Below the speaker "box" is the space for the electronics assembly. Inserted from the rear, it consists of (a) the amplifier; (b) the preamplifier; (c) the master volume control; (d) the amplifier power supply (including transformer, fuse and on/off switch); (e) the notebook computer power supply; and (f) the USB hard disk drive (or maybe even two – there is plenty of room).

These are all mounted on a 2mm aluminimum plate measuring 435 x 350mm, with the longer edge bent up 90° at the 50mm mark.

A 125mm cutout is made in the middle which allows the heatsink to mount on the outer (vertical) surface and the amplifier PC board on its 10mm standoffs on the horizontal plate.

The tray for the electronics and the notebook cover plate start out the same size but require cutouts - and the tray needs a 90° bend to support the heatsink and house the power input socket, switch and master volume control. The cutout in the notebook cover plate depends on the specific notebook computer you use. Don't throw any scraps away - they're handy for brackets to hold the notebook power supply and USB hard disks, along with the mains area safety cover.

Refer to our photographs and diagrams to see the layout. In general, the "noisy" bits – the transformer and computer supply – are kept well away from the amplifier input.

The amplifier itself mounts with its heatsink on the outside of the bent-up section and is secured to it with two 3mm screws (we tapped the heatsink for convenience). Two screws from the underside mate with the 9mm tapped standoffs holding the amplifier firmly in place.

By the way, we’re assuming you have built the amplifier module and set it up as per the instructions (including setting the quiescent current with resistors), so we are not going to re-invent wheels here! Similarly, the ±40V and ±15V power supply: it’s pretty-much self-explanatory and we don’t envisage anyone having any problems putting this together. Fairly obviously, you need to have this completed to set the amplifier quiescent current!

The Ultimate Jukebox in block diagram form. The green blocks are pre-existing SILICON CHIP projects, with the obvious exception of the notebook computer and its peripherals and the commercial speaker crossover. Note that the PreCHAMP is slightly modified from the published design - this is fully explained in the text.

By the way, the -15V supply is not used. We know it’s a waste of a few cents worth of components but if you got them in a kit, you might as well put them in anyway. You never know – one of these days you might need a ±15V supply!

With only the mains transformer connected, confirm that you do indeed have +40V, 0V & -40V and +15V, 0V & -15V at the appropriate terminals. Better to find a power supply error now than have the power amplifier tell you in spectactular fashion!