The Ultimate Integrate Part 6.

Most of the hardware mounted in the box, the only thing missing is a frontpanel. I usually order them from  Schaeffer AG (Front Panel Express in North America) they always do a stellar job and their free CAD program Front Panel Designer is a joy to work with and a great service. This time I was out of luck, Schaffer was out of the material I wanted for my frontpanel and it would not be back in stock for another six month maybe. This gave me the opportunity to tryout the frontpanel services offered by Modushop by Hi-Fi 2000. They do not offer a free CAD program like Front Panel Designer and I was a bit afraid that it would be cumbersome to communicate exactly what I wanted. But I was proven wrong. Swift communication via email with a very supportive staff made it really easy and quick.

I was initially planning for other dimensions but when I tried my initial layout onto the stock 4mm aluminium panel PESANTE 4U it actually looked better than my initial design. I also took the opportunity to buy a pair of round handles 4U to go with this frontpanel. It cost quite a lot of extra to machine on both sides at Schaeffer AG while this service is included in the price at Modushop by Hi-Fi 2000. It gave me the opportunity to mill a pocket for the VU-meters front glass from the backside of the frontpanel to prevent it from being too recessed. I would say that Modushop by Hi-Fi 2000 offers a bit more flexibility compared to Schaeffer AG so if you want to do something extra or super special, talk to them about it and it might come true. Prices are quite competitive too so I can wholeheartedly recommend Modushop by Hi-Fi 2000 for this kind of job.

Note that you can use Front Panel Designer to design your frontpanel and then export it as a dfx-file or you can simply send them your fpd-file straight out of Front Panel Designer. This is how my frontpanel came out.

The cavity machined on the back can be seen in this picture together witch switches headphone jack and the volume control potentiometer. Note than none of these cables will carry any audio signals (except the phono jack), it will mostly be GPIO to the DSP and to the input switchboard. 

I let Modushop drill a 6 mm hole through the panel and I then 3D-printed a kind of housing for the LDR that will control the PWM driving the LEDs on the frontpanel. I then polished a piece of 6 mm acrylic dowel rod to produte through the frontpanel and act as a light funnel. The LDR housing was then mounted to the backside of the frontpanel with double sided adhesive tape.

The parallel resistor prevents the resistance to go too high in a pitch black room.

I first test and I found only six LED producing too much of hot spotting for my liking. I also found the light and color of the VU-meter scale being a bit too warm agains the somewhat cold hue of the aluminium. So I decided to redo the light panel of the VU-meters once again and also make a new scale panel for it.

This time I did what I should have done in the first place. I used a prefabricated 12V high density LED strip.

I then covered the LED strip with a piece of acrylic made a bit flat with wet sanding paper. This to further prevent the LEDs from hot spotting (but it is hard when the acrylic is this close to the LEDs).

The VU-meters are mounted from behind in a fastening bracket that is mounted in the box by the bolts holding the round handles on the front. Small tabs is then added to the fastening brackets and secured with dove tail joints. All these pieces where 3D-printed and makes it easy to attach and detach the VU-meters from the box and frontplate. 

And this is what it looks like with the new light panel. 3000K instead of 2700K and a pure white scale instead of off-white. The light is now really even and the PWM feature works perfectly.

I am really happy with the look and feel of this integrated amp. Everything feels solid except for the source selection buttons. The still produce an annoying key bounce far too often so I might have to construct a new input switching board in the future (or add additional capacitance). Initial sound tests turned out really interesting. It is surprisingly easy to make the DSP sound bad and it needs a lot of tweaking to do exactly what I want it to do as a preamp. But that is for my next post...