There is a known circuit error in the DAC-AH that causes the clipping problem. The fix was described in an old thread that you can find by searching for "DAC-AH error".

Quote: Originally Posted by vvs_75 This mode I think will be the last thing that I will do to the dac. As for now I am waiting for parts. Also look what I found at diyaudio forum! link: http://www.diyaudio.com/forums/showt...0&pagenumber=1 He installed a Hammond 193L in a...

Quote: Originally Posted by vvs_75 Hi! Don't have a practical experience but in theory if trimpot works just like regular pot we can adjust 3.3v on it, and then soldered out, measure the resistance on the ends and replace it with adequate regular thermo stable resistor. What do...

Quote: Originally Posted by 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...

Quote: Originally Posted by bpm2000 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...

Quote: Originally Posted by Halide Ok, after the lid was on for a while for it to heat up I adjusted it to around 3.3V. I have the 6V version (I saw LM7806 on the voltage regulator). I originally had 274 ohms at R35/R36 and I have the red PCB. I added the radio shack 470 ohm 1/2...

Quote: Originally Posted by Halide I just received a stock DAC-AH. I have 510 ohm 1/4w vishay/dale 2% resistors. Can I put these in parallel with R35/R36 with good results? Also, I need to get a decent multimeter from ratshack since this one I have is like 30 years old and doesn't...

Quote: Originally Posted by d-cee hi guys, great advice in this thread so far! my DAC-AH is now running at 8v but i am experiencing quite a bit of vref variation as well and was thinking of replacing my trimpot what value trimpot should i use? the trimpot shlomomofo cited above is...

Quote: Originally Posted by revo_909 i don't know if it makes any impact on sound, but definately there's less voltage drift on the DAC chip. with original trimpot i got around 0.5V variance with bourns trimpot it's around 0.1V variance. this is between the forst time i turned it on and...

Quote: Originally Posted by shlomomofo i notice that many of you have replaced the trimpot with a bourns model. what is the model number of the best part? it seems that there are a few over at digikey that might work... thanks I'm not sure why you would want to replace the...

Quote: Originally Posted by regal Why is everyone going to 150 ohms on the output resistance, I thought we wanted 170 ohm ? 174 ohms is theoretically correct if you assume the typical 2.3mA full scale DAC current in the data sheet and perfect Vref at 3.3V. However the DAC current...

Quote: Originally Posted by DDF BTW 2: its really heating up when left powered on. I'm going to investigate why, maybe something is oscilating. That's interesting about the RF pickup. Is that also with the passive bypass? The DAC-AH does get pretty hot, especially the LM7806...

Quote: Originally Posted by DDF Point of my post was to share my findings. This dac has been discussed for a long time and to my knowledge, this is the first evidence that its unstable and the o/p stage is flat out flawed. Thanks for the great review! Your discussion about the...

Quote: Originally Posted by pelayostyle Thats wierd. The mundorf caps sounded like they had more bass but less detail then the auricaps. Perhaps the added midrange clarity that the auricaps have masks the bass? Kim, if youd like i can let you borrow the mundorf caps so you can see...

Quote: Originally Posted by pelayostyle So ive been thinking......... I feel like i want more bass from my dac. I have read that the value of the output caps determines the bass rolloff. How do i find out what freq. my 2.2uf caps are rolling off at? I want something that will let more...

Quote: Originally Posted by izquierdaste I did adjust the trimpot and resitors with the active output. I still think there is more clarity with the bypass. I should note that I used auricaps for the bypass and have vitamin q for the opamp, so the auricaps probably have more clarity...

Quote: Originally Posted by DDF Hi Kim, Thanks for writing. Verified resistance, soldered to only one side of the board but measured impedance from Ic to connector ground (so pads are OK), and checked 6V. The pads and traces are probably OK, but I noticed that the through-holes...

Dave, Did you listen to the DAC before your mod? Is the weird sound only after the mod? It sounds from your description like the problem is in both channels. Can you confirm this? If you've got the right resistors and bias voltage it's hard to imagine what's wrong. As I suggested...

I'm glad I could help. I got some ideas from you and others in this forum too. I'm also very pleased with this DAC, especially after the mods. It's fun when you make some changes and can actually hear improvement. Even without any mods (except the resistor change) the DAC-AH is a great DAC.

Quote: Originally Posted by _Rand_ Thats just the thing, I can't get mine lower than about 3.85v. Not sure why unless I somehow damaged the pot. Almost forgot, I somehow managed to rip the LED wires off the board, where the hell were those soldered on? Its not a big deal really...

Quote: Originally Posted by fe3836 I gave the pointer to PV; their response was they couldn't fix it because Li Te didn't admit there was a problem I bought my second DAC-AH from www.diykits.com.hk and was told that even though Lite was told about the problem, they still wouldn't...

Quote: Originally Posted by pelayostyle Maybe i do need some type of load on the transformer on the 18v side because i keep blowing a fuse when i try to power it up I forgot to remind you in case you didn't notice that the IXYS bridge rectifier that you are now using has a...

Quote: Originally Posted by pelayostyle Maybe i do need some type of load on the transformer on the 18v side because i keep blowing a fuse when i try to power it up I followed your lead and removed all of the components on the opamp side of my board to make room for larger caps...

You probably don't need to add a heatsink since the bridge rectifier is able to handle 22 amps. That spec usually assumes that a heatsink is used, but since the DACs are drawing less than an amp, it's almost certainly OK without a heatsink. Besides, there is a sort of built-in heatsink -- the...

I'm so sorry. I meant to ask you to measure the resistance between pins 6 and 8. I was thinking of the wrong pinout. You should get about 300 ohms since you changed the resistors to 150 ohms.