Edwin, the current through the series LDRs never gets to 5ma, let alone 10ma, and only increases when you are at the very maximum end of the volume spread where no one will typically be operating the control. If you do the math you will find that a fairly high series resistance of around 90 ohms will attenuate way less than .1 dB so this is not an issue.
The two milliamp readings are for the two shunt LDRs. At many points you will find the two values are not the same, this is because the computer chip is driving the resistance to the same value on each side but the LDRs are different and therefore draw different amounts of current which is reflected in the readout.
I take your point about preferring the non-moving volume value. You do understand that it starts wandering only after two minutes of no control input? I want the display to last forever with no sign of burn-in and leaving the volume value in one position 24/7 might, over a long time, cause some change to those digits. Thus, the value is always visible but wanders around the screen after two minutes. As soon as you touch a control -- either at the panel or on the IR -- the screen returns to normal display and stays that way for two minutes after the control is last adjusted. That doesn't sound like very long but it's totally adequate so when you're using the control it won't blank out while you are in the middle of doing anything.
It's the best compromise I could come up with on a two-line OLED display.
The two milliamp readings are for the two shunt LDRs. At many points you will find the two values are not the same, this is because the computer chip is driving the resistance to the same value on each side but the LDRs are different and therefore draw different amounts of current which is reflected in the readout.
I take your point about preferring the non-moving volume value. You do understand that it starts wandering only after two minutes of no control input? I want the display to last forever with no sign of burn-in and leaving the volume value in one position 24/7 might, over a long time, cause some change to those digits. Thus, the value is always visible but wanders around the screen after two minutes. As soon as you touch a control -- either at the panel or on the IR -- the screen returns to normal display and stays that way for two minutes after the control is last adjusted. That doesn't sound like very long but it's totally adequate so when you're using the control it won't blank out while you are in the middle of doing anything.
It's the best compromise I could come up with on a two-line OLED display.
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Jeez, gonna need an Encyclopedia to run this thing!!
Seriously tho, it's good to see the display has worked out so well and is now pretty complete. I do find the 'slow blinking front led' for mute (zero volume), and when adjusting either the vol/balance to be a quite handy indicator - can you still retain this feature?
Neat idea about the 'wandering display' - rather novel and quite practical - could perhaps use a slow blinking numbers &/or 'dimmed' numbers (or a display shutdown) for steady state operation?
Love the balance sideways movement as you have to look closely at the Pass X2.5 display (for example) to see the difference in the numbers - a 'lop-sided' display shows up straight away - it's surprising how often I use the balance on this unit now that it's so easy, as it's quite common for some cds to have poor/bad balance - pity it can't be fitted into the remote control.
Have a HD cd that's way off (Horace Silver's Songs for my Father) over 5Mbits/sec and quite badly balanced indeed! Maybe they were so busy counting bits that they just forgot to check for correct balance, or something! Unbelievable!
I once built a 'bargraph' volume/balance display (lines of leds, 'peak vol & hold' type of thing) - quite distracting after awhile - quite useful in the studio/desk.
'Blowing in the wind' again - nothing useful to say apart from a 'Good Morning' guys!
Seriously tho, it's good to see the display has worked out so well and is now pretty complete. I do find the 'slow blinking front led' for mute (zero volume), and when adjusting either the vol/balance to be a quite handy indicator - can you still retain this feature?
Neat idea about the 'wandering display' - rather novel and quite practical - could perhaps use a slow blinking numbers &/or 'dimmed' numbers (or a display shutdown) for steady state operation?
Love the balance sideways movement as you have to look closely at the Pass X2.5 display (for example) to see the difference in the numbers - a 'lop-sided' display shows up straight away - it's surprising how often I use the balance on this unit now that it's so easy, as it's quite common for some cds to have poor/bad balance - pity it can't be fitted into the remote control.
Have a HD cd that's way off (Horace Silver's Songs for my Father) over 5Mbits/sec and quite badly balanced indeed! Maybe they were so busy counting bits that they just forgot to check for correct balance, or something! Unbelievable!
I once built a 'bargraph' volume/balance display (lines of leds, 'peak vol & hold' type of thing) - quite distracting after awhile - quite useful in the studio/desk.
'Blowing in the wind' again - nothing useful to say apart from a 'Good Morning' guys!
James, part of the reason for the software balancing was to allow the LED to continue to work so that it would not be strictly necessary to have the display even when using the rotary encoder front end.
However, if you do have the display then you really don't need the LED -- the display flashes in mute just as the LED does, and the numbers on the screen indicate any Balance setting.
Likewise, calibration status is better on the display although also present on the LED. The only thing lost with the display without the LED is the 'slewing to setting' stutter indication on the LED and that is not strictly necessary.
Regarding dimming the OLED, that is a feature that is not available in the hardware so that's that.
Blinking the Volume value without moving it is certainly possible but if it's going to blink, why not move it too so that a variety of pixel locations are involved and each pixel is "on" for a much smaller percentage of the time?
Some compromises were necessary.
This looks really nice.
I like the idea of the volume value randomly moving on the screen vs. just blinking the value, which to me could be a real distraction.
I do have some questions:
1) Can you add some photos of what else is involved in making this setup work? I'm wondering if this is something most people could assemble or if it's quite complicated?
2) Will this need some type of buffer in front of it?
3) Is the whole LED/LDR thing supposed to sound more transparent than volume chips like the Muses 72320?
4) Any idea as to pricing?
Thanks...
I like the idea of the volume value randomly moving on the screen vs. just blinking the value, which to me could be a real distraction.
I do have some questions:
1) Can you add some photos of what else is involved in making this setup work? I'm wondering if this is something most people could assemble or if it's quite complicated?
2) Will this need some type of buffer in front of it?
3) Is the whole LED/LDR thing supposed to sound more transparent than volume chips like the Muses 72320?
4) Any idea as to pricing?
Thanks...
fair enough. Sounds like a good engineering decision.
For my personnel use I would prefer the shut off of the screen to wandering lights, but I suppose you have multiple other uses for the system in mind where your approach might be more valuable.
As a side note I just wonder if this does not create a regular stream of digital pulses, that theoretically could influence the audio circuit. This should not be the case when the display is completely dimmed (or if the current to is is diminished to spare these OLEDS, if at all possible). In that case there should no signal be send to the display while continuous listening.
I'm sure you have already given all these different alternatives a tought and decided for a reason.
Keep up the good work,
Edwin
Making the basic LDR board work is dead easy, everything connects to screw terminal strips which are clearly marked. You need:
1. DC in -- 9~16V, regulated preferred but not essential.
2. Two conventional 10K linear Pots for Volume and Balance
3. One LED with various steady and blink rates to indicate power, calibrating, balance center, slewing to new volume, slewing complete.
4. Three audio I/O connections for each channel -- In, Out, Gnd. (Audio Gnd is floating, not connected to power ground or chassis)
That's the totality.
The entire functional LDR control circuit including very quiet power supply is on a 2.5" x 3.5" circuit card and if you don't need a display or IR remote, this is all you need. If you want a display or remote control (with either rotary encoder or motorized pot) you'll need a front end board. This front end can be one of my design or any other board that can provide a clean 0-5Vdc control voltage.
The front end board includes connections for rotary encoder or motor pots, OLED display, DC in, IR receiver, data out (to LDR board).
The need for a buffer is your choice based on personal preference and the topology of the rest of your system. It's up to you. I don't use one in my system and I love the sound. James doesn't seem to have one in his system and he seems to love the sound. It seems like everyone who has heard an LDR control loves the sound, the only piece I'm contributing is precision control from a simple and small footprint control circuit.
Regarding pricing, I'm tempted to say what I think it will be, but I don't have any hard facts yet so I'll demur.
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Just thought I'd mention that I'm running the system 24/7 (but shutting down the amp o/night) and the vol control has been turned to 'mute' (total silence) for about 8 hours each night for last 4 days without any 'glitches' or problems - led just blinks away quietly - confirms this is okay, too - another 3 days of higher bit rate signals to go yet for 'breaking-in' the new usb digital cable (a bit sceptical about some of this 'better' usb cable hype, but I'm now 'a convert', even if it's my own diy version!)
Thank you for the detailed reply, Wapo.
It doesn't sound as complex as I initially thought.
Can the linear pots be cheapos like Alpha, or do they need to be real good quality?
So in the remote version, is the remote only controlling a motorized pot which in turns alters the volume level through the LED/LDR system?
I think I'll pass on the buffer as well. That's just something else to "alter" the sound.
I have never heard an LDR system. That's why I'm looking forward to your system if it isn't way outside of my budget.
@James, do you leave it on 24/7 for testing purposes or should a system like this be left on all the time?
It doesn't sound as complex as I initially thought.
Can the linear pots be cheapos like Alpha, or do they need to be real good quality?
So in the remote version, is the remote only controlling a motorized pot which in turns alters the volume level through the LED/LDR system?
I think I'll pass on the buffer as well. That's just something else to "alter" the sound.
I have never heard an LDR system. That's why I'm looking forward to your system if it isn't way outside of my budget.
@James, do you leave it on 24/7 for testing purposes or should a system like this be left on all the time?
The "Mute" setting draws only 2.5 mA on each shunt LDR, so I think you could leave it on Mute forever and not bother anything.
I have had a board configured as a 100K pot and it worked fine in my system although I far preferred the sound of the 10K version driving my 20K amplifier load.
Due to the extremely small current draw at that resistance, 100K is probably the absolute limit for controlling the LDRs with any reasonable precision. Fortunately, when using a pot to control volume it is always the lower value resistance side of the wiper that has the greatest control over sound level. Thus, even if you have a 100K pot the smaller R side will always be less than 50K and that is still within the range of "good" control.
With my design it appears that the pot range can be user-modified to work at any pot value between about 5K and 100K as long as there is a calibration performed after the value selection. Also, for the adventurous, R1 and R2 can be calibrated with two separate ranges. This might be useful if you want to play with keeping input impedance high while keeping output impedance low.
I turn the amp (845 valve amp) and computer off overnight, but the dac and the volume control stays on 24/7 (it's not really necessary, but ...) - the new Xover will be 24/7 too, but the valve gain stage will be turned to 'stand-by' like the amps - the 'rest' are 'off' when not in use too.
I use a test-bed rig for 'breaking-in' interconnects, caps, resistors, etc that is 'on' continuously - not very power hungry, thank goodness.
I used a couple of exotic pots just because they were handy (and I'm a bit 'full-of-it', too!)
- there's plenty of reasonable quality (and price) single 10kR linear pots around
'Buffers' can be extremely useful if your system has a problem with impedance matching - some high quality amps have a troublesome low input impedance and a simple buffers in 'just the answer'
There's a couple of 'buffer projects' here on diy that are good kits and fairly straight forward - the DCB1 is an ongoing project and very well known (various versions) and nearly totally transparent - the 'Kuartlotron' has a pcb evolving now and is also quite straight forward with less complicated power supply requirements
As Nelson Pass (and others) are known to say "keep it simple, but not too simple'
I use a test-bed rig for 'breaking-in' interconnects, caps, resistors, etc that is 'on' continuously - not very power hungry, thank goodness.
I used a couple of exotic pots just because they were handy (and I'm a bit 'full-of-it', too!)
- there's plenty of reasonable quality (and price) single 10kR linear pots around
'Buffers' can be extremely useful if your system has a problem with impedance matching - some high quality amps have a troublesome low input impedance and a simple buffers in 'just the answer'
There's a couple of 'buffer projects' here on diy that are good kits and fairly straight forward - the DCB1 is an ongoing project and very well known (various versions) and nearly totally transparent - the 'Kuartlotron' has a pcb evolving now and is also quite straight forward with less complicated power supply requirements
As Nelson Pass (and others) are known to say "keep it simple, but not too simple'
As a matter of interest, when I listen to my system at good volume -- where I can hear the details clearly and enjoy the music -- the display typically indicates between 50 and 60 (on a 1~99 linear scale, so about 20~24 dB attenuation) and within that range the current transitions from 0.1 mA to < 0.1 mA per LDR. At normal listening levels the current flow is truly negligible.
My feeling is that with normal use -- muted when not listening -- the LDRs will not change character for a long, long time, if ever. If you're only interested in how it sounds vs how accurate the pot's log curve is, you may not need to calibrate your board at all. I believe James is using his board as it was auto-calibrated by me before shipping across the Pacific.
My feeling is that with normal use -- muted when not listening -- the LDRs will not change character for a long, long time, if ever. If you're only interested in how it sounds vs how accurate the pot's log curve is, you may not need to calibrate your board at all. I believe James is using his board as it was auto-calibrated by me before shipping across the Pacific.
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This morning I put the final touches on the rotary encoder / IR front end board, and I'm really happy with the result. The encoder and IR volume adjustment are both fast and fully controlled and the display follows volume with no significant delay. Switching between functions is impeccable. I now prefer this board to my original preference of motorized volume and balance pots because it is glitch-free and displays all the useful information.
Yesterday I did a readability test from a distance. With my less-than-stellar eyesight (need a new prescription) I could tell approximately what was displayed from 15 feet, though could not quite read the exact numbers. Translation: Display is useful even from the listening position.
Yesterday I did a readability test from a distance. With my less-than-stellar eyesight (need a new prescription) I could tell approximately what was displayed from 15 feet, though could not quite read the exact numbers. Translation: Display is useful even from the listening position.
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Yes, no changes at all, apart from playing around with different supplies - I was curious if the prolonged 'mutes' would change any of the normal operating conditions, but 'no problems'
I've only ever turned the vol knob past "2 o'clock on the dial" for a couple of very low level recordings and not noticed any change in the character of the sound at all.
I've only ever turned the vol knob past "2 o'clock on the dial" for a couple of very low level recordings and not noticed any change in the character of the sound at all.
No pressure Wapo, but it would be great if it was ready for my birthday in June
Tell your potential "giftor" that a gift given for no reason on no particular day is far more meangful than a "birthday" or "Christmas" present. You need this control as soon as it's available no matter when that is!
Honestly, for a number of years George's Lightspeed LDR control was only of technical interest to me but now that I've heard one, I'm a believer -- they should be everywhere an analog pot is presently being used. It really transformed the sound I can produce from my mediocre system.
BTW, my system is now an old netbook --> Schiit Modi Uber --> LDR control --> homemade chipamp --> modified Klipsch Forte.
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