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Chameleon DAC listening and modifications - Page 36

post #526 of 1144

Is it really "hot"?

Quote:
Originally Posted by PatOMalley View Post
I put those caps on the DACs on the VALAB but forgot or was not really sure of their impact as I did it right away. But after all the mods on the Chameleon it really shows. Tons of bass. Better image separation. Tons of bass.

I used 47uF Nichicon Fine Gold. I also scarified another BlackGate [one of the few who like them] on the power in. I tossed the little links that were there and used the leads from the cap to connect power and ground from DAC board to lower board.

I am glad I waited to add these caps because the impact is enjoyable. Next up is 1uF Jupiter caps because I think those old school wax caps might be a sympathetic sound with the transformer and wiring the power direct from the power input to the BK cap. I do like the Obbligato's but I think they are now adding too much thick tone. [ I thought this before the new BG went in.]

[another crap your pants moment]
Hi Pat,
Did you remove the original SMD caps or did you parallel them?

Second thing, for all the comments about problems with too much heat on the PS please define "hot". Someone must have a thermometer that they can tape or BlueTak to the case to find out what temperatures we are really talking about. I have no problems whatsoever with heat so I am curious.
If you check out the PDF on the power transistor that Teradak uses the PS does not even come close to using much of the capacity of the transistor. They are rated for 8 amps (continuous!!) and 50 watts unless I have the wrong number for the chip. We are using about 1 amp at 8 volts. The PDF also shows the temperature ratings for the junction and the case. If you don't have a thermometer 130 degrees F (about 55C) equates to about 2 seconds of being able to hold your hand on it. Yeah, that's pretty hot and still not hot to that transistor.
post #527 of 1144

Texas Instruments resistors for I/V

I am just going to second or third the comments about the TX resistors. I replaced a pair of Caddock's that I was using. Now if you are using the Caddock's already, they are REALLY good. The TX resistors did not change the tonality or anything like that, they are just clearer. The entire audio band is just a bit cleaner. These are for the folks that want to extract everything from the software that they can. It is not for the "Technicolor" or the "flavoring" folks. Of course, they can be used and then flavored with output caps but that is a whole other story which I will not get into at all. About $20 a pair (and about 2 weeks wait) is all it takes.
post #528 of 1144
I used a digital VOM with a temp probe on my case and got temps around 130 degree's (bottom of chasis, right below the transisters). What you describe is about right, I can hold my hand on the chasis 3-5 seconds before it gets to hot to hang on too. I do understand what you are saying, and the fact that the bottom chasis is the heatsink. It's just unusually hot for a device, but that does not really mean it's out of it's spec range, and may operate perfectly fine. Just not something we are used to seeing. The heatsinks in the old valab got just as hot or hotter though.
post #529 of 1144
Thread Starter 
Quote:
Originally Posted by driguy View Post
Hi Pat,
Did you remove the original SMD caps or did you parallel them?
Damn. I forgot to remove the bypasses. With all that tunnel vision I just forgot.

The case does not seem too hot to me. I can place my hand on it without pulling away. I did drill holes in the top front and one in the top back so the heat could draw from back to front. I added a small heatsink to the top. And I added these geeky tall feet. I think all is ok re heat on my my mah9ionce using the yellow wire.

Damn. Now I gotta go back and nick those small caps off there. Actually now looking forward to pulling the lid off again.

EDIT: On second look I am not going to be able to get to them as the new caps block access. But I bet by attaching a small lead to the iron I can get under the caps ... surgery.
post #530 of 1144
Hey pat, are you putting your hand on the top of the chasis or bottom? the bottom is what gets hot as hell.

Are you sure you want to remove those SMD caps? It may not be a good idea.
post #531 of 1144

Hold on Pat!

Quote:
Originally Posted by MikeW View Post
Hey pat, are you putting your hand on the top of the chasis or bottom? the bottom is what gets hot as hell.

Are you sure you want to remove those SMD caps? It may not be a good idea.
Pat, I did not mean the small .1uF caps. I was only asking about the 10uF SMD caps which looking closely at the picture seem to be gone. Do not remove the smaller caps.
post #532 of 1144

3rd that

Quote:
Originally Posted by driguy View Post
Pat, I did not mean the small .1uF caps. I was only asking about the 10uF SMD caps which looking closely at the picture seem to be gone. Do not remove the smaller caps.
You need a small cap there. I'm using .1 wimas and liking it. No problems with stray signal pickup on the longer legs (my only worry). Got some Vishay-Rodenstein on the way to replace them, they should let even more through then the wima.

Getting 41c on the hot side of my DC-30 now its upside down. Ok with that.
post #533 of 1144
Thread Starter 

good thing I couldn't get to them

So they are still there.
But the druge of new caps and that BG made me add the Russian teflon and man that cap is made to made with that Obbligato. Really nice.

In my VALAB I have a Mundorf silve/oil as well for a mix of: Obbligato 1uF, Mudorf .1uF, Teflon .015uF.

And the VALAB sounds so good ..... so that it's Mundorf .1uF it is for this Chameleon as well as the other two.
post #534 of 1144
I think my Bg's are just begining to earn there keep, but only after 750hrs of burn in, so far! AudioNote reckon on 1000hrs, I think they might be right. This dac, and the Bg'd amp, really are showing up the various cap signitures, and character changes during burn in. Very good sign means getting closer to the recording, but a pain nontheless.

But its worth it, that Valab style magic is starting to come though now, but with added transparency from those extra dac chips.

(sigh of relief in backround)
post #535 of 1144
Michael sent me this email awhile back, it may interest some of you. I've got my Craftsman VOM temp probe taped to the chasis right on top of the transistors I get about 49C (powered on about 20 hrs now). I wonder if some small heatsinks directly applied to the transistors with thermal adhesive would help much. So you'd have heatsinks from both sides, the chassis and directly to the chips. Any thoughts on this?

Quote:
Hi,
I first reply you some questions.
1. To check the clipping, you should feed a standard full-range waveform and measure its output on scope.
2. The applying DC voltage on the TDA1543 chips determines the maximum non-distorted output voltage. Therefore you can increase the DC voltage for the chips to increase its output swing voltage.
3. The default current R-core transformer setting is not good for increasing the DC voltage output. To increase the DC voltage, you can use the high AC voltage input (yellow wire), but it will increase the heat dissipation,too. But its chassis temperature is approximate 46C ~ 48C. It is a little hot, but it may not be an issue. There are two heat sources in the DC-30W. One is the transformer and the other is the transistor. The transformer dissipated heat can be reduced by using high-power rated transformer. The transistor heat can be reduced by decreasing the voltage gap between its input and output. The more voltage gap, the more heat dissipation.

Michael,
post #536 of 1144
Thread Starter 

heat

heatsinks are good. But drilling holes in the chassis is good too.
A set of holes up front with a hole in the back so that air can be drawn through the chassis.

In the picture below you can see a set of six holes at the front.
The hole in the back is on top as well but behind the heatsink. Air at back is cool.

I can hold the chassis with fingers on bottom and top and not let go. Ever.
It's warm and toasty. But no burns. And stoic I am not.

PS: maybe I shoulda put that heatsink on the bottom ..?

post #537 of 1144

NOT too hot

Quote:
Originally Posted by MikeW View Post
I used a digital VOM with a temp probe on my case and got temps around 130 degree's (bottom of chasis, right below the transisters). What you describe is about right, I can hold my hand on the chasis 3-5 seconds before it gets to hot to hang on too. I do understand what you are saying, and the fact that the bottom chasis is the heatsink. It's just unusually hot for a device, but that does not really mean it's out of it's spec range, and may operate perfectly fine. Just not something we are used to seeing. The heatsinks in the old valab got just as hot or hotter though.
Most of us are in fact "used to seeing" these temps, just not on a DAC! It is not on the other hand, "unusually hot". Just look at the regulator heat sink on the Valab DAC. It gets pretty darn hot as you stated. Now remember this unit uses twice the current! I am not berating anyone here, I am just trying to point out that in typical DIY audiophile circles folks get worked up about crazy stuff without looking at the reality of the situation in total. That is why I suggested looking at the PDF datasheet. Please realize that people interested in this unit may be reading this thread and thinking that the unit "overheats" when in fact it does not. We may be screwing up the sales of the very units that most of us think is pretty darn good with inaccurate postings.
Most DACs use one chip for the D/A processing and an opamp for output. They will run much cooler by design. How many draw close to 1 amp for the DAC chips?
I guess the breaking point for me is seeing a posting with a fan installed. Again, here in CrazyTown these postings are "normal" but please remember that real normal folks may be interested in the basic units and that all the hard work the guys at Valab have put in could go up in smoke. Now, I have no economic ties to Valab and I do not know them personally but I do like to see new businesses succeed especially when they make a product I admire. This posting is more of a reality check than anything else. If anyone cares to they can check my other postings to see that they are pretty sober and tempered even when I think I may have found a pretty good mod.
Now, back to the definition of "hot". I guessed correctly about the temperature at the junction point of the transistor to the case (heatsink),it is not even close to any datasheet limits. Even at 130 degrees at that point the casework 2 inches away drops off significantly and of course much more with increasing distance. To anyone who might say it is still hot I say try putting your hands on the heatsinks of a Class A transistor amp (if you can find one). Simply putting on larger feet to raise the unit slightly will reduce the overall casing temperature enough to allay most fears.
Best Regards, Tony
post #538 of 1144

Texas Instruments resistors for I/V (Update)

Well, I did not think these resistors would require much break-in, if any, since their mass is so small. That is why I posted so soon after install. After about 15-20 hours they opened up a pretty fair amount and certainly more than I expected. So, again reality trumps preconceived notions. So what else is new! Really getting some wonderful open airy sound and the highs are a fair bit cleaner and clearer than with the Caddock's. I cannot think of a better spent $20 in all my years messing about with this stuff. This of course is IMO and YMMV.
Tony
post #539 of 1144
Good points Tony. Pat did you see what I did to my DC30W in regards to ventilation? I choose this instead of the holes. 130 degree's was before my mods, now it stays around 120. Maybe I don't need to do anything else then eh? WRT heatsinks etc.

post #540 of 1144
Thread Starter 

yeah, two points

I just don't like the way that looks.
I think the holes do an air draw whereas the way you have it the heat just wafts and floats and emanates.

Now you could say those cones for feet I use are kind of ugly. ... But their chromed.
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