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Circuit error in Lite DAC-AH: Easy fix - Page 6

post #76 of 210
I know the people over at aa seem to highly recommend the auricaps for the dac-ah bypass, so I am looking forward to getting mine. They also suggest adding power supply filtering with a hammond 193l and some auricaps. I doubt I will ever get around to that. I think my plan is to use auricaps for passive out (via a second set of plugs) and the vitamin q's for the opamp output. I think the active output might smooth out some poor recordings- we'll see.

FWIW my vitamin q's took a long time to break in so you might try to give one set some time to see if your opinion changes. In fact, they were unlistenable at first. I feel like mine may have even had a second break-in period for the active to passive mod. They seem to sound much better now than when I initially switched to passive. (Of course, I also switched out the resistors and a couple other capacitors at the same time, so those may have also needed break-in.)
post #77 of 210
A little bit of a hijack here.

I just received my Pacific Valve modded DAC-AH HA!, and I had e-mailed them asking if the circuit error in the recent DACs was fixed in their modded version (I even gave them a link to this thread), and they said that yes it was fixed.

However, I just received the DAC yesterday, and it seems there are a bunch of areas in the sound that actually sound worse than using an analog out on my ESI Juli@. Namely, the bass is noticeably more extended, but it seems to "distort". I dont mean heavy distortion that sounds scratchy, but it is very deep and muddy distortion, if you know what I mean.

Also, when using the DAC-AH HA, if I turn the volume on my preamp all the way up (or most of the way up), there is a very audible whine in the left channel. At first I got very worried and thought the driver in my K1000 was dead, but when I hooked it back up to the analog out on the Juli@ the whine was gone.

Do these things sound like it is the circuit error that is in the recent DAC-AH's? In the first post of this thread a program to measure distortion was mentioned. Can I have a link to that program to test it out? What to you reckon is the problem and what should I do?
post #78 of 210
My dac-ah always had a bit of a noise floor with active output (some stange scratchy noise). I could only really hear it if I cranked the volume way up (i.e. on pause with volume much louder than I could possibly listen to), but my gear is not as revealing as yours. I would think that PV would fix that with an extensively modded one? With the passive output, the scratchy noise went away. As far as the circuit error, you would probably need to reed the resitor values of r35 and r36 and check the voltage to make sure the problem hasn't been addressed. If you have 6V across the dac chips and the resistor value is 270 (code red violet black black brown/gold), then you have a problem. The bass noises sound like what I experienced (at very low levels) before I fixed the circuit error. You may also need to let the dac burn-in, but I don't know how long that takes since I bought mine used.

good luck
post #79 of 210
Quote:
Originally Posted by izquierdaste
My dac-ah always had a bit of a noise floor with active output (some stange scratchy noise). I could only really hear it if I cranked the volume way up (i.e. on pause with volume much louder than I could possibly listen to), but my gear is not as revealing as yours. I would think that PV would fix that with an extensively modded one? With the passive output, the scratchy noise went away. As far as the circuit error, you would probably need to reed the resitor values of r35 and r36 and check the voltage to make sure the problem hasn't been addressed. If you have 6V across the dac chips and the resistor value is 270 (code red violet black black brown/gold), then you have a problem. The bass noises sound like what I experienced (at very low levels) before I fixed the circuit error. You may also need to let the dac burn-in, but I don't know how long that takes since I bought mine used.

good luck
I am very bad with electronics; can you post a picture of the dac-ah before the circuit error was fixed and circle what I should be looking for? Or make a picture in MS-paint if it will get the point across. Keep in mind I am a total noob with this kind of stuff.
post #80 of 210
Quote:
Originally Posted by 003
I am very bad with electronics; can you post a picture of the dac-ah before the circuit error was fixed and circle what I should be looking for? Or make a picture in MS-paint if it will get the point across. Keep in mind I am a total noob with this kind of stuff.
you'll need a multimeter for this maybe...

in the picture I've attached, the yellow box outlines resistor r35 and r36. Check if those are 270ohms (maybe 274ohms). If they're not, then PV have fixed the circuit error.

the red dots in the picture are voltage outputs of the regulators, they should be 8volts if the resistors r35 and r36 are 270 ohms. so put the negative terminal of your multimeter to an rca socket and measure the voltage at those red dots with the positive terminal of multimeter.

so if you measure 6volts and the resistors r35 and r36 are still 270ohms, then PV didn't fix the error.


post #81 of 210
Quote:
Originally Posted by pelayostyle
Then added heatsinks on the dac chips.
I like the heat sinks, I'll be doing the exact same thing. Where'd you score those? Applied with thermal tape?
post #82 of 210
Quote:
Originally Posted by DDF
I like the heat sinks, I'll be doing the exact same thing. Where'd you score those? Applied with thermal tape?
http://sidewindercomputers.com/mimi.html

yes
post #83 of 210
Quote:
Originally Posted by pelayostyle
Are those the heatsinks you guys use? Do they fit all right? How many packs do you need to order, just one?
post #84 of 210
Quote:
Also, when using the DAC-AH HA, if I turn the volume on my preamp all the way up (or most of the way up), there is a very audible whine in the left channel. At first I got very worried and thought the driver in my K1000 was dead, but when I hooked it back up to the analog out on the Juli@ the whine was gone.
Stupid question, but are you connected to a PC?

I just received my DAC-AH this week (stock, and I haven't touched it yet) and I noticed I was getting a high pitched hiss in the right channel.

After playing around for a while with various cabling configurations I figured out that line in was not muted in my soundcard properties, doing so completely eliminated any noise, well except at near maximum volume, but at that volume my headphones are easily heard about 6-10' away . I also get a high pitched whine (not hiss) out of the right channel when no cable is connected to whatever input the DAC is switched too. This obviously isn't really a problem since I will have to have it connected to hear anything, but I am curious why it happens.

I do plan to fix this error at least, but can anyone link to clear instructions for the passive mod? Im vaguely interested in trying it, that or upgrading the opamps. Also if I do upgrade the opamps is replacing the output caps necessary?
post #85 of 210
Quote:
Originally Posted by _Rand_
I will have to have it connected to hear anything, but I am curious why it happens.
Sounds like a stability issue when either its input isn't grounded, or it sees a high source impedance. Some electronics can do that. For example, when my go-vibe5 input isn't connected, I can hear subtle motorboating through the headphones. Not a big deal as it's all good once connected. To test the theory, run an aligator clip from the input coax to your source card, but not the signal pin. If it still whines, then it needs to see a low source impedance.

This really makes me wonder what happens when you use the optical input? Does it still make the whining sound when usiing that input?

Rand, or anyone with that problem, can you try this and report back? Is this a common issue?
post #86 of 210
Quote:
Originally Posted by 003
Are those the heatsinks you guys use? Do they fit all right? How many packs do you need to order, just one?
They fit perfect. You can order them individually , so just order 10 for $10

(if you order less then 10 its $1.25 each so 8x1.25 is $10. Might as well get 2 more just incase you mess up while applying them.)
post #87 of 210
Quote:
This really makes me wonder what happens when you use the optical input? Does it still make the whining sound when usiing that input?
Its actually getting odder.

I get a whine when switched to optical and nothing is plugged into optical, but only if something is plugged into the coax. I have nothing that outputs an optical signal handy to see if it disappears if there is a signal going into the optical at the same time.

The whine over optical isn't quite the same as the whine over coax btw, its more staticy on optical than it is coax.

Perhaps the DAC-AH can only take one input at a time? Switched or not?

As for the whine on coax, connecting the ground does nothing but it disappears when the signal pin is connected, even if not fully. Either way the whine is gone when its in use.
post #88 of 210
Quote:
Originally Posted by _Rand_
Its actually getting odder.

I get a whine when switched to optical and nothing is plugged into optical, but only if something is plugged into the coax. I have nothing that outputs an optical signal handy to see if it disappears if there is a signal going into the optical at the same time.

The whine over optical isn't quite the same as the whine over coax btw, its more staticy on optical than it is coax.

Perhaps the DAC-AH can only take one input at a time? Switched or not?

As for the whine on coax, connecting the ground does nothing but it disappears when the signal pin is connected, even if not fully. Either way the whine is gone when its in use.
You have a ground loop problem. I don't know if you're using a computer but it is common with them. I had a similiar problem with a sub woofer and bought an rca ground loop isolator. I don't know if one is made for a digital coax. With a computer you should always use an optical connection.
post #89 of 210
I don't have an optical connection unfortunately.

At least not without spending $50 on a breakout box thingy for my X-fi. Ill just have to deal with my weird as hell 1/8" mono - RCA cable . Besides, I paid $20 for the thing.

I get no hiss/squeal as long as the coax is connected or only optical is connected so there is no real problem. How often am I going to be using my headphones with no input cables connected after all?

If your curious I'm using X-fi Xtreme music -> DAC AH -> Headfive -> HD580s. A fairly decent, though somewhat low budget setup.

I plan to get DT880s or maybe K701 or HD650s in the future though. Im leaning towards DT880s at the moment.
post #90 of 210
so i have 274-ohm resistors at r35 and r36. but i don't have a multimeter on hand to test whether the voltage is correct. i'm selling my dac-ah and i want to let people know whether it has the problem or not.

btw, my dac-ah is an older version, bought last november directly from diyclub...it has a red PCB and some of the parts used are different than the pictures posted so far in this thread...any ideas/suggestions?

i've also not experienced distortion at high volume levels, but that may not mean anything...

here are pics...any thoughts?



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