[sydneyaudio]

Yeah, I have noticed similar issues with some tracks on my DAC-Ah. I did an opamp upgrade with HDAMs which improved sound quality but did not affect the distortion on lower quality CDs. I switch inputs on my amp which bypasses the DAC for these CDs. I have ordered replacement CAPs for the output stage and will see if this makes a difference.

 

[randyruiz]

I am very interested in your experience. I just got my HDAM's from burson(I think that is the spelling) and they sound great. very expansive sound with more blackground and resolution. However in the very upper registers I am hearing a bit of graininess and I am wondering if its the recording or the DAC. My next step is investigating the output cap upgrade but I am not sure if it is neccessary with the HDAM's in place.
P.S.
I have the upgraded version of the DAC-ah from DIY with the HDAMs.



Quote:

Originally Posted by sydneyaudio Yeah, I have noticed similar issues with some tracks on my DAC-Ah. I did an opamp upgrade with HDAMs which improved sound quality but did not affect the distortion on lower quality CDs. I switch inputs on my amp which bypasses the DAC for these CDs. I have ordered replacement CAPs for the output stage and will see if this makes a difference.

 

[eladioc]

Wow... I just had the same issue that I brought up in the cables, power, etc. forum yesterday because I thought it might be the power. I lowered the output in foobar and the clipping went away for the most part. I think there might be some placebo effect when I listen to my "reference" songs to hear the clipping because I half expect it to be there. Is the way to really "fix" the problem to upgrade the dac (and perhaps get better recorded cds)?

 

[warrior05]

i think it is a combination. lowering the volume in foobar to about 90% has entirely eliminated the clipping distortion i was hearing in the ambient track i referenced in my original post. however, i still hear the distortion a bit in the Tunstall song i referenced. keep in mind, i do not hear this distortion when i go analog from my juli@ even with the foobar volume pegged. so is this an issue from the original recording that my more revealing system is showing me or is it the DAC-AH? i'm not sure about the answer. the distortion others are reporting may also be recording source issues rather than the unit.

wasn't someone going to run some frequency sweeps? that should help isolate the source of the problem. this has been an interesting can of worms i've opened up.

all in all - i still am very happy with my modded DAC-AH. i think it'll suit me for a while and keep the upgradeitis bug at bay. of course my moditis is totally gnawing at me and screaming at me to open this puppy up and start fiddling!

 

[Jahn]

what you really need to do is bring that bad boy to a meet where someone can A/B your DAC against another DAC that has good resolution, and see if they can reproduce that nasty bit in the KT Tunstall track. If they can, it's definitely the source recording, not the DAC. The problem here is that the DAC-ah is probably the best DAC you have at home, and thus there are no equally/better revealing DACs to test this theory out.

 

[slindeman]

I believe the DAC-AH uses TDA1543 DAC chips, is that right? My two DIY DACs (Scott Nixon) also use the TDA1543 with passive I/V and I don't experience the distortion you are mentioning. You should never have to reduce the volume in your computer from full-scale when outputing a digital signal to a DAC.

Anyway, here is a handy utility to generate 0db test tones of various frequencies:
http://www.steiniche.dk/projekter/So...weepgen310.htm
It requires the Delphi 5 runtime, which I found here: http://www.hac4.com/downloads/vcl50.zip

That way you can easily tell if its the particular CDs you are listening to, or the DAC itself.

 

[sevenjohn]

Well, i just did a bit of checking with a sweep generator on my pc>soundblaster>DAC AH. It just confirms what I heard and feared. Buzzing on both channels from 20Hz at 0dB. It's very pronounced but drops off around 2000Hz. It's directly related to output level as the distortion lessens in intensity as output level is reduced. With the output level reduced to -6dB there is no sign of the distortion, well none that my ears can hear.
So I guess that my solution is just to limit the output, and at some stage, when I have the nerve take a look in my dac. I am peeved that a new dac can be shipped with being fully tested, but i suppose it is considered a 'budget' buy.


ps. doing tone sweeps with headphones gives you a headache.

 

[warrior05]

sevenjohn, are you using the -6db limiter within foobar? your findings certainly fall in line with what i was hearing. thanks for doing the research!

so what can be done about this is the next question?

 

[sevenjohn]

The -6dB cut was in the tone sweeper. I'm using 'bout the same cut in foobar on pc and itunes on mac.
As for the solution- I will have a polk around inside the dac and try to follow the schematic, from what i've read on these forums alot of people have made changes to these dacs with success. So i'll do a bit 'o research too, i'll let you (warrior05) know if i find a solution. Meanwhile let us enjoy at -6dB.

 

[sevenjohn]

The -6dB cut was in the tone sweeper. I'm using 'bout the same cut in foobar on pc and itunes on mac.
As for the solution- I will have a polk around inside the dac and try to follow the schematic, from what i've read on these forums alot of people have made changes to these dacs with success. So i'll do a bit 'o research too, i'll let you (warrior05) know if i find a solution. Meanwhile let us enjoy at -6dB.


edit. oh you meant the -6dB limiter plugin, i thought it made little difference

 

[sydneyaudio]

Quote:

Originally Posted by randyruiz I am very interested in your experience. I just got my HDAM's from burson(I think that is the spelling) and they sound great. very expansive sound with more blackground and resolution. However in the very upper registers I am hearing a bit of graininess and I am wondering if its the recording or the DAC. My next step is investigating the output cap upgrade but I am not sure if it is neccessary with the HDAM's in place. P.S. I have the upgraded version of the DAC-ah from DIY with the HDAMs.

There are a whole range of simple upgrades to this DAC which really improve sound quality. I ended up with the HDAMs after finding them cheap on EBAY, as well as being from a local supplier. Give it some time and it gets even better!

I think what everyone is complaining about - the graininess / distortion - is a function of the DAC it self? It does not affect 99% of CDs I listen to. The ones it does it seems to be only certatin tracks / sounds. Mainly multiple vocals, harmonising in the lower to mid treble range - but only certain tracks. I dont know if its a problem with poor quality recordings or a fault of the DAC itself. If the passive output mod fixes the distortion it would seem that the problem is actually the output stage of the DAC. The HDAMs have not solved the problem so I will try changing the caps and let people know the outcome.

 

[eladioc]

so... what do we do? Something must be wrong with me because i'm looking at an entech number cruncher (only ~$50!). Actually I'd really like to get my dac running at full potential. I'm at -13 db and I still hear some fuzziness but that could also be the fault of the source file. Does the passive mod fix the problem?

 

[d-cee]

because it was such a cheap DAC i sort of accepted its faults for what they were (i was semi-expecting graininess in top end from my reading - and it's just what i go)

i do tell you this though, the upper end harshness does get fixed with the passive mod and it helps things a lot. it's the only thing i've modded in the DAC and i feel it greatly improves the unit

 

[warrior05]

did some scouring of previous mod threads and now i've really got the itch to open my DAC up. my first thought is changing the output caps. i don't want to do the passive mod because that would render one of Pacific Valve's main mods useless which translates to a waste of money on my part.

so i first want to explore what adding or replacing pieces with upgraded parts will do. i want to do this a step at a time so any suggestions?

um... i guess i'm hijacking my own thread.

 

[regal]

For what its worth the DAC-AH fails the udial clipping test not matter what source I have tried. My guess is being filtterless the imaging above 22khz overloads the TDA1543's output.