[bpm2000]

I finally was able to hook up my stock Dac-AH for the first time and was floored by the distortion in any sort of loud/bassy passage. It is basically unlistenable in its current state.

I have tried reading the modding threads but I'm afraid all the talk is over my head. Which mod is the one that is supposed to remove the distortion? The bypass? The resistor change one?

I need to know what is the most minimally invasive mod to get rid of this distortion.

Or if anyone in Seattle wants to do it for me...

thx

 

[mrarroyo]

Something is not right, I have an un-moded Lite Dac-Ah and I love the way it sounds. Have you checked all your connections? Are the cables in good shape?

 

[d-cee]

strangely although my DAC-AH operates at 6v it never had the distortion problem. it had some grain in the top end but bass was deep and powerful

the resistor stacking is definitely the easiest, and was meant to remove the distortion

the passive bypass is a close second in ease, but deson't fix the distortion

do the resistor mod, it will clean up the distortion, and with luck you can do it all from the top of the board (no disassembly required, which i assure you with the DAC-AH is quite a feat)

edit: forgot to mention that it now runs at 8v, so i've done that mod as well, which is a bit trickier

 

[coemaudio]

Quote:

Originally Posted by bpm2000 /img/forum/go_quote.gif I finally was able to hook up my stock Dac-AH for the first time and was floored by the distortion in any sort of loud/bassy passage. It is basically unlistenable in its current state. I have tried reading the modding threads but I'm afraid all the talk is over my head. Which mod is the one that is supposed to remove the distortion? The bypass? The resistor change one? I need to know what is the most minimally invasive mod to get rid of this distortion. Or if anyone in Seattle wants to do it for me... thx

Hi bpm2000,

this does sound very strange, but what you can try do is fiddle around with the vref voltage. this is done by measuring the voltage between either pin6 or pin8 (of the TDA1543) and ground. adjust the trimpot until you get the correct voltage reading, I'm not sure what it is off my head sorry.

if you still get problems, then you may have to perform the resistor mod.

 

[bpm2000]

Well per mrarroyo's post - I swapped out the optical cable for a higher quality one I got in the mail today - it is actually listenable now and much of the distortion is gone! MUCH better (I am still a cable skeptic though, for non-optical connections )

The distortion is still present, although in a much smaller amount.

Bear with me here, I have NO IDEA what I am talking about:

Per Kim Hardee's thread about the circuitry error, Kim recommends adjusting the trimpot "until the outputs of the TDA1543s are at about 3.3V. That's it."

But it was suggested to do this in conjunction "the 470 ohm resistor across R35 and a 470 resistor across R36." Is it ok to fiddle with it WITHOUT doing the resistor additions?

The DAC in question is the one pictured under Kugino's post in this thread:
http://www.head-fi.org/forums/showth...dac+distortion

thx for the help

 

[Kim Hardee]

Quote:

Originally Posted by bpm2000 /img/forum/go_quote.gif But it was suggested to do this in conjunction "the 470 ohm resistor across R35 and a 470 resistor across R36." Is it ok to fiddle with it WITHOUT doing the resistor additions?

It's a good idea to adjust The DACs output voltage to about 3.3V, but you will still hear distortion on the loudest passages unless you also do the resistor mod.

 

[bpm2000]

Ok so I read over the thread one more time, and am picturing this:

Is that the correct way to put on the resistors? and is there a +/- or some sort of orientation I have to worry about?

My other question is the pin #'s of the chips, so I can measure the correct voltages.

And will any resistor work as long as I have the correct value? Any adv/disadv of certain brands/types?

thx for the help - i know these are rather elementary questions!

 

[Kim Hardee]

Quote:

Originally Posted by bpm2000 /img/forum/go_quote.gif Ok so I read over the thread one more time, and am picturing this: Is that the correct way to put on the resistors? and is there a +/- or some sort of orientation I have to worry about? My other question is the pin #'s of the chips, so I can measure the correct voltages. And will any resistor work as long as I have the correct value? Any adv/disadv of certain brands/types? thx for the help - i know these are rather elementary questions!

Your drawing is correct with respect to the resistors. I would suggest using at least 5% resistors (1% would be better). I originally use Radio Shack 1/4W 5% resistors and they sounded fine.
With respect to the DAC pinout: pin1 is as shown in your drawing and pin2 is next to (below)it, and pin8 is across from pin 1.
I hope this helps.

 

[pho_boi]

i biased by dac-ah differently to you guys i think...
i didn't use pin7 and pin5.

i followed the directions on this page:
http://www.dddac.de/ma_dac25e.htm

and it says to measure the voltage at pin6 and pin8!

 

[d-cee]

look at the data sheet here: http://www.datasheetcatalog.com/data.../TDA1543.shtml

has the pin layout on page 4

you need to measure pins 6 and 8 for output that's correct

 

[bpm2000]

I'm not sure where I even got 5 and 7. All these threads are starting to merge into one in my head - thx for the confirmation!