[samsquanch]

Quote:

4 channel balanced Beta22:
relay stepped attenuator (64 steps @ 1dB) controlled by an ATTINY26 MCU, used a linear pot. with the internal ADC as control.
Some labeling work left to do, I'm thinking of using Dymo tape.
There IS a bit of hum when using with sensitive IEMs, I might add a bit of shielding around the transformer, see if that helps.
 

 
My first suggestion would be to clean up your wiring, a good rule of thumb is keeping wires, carrying voltages with a peak to peak difference of 10 or more, at least 1 foot (30cm) apart.  A quick google search for Hong Kong wall voltage is 220VAC, your audio inputs, which we'll err on the safe side, at 1.5v is a difference of 146, even your outputs, run wide open at 8x gain (12v) would be a difference of 18.  So all that said, if you have the ability do a reading off the output to see what frequency the hum is, once again google says your wall is putting out 220VAC at 50Hz, so if you're reading a 50Hz signal, then I'd say that the wires bringing in your mains voltage are causing your trouble.
 
If that's not the trouble, try disconnecting the wires that are used for gain switching, even though they're shielded, they might be picking up some noise, or as stated elsewhere in this thread, the issue with C2-C5 might be the culprit.
 
If you have a spare case, I would move the transformer and power supply board to it and see if that clears up any of your issues.  I have mine built in a two cases and I've noticed that if I place the two close together, I'll start to hear some hum in my headphones.  The solution?  Keep them far apart and never think about it again.
 
Now, just because I don't see it, doesn't mean it isn't there, but, do you have the ground loop breaker installed (might not be necessary with your set up, but I don't know you're full topology)?
 
 

Ground loop breaker

[size=small]For option 3 above, the ground loop breaker is a 10Ω 5W resistor in parallel with a 0.1µF capacitor rated at least 250VAC. For safety this capacitor should be rated for class X or Y (good for across-the-line use) with flame retardant casing. The ground loop breaker should be connected between the signal ground and the chassis (which is in turn connected to AC earth ground via the IEC power entry receptacle). Mount the resistor and capacitor in a secure manner so that it will not come loose and come into contact with other circuitry. A good way to do this is to use a [/size][size=small]terminal strip[/size][size=small].[/size]

 
 
You say you're going to do some tests, for fairness sake, you should get yours operating correctly, and without modifications, first.

 

[akiroz]

Quote:

I'm not going to engage you any further. It is pretty clear from your attitude, and your post-count-per-day, that you are more interested in talking than listening to good advice.

 
I'm not really mad or anything. :/
 
It's just that after all these years of taking audiophile BS from magic rocks to snake oil, made it really hard believe anything without empirical proof or evidence. So I have a habit of trying to falsify theories that doesn't agree with my knowledge rather than just blindly believing everything people say. I you're annoyed by that then I'm sorry, It's just my way of learning.
 
 
Quote:

 
My first suggestion would be to clean up your wiring, a good rule of thumb is keeping wires, carrying voltages with a peak to peak difference of 10 or more, at least 1 foot (30cm) apart.  A quick google search for Hong Kong wall voltage is 220VAC, your audio inputs, which we'll err on the safe side, at 1.5v is a difference of 146, even your outputs, run wide open at 8x gain (12v) would be a difference of 18.  So all that said, if you have the ability do a reading off the output to see what frequency the hum is, once again google says your wall is putting out 220VAC at 50Hz, so if you're reading a 50Hz signal, then I'd say that the wires bringing in your mains voltage are causing your trouble.
 
If that's not the trouble, try disconnecting the wires that are used for gain switching, even though they're shielded, they might be picking up some noise, or as stated elsewhere in this thread, the issue with C2-C5 might be the culprit.
 
If you have a spare case, I would move the transformer and power supply board to it and see if that clears up any of your issues.  I have mine built in a two cases and I've noticed that if I place the two close together, I'll start to hear some hum in my headphones.  The solution?  Keep them far apart and never think about it again.
 
Now, just because I don't see it, doesn't mean it isn't there, but, do you have the ground loop breaker installed (might not be necessary with your set up, but I don't know you're full topology)?
 
 
You say you're going to do some tests, for fairness sake, you should get yours operating correctly, and without modifications, first.

Thanks, I'll try that.
Most of the wiring mess you see is actually just control signals with 5VDC for the push buttons and volume control.
 
I actually haven't grounded the circuit to the real earth, might do that first.

 

[miceblue]

I have a question for the D.I.Y community here. This is for a personal project outside of audio but it relates to the O2's potentiometer.
 
From the designer's part list for the O2, it uses an Alps RK09712200MC 10k potentiometer. The project I'm working on uses a regular 'ol 10k trimmer potentiometer, but I would like to put the finished product in a nice aluminum enclosure with [hopefully] easy access to the potentiometer. Would using the Alps pot instead of the trimmer work as a replacement?
 
Right now I'm just using one of these really cheap trimmer pots:

 

[tomb]

Quote:

I have a question for the D.I.Y community here. This is for a personal project outside of audio but it relates to the O2's potentiometer.
 
From the designer's part list for the O2, it uses an Alps RK09712200MC 10k potentiometer. The project I'm working on uses a regular 'ol 10k trimmer potentiometer, but I would like to put the finished product in a nice aluminum enclosure with [hopefully] easy access to the potentiometer. Would using the Alps pot instead of the trimmer work as a replacement?
 
Right now I'm just using one of these really cheap trimmer pots:
 

I'm not sure you whether you are aware of the differences.  You haven't described any details about your "personal project outside of audio."  Audio potentiometers meant for volume control are based on a logarithmic scale.  That's the real-world approximation of human hearing (it gets more complicated with Fletcher-Munson curves).
 
However, almost all trimmers used outside of an audio output circuit are linear-based.  If your "personal project outside of audio" uses a linear trimmer, then a volume pot is not going to be a good thing.
 
Just an FYI, but there are many trimmers that are large and meant to be turned with a knob instead of a screwdriver/trimmer tool.  They are also linear.  Maybe you should look at one of those?  Bourns makes all sorts - trimmers driven with a trimmer tool, or large ones with shafts that allow you to clamp on a knob.

 

[miceblue]

Quote:

Quote:

I have a question for the D.I.Y community here. This is for a personal project outside of audio but it relates to the O2's potentiometer.
 
From the designer's part list for the O2, it uses an Alps RK09712200MC 10k potentiometer. The project I'm working on uses a regular 'ol 10k trimmer potentiometer, but I would like to put the finished product in a nice aluminum enclosure with [hopefully] easy access to the potentiometer. Would using the Alps pot instead of the trimmer work as a replacement?
 
Right now I'm just using one of these really cheap trimmer pots:
 

I'm not sure you whether you are aware of the differences.  You haven't described any details about your "personal project outside of audio."  Audio potentiometers meant for volume control are based on a logarithmic scale.  That's the real-world approximation of human hearing (it gets more complicated with Fletcher-Munson curves).
 
However, almost all trimmers used outside of an audio output circuit are linear-based.  If your "personal project outside of audio" uses a linear trimmer, then a volume pot is not going to be a good thing.
 
Just an FYI, but there are many trimmers that are large and meant to be turned with a knob instead of a screwdriver/trimmer tool.  They are also linear.  Maybe you should look at one of those?  Bourns makes all sorts - trimmers driven with a trimmer tool, or large ones with shafts that allow you to clamp on a knob.

Oh, I see. I didn't know that, but thank you so much for pointing that out! The project I'm working on is just a triangular voltage generator.
I'll be sure to look through Bourns' website then for a linear potentiometer knob.

 

[KimLaroux]

Quote:

I have a question for the D.I.Y community here. This is for a personal project outside of audio but it relates to the O2's potentiometer.
 
From the designer's part list for the O2, it uses an Alps RK09712200MC 10k potentiometer. The project I'm working on uses a regular 'ol 10k trimmer potentiometer, but I would like to put the finished product in a nice aluminum enclosure with [hopefully] easy access to the potentiometer. Would using the Alps pot instead of the trimmer work as a replacement?
 
Right now I'm just using one of these really cheap trimmer pots:

 
I'm not sure I get the question... you want to use a stereo audio log pot to replace a single linear multiturn trimmer?
 
If that's the case, then no it's not a good idea.
 
You'd need something like these:
http://ca.mouser.com/ProductDetail/Vishay-Sfernice/PE30LLFL103KAB/?qs=sGAEpiMZZMtC25l1F4XBUwRZBBMBj1ZqihfVXXfPTkw%3d
http://www.digikey.ca/product-detail/en/3590S-2-103L/3590S-2-103L-ND/1088586

 

[miceblue]

Quote:

Quote:

I have a question for the D.I.Y community here. This is for a personal project outside of audio but it relates to the O2's potentiometer.
 
From the designer's part list for the O2, it uses an Alps RK09712200MC 10k potentiometer. The project I'm working on uses a regular 'ol 10k trimmer potentiometer, but I would like to put the finished product in a nice aluminum enclosure with [hopefully] easy access to the potentiometer. Would using the Alps pot instead of the trimmer work as a replacement?
 
Right now I'm just using one of these really cheap trimmer pots:

 
I'm not sure I get the question... you want to use a stereo audio log pot to replace a single linear multiturn trimmer?
 
If that's the case, then no it's not a good idea.
 
You'd need something like these:
http://ca.mouser.com/ProductDetail/Vishay-Sfernice/PE30LLFL103KAB/?qs=sGAEpiMZZMtC25l1F4XBUwRZBBMBj1ZqihfVXXfPTkw%3d
http://www.digikey.ca/product-detail/en/3590S-2-103L/3590S-2-103L-ND/1088586

Ah okay. I'll probably just stick to using the cheap potentiometers I'm currently using since $10+ for potentiometer sounds a bit unreasonable for the project at hand, not to mention the shipping costs. If I do a more elaborate project in the future, I'll be sure to keep those in mind though.
Thank you for the suggestions!

 

[Speedskater]

The real question is, are you going to use it as the main volume control or as a set it and forget it level control?
If it's just a level control then it doesn't matter much if it's logarithmic or linear.
If it's a volume control, a trimmer well quickly wear-out.
 
I don't have the O2 schematic handy,  what's the original purpose of the pot?  Input level, output level, gain adjust?

 

[KimLaroux]

Yeah his question is weird. He doesn't want to change something to the O2. He has another project which isn't audio related, and wants to replace the trimmer in it with the same pot used for the O2's volume control...
 
You've gotta give NwAvGuy credit: his marketing is simply outstanding. He should go work for Apple, or Beats. To think that he managed to rebrand one of the most popular stereo audio potentiometer...
 
But yeah I was gonna ask too:
 
Will the control be used regularly?
If yes, then you'll be better off using a pot, or, as tomb suggested, use a beefy trimmer meant to be used regularly.
If not, then you can just drill a hole in the enclosure to adjust the trimmer using a screw driver without opening the enclosure.
 
Do you need the same level of precision as a 10 turn trimmer?
If yes, then you'll need a multi-turn pot.
If not, then you may be able to get away with using a cheap single turn pot.

 

[Speedskater]

One thing about a trimmer pot, it might be used in or near the feed-back loop of an op-am.  Feed-back loops are not happy with long wires to remote parts.

 

[kolyas]

[size=small]withdrawn[/size]

 

[joeyjojo]

Shame the link is down. Why not just use step down audio transformers? They would have been much cheaper and probably higher quality.

 

[kolyas]

Joeyjojo
 
Link seems to be working now. Please look at the ecp site before making such comments. What cheap step down transformer would adjust volume and be better than an amorphous core autoformer?

 

[crispchicken]

Sup guys (and girls)!
 
I've been working on a few projects recently. Most importantly though, my SkeletonDAC arrived in the mail. I think I might be using it internally with my objective2 (in the battery area) for a desktop dac-amp unit. I shall post my other projects soon when I have the time to write up and photograph (and get them fully prepared to be photographed...)
 
The DAC is my very first project with surface mount components. The only other experiemnce with smd was with desoldering a few off an old motherboard. I think it came out well for my first atempt. i started at the front side, i suspect you're probably able to tell

 
Anyways, I've taken some photos for your enjoyment. Sorry the quality is not amazing by any stretch as I took them with my phone.
 


Heres a couple of close ups of both sides... Remember this is my first time soldering smd too, please...

 

The full DAC unit. Its getting a small metal case as soon as jaycar opens (easter weekend in NZ, people love to close shop whenever the whim hits...)
 

And this is how I'm keepng it safe for now. Its sitting on top of my amp, which is a metal case, so I wrapped it up in zip ties until it was fairly insulated.
Personally I think it looks really cool this way!
 

And finally, here is the interconnect I made up for the headapm to my power amplifier for speakers.
I use my Cmoy as a preamp , and it works great.
 
On a final note, to anyone lookng at the skeleton and wondering if it's any good for such a low price, I will say, YES. It totally is, its only 20ish dollars US for the kit with no case, which has to be the best performance-dollar ratio there is in dacs. I've heard the pupdac, several Fiio ones, total bithead and other diy gear too, and personally this thing really keeps up with it's far more espensive and complex designed competitors. I think there's a lot to be said for simplicity aand minimalism especially in this case, plus its just such a fun build! I'm eager to try more smd work now that I've gained a little confidence

  The beezar kit was amazing to build because it was so well organised. It was a totally amazing experience over-all

 
Thats enough ranting, and I guess i sound like a shill at this point
 
peace
 
chris

 

[DefQon]

Quote:

 
Following in the footsteps of Trevor Networks, that's the spirit!
 

+1, was thinking along the same line back when he used to build those Dynahi's that were never delivered.
 
I'd personally go with having the power supply in a separate enclosure just to be on the safe hum free side.
 
@b1o2r3i4s5: How much in total have you spent on the whole project so far? Not bad but assuming you're still going to be using those for IEM's and even if yo do have any balanced source/dac's, still overkill lol