First Helios Channel Module

Using Frank's front panels, I finally got all the parts together to start building one of the channel modules with Helios 69 type passive EQ. I need to shorten the shafts on some of the pots so the knobs seat properly (why do pot manufacturers have so many different shaft lengths???) and the knob colour scheme is not finalised but still the module looks pretty good. Next job is to wire all the pots and switches.

First Real Channel Panels

The first panels arrived the other day from Frank Roller. The finish is absolutely first class. The white in-fill on the blue anodised background looks very professional and they only cost about 50 Euros each. Well done Frank!

The change in colour from top to bottom is caused by the camera flash. The colour at the top is closest to its real appearance.

Professional Looking Panels

Having decided not to make my own front panels for this mixer after stabbing myself with a needle file, I need to find a route to fabricating front panels of a professional appearance.The obvious route is to use the excellent Font Panel Express program provided by Schaeffer and have them make the panels.

Unfortunately there are two stumbling blocks to overcome. The first is that I have zero artistic skills  This means that, although I can draw a perfectly functional front panel layout it will at best  not offend the eye. I can tell a good, eye pleasing layout when I see one but there is no way I can create one. Fortunately, in the last few days Braeden, a fellow member of groupdiy.com, has begun to publish his versions of the layouts of my Helios and Pultec channels as well as ones for other other popular DIY audio projects and it is clear his artistic skills are streets ahead of mine Here is a composite picture of Braeden's Helios 69 channel layout (left) side by side with mine (right).

Check out Braeden's other designs.

The second stumbling block is that although panels made by Schaeffer look really good, they are rather expensive and the company does not provide any feedback on your proposed layout. Once again, someone on groupdiy.com knows of an alternative supplier and in this case it is NRG in Germany. NRG is run by Frank Röllen who can accept panel layouts drawn in Front Panel Express but will make them for 30% less than Schaeffer. His range of materials covers various colours of anodised aluminium as well as some plastic materials but the best part about using Frank is that when you send him a panel design he emails you back  to check you have thought of everything from a mechanical engineering point or view. Things like clearances for pots and switches and adding radii to slots. When you are both happy he makes the panels. I was so impressed by Frank's approach I have already ordered a pair of Braeden's Helios 69 front panels and, as soon as Braeden has finished it, I plan to order a pair of EQP1A versions too.

OUCH!!!

That's it, no more hand crafted mechanics for me. I was filing out the push buttons slot for the third of the four channels when my hand slipped  and I managed to stab my thumb nail right through with a needle file!!!! Boy, does that hurt!!!! I know it went right through because the top of the nail is bleeding.

So, from now on I am going to bite the bullet, open my wallet and get my front panels from Front Panel Express. It also gives me an excuse to try the sleek looking layouts produced by Braeden.

Time for tea.

Sub-Rack Build

The sub-rack arrived today from SRS so I have spent the evening assembling it.  SRS sent the basic rack already assembled which saved me a lot of work.

As this is a four channel mixer, I needed to divide the rack into one space of 4 channels each 6U high and another space two channels wide but divided into two 3U high spaces. In the top space will go the bus amplifiers and in the bottom space will go the monitor section of the mixer. Here is the SRS divider kit:

And fitted to the basic rack.

 You can clearly see the divider towards the right and the two 3U high spaces it provides.  Next I added the EZ Tube Mixer backplane PCB:

Notice haw both 6U and 3U modules can plug into the one backplane. You could also have active modules in the lower 3U space if desired. Rather than have another backplane PCB spanning the whole width of the mixer just for two modules, SRS do a converter kit that allows you to fit a pair of regular 32 way connectors direct to the rails. One of these modules could be a headphones amplifier made from a standard EZTubeMixer Eurochannel V3 card where the output stage current has been increased. The other could perhaps be an opto conpressor. For now it is just going to be a simple monitor section.

SRS also provided top and bottom screens but I will not fit them until I have finished wiring the monitor section as access will be easier. I then placed a prototype module and some drilled panels to get a feel for the completed unit:

And lastly tried the rack in the mixer enclosure:

Note the 2U space below the sub-rack. I will fit a standard 2U panel in here and fit later the rotary faders to it.

Drilling Front Panels

After centre punching, the panels are drilled. A pillar drill is essential for this; it is well worth the investment. It is also well worth investing in a good set of drill bits. The slot for the push buttons (top left) is drilled as a rough series of holes and then filed by hand.

Making Front Panels

I have now finalised the position of all the controls on both the Pultec and Helios type channels. The next step is to drill all the holes in the blank panels. To do this I print off copies of the front panels from Front Panel Designer with the 'Print Reference Points' option selected. This prints the panel with the centres of all the holes marked by a small red cross. I then carefully cut out the prints of the panels and glue them to the blank aluminium panels using diluted PVA. When that has been done I centre punch every hole ready for drilling. It does not matter if the paper legend gets damaged during drilling as it will be removed after drilling and replaced with a vinyl one. The picture below shows the four channel panels with their stuck on paper legends after centre punching.