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The GrubDAC - Page 66

post #976 of 1072
Quote:
Originally Posted by zhoob2004 View Post
 

ok, so I fixed the 3v3 (didn't connect fully when I resoldered it).

 

now the symptom I'm having is it connects just fine, recognized by lsusb and alsa. Then, after a short bit, I lose it and dmesg says "Port disabled by hub (EMI?), re-enabling..." after which, it doesn't show up.

 

here is a pic of the topside I just took, not sure if you can see anything or not,

 

http://img9.imageshack.us/img9/9046/4ukb.jpg

 

or at least there would be if I had upload permissions. I'll see if after I post this I have enough posts and then I can edit this one with it, or I'll just use imageshack or something.

 

 

Quote:
Originally Posted by geofftnz View Post
 

 

I'd look at getting some solder wick and getting rid of the extra solder on the crystal oscillator. I had problems on my pupdac with too much solder on the oscillator shorting against the case (was so small I didn't notice it initially). USB hubs will disable devices if they draw too much power, so that's an option too, although you should have noticed regulators/inductors getting super-hot.

 

Is that a small bridge lower right-side of the PCM2706?

 

Excellent photograph!

 

Geofftnz is correct - if you solder flowing up and touching the top "can" of the oscillator, it will be shorting out.  Could be a miniscule bridge on the PCM chip as he notes, but it looks like either lint or something you could easily swipe away with an X-acto knife.  Except for that, all the joints on the PCM and Wolfson look pretty good to me.

post #977 of 1072

I think I saw what you mean by the potential bridge, and it was just a piece of lint. I touched it up anyway just to be sure, though. I checked all my connections that I could with a multimeter and a cursory inspection of where traces connected (using the layout and board images on the site mostly). I've been trying it on and off for a while now and not got any recognition from the computer, or my error and then suddenly, I plug it in and it works just like magic. I'm testing it on my desktop right now (booted into linux right now) and the audio dropped on me once, but I attribute that to an application taking exclusive control of the device away because after I restarted playback it began to work again. Now I'm just running it for a while with music to see if I can't get it to drop again, but it seems more stable than it has been so far.

 

only thing I notice is there is a high-pitched squeal coming from the speakers, but that may be my monitor speakers or it's integrated amp (I apologize for not having a proper setup to test/use this with currently, penniless college student)

 

I'm also sure it wasn't the crystal because I checked continuity between the top and the 4 contacts and only the bottom-right (which I'm pretty sure is already ground) had continuity

 

 

Edit: 

 

If I want to drive IEMs directly with my grubdac, what should I do to make it sound right? the bass is really washed-out if I try


Edited by zhoob2004 - 10/20/13 at 7:45pm
post #978 of 1072
Quote:
Originally Posted by zhoob2004 View Post
 

I think I saw what you mean by the potential bridge, and it was just a piece of lint. I touched it up anyway just to be sure, though. I checked all my connections that I could with a multimeter and a cursory inspection of where traces connected (using the layout and board images on the site mostly). I've been trying it on and off for a while now and not got any recognition from the computer, or my error and then suddenly, I plug it in and it works just like magic. I'm testing it on my desktop right now (booted into linux right now) and the audio dropped on me once, but I attribute that to an application taking exclusive control of the device away because after I restarted playback it began to work again. Now I'm just running it for a while with music to see if I can't get it to drop again, but it seems more stable than it has been so far.

 

only thing I notice is there is a high-pitched squeal coming from the speakers, but that may be my monitor speakers or it's integrated amp (I apologize for not having a proper setup to test/use this with currently, penniless college student)

 

I'm also sure it wasn't the crystal because I checked continuity between the top and the 4 contacts and only the bottom-right (which I'm pretty sure is already ground) had continuity

 

 

Edit:

 

If I want to drive IEMs directly with my grubdac, what should I do to make it sound right? the bass is really washed-out if I try

One other possibility is either flux or cleaning fluid (I use alcohol) that's gotten under one of the chips.  It can cause intermittent shorting.  I've had to wait for several hours before plugging in a pupDAC after cleaning it.  Otherwise, all sorts of weird things happen.

post #979 of 1072

could be that, as I have been cleaning with alcohol (80%, not as high as I like, but all I could get easily), but I didn't hear it in my headphones (but there are a lot of things I didn't hear in the headphones, like proper music).

 

I suspect that the issue with the headphones might be due to the integrated microphone, since I've seen that cause issues with computer audio output before.

post #980 of 1072
Quote:
Originally Posted by zhoob2004 View Post
 

could be that, as I have been cleaning with alcohol (80%, not as high as I like, but all I could get easily), but I didn't hear it in my headphones (but there are a lot of things I didn't hear in the headphones, like proper music).

 

I suspect that the issue with the headphones might be due to the integrated microphone, since I've seen that cause issues with computer audio output before.

91% alcohol is readily available at Wal-Mart.;)

post #981 of 1072

let me rephrase that: 80% is all that I could get for free and on a moment's notice, but no matter, because it's been working great since I last posted, although something is up with my audio drivers on my linux install since it only likes to have one application using it at a time.

post #982 of 1072
Quote:
Originally Posted by zhoob2004 View Post
 

let me rephrase that: 80% is all that I could get for free and on a moment's notice, but no matter, because it's been working great since I last posted, although something is up with my audio drivers on my linux install since it only likes to have one application using it at a time.

Sounds like it might have been the alcohol.;)   Glad you got it working, but sorry about the Linux issues.

post #983 of 1072

No worries. It's probably something that's my fault anyway. That's the cost you pay for using Arch as your distro of choice.

post #984 of 1072

Okay, so a couple of months ago I got gifted a GrubDAC kit. Built it up nice and clean, added a few mods here and there, and I must say that I really, really like the sound of this little thing. Balanced sound, no coupling caps, nice output level. BUT what was annoying me to no end were the HF interferences manifesting themselves as clicks, pops, and especially drop-outs of the DAC whenever any power switch of some sorts was actuated. Anything from the fridge, oscilloscope, soldering station, light switch in any room of my apartment, maybe even one or two power sources that my neighbour is running, it all disturbed the DAC in some varying degree.

 

For reference, here's the setup that I was dealing with: Netbook to (bus powered) GrubDAC via super short USB cable, from there shielded RG316/U cable with BNC plugs to the input of my preamp. At the input was a 25k Alps pot, connected via Cat5e twisted pairs, going into a DC coupled unity gain JFET buffer (a so called DCB1 Mezmerize), which then connects to an active crossover that feeds two stereo amps. Here's a pic:

 

 

The crappy boar shaving brush (too floppy when wet, no backbone) is my dedicated electronics dust-off brush, I highly recommend it.

 

On with the story. Trying to get rid of these interference issues, I implemented many a thing. My source is a netbook, so I ran it on battery. Didn't change a thing, it seemingly wasn't entering the DAC from this side. Added ferrite cores, chokes, line filters to preamps and amps (100% DIY), bypass and decoupling caps, bigger resistors and bigger caps (not that I expected anything from those last two), nothing changed. Then I googled and saw that other people are having that problem too, but no solution was to be found. The GrubDAC looks like this now:

 

 

 

Unrelated to the DAC issues I added something to my system yesterday: Another JFET buffer with relay based source selection, for convenience really. Here's another pic:

 

 


The GrubDAC connects to the two BNC connectors (to the left of the two unoccupied RCA jacks). As you can see the whole thing is not exactly inside a chassis. The whole pre doesn't even have a line filter at the mains input. Noticed how the first paragraph is in past tense? That's right, the issues are gone.

What changed? I left the volume control where is was before, at the input of the Mezmerize. In front of the volume pot I added the additional JFET buffer, and at this buffer's input I simply put two 22k1 Dale RN60D resistors to ground (instead of a pot), which in parallel to the buffer's own input impedance form a fixed(!) input impedance of pretty much 20k. The rest is virtually the same. The same cables, the same plugs, the same circuitry. The relays are Nais TQ2-5V and I doubt that they have something to do with the resolving of the issue. All the buffers use the same JFETs (2SK170BL) and resistors (RN55D), all unity gain, no coupling caps.

So the new setup is: Netbook, GrubDAC, fixed 22k1 RN60D resistor, buffer, volume pot, buffer, crossover, amps.

 

I'm still not sure what is actually going on, but the simple resistor at the input must have a flatter impedance than the pot for the HF portions of the power switch spark e/m crap. Or something like that.

TL;DR: Buffer your volume pots.

I hope this helps. Comments, criticism and alternative explanations welcome.

post #985 of 1072
Quote:
Originally Posted by Rodeodave View Post
 

Okay, so a couple of months ago I got gifted a GrubDAC kit. Built it up nice and clean, added a few mods here and there, and I must say that I really, really like the sound of this little thing. Balanced sound, no coupling caps, nice output level. BUT what was annoying me to no end were the HF interferences manifesting themselves as clicks, pops, and especially drop-outs of the DAC whenever any power switch of some sorts was actuated. Anything from the fridge, oscilloscope, soldering station, light switch in any room of my apartment, maybe even one or two power sources that my neighbour is running, it all disturbed the DAC in some varying degree.

 

For reference, here's the setup that I was dealing with: Netbook to (bus powered) GrubDAC via super short USB cable, from there shielded RG316/U cable with BNC plugs to the input of my preamp. At the input was a 25k Alps pot, connected via Cat5e twisted pairs, going into a DC coupled unity gain JFET buffer (a so called DCB1 Mezmerize), which then connects to an active crossover that feeds two stereo amps. Here's a pic:

 

 

 

The crappy boar shaving brush (too floppy when wet, no backbone) is my dedicated electronics dust-off brush, I highly recommend it.

 

On with the story. Trying to get rid of these interference issues, I implemented many a thing. My source is a netbook, so I ran it on battery. Didn't change a thing, it seemingly wasn't entering the DAC from this side. Added ferrite cores, chokes, line filters to preamps and amps (100% DIY), bypass and decoupling caps, bigger resistors and bigger caps (not that I expected anything from those last two), nothing changed. Then I googled and saw that other people are having that problem too, but no solution was to be found. The GrubDAC looks like this now:

 

 

 

 

Unrelated to the DAC issues I added something to my system yesterday: Another JFET buffer with relay based source selection, for convenience really. Here's another pic:

 

 

 


The GrubDAC connects to the two BNC connectors (to the left of the two unoccupied RCA jacks). As you can see the whole thing is not exactly inside a chassis. The whole pre doesn't even have a line filter at the mains input. Noticed how the first paragraph is in past tense? That's right, the issues are gone.

What changed? I left the volume control where is was before, at the input of the Mezmerize. In front of the volume pot I added the additional JFET buffer, and at this buffer's input I simply put two 22k1 Dale RN60D resistors to ground (instead of a pot), which in parallel to the buffer's own input impedance form a fixed(!) input impedance of pretty much 20k. The rest is virtually the same. The same cables, the same plugs, the same circuitry. The relays are Nais TQ2-5V and I doubt that they have something to do with the resolving of the issue. All the buffers use the same JFETs (2SK170BL) and resistors (RN55D), all unity gain, no coupling caps.

So the new setup is: Netbook, GrubDAC, fixed 22k1 RN60D resistor, buffer, volume pot, buffer, crossover, amps.

 

I'm still not sure what is actually going on, but the simple resistor at the input must have a flatter impedance than the pot for the HF portions of the power switch spark e/m crap. Or something like that.

TL;DR: Buffer your volume pots.

I hope this helps. Comments, criticism and alternative explanations welcome.

 

Your particular setup, while quite interesting and unique, is so non-standard that I'd only be guessing.

 

I'm not sure that others have necessarily commented on sound glitches or interference with the GrubDAC, but my memory is not so good these days.  JMHO, but an open amp with unshielded hookup wire seems more likely to pick up those noises than the DAC.  Cell phone interference, for instance, can be maddening sometimes but they usually enter into a circuit through the large traces, leads, and wiring associated with amplifier connections.  The DAC knocking offline because of power switching?  Yes, absolutely.  In my own setup, I even have a powered-USB hub and sometimes my mouse or keyboard gets knocked offline when I throw the power switch on to my headphone amp.  Things re-connect almost instantly, so it's a minor irritation.

 

As for the volume pot - every pot should have an input grounding resistor (tied between the wiper and ground ~10x the pot impedance) or the source will see a varying impedance as the volume control is adjusted.  It's possible that the Wolfson chip would misbehave in those circumstances.  I'm not sure if you included that before, but if not, maybe your resistors corrected that issue.

 

Is your super-short USB cable to the GrubDAC shielded?  That could cause issues, too, if not.

post #986 of 1072

Just 20 posts ago you commented on this exact issue it seems. http://www.head-fi.org/t/445155/the-grubdac/960#post_9777034

And of course that USB cable is shielded, and properly terminated at both ends.

The wiper-to-ground resistor is not really that common though.


Edited by Rodeodave - 11/3/13 at 12:33pm
post #987 of 1072
Quote:
Originally Posted by Rodeodave View Post
 

Just 20 posts ago you commented on this exact issue it seems. http://www.head-fi.org/t/445155/the-grubdac/960#post_9777034

And of course that USB cable is shielded, and properly terminated at both ends.

The wiper-to-ground resistor is not really that common though.

Sorry, but this was what I stated in the previous post: The DAC knocking offline because of power switching?  Yes, absolutely. ?  That is the subject of the other post you just referenced.  I also beg your pardon, but you'll find the wiper-to-ground resistor in every reputable DIY design:

 

Millett Hybrid

Millett MiniMAX

Torpedo

CMoy

PPAV1 and PPAV2

PIMETA

M3

B22

 

just to name a few ...

 

I wasn't trying to set up some sort of competition about what was said or not said ... just trying to offer some guesses as to what could cause the issue with respect to interference.  Power issues should be viewed as a separate matter, IMHO.

 

EDIT: for politeness, excuse me ...


Edited by tomb - 11/3/13 at 12:54pm
post #988 of 1072
Quote:
Originally Posted by tomb View Post
 

Sorry, but what part of this in my previous post did you not read: The DAC knocking offline because of power switching?  Yes, absolutely. ?  That is the subject of the other post you just referenced.  I also beg your pardon, but you'll find the wiper-to-ground resistor in every reputable DIY design:

 

Millett Hybrid

Millett MiniMAX

Torpedo

CMoy

PPAV1 and PPAV2

PIMETA

M3

B22

 

just to name a few ...

 

I apologize, it's late, my attention span is getting low. I got hung up with the glitches and interference part. My mistake. It got me really confused because I just had read your post I linked to before.

 

And the resistor to ground thing I got wrong too, that's what I meant with "buffer's own input impedance", it's a 221k resistor to ground at the wiper. I confused it with the 1M resistors that you sometimes find at the input jacks.

 

I should read more closely.


Edited by Rodeodave - 11/3/13 at 12:58pm
post #989 of 1072
Quote:
Originally Posted by Rodeodave View Post
 

 

I apologize, it's late, my attention span is getting low. I got hung up with the glitches and interference part. My mistake. It got me really confused because I just had read your post I linked to before.

 

And the resistor to ground thing I got wrong too, that's what I meant with "buffer's own input impedance", it's a 221k resistor to ground at the wiper. I confused it with the 1M resistors that you sometimes find at the input jacks.

 

I should read more closely.

I should apologize, too.:o

post #990 of 1072

Wow! That's quite the GrubDac, some sexy cap choices there :) Let us know when you get 'er running!

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