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  1. M

    Audio Sense schematic needed

    If this is for your multichannel TPA3255 project, then I have a schematic and PCB design and control software (and some built PCBs) for a 4-module TPA3255 controller using a Pi Pico or Pico W. That's why the sense circuit has 20dB gain, because the Pico ADC only has 8 bit resolution so gets...
  2. M

    Audio Sense schematic needed

    Thanks for chiming in @Rick Sykora . Any thoughts you can share on distortion issues would be appreciated, is it not sufficient to simply have a 100k input impedance and small decoupling cap? The actual power amp buffer runs in parallel to this.
  3. M

    Audio Sense schematic needed

    Hey @MCH, I too have been frustrated by the complexity and component count of music detector circuits. Also a lot of them have low input impedances. So, if you're using a microcontroller, maybe this one I designed could work? It connects to an ADC input rather than the GPIO, to enable signal...
  4. M

    Heat pipe cooling in power amps

    I should have added some extra context. In practice an 8ch TPA3255 made of 4 2ch modules and an 800w SMPS idles at around 30W. With a 2U steel case and a small fan it stays around 10c above ambient.
  5. M

    Heat pipe cooling in power amps

    Your bigger issue is going to be that you may need to design a custom board in order to meet your size constraint. Cooling it will be relatively simple. The TI reference design is easy enough to implement I suppose, with maybe a single tunnel style heat sink with 2 chips mounted to each side?
  6. M

    Center with good directivity for Revel M126Be?

    Never move the cat. They hold grudges and attempts to appease them with wet meat will be seen, rightly, as signs of weakness. Interesting point about the dialogue mix, but I think this is a common misconception about the centre channel. It is not a dialogue channel! When you have a centre...
  7. M

    Center with good directivity for Revel M126Be?

    Do you really need a centre? Just asking!
  8. M

    DIY amp testing (with AES17 filter)

    The self-noise of a 10k divider is -115dBV (waves hands about how much of that leaks to the ADC, but presumably not all of it). Assuming use of ADCiso ADC with 10V input range, that will be -135dBr for a 100V amp output. The state of the art for amps is 137dB of dynamic range I think (Hypex...
  9. M

    DIY amp testing (with AES17 filter)

    I will update the documentation to be clear about the potential issue so users aren't surprised when they measure DACs and get a bit of HF rolloff they weren't expecting. Thank you so much for your feedback and collaboration, it's made the end result much better than the original!
  10. M

    DIY amp testing (with AES17 filter)

    I figured out the rolloff issue. It's because of the output impedance of the D10 balanced (88 ohms). Which makes sense as the filter is designed primarily for amp testing. The rolloff is actually extremely sensitive to the exact combined impedance, but since any non-broken amp will have an...
  11. M

    DIY amp testing (with AES17 filter)

    Good news @sarieri! v2 seems to solve the HD3 issue, although the rolloff at 20kHz is still higher then expected at 0.5dB despite the tighter component tolerances. Here are my measurements of the new filter version. The chain is D10 balanced -> DIY AUX-0025 v2 -> Cosmos Scaler @ 0dB -> Cosmos...
  12. M

    DIY amp testing (with AES17 filter)

    I'm getting -133dB H3 with D10 Balanced -> v2 filter -> ADCiso. The new board layout does seem to help, but I need more time to do a full set of measurements before I'm confident. Also got an APU ordered so we can compare then.
  13. M

    Question about driver range overlap.

    That is true, although I don’t think it’s really a reason for making the design choice, more a nice side benefit!
  14. M

    Question about driver range overlap.

    There are two reasons to use a midrange driver. One is to enable higher power handling, as tweeters often struggle to be efficient when crossed low to a woofer. The other is to avoid the narrowing of the woofer‘s output at the top of its range, giving wider more even dispersion overall. In...
  15. M

    DIY amp testing (with AES17 filter)

    Hypex uses balanced power supplies (e.g. +/- 48V referenced to neutral AC input) which naturally gives a 0 DC offset at the output - you should connect it across the whole LPF. Even TPA3255 which uses a single ended power supply has ~20mV DC offset at the speaker terminals at idle. This is...
  16. M

    DIY amp testing (with AES17 filter)

    It is a bit silly, but those are the specs of the AP device, so here we are! In countries with 240V mains it’s normal to have a 15A circuit, so 3.6kW.
  17. M

    DIY amp testing (with AES17 filter)

    There’s a list with links in the readme, but no uploadable BOM.
  18. M

    DIY amp testing (with AES17 filter)

    The new v2 board has the inductors way more spaced out, amongst a few other layout and component improvements. It'll be interesting to see how it works out and if it solves the excess HD3 and the higher 20Kz rolloff. Bear in mind we are talking about stuff below -120dB, so it's not really a...
  19. M

    Budget Directiva Project

    Vance Dickason has reviewed the SiG180 in the latest issue of voice coil magazine. He likes it a lot, especially for the price. The only real quibble would be that distortion, while lacking any severe resonances, does bump around the 1% mark for a while. Still, very good for the price.
  20. M

    DIY amp testing (with AES17 filter)

    I've had one more go, this time putting a full divider network post-filter (as opposed to v1, where the divider used the input impedance of the DAC). It works fine, and all resistors are under 10k and 1W or less even with a 140Vrms continuous signal. I don't love it but it does the job, and is...
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