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Chameleon DAC listening and modifications - Page 73

post #1081 of 1144

Hi skibum It took about 6 weeks for my TXs to arrive. I had a pair of Sonicap 4.7uf in it...so big change. While I was enjoying the sound with the caps, the TXs opened up the stage in all directions. More space and air, smoother top end, bass about the same, detail improved but not etched, more relaxed sound. Very easy to listen to and not broken in yet.

 

One problem I did encounter with the TXs is that now on certain discs with more output, the dac is clipping. I had not checked the voltage to the dac because everything was ok. Did so last night and found it to be 7.71v. This is with 175R I/V. I upped it to 8v and haven't had a chance to check it today. I'll let you know when I do.

post #1082 of 1144

Well, still clips at 8v so I lowered it to 7.6v and still clips. I know there is a formula for this somewhere on this thread so I guess I'll go find it and check back after I futz some more.

post #1083 of 1144

In post #503 rhodes54 says clipping issue can't be completely solved. I've tried 6.9 to 8.2v and still I have clipping on certain discs. I just didn't notice it with caps in there. I think I may pull the TXs and put the caps back in just to see. I know there probably aren't many watching this thread anymore but if someone reads this and has an idea, I would sure appreciate the help.

post #1084 of 1144
Thread Starter 

Not sure if this will make the difference but early on i did a mod to clear up some distortion.

Dropping the resistance on input to the dac board to 1.2k using 2k + 3.3k on the board I had.

ASRCmod.jpg

post #1085 of 1144

Thanks, Pat. My dac came with 680R in those two spots.

post #1086 of 1144

Quote:

Originally Posted by Chris Adams View Post

OK, I have a problem and I know there are a couple others with trannys...Newk Yuler, yes?


I have a pair of steel core same as Pat's.  I bought a metal project box to house/shield them and a proper interconnect from Blue Jeans Cable to cut and use on either side of the transformers.  I changed my mind and decided to hard wire them into my modded Valab.  Kept up with this Chameleon thread while waiting to buy in, anticipating great things comparable to the Valab threads but Chameleon apparently hasn't taken off like the Valab.  (Although Steve Nugent of Empirical Audio has suggested it in the CA forum recently as he did the Valab a couple of years ago which did a lot for the Valab.  Unfortunately he keeps misspelling "Chameleon" which makes Googling his comments less accurate.)  That's not to say the regulars here haven't done great things with Chameleon because they certainly have.  Chameleon's relatively low popularity (sales) means development of additional daughter cards is unlikely and that's a huge shame.  About the time it became apparent Chameleon was going to stall I discovered this combo and a week later bought into that instead (turned out to be a great decision).  That set replaced the Valab and the preamp I was using.  I haven't done anything with the Cinemags but I've been thinking lately about finishing the project box.

 

I surely mean no disrespect to anyone pursuing Chameleon and mods for it.  Is there any news and/or developments for Chameleon from Teradak?

 

When I purchased the Cinemags the gentleman running Cinemag was in the midst of a terrible family issue that caused business fulfillment delays.  Coupled with intermittent production runs based on product demand caused a pretty big span of time between ordering and arrival.  It's possible he's still dealing with the same family issue (his wife is terminally ill).  If he is, it may be worse now than it was some months ago when I ordered.
 


Edited by Newk Yuler - 9/8/10 at 4:37pm
post #1087 of 1144

Newk Yuler, Thanks for the reply. That DAC-19 DSP looks interesting. I'm going to try and resolve the issue I have with the Chameleon because I like the sound with the TXs in it. I think perhaps I need to change my I/V value. I wrote to Michael and I'll wait to see what he has to say.

post #1088 of 1144

Nothing from Michael yet. Can anyone with TXs tell me what you're using for I/V. I tried 175R, 185R and 150R (came with 160R) and the distortion with certain high gain CDs remains the same. I'm about to pull the TXs and reinstall the caps.

post #1089 of 1144
Thread Starter 

Did you remove the filter?

And are you coming directly off the DACs instead of off the PCB?

I know that's an ugly picture but it shows the missing filter and the silver wire go over to each DAC fore output ...

 

 

chameleon.jpg

post #1090 of 1144

Filter was the first thing out when I got it. Connected directly to dac pin 8 for R and 6 for L. Each primary + and - to a separate 175R to ground. Secondaries to RCAs. Low output discs sound great, high outputnot so good, clip like crazy. Put the caps back in and I can only catch a bit of a clip on the highest output CDs. All the rest are fine.

post #1091 of 1144

well did you figure out if the clipping is from the large current output from multiple dacs being too hot, or the IV resistor being too low, so not converting all the current to voltage, thus clipping from output being too low? being that you are using transformers, remember that if using resistive IV on the primary side, the reflected ratio of the TX means that the reflected output impedance may be even higher than that, this may not be at all good for interfacing with the next stage (pre or amp?) input impedance. I would say that since you still get clipping with the caps, that its mostly to do with the current being too high and this is most likely saturating the TX as well, how about DC offset? anyone measured that yet? I have asked this before when someone has mentioned clipping in here and it seems nobody has measured it still. I would imagine its pretty large  what with being no servo, no caps, no anything to temper what is probably considerable single ended DC current and voltage.

post #1092 of 1144

qusp, you got me thinking, just what I needed. I have very little knowledge of electrical circuits but can follow directions well. Let me clarify for myself what you said. The I/V resistance may be too low so not converting all the current to voltage. I will try a higher value...any idea or formula I should use? I tried 185R but didn't improve much if at all. The TXs are 1:1 and input impedance is 600ohms. The impedance of my buffer is 20k. I did not measure DC offset with TXs and will do so. I measured it a while back with the caps and it was a .0X figure, don't remember exactly what. I'll check it again. I was also told by the fellow at CineMag, there's no way I'll saturate the TXs. Thanks for checking in!

post #1093 of 1144

If anything this thread may well be doing its bit to discourage someone like myself that may or may not carry out mods from actually buying this thing.  There has been little analysis of this unit, purchased as is, as compared directly to competitors at its price point.  If there is, I may have missed it with all the "fault rectifications" being carried out with this unit. 

 

The thought of an inexpensive R2R DAC design that competes well in the under 1k category - appeals to me, unfortunately for the Chameleon this category seems locked by Audio GD via plenty of users able to contrast it with competing products.


Edited by SP Wild - 9/12/10 at 8:43am
post #1094 of 1144

SP Wild, Stock unit works sounds terrific, no mods necessary...just 200-400 hours of break in.

 

So I pulled the caps and FIM and reinstalled. But I ran the output of the caps back past the 47k resistor because even with signal cables connected to amp, the caps took forever to settle down when I checked DC offset. Offset is now about 1mV on each channel. I also ran the grounds of the rca jacks back to the board. No clipping. I may try TXs again but I think I'll just listen for a bit.

post #1095 of 1144

 

 

Quote:

qusp, you got me thinking, just what I needed. I have very little knowledge of electrical circuits but can follow directions well. Let me clarify for myself what you said. The I/V resistance may be too low so not converting all the current to voltage. I will try a higher value...any idea or formula I should use? I tried 185R but didn't improve much if at all. The TXs are 1:1 and input impedance is 600ohms. The impedance of my buffer is 20k. I did not measure DC offset with TXs and will do so. I measured it a while back with the caps and it was a .0X figure, don't remember exactly what. I'll check it again. I was also told by the fellow at CineMag, there's no way I'll saturate the TXs. Thanks for checking in!

 

 

 

that was the idea mate, I dont have specific experience with the chameleon, but with so many dacs in parallel and yours not being an isolated case; good chance the output is simply too hot. I mentioned the possibility of the R being too low and not converting all I to V as a matter of completeness, its unlikely, but one possibility. I think the output is rather more likely too hot. so we can probably rule that out. i've never heard of a TX that cannot be saturated, but lets put that aside for now. where is your buffer? thats pretty low input impedance for a buffer, you have a pot on the input yes? normally a buffer would have much higher input Z than that, thats kinda the point, very high input Z and very low output Z. so the TX is a line trannie, cool at least there is nothing to complicate the gain as power in should be power out. I would be tempted to house the TX and the buffer in the same enclosure, or lose the TX and replace with the buffer. you have the buffer to drive long cables? or is part of a volume control/pre? is the buffer unity gain? good chance that its not quite unity gain and so therefore is adding a touch of current and making it too hot. I think the best way to go here is to attenuate the output and since you have a buffer, provided the input to the buffer isnt clipping, you should be able to modify the gain so it is lower than unity and therefore presents a more suitable signal strength to the amp. can you download or generate a full strength sine wave file and measure the output voltage it produces? if you cant google one, let me know and i'll render one for you and email it to you, or perhaps post it in this thread as it seems you arent the only one. 

 

 

@ SP wild

 

errmm this is the mod thread, most faults in here are caused by the user fooling around and thats kinda the point of this dac. aud-gd on the other hand is for those who want a prepackaged sound and accept somebody elses idea of what is best for that. not really a valid comparison imo. people mostly buy the chameleon to get their hands dirty and good luck finding 2 units in this thread that are the same, so comparisons with other standard and static designs are difficult and kinda meaningless. I dont own the chameleon, but I would buy it well before the coca-cola over at aud-gd

 

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