[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 a 1k ohm trimpot, like which one would give me most stability/precision

because it dont know if it's just the hot weather in australia, but the longer i leave my DAC on the lower the voltages drop, by 0.1-0.2 volts

I'm thinking one of these will work:

http://www.jaycar.com.au/productResu...Min=&priceMax=

thanks a lot!

 

[Kim Hardee]

Quote:

Originally Posted by d-cee /img/forum/go_quote.gif 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 a 1k ohm trimpot, like which one would give me most stability/precision because it dont know if it's just the hot weather in australia, but the longer i leave my DAC on the lower the voltages drop, by 0.1-0.2 volts I'm thinking one of these will work: http://www.jaycar.com.au/productResu...Min=&priceMax= thanks a lot!

I think a 0.2V drift should not be a problem, but if you want to replace the trimpot I would suggest somehow repositioning it further away from the DACs to reduce temperature effects. I'm getting about 0.5V drift with my DAC-AH so I'm interested if there is a trimpot that can reduce the drift compared to the stock one.

 

[ak622]

Wow I've been trying to understand what the mods are but I really have no electronic background at all and don't know where to start... Like mrarroyo, if anyone is willing to help out another head-fi member with these upgrades please PM me and maybe we can work something out??

Thanks!

 

[revo_909]

Quote:

Originally Posted by d-cee /img/forum/go_quote.gif 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 a 1k ohm trimpot, like which one would give me most stability/precision because it dont know if it's just the hot weather in australia, but the longer i leave my DAC on the lower the voltages drop, by 0.1-0.2 volts I'm thinking one of these will work: http://www.jaycar.com.au/productResu...Min=&priceMax= thanks a lot!

the jaycar stuff is probably the same quality as the one on your DAC. you can get bourns from RS components and they are so much better.

 

[d-cee]

Quote:

Originally Posted by Kim Hardee /img/forum/go_quote.gif I think a 0.2V drift should not be a problem, but if you want to replace the trimpot I would suggest somehow repositioning it further away from the DACs to reduce temperature effects. I'm getting about 0.5V drift with my DAC-AH so I'm interested if there is a trimpot that can reduce the drift compared to the stock one.

that's what i was suspecting, could anyone confirm whether temperature affects the trimpot's ability to hold its resistance?
Quote:

Originally Posted by revo_909 /img/forum/go_quote.gif the jaycar stuff is probably the same quality as the one on your DAC. you can get bourns from RS components and they are so much better.

thanks for that mate! the RS components pickup point in NSW is very close to me, i might just grab one for the heck of it

of the ones in stock, i'm not sure what the differences are and which would be better for this application:

http://www.rsaustralia.com/cgi-bin/b...eID=aunetscape

http://www.rsaustralia.com/cgi-bin/b...eID=aunetscape

http://www.rsaustralia.com/cgi-bin/b...eID=aunetscape

they're all the same cost and although price isn't too much of a concern just wondering what the differences if any are?

 

[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 appear to be working correctly.

[edit] bought 470 ohm 1/2 watt resistors and installed them (really difficult with flat tip soldering iron!)

also, i have like no idea what im doing, but i turned the trimpot thing until the voltage across R35 read 3.85V is that good?

 

[Kim Hardee]

Quote:

Originally Posted by Halide /img/forum/go_quote.gif 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 appear to be working correctly. [edit] bought 470 ohm 1/2 watt resistors and installed them (really difficult with flat tip soldering iron!) also, i have like no idea what im doing, but i turned the trimpot thing until the voltage across R35 read 3.85V is that good?

Adjust for about 3.3V after waiting a while for heat to built up (about 10 minutes with top on). That should work fine.

 

[Halide]

Quote:

Originally Posted by Kim Hardee /img/forum/go_quote.gif Adjust for about 3.3V after waiting a while for heat to built up (about 10 minutes with top on). That should work fine.

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 watts, which measured to be around 460 ohms, in parallel with R35/R36.

Let me first state that I'm not using headphones... I'm using 2 bookshelf type speakers spaced about 5-6 feet apart and then I sit about 6 feet from each speaker in the center.

Both before the mod and after the mod, the DAC-AH seems to sound a little "hollow". It's hard to describe. Either the stereo separation is messed up somehow (too wide?) or my speaker placement is bad or something. I originally was using an M-Audio Revolution 7.1 soundcard for my source and I think I might even say the DAC-AH isn't noticeably better--maybe worse (regarding the hollow sound)? Maybe I need to let it burn in some more? Anybody have any suggestions please?

 

[Kim Hardee]

Quote:

Originally Posted by Halide /img/forum/go_quote.gif 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 watts, which measured to be around 460 ohms, in parallel with R35/R36. Let me first state that I'm not using headphones... I'm using 2 bookshelf type speakers spaced about 5-6 feet apart and then I sit about 6 feet from each speaker in the center. Both before the mod and after the mod, the DAC-AH seems to sound a little "hollow". It's hard to describe. Either the stereo separation is messed up somehow (too wide?) or my speaker placement is bad or something. I originally was using an M-Audio Revolution 7.1 soundcard for my source and I think I might even say the DAC-AH isn't noticeably better--maybe worse (regarding the hollow sound)? Maybe I need to let it burn in some more? Anybody have any suggestions please?

Depending on the quality of your system you may or may not hear a difference. I think the DAC-AH sounds pretty good stock but much better with the passive bypass. I can definitely hear a difference with my World Audio Design HD83 headphone amp and HD600s with Cardas cable, but I have no idea if you would hear a difference on your system.

 

[Halide]

So the stock DAC-AH is supposed to sound better than an M-Audio revolution (you would think since it is ~$85 sound card)? Maybe my system isn't "good" enough... I don't know... I have a $400 stereo amp (rotel rb-1050) and I DIY'd some 2-way speakers which cost me about $400 including all parts. I would hope that I could notice a difference, but I guess either I don't know what to listen for or my system isn't revealing enough.

 

[vvs_75]

Quote:

Originally Posted by Kim Hardee /img/forum/go_quote.gif Thanks for the info. That's really interesting. I had assumed that the voltage drift was mainly due to the DACs heating up. You're describing about a 12% change in the resistance of the stock trimpot as it heats up, and almost no change in the DAC ouput current as they heat up. I agree that if a new trimpot can reduce the drift by a factor of 5 then it's well worth the change. I'd also be interested in the part number of your replacement trimpot. Maybe you could post it.

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 you think guys?

 

[Kim Hardee]

Quote:

Originally Posted by vvs_75 /img/forum/go_quote.gif 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 you think guys?

Sounds OK to me. Just be sure to wait a while for the temperature to stabilize.

 

[vvs_75]

Quote:

Originally Posted by Kim Hardee /img/forum/go_quote.gif Sounds OK to me. Just be sure to wait a while for the temperature to stabilize.

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 output stage!

Very interesting! What do you think?

And anothe person said that he tried other modes from our forum and the results not as good as with 193L.

 

[Kim Hardee]

Quote:

Originally Posted by vvs_75 /img/forum/go_quote.gif 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 output stage! Very interesting! What do you think? And anothe person said that he tried other modes from our forum and the results not as good as with 193L.

That 193L is actually across the power mains to filter the AC line noise. Seems like a power conditioner would do the same thing.

 

[danmagicman7]

Completed this mod!

I was really pissed off that I would hear distortion on some songs...I was listening to Regina Spektor song, and the bass was distorting her voice. I was really angry! I was like...this should not be happening.

Then, completed soldering the 470 ohm resistors on R35 and R36, and voila, no distortion. Happy camper.

This was my first little adventure into modding and soldering, so I figure I would post pics.

I melted the blue "thing" or whatever that is next to one of the resistors, but it is but a flesh wound. It makes my DAC my DAC

.

Before:

After:

I ended up buying a new soldering iron to do this mod. For those of you that are timid to complete this, it was pretty easy, and I just practiced soldering on an old network card I had laying around the house.

BTW, if anyone wants to see my review of the Lite-DAC (pre-mod) see this thread: http://www.head-fi.org/forums/f4/sen...oshoot-389313/