High quality amplifier (with PICAXE)

N

nbw

Senior Member
Hi all, I've recently finished building a nice high quality amplifier based on National's LM3886T IC. It has some cool features like audio grade caps, solid copper bus bars between power caps, active tone control, a copper plated case, custom made and painted PCBs, etc so forth.

Anyway.......

it also features a picaxe that drives the 24x2 red LCD, that displays capacitor voltage, current averaging through the amplifier, and chip heatsink temperature (DS18B20). As a novelty, it has a DS1307 RTC that recorded the start point of the amplifier's life, and when you switch it on, it displays in years/months/days/hours/mins how long it's been since it was 'created'. It also displays Happy Birthday messages according to the date and family birthdates....

:)

The link is here:
www.howfm.com

There's a button to click on to view the gallery.

cheers
Barney
 
D

Dippy

Moderator
Looks nice Barney, well done.

Oh, I see you used Blue paint. I hear that light green paint reduces the THD significantly.

That brings back memories of the UK Hi-Fi obsession 20 years ago when some bloke in What Hi-Fi was extolling the virtues of gold-plated mains plugs to improve the amplifiers transient performance....
 
N

nbw

Senior Member
cheers Dippy

Oh man, now I'm going to have to pull the whole thing apart and paint from scratch. Actually, given that things painted red (e.g. cars) are KNOWN to be faster than those otherwise coloured... if I painted the TL074 op-amps red, their slew rate would improve even more.... oh, the possibilities!!

It took 400 - 500 hours to make the amp BTW, and most of that was in the hardware, case etc. The electronics was the easy part...........!!
 
K

KeithRB

Senior Member
nbw said:
it also features a picaxe that drives the 24x2 red LCD, that displays capacitor voltage, current averaging through the amplifier, and chip heatsink temperature (DS18B20). As a novelty, it has a DS1307 RTC that recorded the start point of the amplifier's life, and when you switch it on, it displays in years/months/days/hours/mins how long it's been since it was 'created'. It also displays Happy Birthday messages according to the date and family birthdates....

Barney
Click to expand...
You can add one of these:
http://www.sparkfun.com/commerce/product_info.php?products_id=10024

For an even cooler output display.
 
N

nbw

Senior Member
Ooooh, that would be nice. And for a slightly-retro look, could use low voltage pint-sized filament bulbs, you know - the little screw in jobs. Maybe five or six per band :)
 
W

wall_axe

Member
Current Sense

Nice looking project. I noticed you have a hole and a note for current sense input. Can you expand on that? Any sample code or schematics?
 
N

nbw

Senior Member
hi there, yes - current sense is a bit of a novelty more than anything. I wanted a feel for how much power was going through the amp, so - just before ground (for both speakers), I dropped the remaining voltage across a shunt of known resistance (about 0.165 ohms, from memory). A low-noise op-amp ups the signal by about 10 so the PICAXE can ADC-read it. Of course, the current is changing very fast each second, so even with lots of ADC reads, it's use is kind of limited. But, you could use it for a peak meter to show the highest current draw. I've attached the schematic:
 
You must log in or register to reply here.
Top