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  1. #11
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    Excellent to see this information come back to life, thanks mate Doner unit will be on its way shortly my friend
    Lounge - SB Touch with TT3.0, DC cap mod, XBMC ASRock, Proceed AVP2, CinePro 3K6, Monitor Audio GR20's, 10TB unRAID
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  2. #12
    Quote Originally Posted by JohnSwenson View Post
    I don't know what those are, but I have used LT1761 regs many times which will be pin compatible. You just add a 0.01uf cap between the NR pin and the OUT pin. With the LT1761 its important to not use a larger cap, if you use a 0.1 (maybe to try and get better low frequency performance) the regulator shuts itself down. (don't ask how I know this!) I like to use the Panasonic film SMD caps for this, they work really well.

    John S.
    With respect to the effects, I think with soundcheck software mod, its already discounted? I could isolate the output of each mux chip by removing R197 and R232 one at a time to identify which chip clocks the player and which one the Wolfson CODEC chip. I guess its then a case of deciding if you want these effects sounds or not. In my case I'm not interested in them. I'd already discounted the wolfson chip as unimportant :-)

    I was looking at the Nat Semi LP2985 which is rated at 150mA. It will use (as you suggest) 0.01uF C0G on the NR pin to ground for ultra low noise operation! The noise figure quoted is 40uV. I've ordered a couple to try in Andy's Touch but I'll compare the specs against the LT1761 as you suggest.

    I also wondered about running the main voltage rail at about 5.3-4v. I suspect this will not be over voltage enough to cause a problem anywhere, but would then give the the drop out to run the 5v DAC reg directly from the input supply thus avoiding the internal SMPS that gives you 10v (approx) for this rail in the std config.

    Do you think there is any advantage in changing some of the other regulators? Obviously the processor does many things and I've never looked at improving the rails on a cpu previously!

  3. #13
    Quote Originally Posted by andyjayh View Post
    Excellent to see this information come back to life, thanks mate Doner unit will be on its way shortly my friend
    You're sending me a kebab!!? lol

    BTW I just noticed that the LT device quotes half the noise of the Nat semi device (albeit, its only quoted as 100mA vs 150mA on the 2985). I've ordered a couple of those too! (Thanks for the heads up John!!)

  4. #14
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    Oops, You never know what's going to turn up in the post now, lol
    Lounge - SB Touch with TT3.0, DC cap mod, XBMC ASRock, Proceed AVP2, CinePro 3K6, Monitor Audio GR20's, 10TB unRAID
    Workshop - SB3, T-Amp, JBL C1's
    Office - SB Touch, CLabs 2.1

  5. #15
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    Quote Originally Posted by UV101 View Post
    With respect to the effects, I think with soundcheck software mod, its already discounted?

    I also wondered about running the main voltage rail at about 5.3-4v. I suspect this will not be over voltage enough to cause a problem anywhere, but would then give the the drop out to run the 5v DAC reg directly from the input supply thus avoiding the internal SMPS that gives you 10v (approx) for this rail in the std config.
    Yes TT3.0 kills the jive_alsa process which sends data to the Wolfson DAC, so there will never be any sound over that anyway.

    On the running the whole thing a little high, Hmmmm, interesting thought. Running the whole thing at 5.4 volts should not cause any issues. You just need to make sure that the 5.4V - any noise on it is above the cutoff of the regulator. It might be a good idea to feed the reg with a ferrite bead to help cut down on any HF noise on the input.

    John S.

  6. #16
    Excellent! I'll try dropping down to 1 mux as Ive no interest in the effects.

    I'll run the external PSU at 5.4v to try these low noise regs. Based on the results so far with mine, I think this might be a pretty smart cost effective approach. One of my regs in the external PSU feeding into a few of these LT regs internally should be quite effective.

    I'm interested in your experience with the regs, did you only have issues with a higher value cap on the bypass or were there issues with post reg capacitance? On my clocks, I'm using a 1200uF solid polymer and I wonder if such a high value low esr cap will cause the reg an issue?
    Last edited by UV101; 2012-02-23 at 15:30.

  7. #17
    Senior Member
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    Quote Originally Posted by UV101 View Post
    Excellent! I'll try dropping down to 1 mux as Ive no interest in the effects.

    I'll run the external PSU at 5.4v to try these low noise regs. Based on the results so far with mine, I think this might be a pretty smart cost effective approach. One of my regs in the external PSU feeding into a few of these LT regs internally should be quite effective.

    I'm interested in your experience with the regs, did you only have issues with a higher value cap on the bypass or were there issues with post reg capacitance? On my clocks, I'm using a 1200uF solid polymer and I wonder if such a high value low esr cap will cause the reg an issue?
    The issue with the reg is that it has an output voltage ramp time detector. The assumption is that if the output voltage is rising slowly it assumes there is a short on the output and shuts down the regulator. The bypass cap is filtering the internal voltage reference, a large value causes the ref to rise slowly to its final value. Since the output voltage is related to the ref, it also rises slowly, which causes the ramp time detector to kick in and shut down the regulator.

    A very large cap on the output may also cause the same thing. The largest output cap I've ever used with one of these is 100uf, which has no problem.

    My preference is NOT to use large caps with the regulqators, they have very good low frequency capabilities, the high frequencies are what need the output caps so I generally go with caps that are small enough to have low inductance so they can have very good high frequency performance. On any reg I build the largest cap I ever use on the output is a 270uf solid polymer. Some people prefer higher, but I have had the best results with that.

    John S.

  8. #18
    Thanks, I'll see how I get on when the regs arrive. I'll try with lower value solid polymer and see how I get on.

  9. #19
    Right so I'm now in receipt of andyjh's touch and some 20uV and 40uV noise (very low) regs that should swap out with the originals.

    What I plan to do is run his stock unit against my modded unit to start with as this will give me a cast iron comparisson of the hardware changes i've made so far. (could really do with a 3rd to leave standard for the duration lol) What I'm hoping to hear is a a significant gap which will narrow as the mods are applied to Andy's touch. I'll update the thread as I make changes and compare the results.

    This is what I intend to do

    1: Baseline - compare with identical software settings to my own modded unit
    2: Increase input voltage to 5.4v to allow dropout for 5v regs connected directly to the input supply (thus avoiding one of the internal SMPS)
    3: Work on the 5v rail for the internal DAC
    4: Work on the 3.3v rail for the clock and associated components
    5: Look at the clocking - See if I can improve on the layout (as compared to my external clocks)and get the clocks inside the case again
    6: SP/DIF - along side I will be looking further back before the buffer to see if there is anything else further back in the circuit that can be improved
    7: External PSU
    8: External Wifi Antenna??

    That should keep me busy!!!

    **I'd better tell Andy the plan eh!!!
    Last edited by UV101; 2012-03-02 at 15:37.

  10. #20
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    Sounds like a good plan mate, lol

    Watching with interest
    Lounge - SB Touch with TT3.0, DC cap mod, XBMC ASRock, Proceed AVP2, CinePro 3K6, Monitor Audio GR20's, 10TB unRAID
    Workshop - SB3, T-Amp, JBL C1's
    Office - SB Touch, CLabs 2.1

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