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Chameleon DAC listening and modifications - Page 25

post #361 of 1144
Quote:
Originally Posted by Wood View Post
Well I took the Challenge and won!

Very nice mod, less is king. Music seems more involving now. A keeper for sure, which is fortunate really as there is no going back.

Thanks Rhodes54
Wood, Can you check if the USB input is also functioning ok? I can't check it at home as I don't have a USB source available.
I would like to give Michael feedback on the 74HC04 mod but I can't provide him all information now.

The Chameleon has been running 24/7 without any problems since I removed the 74HC04 friday night. No signs of errors, drop outs or what so ever.
post #362 of 1144

The Signal Integrity

I've been going through the schematic carefully again this weekend to see if we can further enhance the digital signal integrity.

There's only one more really weak point in the design: The 74HC157. This chip switches between the USB and S/PDIF Input.
Unfortunately this chip is really needed when you want to use both the USB and S/PDIF Input but if you are planning to use only one of the two this chip can probably also be removed. Less is....
Without the 74HC157, the digital signalpad will be as short as possible (without the ASRC board):
S/PDIF Input -> Transformer -> 0,1uF Cap -> WM8805 -> R401/R402/R403 (BCK/LRCK/DATA) -> TDA1543's. YUMMIE!

There's one more thing to look at: R401, R402 & R403 are directly in the digital signalpad so these resistors should be high quality. As we want to avoid normal resistors here we should look out for a quality SMD replacement.
I'm not really into SMD so any input on this is more than welcome.

Thanks again!

Edit: I didn't know Texas Components also makes a SMD version of the Z-Foil resistors, the ASMP. Could be the solution we are looking for. I already asked them a quote.
post #363 of 1144
Rhodes54, just checked the usb, its fine.

While your at it (updating Michael) please ask him about the new PSU board, and if its retrofitable on older DC-30w's the black ones.

tah!

I changed the 75r smd to texas through the hole, with no issues, so perhaps smd here is not so critical as in say a Tripath amp.
post #364 of 1144
Quote:
Originally Posted by Wood View Post
Rhodes54, just checked the usb, its fine.

While your at it (updating Michael) please ask him about the new PSU board, and if its retrofitable on older DC-30w's the black ones.

I changed the 75r smd to texas through the hole, with no issues, so perhaps smd here is not so critical as in say a Tripath amp.
I think Bill keeps us informed about the status of the new PSU board. I will send him a P.M. to him to be sure.

I know a normal resistor will work but we wanna avoid those legs of normal resistors and caps as much as possible.
post #365 of 1144
Thread Starter 

will do

Quote:
Originally Posted by marcelnl View Post
the 2 V DC should not harm your trannies, as the power the DAC is capable of is probably nowhere near enough to saturate the iron core of those relatively large clunks of iron.

I'd dare to try it without, if you hear distortion your trannie cores may be saturating, but I'm betting that won't happen.

2mA output current per DAC, times 8 is ~16mA at 2 V DC , which does not amount to much and imho not nearly enough power to saturate those cores.

the 47 is not there to bring any DC to ground nor s the 180 R enough, your trannie will isolate the DC from the rest of the chain and will not be able to do any harm IMHO.
Your trannie is equivalent to ~600 Ohm AC input resistance if I read the right specs, which should be OK without any further resistors as the DAC has a lower output resitance, you are dealing with analog here and the risk of reflections is not as prominent as in the digital domain of the Lundahls.

(hey if you are bold enough to cut out a whole IC this should be peanuts)

So I leave the 175-180 i/v resistor in place.
No need for the 47k at the secondary.
Just remove the caps and plug the trannie in it's place is all, right?

Easy peasy.
post #366 of 1144
SMT resistors: IRC PFC? These are available in 0805, 1206, etc. sizes (0805 linked).
PFC-W0805LF-03-75R0-B IRC Thin Film Resistors
Since all these are doing is terminating the SPDIF line, I wouldn't think they would need to be anything special? The single wires, etc. I see leading from the jack are already non-impedance controlled, so if you are hearing differences here, ???

I agree with rhodes that SMT would be best on anything touching the SPDIF signal.
post #367 of 1144
Quote:
Originally Posted by Pars View Post
SMT resistors: IRC PFC? These are available in 0805, 1206, etc. sizes (0805 linked).
PFC-W0805LF-03-75R0-B IRC Thin Film Resistors
Since all these are doing is terminating the SPDIF line, I wouldn't think they would need to be anything special? The single wires, etc. I see leading from the jack are already non-impedance controlled, so if you are hearing differences here, ???

I agree with rhodes that SMT would be best on anything touching the SPDIF signal.
You are right, it is not needed to take a high quality SMT resistor for the 75R termination. This is different for R401/402/403. The I2S data is going through these resistors.
post #368 of 1144
If you mean R106 75r, my ears tell me not to neglect this resistor.
post #369 of 1144
Pat , that should do the trick....

I am with Wood on the 75R , although they are not in the analog sound path the a.o their rise time and overshoot (etc) behaviour could affect the digital signal. I'd also opt for a decent Quality resistor there (I ordered TX for that position)
post #370 of 1144
Thread Starter 

yep and yep

I did use a TX 110ohm on the VALAB and it made a nice improvement.
I likie evry little about the plugin board for input.
I would rather have that on the motherboard but space beuing the issue I understand why it is the way it is. Doesn'nt mean I have to like it.
post #371 of 1144
Quote:
Originally Posted by PatOMalley View Post
I did use a TX 110ohm on the VALAB and it made a nice improvement.
Pat, it was your idea I nicked in the first place, thanks.

I guess the only way is to solder it in when its done... but that would take away the fun.
post #372 of 1144
Just got my 175 ohm texas resisters today, poped them in, and immediate impressions, ~omg wow. Big difference over those metal film resistors, now I understand what the big deal is over these things, well worth 10$! ( I think i'd pay triple that!)

I really had no idea a resister could make this much difference. I wonder how much of it is the Texas components magic, and how much of it is having it at the exact ideal value of 175R. I think the stock ones are either 180 or 160r.
post #373 of 1144
Quote:
Originally Posted by MikeW View Post
Just got my 175 ohm texas resisters today, poped them in, and immediate impressions, ~omg wow. Big difference over those metal film resistors, now I understand what the big deal is over these things, well worth 10$! ( I think i'd pay triple that!)

I really had no idea a resister could make this much difference. I wonder how much of it is the Texas components magic, and how much of it is having it at the exact ideal value of 175R. I think the stock ones are either 180 or 160r.
LOL, nothing to do with the exact value. It is "Texas Components Magic". Nothing more, nothing less. :-)

Once you heard them, there's no way back.

I just ordered 24 of these magicians for my passive volume controller. They are that addictive....
post #374 of 1144

Ssshhh!

Quote:
Originally Posted by MikeW View Post
( I think i'd pay triple that!)
We would, and they might hear you

I think the stock are 160r and the board is marked 180r, so you would of got more output. But most of it, is their magic, as you say, which is that utter neutrality. Yeah its fun powering them up for the first time, its like having a new dac.
post #375 of 1144
Thread Starter 

you guys are crazy!

Everybody says the Texas Components resistors are all that. They must have shipped Mike's and mine the same day because I got mine today too.

And it is unbelievable. I swapped the caps out and the sound went to mush. Quickly shut down and put the caps back. I put the resisters in there when I pulled the caps and did not expect the hit I thought I was gonna get from the TX.

The signal is only going past these things, not thru them. Damn. High enegy dropped away, paced slowed, and an incredible amount of color and texture, etc on and on. Crazy.

Nothing like the Caddocks used before.

That's it. Hooked. rhodes and wood, pass the pipe.

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