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Chameleon DAC listening and modifications - Page 34

post #496 of 1144
Driguy, Thanks for your insights.
Yes I will start with these easy mods. first.
For point 1, what do you think about this combination: 4.7 uF V-cap OIMP to be bypassed with V-cap TFTF 0.022 uF? I got this recommendation from another thread for caps comparision topic.
Regarding point 5, any recommended film caps on top of BK FK?
I have lowered the voltage to 7 VDC and the sound is a little more relax, clearer but the PS case is still quite warm-hot. should I revert to blue wire?
The R106 75Ohms is for impedance adaptation, will there be any gain in SQ if it is removed?
Thanks.

Quote:
Originally Posted by driguy View Post
It is OK to measure the voltages the way you are so long as the DAC section is hooked up. This gives the regulators a path to bleed off current and voltage. If you measure it without the DAC connected your readings will suck.
I measure 0.00 volts ripple from both rails. What you are reading is not too bad but a decent size cap at the load will probably get rid of the small amount of ripple that you do have. If you do my FRM with a decent size cap you will gain a lot in sound and will probably measure no ripple as well. I would use a 10uF cap or better here and a film cap is best. You can put the same on the digital side if you want to and if room permits.
I find no advantage to staying at 8 volts to the chips. As per a previous post 7.5 volts or even 7.0 volts is better. The max rating for those chips is 8.0 volts.
Don't worry about the 100mV drop. You cannot apply voltage across a complete circuit and not get a voltage drop over any part of it with resistance. The connectors, wire and circuit card traces have resistance. You are measuring a 1.2% drop. If you have not noticed it yet most of the posters are pretty obsessive here and most other forums. If you are just starting out it is a very bad cycle to fall into without some decent electrical background. Keep your mods simple! Inexperience in soldering (especially on the digital side of things) has led to more problems than anything I have seen in all my years messing with this stuff and at my old job. This Chameleon DAC sounds so good out of the box that you can get sound that is incredible with just a mod or two. If you read the whole forum and the other Valab threads start counting how many folks encounter problems only AFTER they start messing with their units. I would recommend the following easy to do mods as they can be done by almost anyone with the smallest chance of screwing things up.
1. Changing output caps. Try not to use caps that require bypassing to sound good. The Wima's are exceptional as they are. Some decent money has to be spent (IMO) to get better sound.
2. Film Reservoir Mod. Excellent bang for the buck if you use the Wima's that you may have already replaced.
3. Replace the I/V resistors! Very cheap and easy to do. Caddock's or the Texas Instruments are excellent. Huge improvement.
4. Nuke the filter cap. Zero cost and most beneficial. Just lift one leg if you want to hear the difference. After that you can just cut it out.
5. Add to or replace the 10uF caps at each DAC chip. Film caps or Blackgates are best.
If you delve into more complex mods without doing these first you are going about things backwards. After these mods it is more about much smaller differences for much more risk.

Your 0.1 Vishay caps will probably be OK on the digital side as the current draw is low and more consistent but it will not be sufficient as a FRM. It may reduce ripple but it will not accomplish what it mod is designed to do.
post #497 of 1144

Clipping problems

Hey gang, I noticed recently, listening to Sarah Mclachlan's Angel, I had some fairly nasty clipping issues. Oddly enough they where not too audible in most of my songs, but this one made it quite clear.

I was able to get rid of the cliping by reducing the windows volume to 75%. Im assuming this started when I replaced the passive i/v resisters with 175r. Now im wondering if this is the correct value. I can't seem to get rid of the clipping via the trim pot, which has always worked before. It's rather annoying as the texas resisters are quite expensive, and it looks like 175 may be the wrong value. It also could be that im runing the voltage of the chips at 7v. I don't know how to do the math to figure out the correct passive i/v values. Some of the forumula's where posted earlier, and im abit ashamed to admit, I don't know how to use them. Math was never my strong suit.

Just a heads up, to those that are replacing the iv resisters, make sure to get the right value.

Im also having the issue with high pitch whine sound out of the optical/coax again. I thought I solved this, but when I got my new Digital input board the issue has came back. I think it may be the connection, but im not 100% sure. I tinned all the leads to the board slightly, the first time I did this it was a little bit sloppy and the connection was very tight, when I powered the dac up I heard a slight scratching sound momentarily, and then everything cleared up and worked nicely, no noise. I then removed the card again and cleaned up the tinned leads, and the noise came back yet again. I've also put some Arctic silver thermal compound on the leads to no effect. This compound is a heatsink compound that has silver in it, it's supposed to be electrically conductive, but im not sure how much, as this is not the intended purpose of this grease. Im going to the electronics store later to pick up something called "Carbon conductive grease" hopefully this will clear up my issue, as I don't really know where to go from here other then removing the plastic socket and directly soldering the board in place. It looks like it would be pretty hard to remove though.
post #498 of 1144
MikeW,
Did you still have yellow connected or you revert back to blue wire?
Have you had a chance to make measurements with the lid closed when connecting yellow wire?
I seem to have issue on sound...Iget feeling that the sound from my unit is slow like pedestrian!!! what do we do to improve this? I have both ASR and re-clock boards installed.
Thanks.
post #499 of 1144
I don't think it's related to the PSU. The blue wire is connected, and my issues happen regardless of yellow vs blue. But the yellow wire simply heats everything up to much to be practical in my case.

I think you are hearing the effects of unburned in unit. That is typical. Give it 250-300 hrs and things will improve alot.
post #500 of 1144
Thanks.
Did you try floating the SPDIF inputs and hear any improved SQ in comparing with direct SPDIF input?
post #501 of 1144
I connect the spdif ground straight to the pulse transformer, and leave the primary alone. I did notice an improvement doing this. Some connect both wire directly to the pulse transformer, and this is probably the best approach if you know for sure your source has no dc offset.
post #502 of 1144
Well, spent awhile working on the dac, trying to get the high pitch whine solved. Unfortunately had no luck. I tried tinning all the leads to the digital input board, it fits very tight. Still does not work. I can rule out everything after the digital input board I think.. as USB works perfect, and it go's thru the dac board output stage etc. I have 2 boards and they both have this same behavior, my old board will actually stop doing it after a little while, but the new fully working board i've got (USB does not work on old board) always whines. With nothing connected to it (no input) it whines, with optical and coax. As soon as usb is plugged in the whine instantly stops and everything is good. The only difference between my 2 input boards is one is half functional and the other works completely. I even replaced the pulse transformer coupling cap with a .1uf wima so that both boards are identical. I guess the power supply could still be a possible problem. I also applied alot of arctic silver thermal grease to the socket, as it's the only thing I have availible. it is 88% silver. Not quite as good as what Pat was using, but pretty close. Im pretty fed up with troubleshooting it though.
post #503 of 1144
Quote:
Originally Posted by MikeW View Post
Hey gang, I noticed recently, listening to Sarah Mclachlan's Angel, I had some fairly nasty clipping issues. Oddly enough they where not too audible in most of my songs, but this one made it quite clear.
Hi Mike,

The clipping issue can't be completely solved, even when the exact value of the I/V resistor is chosen.
I have a few cd's where clipping is audible. Both the Valab and Chameleon have the same amount of clipping.

I got rid of the problem by ripping the clipping cd's to my harddrive, lower the volume with a few db's and then burn them onto a cdr again.
post #504 of 1144
but when i listen to the same song on the valab 3.0 with 330r PRP resisters and trim pot adjusted via the same methods I don't hear any clipping in that song. Everything else is stock, on the 3.0, just swaped resisters for 330r prp's.

Im seriously considering ripping that daughter card connector out and soldering the digital input board direct. Then at least, I know 100% that my problem is, or is not related to the connection.

Can someone explain a little better how these daughter cards work anyways? It looks like it has 2 pins that have the exact same data? Is it redundant? If so, it seems like it would be hard to get a bad connection, because you'd have to get 2 of them.. ?

Can I "bypass" these daughter card connections by soldering a wire directly to the "leg" on the digital input board, and follow the trace and connect the wire straight to the corresponding location on the pcb? (data, lclk, rclk bclk for example)
post #505 of 1144
Thread Starter 

before soldering anything for good

try conductive grease.
try conductive grease.
try conductive grease.
try conductive grease.
try conductive grease.
try conductive grease.
post #506 of 1144
Thread Starter 

for your consideration

A test CD ...
Review at: TNT

post #507 of 1144
Well pat, I did try the Arctic silver with no luck. It's not quite up to par with what you used, but its' probably close. (88% silver content by weight). That grease is quite expensive.

I put my old board with broke usb back in for now. It's silent with coax/optical. It's a desperate solution. Im all out of idea's.

I also solved my clipping issue, which kind of makes the yellow wire needed, oh well. I've found that I must run the dac chips at at least 7.8 volts for the clipping to go away with the 175r resisters, and 100% output volume.

Actually it might be a little lower then that, I tried to get it to not clip at 7.5 volts and I could get up to 90% output volume but at 100% would still clip. Then i went straight to 7.85 volts and the clipping disappeared. I have not tested between 7.5 and 7.8. So it may be a little less.

Unrelated, but it also occurred to me to take the output from the digital input cap straight to the pulse transformer leg. This is akin to the direct input mod, not quite, but it works better then following the pcb trace.
post #508 of 1144
Quote:
Originally Posted by MikeW View Post
Well pat, I did try the Arctic silver with no luck. It's not quite up to par with what you used, but its' probably close. (88% silver content by weight). That grease is quite expensive.
Arctic Silver as in Arctic Silver thermal compound? That stuff is non-conductive. In fact, that's what you should use on the DAC chips to help transfer heat to the case.

Arctic Silver Incorporated - Arctic Silver 5
post #509 of 1144
Thread Starter 

indeed

Arctic Silver is what I am using on my DACs on my VALAB. It is slightly conductive and there is a warning to keep it from hitting traces, etc.

What you want to do is increase the conductivity going on around the open space where the pins do not touch or may make poor contact.

For that you need conductive grease, or solder the board, which is the best thing to do.
post #510 of 1144
Damn, I thought AS5 was more conductive then that. Yeah I know what it's intended purpose is, i've used it for years on CPU's. It's supposed to be 88% silver by weight, I assumed it would be more conductive then they make it out to be. Guess i'll have to buy some of that fancy silver goo. I saw a different brand on Mouser, MG Chemicals, for 15.95 instead.

Im playing with the yellow wire mod again, I put the unit upside down and got some larger feet for it, and put 1/4in nylon spaces on the rear to make an air gap. I think i'll buy a heatsink for it. I think the heatsink would be alot more effective if the unit was upside down and heatsink placed directly on the transistors pat.

Does anyone know the thread size for the allen head chasis screws? I need some longer ones. I tried to find some at lowes but it was a no go.

Edit: it's an "M3" size screw, 3mm. A little hard to find, but I did find some at a local hardware store today.
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