the chassis which holds the DSP must do these obvious, practical things:

it must be dead silent.
it must keep itself cool.
it must accept 24V DC power.
it must have six amplifier outputs.
it must accept digital & analog audio inputs.
it must have controls for volume, input mixing and other programmable features.

it must also do these less-obvious practical things:

it must not waste.
it must explain itself.
it must want to be used.

so let's analyze these needs in that order.

it must be dead silent.

it must keep itself cool.

silent things don't use cooling fans. but amplifiers without cooling fans tend to heat up. we are using Class-D amplifiers of course, but the risk is still real.

the amplifier board i have picked was built to use a fan, but i am not pushing it anywhere near its rated limits. if i remove the fan, i will be relying on convection to cool the amplifier. the chassis must hold the amplifier upright to maximize convective air flow.

it must accept 24V DC power.

it must have six amplifier outputs.

it must have accept digital & analog audio inputs.

it must have controls for volume, input mixing and other programmable features.

consider the layout of the amplifier & DSP.

inputs & controls are below and outputs are above. the DC power jack is to the left. — inputs & controls are below and outputs are above. the DC power jack is to the left.

the amplifier's heat sink must be upright for good cooling, with extensive venting for airflow. hence the DC power jack will be either above or below the chassis. it should clearly be below, or we'd have a power jack sticking out the top of the chassis. the horror!

so here we are:

it must not waste.

it has no more internal volume than it needs. that means less surface area, which means less plastic.

acrylic and brass are already beautiful. we will not use glue or paint.

it must explain itself.

the volume control and mix control knobs both control loudness - they can be the same color.

the multipurpose adjust 1 and adjust 2 knobs will be a different color.

the mix control knob is between the digital & analog inputs. turning it up (towards the digital input) or down (towards the analog input) has the expected effect.

the front panel contains LEDs which indicate power, SPDIF status and analog signal clipping.

it must want to be used.

the chassis is quite small. it will probably sit on a low table or the floor, between two speakers. it will probably be below the user.

to use the inputs & controls, the user will have to look down at it. it is only polite that it look back up.

the chassis is built as a box with angled feet, so that it looks up by 10 degrees.

various lines on the front-plate are positioned to harmonize and emphasize this angle.

Conclusion

after all that, what do i end up with? this:

you can see the venting holes above and below - the lat LAB logo is also a vent.

so let's install it!

DSP 01 in new chassis, with rainbow programming cable

next update: i actually do something with it.

Tshen2 2015

analog signal processor, front panel, circa 2013

the single biggest difference between 'hacky' and 'solid' audio gear is the box it comes in.

this isn't just vanity. well-constructed equipment lasts, which justifies its cost in cash and time. you won't worry when you move it. you won't worry when you touch it. the interconnects won't wiggle out of place, the volume control won't crackle or free-spin. the bloody thing won't catch fire.

if it's performing for you, or you're performing with it, it won't give up, turncoat and die.

it is a real pity that most hackers half-ass their boxes. above is my own attempt, in 2013, to turn a cigar box into an electronics chassis. there's no symphony to the position of anything. it's hacked together in all senses of the word.

the inside is worse.

analog signal processor, inside view, circa 2013

are the circuit boards anchored by the tension of the wires? yes.

are the jacks Loctite-ed with hot glue? yes.

is the volume pot protoboarded and bolted to scrap plastic? yes.

is every input and output tight-roped on unshielded wires? yes.

this isn't even all. there were two stereo amplifiers and three separate power supplies, all with their own hacked-up boxes, and cables strung in between.

it even took ages to hand-cobble this disaster. i'd completely overlooked mechanicals during the design phase. here was the result. never again.

DSP 01 would be a singular, hyper-integrated thing. i would nestle the user interface, DSP core and quad-channel amplifier board into a single box. one 24V power supply would power the amplifiers as well as the DSP, through a 5V buck regulator.

the UI board plugs directly into the main DSP board, giving it RCA inputs, RCA/3.5mm outputs, two adjustment pots and indicator lights. i added a tiny knob to dim the power light. i lasercut holes in the front panel with my mechanical Eagle CAD technique, to exactly fit the pots and RCA jacks. the amplifier's heat sink would orient vertically to maximize passive cooling.