..... "optimistic"  :loco
TDA2003 datasheet:
http://www.st.com/web/en/resource/technical/document/datasheet/CD00000123.pdf
QuoteDC CHARACTERISTICS
Vs Supply voltage 8 to 18 V
AC CHARACTERISTICS ( Gv = 40 dB = 100X)
Po Output power d = 10%    f = 1 kHz
RL = 4r       6W   
RL = 3.2r    7.5W
RL =  2r     10W
RL = 1.6r    12W
it can work with 8 to 18V supplies, above rated power is with a freshly charged "12V" battery .
I'd suggest you first build it with a "12V" supply , made with a standard, cheap, easy to find 12VAC 1A transformer, a bridge rectifier and a  4700uF x 16 (25) V capacitor, which will actually give you raw +16V DC , well within specs and give you even higher power.

Later you can add a 12.6V gel cell battery for portability, and you can charge it with the supply you already have, so you are not wasting $$$ at all.

At home you use the amp plugged in the wall, and at the same time you charge your battery; on the street you run from the battery alone, best of both worlds.

And as you see this versatile amp can drive any speaker from 8 to 1.6 ohms  <3)

I made "mini Twins" with 2 x 4" car type speakers, 3.2 or 4 ohms each, in parallel.

FWIW **now** I'm designing a power amp and supply PCB for a 30W amp based on its bigger brother, the TDA2050 chipamp , hope I finish it now , it's late and cold, almost midnight, and tomorrow will burn the silkscreen and print a couple dozen.

So, believe it or not, I'm also thinking chipamps today  :dbtu:

No6h

What would the most sensible way to build this (ie vero or perf) because I don't want to go into PCB production and also how would you implement prototyping on a breadboard. Just so you know I will be purchasing from taydaelectronics.com.  :)  Also what value potentiometers should I use? Its not marked on the schematic. In terms of the transformer, do you mean 230vAC in and 16v DC out? What about a 16v DC wallwart, the only thing is that they are ridiculously expensive in New Zealand.


J M Fahey

Vero is fine, and there are Vero layouts on the Net, I think I have one in my other PC.

Perfboard is also fine, if a little less tidy ... but for your own use, who cares ?  ;)

phatt

Quote from: No6h on July 16, 2015, 10:17:41 PM
  In terms of the transformer, do you mean 230vAC in and 16v DC out? What about a 16v DC wallwart, the only thing is that they are ridiculously expensive in New Zealand.

Yes.

As to wall wart/plug paks,, consider hitting the junk shops, Salvation Army stores and like places.
Don't forget a lot of surplus laptop computer chargers are often good for 2~4 Amps at 12~20 VDC.
Though some can be noise prone.
If money is tight then you have to think outside the norms.

Years back I used two psu's from junked printers giving split supply rails 30-0-30 VDC at around 2 Amps, breadboarded many circuits from that setup and cost me nothing. :dbtu:
Phil.

No6h

I cant find any...  >:( I definitely do not want to mess with AC mains voltage. Ill have to try my luck with a breadboard first, then maybe a perma-proto board? I dont know.

J M Fahey

Fully agree with playing it safe  :dbtu: , but by using a ready made wall wart (instead of the homemade supply I suggested), *they*  deal with that, you just use the other cable,which has anything from 12V to 18V .

I guess you must have cheapie "dollar stores" carrying all kinds of Chinese junk, there you'll find:

labelled as a "multi voltage supply" they have switch selectable voltage ... always higher than claimed (check it yourself) , nominal 12V is usually 14 or 15V DC, in this case not bad.

Or as Phatt suggests, you may find junked supplies for peanuts.

No6h

How would you go about moving the design onto a breadboard? Also would it be safe to round the two 11k resistors to 10k?

J M Fahey

#39
Quote from: No6h on July 18, 2015, 01:27:29 AM
How would you go about moving the design onto a breadboard? Also would it be safe to round the two 11k resistors to 10k?
Which 11k resistors?
Please post the schematic or tell me which one it is.
But in general 10% variation in parts value is no problem, except in a few very specific cases (such as biasing).

As in "going from schematic to breadboard" .... well, that's what you are learning ;)

Get a couple sheets of paper, a pencil, a good eraser (you'll need it ;) ) , draw parts wherever you find they fit, and start penciling connections.

Unless you are very very lucky, you'll see that some positions are awkward, you'll need to move them, or rotate them, so connections are shorter, cleaner.

Repeat as needed, paper is cheap and time is not wasted.

Eventually you'll get to something you like, then build it on perfboard.

The idea is to try to pass leads through holes and bend them so they can be soldered together, minimizing use of actual wire .


Some examples:




the evolution of perfboard is veroboard/stripboard, which already has strips of copper alreadyb etched and you break them with the tip of a drill, and use wire jumpers, very neat and almost PCB class:


I suggest you visit the pedal sites and build a couple projects on perfboard or stripboard, their design, just to  practice ... and enjoy the pedals of course ;)
https://www.google.com.ar/search?q=perfboard+layout&hl=en&biw=939&bih=465&site=webhp&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMI2del5dHkxgIViH-QCh0SdAH3#hl=en&tbm=isch&q=perfboard+pedal+layouts

Not only pedals, you might make a nerdy girl happy with a blinking heart, for example:




No6h

How much of an increase in wattage will the TDA2003 make by replacing the 386?

J M Fahey

#41
Just read the datasheets  ;)

Just as an advance, the LM386 is called a "1 W amplifier" but usually has less when powered from a 9V battery, there's simply so much juice they can put out ... and it's not that much.
Many microamps use basically that:

Read all about microamps here:
http://www.premierguitar.com/articles/measuring_up_micro_amps?page=1

Now the TDA2003/LM383 is a real powerhouse, typically real 6-8W with any random speaker and up to very loud real 12W RMS if you can get 2 x 3.2 ohms speakers (think old car radio 6"x9" from the local junkyard) and feed it the proper power source.

Now if you feed a TDA2003 from a 9V battery, you won't even get a Watt.
Why?

As Enzo always says: "the actual power source is the power supply, the amp just audio modulates how much gets to the speaker" .... or something like that.

Sometimes he shortens that (which is asked often) to "the amp is the thingie between the supply and the speaker" ..... same thing.

In fact, if I were you ... I'd build both.
I'd start with a fun filled LM386 amp, which together with a 2" (or smaller) speaker can be mounted anywhere,even in an (empty) beer can (the BIG problem is where to get an empty beer can ;) ), enjoy it, and then attack the TDA2003 amp.


https://www.youtube.com/watch?v=EKOYc971tiY


No6h

currently working on a cricket, should be done in a week or so

J M Fahey

Quote from: No6h on July 21, 2015, 03:20:52 AM
currently working on a cricket, should be done in a week or so

Cool  :dbtu:
Keep us updated .

No6h

I'm interested in housing it in a Vox AC4TV style cabinet. ATM i'm trying to draw up some plans but no luck. Do any of you have experience in building cabs or any plans? I couldn't find any online.