Head-Fi.org › Forums › Equipment Forums › Dedicated Source Components › Circuit error in Lite DAC-AH: Easy fix
New Posts  All Forums:Forum Nav:

Circuit error in Lite DAC-AH: Easy fix - Page 13

post #181 of 209
So I kept it at 6V and then replaced the resistors with 150ohm then adjusted to 3.3 and I still think I'm clipping. Can I turn it down to get away from that? Its only on some loud passages but its annoying cause it sounds sooooo nice when it doesn't clip.

BTW - Just installed a Blue Jeans 1694a digital cable and its ridiculous! Granted I was using a generic belden coax for the time being but replacing it was similar to how a dirty car looks after a good detail. Still the same car but just looks so fresh!

Gear mentioned in this thread:

post #182 of 209
Quote:
Originally Posted by recca View Post
So I kept it at 6V and then replaced the resistors with 150ohm then adjusted to 3.3 and I still think I'm clipping. Can I turn it down to get away from that? Its only on some loud passages but its annoying cause it sounds sooooo nice when it doesn't clip.

BTW - Just installed a Blue Jeans 1694a digital cable and its ridiculous! Granted I was using a generic belden coax for the time being but replacing it was similar to how a dirty car looks after a good detail. Still the same car but just looks so fresh!
recca, I had to wait a while for my chips to heat up before adjusting the voltage. Sometimes I would adjust the voltage one way, then go WTF it went the OTHER direction?! This was because between the time I was testing it with the meter and the time it took me to adjust it (somtimes it took a while) and then measure it again, the unit heated up. So, leave it on for 10-15 minutes, see what your voltages are at, then adjust as necessary.
post #183 of 209
Quote:
Originally Posted by Kim Hardee View Post
Regal,

Yeah, just measure the DC voltage (with no sound input) on the top of C38 and C39. That's also AOR and AOL of the DACs. 3.3V will put the outputs in the "sweet spot" which is halfway between 6V-1.2V and 1.8V (the max spec output swing). You will probably see a slight difference between the left and right channels. Just set the average to 3.3V. If you want more margin use 330 ohm resistors instead of 470 ohms across R35 and R36. This will give an effective resistance of about 150 ohms, but will decrease the output level slightly.

I wasn't so happy with the sound of this DAC until I made this change. Good luck.
I have read this thread and still quite cant figure out where to take teh voltage readings from. Any photos with it all pointed out?
post #184 of 209
Pins 5 and 7 on any of the chips that are in the center of the board (the 8 that are in a line).

OO
OX
OO
OX

The X's is where you measure.

You can also measure between the bottom corner of the chip and the left side of either R35 or R36.
post #185 of 209
Thank you!
post #186 of 209

After adjusting lite dac ah resistors, no bass response

Hoping some of the experts on this can help.

I just bought a lite dac ah with the following mods already done:
Op-amp output stage gone, direct coupled from the dac chips to the RCA's with Aerovox 4UF motor run caps.
Caps c1 and c2 on the digital input have been upgraded to NOS PIO caps.
All powers supply diodes have been replaced with Ultra Fast diodes. Heatsinks have been added to the 8 dac chips.

The sound of the unit was very nice before the mod. I attempted. Following this thread, I determined that I had the 6 volt supply, and the 260 ohm resistors. I replaced the resistors with 169 ohm (measured) resistors (actually, 3 510 ohm resistors in parallel).
I adjusted output voltage to 3.3 volts by measuring across these resistors, and then took a listen.

Everything sounds very nice, except that the bass is gone. Prior to the mod. , I would say that the bass was perhaps overdone if anything, now I have very little bass, it does not sound very good.

Any ideas what I could have srcrewed up given this description?

I will say that I have triple checked the resistance values, they are both 169 ohm. Thoughts?
post #187 of 209
Is there still a circuit error almost 4 years later or have they updated it?
post #188 of 209
Quote:
Originally Posted by Netdewt View Post
Is there still a circuit error almost 4 years later or have they updated it?
I just received mine today. I'm running it in currently, but I'll check it this weekend (likely while modding it to passive). Anyone have a good suggestion on an initial set of output caps? I see lots of recommendations in this thread, so I'm not sure where to start. I've only got 4 hours on it so far, but it sounds a bit muddy at this point.

--Matt
post #189 of 209
There's definitely still a circuit error on my brand new one. I see 6.04v at both points and have 274 ohm resistors at r35 and r36. Fortunately, the muddiness seems to have improved quite a lot after 28 hours of run-in.

I've ordered 150ohm Takman Resistors for the power mod and Auricap 2.2 uf caps and 100 ohm Kiwame resistors for the passive mod. I'm hoping I made good choices, especially since the caps are 20 apiece.

Am I correct in understanding that everything on the op amp side of the pcb can be removed when running passive? If so, is the existing ground for the line out jacks still usable or do I need a new source?

--Matt
post #190 of 209
The more I read through this marathon thread, the more I am worried that passive may not be the best idea while maintaining the 6v input. There seems to be a (minority) opinion that going passive isn't the best as well. Am I likely to end up with a lower quality source after making the resistor fix and passive mod?

-Matt
post #191 of 209

hi guys sorry to be bringing up the old thread but i'm planning to mod this dac which i haven't yet purchased. quick question- what values are the blue bypass caps that come after the dac chips? i'm assuming the little ones are .1uf but the bigger bros?

post #192 of 209

Just wondering... C38 and C39 are 0,001uF film caps (102J means that) but what's their voltage? 630V as written on them?

 

Are they really necessary? With the passive mod we've bypassed the output stage altogether.

post #193 of 209

Just wondering if this thread is still alive? 

 

I just have 2 questions about replacing the caps C5,6,7,8,12,13,14,15 in the Lite Dac. I read more than once in the thread that the caps are being replaced with ".1uf 63V Polypropylene Film caps". But what does .1uf mean?

 

Does it mean the caps C5,6,7,8,12,13,14,15 are 0.1uf (100nf)? or 1uf (1000nf)? And the voltage is 63VDC? 

 

And I also have the same question as Donluca.  Are the caps C38 and C39 different caps? Are they 0,001uf (1nf) and 630VDC. I'm just wondering about the voltage because the caps of C5 etc. are 63VDC.

 

By the way this is still a good thread! I found a lot of information about the mods and tweaks. Hopefully somebody will answer my question!! Because I want to take the DAC apart and tweak it.


Edited by Bronco2011 - 10/8/13 at 10:58am
post #194 of 209

It's alive again now :D

 

Yes the .1uF are 0.1uF (100nF) caps - marked '104' on the silkscreen which you'll see when you pull them out.

 

Yes C38,39 are different caps - they are filtering the audio (across I/V resistors rather than PSU decoupling).

 

The voltage of all these caps hardly matters because the supply here is 5/6V (or 8V if you've modded the regs).

 

I agree this is a great DAC for modding, I've modded quote a few. PCB track mods are my forte though rather than cap upgrades - its amazing how much better sound can be had from this with no cap upgrades at all....

post #195 of 209

@Sapietniam

Many thanks for your answers! I must honestly say that I’m a newby. 

 

I already did some modding on the Dac. I chanced the value of the R36/R35 resistor to 240 ohm and put in 2 opamp sockets  because I’m using 2 Dexa NewClassD discrete opamps. Plus I chanced the output caps to LeClanché PPM MKP 3,3uf. I didn’t change the regs to 8V. I also tried the passive mod. But it is not my thing. The sound of the Dac is less dynamic. But that is my personal opinion. 

 

I just ordered a second Lite Dac. This time only a assembled PCB  board and also ordered a large chassis (makes working on the Dac easier). With the second Dac I want to do the same mods as I’ve done on the first one.

But also I want to the change the other caps, built in an additional pair of RCA output jacks (output for the passive mod) and change the power supply. 

 

I’m thinking about using toroidal transformer. But is that even possible? Is the dac really using 18V, 9.5V and 10.5V (3 different voltages)? Does it mean that the PCB needs 2 toroidal transformers to power everything?

 

Did you ever mod the Power supply on the lite Dac’s? And do you have suggestions?

I never came across somebody that did mods on PCB tracks. Sounds like mods for advanced techies!

 

Thanks again for your help. Hopefully the PCB board will arrive soon so that I can start modding. 
I still very pleased with my first modded Lite Dac. It sounds really great and hopefully the second one will even sound better!

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Dedicated Source Components

Gear mentioned in this thread:

Head-Fi.org › Forums › Equipment Forums › Dedicated Source Components › Circuit error in Lite DAC-AH: Easy fix