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'noodle' dac (ebay special) - Page 2

post #16 of 180
8/25/08 at 1:12pm
Thread Starter 
the chap that did the mods originally suggesta resistor is needed to load the dac.

I just dont see why this is needed, inline with that you will have 50k, what difference a 68k resistor makes i do not know.
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post #17 of 180
8/25/08 at 4:14pm
Is your fire insurance up to date?
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post #18 of 180
8/25/08 at 4:20pm
Quote:
Originally Posted by HeadphoneAddict View Post
Is your fire insurance up to date?
Please explain....
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post #19 of 180
8/25/08 at 4:26pm
Quote:
Originally Posted by keiths View Post
Please explain....
I'd be afraid the box would catch fire. Maybe I'm wrong, just looks scary.
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post #20 of 180
8/26/08 at 8:38am
Quote:
Originally Posted by HeadphoneAddict View Post
I'd be afraid the box would catch fire. Maybe I'm wrong, just looks scary.
It's going in a propper case. It was only connected up in the box for a quick test!

I was worried that you were suggesting that the capacitor mods would make it liable to catch fire!
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post #21 of 180
8/26/08 at 2:25pm
Thread Starter 
for all those worried about my cardboard box (sorry about the crappy phone pics) :



its now house in the top unit.
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post #22 of 180
8/26/08 at 7:38pm
Have you done any of the mods to it?
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post #23 of 180
8/27/08 at 4:27am
Thread Starter 
re,oved the signal electrolytics, replaced with obbilgato film. changed the opamp to a opa2107. sounds lovely.
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post #24 of 180
8/27/08 at 5:41am
Quote:
Originally Posted by adamus View Post
re,oved the signal electrolytics, replaced with obbilgato film. changed the opamp to a opa2107. sounds lovely.
Do you have a picture of your mods?
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post #25 of 180
8/27/08 at 10:35am
Thread Starter 
same as the guide picture i showed you.

except i have obbligatos in the signal chain. I am confused by the apparant need for the resistors. I can only assume its for when nothing is connected, otherwise putting a 68r resistor in line with a pot (50k!) cant make any difference. Eitherway, i didnt put the resistor in line and havent experienced any issues yet.
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post #26 of 180
8/27/08 at 1:36pm
Quote:
Originally Posted by adamus View Post
I am confused by the apparant need for the resistors. I can only assume its for when nothing is connected, otherwise putting a 68r resistor in line with a pot (50k!) cant make any difference. Eitherway, i didnt put the resistor in line and havent experienced any issues yet.
Think one second about it. What happens if you short the output to ground, with and without the resistors ?
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post #27 of 180
8/27/08 at 2:21pm
Thread Starter 
cap will dump resisdual charge back into g.

why would i short the input though? if its just left pulgged into my amp.
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post #28 of 180
8/27/08 at 3:47pm
Quote:
Originally Posted by adamus View Post
cap will dump resisdual charge back into g.

why would i short the input though? if its just left pulgged into my amp.
tss, tss, you have to think like a DAC builder: sooner or later, one of your customer will short the output, while the dac is playing. The opamp will try to push 2Vrms into a short. It could fry and the customer won't be happy. If you put something like a 100 to 1k resistor in line with the output, the opamp will survive easily and the sound quality won't suffer at all. No need for very low output impedance here.

As a guess, the resistors protecting the output were R28 and R29. On the pic you show, the modder removed those (among others). He thus had to put some new resistors to protect the output against a short.
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post #29 of 180
8/27/08 at 4:19pm
Quote:
Originally Posted by 00940 View Post
As a guess, the resistors protecting the output were R28 and R29. On the pic you show, the modder removed those (among others). He thus had to put some new resistors to protect the output against a short.
From the schematic supplied with the DAC, R28 is a 100K resistor connecting the LOUT with ground whilst R29 is a 100K resistor connecting ROUT with ground.

I'm currently modding my DAC and have only removed the 6 electrolytic capacitors (replaced with wire links) and added 0.47uF film caps to the outputs - I haven't touched R28 and R29 - so do I need the extra resistors?
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post #30 of 180
8/27/08 at 4:51pm
Bad guess thus R28 and R29 are thus simple pulldown resistors, to avoid "pops".

Still, all the rest stays true. You really need a resistor in serie with the output to be safe. There might be some on the pcb already ?
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