atomicbob's SMPS Noise Nuke for HP amps with external SMPS

Discussion in 'Headphone Amplifier Measurements' started by atomicbob, Sep 26, 2017.

  1. atomicbob

    atomicbob dScope Yoda

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    I'd be willing to bet the allo device is a glorified pass regulator system. 5mV ripple isn't that hard to achieve.
     
  2. Dr J

    Dr J Friend

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    That is what I understood from the documentation.

    Thanks to everyone who took a look at this.
     
  3. Armaegis

    Armaegis Friend

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    What if one needs 4A? A quick look on digikey does not show any options at 6mH that can handle more current. Can you parallel chokes? My hazy memory from electronics class tells me I'd have to double my inductance to get the equivalent, but again a cursory scan through digikey does not show anything that matches that. Do I have other options?
     
  4. atomicbob

    atomicbob dScope Yoda

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    Check mouser.com - look for Hammond 157E
     
  5. Armaegis

    Armaegis Friend

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    :bow:
     
  6. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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    Hey @atomicbob , on the topic of noise nuking - what's your take on low-passing analog inputs/outputs? As we all know, electronic components are notorious for not reading their datasheets and schematics, so every connection can potentially be treated as an input for HF noise. I know that @tomchr uses chokes in many of his devices at least on the input side.
     
  7. dark_energy

    dark_energy Friend

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    Amp Input RFI Protection?
     
  8. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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    Yeah, that. The problem, however, is that RFI doesn't care what's the designated input on your amp and will creep in through outputs and power lines as well. The question remains, how does it impact the operation parameters.
     
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  9. atomicbob

    atomicbob dScope Yoda

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    Pro audio mic preamps and line in with active component inputs often have at least chokes but often RCLC protection against ESD and RFI. Those with transformer inputs have no need. Audiophile components often shun the extra protection with nervosa citing potential changes to sound quality. Can be telling to set a cell phone or a lamp dimmer near the inputs and listen. With cell phones it may be necessary to wait a few minutes for the phone to ping the tower.
     
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  10. Armaegis

    Armaegis Friend

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    Who remembers the days of having a cell phone near your speakers and heating the beep-beep-beep sequence before your phone call or text arrived?
     
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  11. ofilippov

    ofilippov Acquaintance

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    The lyrics is under the spoiler.
    So, here is my story. I've got a 502DAC that I use as a streamer. And I tried a really old and cheap LPS instead of the phone charger, when I just got it. And heard the difference. That cheap LPS was really meh. But the difference was quite obvious. So I asked one guy to make me some good LPS with two channels. He asked me what is it for, I described him, stated desired params and thought it's as good as done. But here is the thing. The engineer appeared to be very smart. He asked me "Is it okay if I build you a great PSU based on the <forgot_the_model> regulator?". "Sure, you choose what you want" I said. I didn't check the model of course. You can imagine my surprise, when he brought me a small PSU with one small transformer...
    - Is it SMPS?
    - Yes, it's for digital, like you said. You don't need LPS there.
    - :mad:...

    But eventually, it was better than a cheapo phone charger, so it stayed in the system. I saw the saw on the oscilloscope anyways, so it was bothering me for a while. But I didn't want to spend a lot of money on LPS. Then I found a guy mentioned this topic in the pi2design thread.

    So I put one together. I plugged it after one of the channels of my super-duper cool custom made PSU. The other channel was with initial LC filtering (a tiny coil with burned insulation on the picture below and a little cap). Feeding the streamer with single channel through 502DAC terminals. Didn't get the connectors yet.

    What it gave me in comparison?
    • better microdynamics, especially noticeable in the highs
    • more cohesive analog-like sound, instruments sound more natural, with better timbre
    • more delicate (in a good way) and to the point transients
    • I guess more depth, but I may comprehend it that way because of the aforementioned stuff
    I tried my best to describe what I hear, but I can be clumsy with words, so please bear with me. The difference is quite noticeable in my system. I feel more emotional attachment to the music. YMMV of course.

    The pictures are here. I'll probably pack everything in one tidy box later.

    The downside is that the voltage under the load dropped from 5.05V on the default channel to ~4.93V. Still 5.1V with no load. Raspberry blinks with the red light. Asked the guy to up the voltage a bit. Would it be better to use some caps with small internal impedance in this digital chain? I don't know. I'm dumb in electronics.

    P.S. atomicbob, thanks for the design and components selection!
     
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  12. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Please note that the 5V input on the 502DAC is only minimally filtered. Then it is presented directly to the pi. Whereas the PI2AES takes a higher voltage in and creates an internal 5V rail. While this is still a switcher, it is a low ripple switcher and overall will be much less sensitive to the external voltage supply.
     
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  13. Azimuth

    Azimuth FKA rtaylor76, Friend

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    Based on the pictures, is this the circuit?

    Pardon the crude drawing and shadow, lol.
    20201026_203412.jpg
     
  14. atomicbob

    atomicbob dScope Yoda

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    Yes, which you can verify against L2 and C2 in the spice simulation circuit diagram in the first post. Two smaller capacitors in parallel fit better in the package than one big capacitor.
     
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  15. Armaegis

    Armaegis Friend

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    Tangential question: Say we have some equipment/appliance/etc in the house that generates tons of noise and we want to minimize how much gets back out onto the mains. Can we use one of these except in reverse? Any other considerations required?
     
  16. atomicbob

    atomicbob dScope Yoda

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    No, the noise nuke is a low current, DC power filter. Suitable for reducing noise from SMPS DC power output to the intended DC device.

    Appliances typically run on AC mains and may consume very large AC current. Motor start inrush current can be particularly large. One rarely finds electrical noise reduction systems for appliances due to the large size and cost of components that would be required. Better to separate noise generating devices and noise sensitive devices onto separate branch circuits and filter the power for the noise sensitive devices, which uses much smaller and less costly components.
     
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  17. Armaegis

    Armaegis Friend

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    I figured that was the case for appliances, but what about particularly noisy but lower power electronic devices?

    My boss was telling me he has this remote startup device at his cottage that's probably 30 years that he uses to turn on his power the day before he arrives. Something about phoning into it and it triggers some RF receiver in his circuit breaker. Anyhow, he says he has to unplug this thing while he's there because something in it muddies up his power so bad that it interferes with his ISP router and causes other computer issues.
     
  18. atomicbob

    atomicbob dScope Yoda

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    The remote device described might rely on sending signals over the power lines. If so a line filter would interfere with proper operation. It would be best to understand the communication method and spectrum, and noise spectrum. If they don't overlap a filter could be designed to reduce electrical noise introduced into the power lines.
     
  19. Armaegis

    Armaegis Friend

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    The way my boss described it, it sends a wireless signal but the circuit itself is just old and generates ridiculous noise. That's all I know. *shrug* I was just going to tell him to put this remote starter device on a Furman or Tripplite transformer and see if that helps.
     
  20. rhythmdevils

    rhythmdevils Best SBAF member of all time

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    I know the NoiseNuke does not work with the Cavalll Liquid Platinum because of the power up sequence.

    I just got a Monoprice Liquid Gold X and I’m wondering if it would work for that amp. I know @atomicbob you have measured the LGX. Do you have any thoughts on whether it would be ok to use with the LGX (or helpful at all)? Thank you!
     

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