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Showing content with the highest reputation on 05/01/2021 in all areas

  1. I've noticed something very interesting I wouldn't have believed was true when experimenting with my Hypex amps yesterday. These amps needed to be "broken in" with a high level signal or they'll run at unusually high distortion. Sounds like snake oil to me, but heres what I've seen from the data: General info: -Sweep of the audio interface max 0.005% THD 100Hz-24khz (sweep went to 48khz) -THD somehow off rising to 1% at 20Hz (has been RMA'd once, guess it's still slightly damaged) -THD numbers in the following paragraph are mostly constant through the frequency range, so I'm picking a 1khz reference -Load is resistive; no water for cooling because heat dissipation is 100W max. Step by step results: -10V @ no load: 0.003% THD -10V @ 8R: 0.048% THD -10V @ 4R: 0.109% THD -30s 200Hz signal @ 20V into 4R -10V @ 8R: 0.004% THD -10V @ 4R: 0.01% THD Results were verified multiple times (like multiple sweeps @high THD and then multiple sweeps at low THD after 'break-in'). Results were the same for all 6 amps (with 3 channels each) I tested, but some didn't have high THD because I've had them in use before already. Results were the same after I let the amps cool off (always low THD after being 'broken-in'). Results were the same the next day. Whatever happened here, driving the amp modules to their maximum once lowered overall distortion by an order of magnitude (forever?). Maybe someone can help tracing the issue. Whatever generates the current in the amp is affected by this, so it might be the transistors. Might be the solder heating up and changing its properties (but I don't think the amp is getting hot enough for that; at least I hope so because that would be approaching 200°C). Might be the power supply. I'm not an expert in this subject, but I believed that electronics components don't change (excpet caps with age), as long as they're not hardcore overdriven and like literally melting.
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  2. Thanks for doing this! Those CVR amps definitely look attractive from a value perspective. It's nice to know your doesn't run like a furnace. Amps typically sound very similar when operating within their performance capabilities. However, differences are still possible for a few reasons: Amps typically use a high-pass filter to protect them and/or the speaker(s) from inaudible DC signals, and they vary a lot with regard to where the HPF kicks in. However, most amps don't start rolling off until 20 Hz if not much lower. This is something that should show up in the REW measurements if there's much difference. I certainly don't see it here. Another reason is low pass filtering used specifically with Class D amps, which together with speaker characteristics (response and impedance both) affect how treble frequencies are reproduced. Such differences could not only impact how the treble sounds but could also alter perception of the bass including the bottom end. However, this only comes into play when the amps are being used to play treble and not if the amps are only used for lows and/or subs. I believe these are the most audibly significant reasons. There will always be unusual amps that were either designed with a "house sound" or screwed up in the design process somewhere. However, I believe this is more common in the audiophile world than with pro stuff which is pretty much designed to sound neutral, excepting the necessary filters discussed above. Of course, all bets are off once you start pushing the amp(s) close to their limits, which for some amps needn't necessarily involve a lot of power output if working with very low frequencies. That's part of the original reason for this thread. Many amps can measure and perform great at quiet levels and can meet their published power handling specs at "1 kHz", but if you try a strong 20 Hz tone, they might not put out anywhere near their rated capability and may even malfunction. High power amps are most likely to be used to drive subwoofers, so understanding their output capability with heavy low frequencies is very helpful. On another note, have you thought about trying to improve the acoustics of that room? Or do you not use it for sound normally?
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