Bottlehead Forum
Other Gear => Digital => Topic started by: John Swenson on September 15, 2013, 03:46:32 PM
-
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.
-
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
-
Don't care about dimming. But that's just me.
-
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.
-
I forgot to add: I would much prefer the segment display showing a number over the "dots" for each sample rate.
-
I'm still partial to the idea of using Nixie tubes for any display.
-
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!
-
How about instead of dimming it just the ability to switch it off. Otherwise I like Adam's filter idea...John
-
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.
-
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.
-
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? ;)
-
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
-
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.
-
My vote would be whatever is most expedient and convenient, as the sonic impact of these decisions is zilch.
-
My vote would be whatever is most expedient and convenient, as the sonic impact of these decisions is zilch.
Amen!
-
My vote would be whatever is most expedient and convenient, as the sonic impact of these decisions is zilch.
I couldn't agree more!
-
I fourth that! :)
-
I'd fifth it, but I quit drinking...
-
Dan,
You make me laugh! There are no "fifths" any more. That was a fifth of a gallon, a cheap way to sell a premium liquor against a quart of a cheaper one.
Some time I will look at the new metric "equivalents" and see how much we who still drink are being cheated.
You have to be as old as Dan, Paul J, and I to know what I'm talking about.
-
If a display were useful to me, I'd vote for the easiest and simplest as well, but really I'll opt for the non-display version. ;-)
-- Jim
-
For me the display is not something I would be looking at all the time, or would want to. I would just like to verify that a hi res download was working from time to time. If that was deciphering a pattern, Binary style or counting down a row of LED's, that would be fine.
Another vote for whatever is easiest...John
-
If a display were useful to me, I'd vote for the easiest and simplest as well, but really I'll opt for the non-display version. ;-)
-- Jim
It took me a second, then I looked at the poster. I laughed. True, you need a speaking interface.
-
My vote would be whatever is most expedient and convenient, as the sonic impact of these decisions is zilch.
Agree and therefore +1 to the suggestion of a standard brightness that's on the "dimmer" side (i.e. not too bright). Overly bright LEDs is one of the biggest aesthetic complaints I seem to read about.
I would definitely use the display as the reality check mentioned earlier to ensure correct output settings from the PC media player, but I wouldn't want it to be a stand-out feature of the unit - for me it's just a resource tool so as long as it looks complete and finished, I'm happy.
No doubt others will find crazy and wonderful ways to modify the stock display design in no time.
-
Ok, so we definitely won't use a 7w Cree projector lens led.
-
I can't say that I entirely agree. Sure, the sonic impact is zilch, but it is worth making the right decision upfront, rather than having every kit builder be forced to implement a work around as a result of making an expedient, but impractical, decision just to keep things moving. If you read equipment reviews, people tend to spend as much time on the practicalities of a device as they do on the sound quality. Maybe that reflects misplaced priorities, or maybe it reflects real life. Stuff that is irritating to use in practice winds up being an annoyance, even if the sound is great.
Personally, I like the idea of being able to switch the display on and off. That seems way more useful that a system that would force you to plug or unplug the display module. And it also seems much simpler than implementing a dimming mechanism.
As for the kind of display, I'm indifferent, as long as it is useful and easy to understand. If two rows of the red and green LEDs are the simplest way to do it, I can live with that, although I can't say that I love it.
I do like the idea of using different color LEDs for different sample rates. If you know what color you expect to appear, it would be obvious if a different color lights up as the sample rate changes. Just so I understand, what is it that makes this difficult? Are you saying that the problem is that (A) in order to get 8 different colors, you would have to use multi-color LEDs (because there aren't enough different kinds of single-color LEDs), which in turn requires a complex circuit in order to change their color, or are you saying that (B) because different color LEDs have different characteristics (e.g., in terms of the voltage drop), you would have to design the circuit to compensate for those differences, which would then be complicated?
Offhand, I seem to remember the following colors being fairly common among single-color LEDs:
1. Red
2. Orange / Amber
3. Yellow
4. Green
5. Blue
6. Purple / Violet
7. White
If you need 8, I would be fine with just doubling up on one color. You could either (i) double up on the two least-common sample rates, or (ii) double up on the first and last sample rates, with the assumption that people can figure out which one is lit based on position (something that is easier when comparing, say, position #1 vs. #8, than it is when comparing position #3 vs. #4).
Thanks for your work on this, John.
Best regards,
Adam
-
Once we come out with the Nixie display the other choices will likely die on the vine. Then the two choices will be "OOh pretty" in which case you plug in the nixie display, and "who needs a display? the thing automatically sets the sample rate for me" in which case you run without any display. That second version is working quite well for me at the moment.
-
But with the Nixies we can still say it's got tubes. That's important, even if those tubes aren't in the audio path. ;)