Display type for BH DAC

[John Swenson]

For the BH DAC I've included the capability to have a display of the sample rate. This is via an edge connector on the top panel, a display board plugs into this connector. For those that don't want a display, don't plug one in. The display is designed to be completely static during music playing, the only time there will be any changes on the traces to the display board is when the sample rate changes. Thus there should be no sonic degradation from having a display.

There are two common ways to display sample rate, one is a separate LED for each rate, that would be 8 LEDs. The other would be three seven segment digits displaying the number.

Which would people prefer? It's theoretically possible to have more than one type available and just plug in a different board. Supporting more than one type takes more programming, and I have to design the main board to support it, but it certainly can be done. But if everybody wants one type, there is no reason to add the capability to have different types.

Now for the big one, dimming. Most displays implement dimming with pulse width modulation, this is simple and easy to implement, BUT it means there are clocks and changing signals constantly emitting RFI into your environment. I refuse to do this.

There IS a way to do dimming without PWM, but it takes an adjustable CCS for every LED on the display, thus 8 for the LED per rate, and 21 for the seven segment display. This can be done, but adds a lot of complexity and expense to the display board.

So the big question is: how many of you would be willing to spend an extra $150 or more for a display board with dimming?

And of course Doc needs to chime in on this to let us know how he would like to sell this, do you get to choose one board or the other with the purchase, or have them as separate boards that those who want a display can buy, or the purchase comes with one and you can buy others if you wish.

And of course I have to mention that long term I would like to develop a Nixie tube display, but that is probably way off in the future.

John S.

[galyons]

To me display & dimming really will depend on the form factor.  Is the DAC going to follow traditional BH design with a rectangular wooden frame base and an aluminum top plate? Where will the display be placed?  Firing up from the top plate or aimed in a "User-ly" direction?

Cheers,
Geary

[denti alligator]

Don't care about dimming. But that's just me.

[adamct]

John,

This is probably a dumb question, but I'm used to dimming LEDs with resistors. I doubt people will want to keep changing the dimming setting - they usually just find a setting they like, then leave it there forevermore. Would it be possible to just include a set of resistors in the stock kit, then tell people what values they could use to make it brighter or dimmer if they don't like the stock brightness level? Resistors are cheap and readily available. People can buy their own.

I'd make the stock resistors suitable for a fairly dim setting.

Also: I like the idea of the display pointing "up" off the faceplate. There if I want to check, but not staring me in the face all the time when I don't.

Another thought: there is more than one way to skin a cat. You could implement a plastic cover over the LED display. People could insert various grades of neutral density photography filters into the window to dim the light that gets passed through. These cost pennies when cut out of large sheets. I can provide additional information if you're interested.

[adamct]

I forgot to add: I would much prefer the segment display showing a number over the "dots" for each sample rate.

[johnsonad]

I'm still partial to the idea of using Nixie tubes for any display.

[keto]

Its cool to see the DAC project is advancing. I would be happy with either LED's or a numerical display. As adamct points out, if the display is aimed upwards, a dimmer wouldn't seem very necessary. Thanks!

[2wo]

How about instead of dimming it just the ability to switch it off. Otherwise I like Adam's filter idea...John

[kgoss]

I would like to have a sample rate display just to have a sanity check for the up sampling JRiver is doing but I would prefer a switch to turn the display off rather than dim it.  It's just not something I would check very often, plus I suspect it will be on the top plate so won't be visible from the listening chair anyway.  I'm sure this DAC will be awesome no matter how these details get worked out.

[odamone]

I'd like whatever is most readable. Single dots of the same color that vary by position are hard to read. Number of dots indicating sample rate would be more readable and look cool. Different colors for different sample rates could work too, especially if they went from cooler to warmer as the rate increased, or some other logical progression. Bit depth would also need to be indicated. I'm fine with numerical display, but I think there are cooler designs possible with led lights.

One idea is to place the LEDs behind the wood frame and then drill holes for the light to pass. The holes would dim the light and create a cool housing or panel.

+1 to the idea that the default brightness be dim.
+1 to the idea that the indicator be switchable rather than dimable

I don't like the idea of an up firing indicator. This limits placement of the DAC to low open shelves.

[Doc B.]

As one would expect we will see a range of taste here. Remember that this is a kit, there will be the option to incorporate the kind of ideas being offered here into exactly what floats your own boat when you build it. I always look at this kind of cosmetic thing as one of our kits most important attributes - the ability to personalize them.

Now would someone please hurry up and design the Nixie tube tach and speedo for my bike? 

[2wo]

I was working on that. The problem I was having, was that rather then display speed as MPH, I was getting furlongs per fortnight...John 

[John Swenson]

As a clarification the display board plugs into an edge connector on the top plate. Thus it rises vertically from the top plate, thus the display of whatever type will be pointing horizontally out at the  listener.

I'm  not good at making 3D drawing of this sort of thing, if any of you have 3D rendering software and want to try a sample feel free, I can comment on it if its looking not quite right.

If I do a one LED per sample rate, they will probably be the same color, getting eight different colors can only really happen with  tri-color LEDs,  which require a constant current source  for  the different LEDs to get the right colors, not a simple circuit. (I HAVE done  it before,  and belive me, it  is not a simple circuit!)

Compared to the above 3 seven segment displays is a piece of cake!

There are two ways to turn the display off:
1) pull the board out of the socket, presto it is off.
2) we put a switch on the back or front to urn it off

All along I have just been thinking of #1, those that want to see a display plug the board in and those that don't want to see the display, don't plug in the board. I hadn't thought of the usage where it is frequently being changed from off to on. I suppose there could be some holes on the board, those that want the  switch solder in the switch and those that don't, leave it out and it is always on.

Hmm, thinking about how to do a "LED per rate" display that is  easy to read, how about two horizontal rows  of LEDs, one is green the other is red. For a specific sample rate, a single green  LED is lit  and all the other red LEDs are lit, that way it is easy to see where  in the sequence it is. That is something that is easy to implement.

The LEDs I'm thinking of using for these mount on the back and have a little "stalk" that goes down through a hole in the board. The "non-component" side of  the board then faces the user and what you see is the top "dome" of these stalks flush with the surface of  the board. It looks very nice.  All the components are surface mount on the "back" so all you see on the front of the board are these little domes.

John S.

[Paul Birkeland]

My vote would be whatever is most expedient and convenient, as the sonic impact of these decisions is zilch.

[pdxgrampa]

My vote would be whatever is most expedient and convenient, as the sonic impact of these decisions is zilch.

Amen!