You may have seen my recent thread about the MSCA (Modified "Silicon Chip" Amp). This kit amp is available online from Jaycar Electronics and Altronics, both of which should ship internationally. For a few South-Pacific Pesos (about 10 USD + shipping), this amp is a steal!
"MSCA" is named after the magazine which published the kit in May 2002. Their website allows you to download the PCB artwork for free if you are that way inclined. Dick Smith Electronics definitely ships overseas but now they seem only to have the circuit board available, not the full kit. You would need a copy of the article...
The kit includes instructions, the printed circuit board & components, an el-cheapo volume control pot (with knob), a 6.3mm headphone socket and RCA panel sockets. What you don't get is a power supply, +/-15 volts required. However, the amp is very similar to a cmoy, for which there are various power supply ideas available online. If you go for batteries, be advised that while the TL072 is a sweet-sounding JFET op-amp, it does like its volts and you may be advised to swap it out for an alternate amp chip.
The modifications I made are optional, as follows:-
1. The "Virtual" Zero-Ohm Output Impedance Mod - Replace the 68 ohm (evil) output resistor with a wire link, and replace the pair of 33 ohm emitter resistors with 100 ohm resistors to maintain the current-limiting protection for the output transistors.
2. Reduced Gain Mod - The original design provides a maximum gain of 15dB, but you need only 3dB above line level to drive HD580's LOUD (unless you're a mad headbanger suffering from tinnitus deprivation
). Replace the 330k-ohm & 4.7pF feedback components with 82k-ohm & 33pF. This gives you 50kHz bandwidth and a nice, accurate volume control which you'll operate between 12 o'clock and 5 o'clock instead of the normal 8 o'clock to 10 o'clock range.
Beware also that the "L" & "R" tags on the circuit board are back-to-front! (
sad but true ).
I built my MSCA into my digital parametric equalizer (
yep, I said the "E" word... bet you wish you hadn't opened this thread now! ), so I "borrowed" the +/-15V rails from there. Here's how it looks:-
"MSCA" is named after the magazine which published the kit in May 2002. Their website allows you to download the PCB artwork for free if you are that way inclined. Dick Smith Electronics definitely ships overseas but now they seem only to have the circuit board available, not the full kit. You would need a copy of the article...
The kit includes instructions, the printed circuit board & components, an el-cheapo volume control pot (with knob), a 6.3mm headphone socket and RCA panel sockets. What you don't get is a power supply, +/-15 volts required. However, the amp is very similar to a cmoy, for which there are various power supply ideas available online. If you go for batteries, be advised that while the TL072 is a sweet-sounding JFET op-amp, it does like its volts and you may be advised to swap it out for an alternate amp chip.
The modifications I made are optional, as follows:-
1. The "Virtual" Zero-Ohm Output Impedance Mod - Replace the 68 ohm (evil) output resistor with a wire link, and replace the pair of 33 ohm emitter resistors with 100 ohm resistors to maintain the current-limiting protection for the output transistors.
2. Reduced Gain Mod - The original design provides a maximum gain of 15dB, but you need only 3dB above line level to drive HD580's LOUD (unless you're a mad headbanger suffering from tinnitus deprivation
). Replace the 330k-ohm & 4.7pF feedback components with 82k-ohm & 33pF. This gives you 50kHz bandwidth and a nice, accurate volume control which you'll operate between 12 o'clock and 5 o'clock instead of the normal 8 o'clock to 10 o'clock range.Beware also that the "L" & "R" tags on the circuit board are back-to-front! (
sad but true ).I built my MSCA into my digital parametric equalizer (
yep, I said the "E" word... bet you wish you hadn't opened this thread now! ), so I "borrowed" the +/-15V rails from there. Here's how it looks:-
