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Hey I resemble that remark!  

EDIT: The testing methodology was updated to use a non-reactive load (water heater elements). I purchased 10 of these (Camco 6000w 240v low watt density): https://www.amazon.com/Camco-Screw--Foldb

The output power of a K20 vs an X4 K20:  145 V RMS for less than a second at 2.05 ohms both channels driven Then it limits to 58 V then it goes down to 52.  This means 10.5 kw per channel for

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2 hours ago, Ricci said:

Hmmm. Interesting. Frequency response spec looks not so great though. 

Does that matter when you're applying a correction curve anyways? I calibrate the devices which are not part of the DUT section, so I tend to not care so much.

Good pro audio gear is expensive, but it's still nothing compared to proper measurement 'lab' gear. I'm going to get 4 of those BSS DI boxes on Saturday, I can post a FR if you like.

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It may be relatively flat down to 5Hz. Can't say for sure without measurements. Curious that the spec is 30-20kHz though. If it was 20-20kHz I wouldn't question it, but 30Hz is a bit odd for an electronic component, which is why it stuck out to me. I wonder if it changes with input pad?

I avoid cal files as much as possible for a measurement rig. Especially if big corrections are needed. They are a necessary evil sometimes though. 

Good luck. Post a frequency response if you get a chance to take one. 

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Hey guys. While not as rigorous as the excellent testing in this thread I put together a little vid doing some light testing and listening comparisons between the chinese CVR branded 3002 amplifier up against a Powersoft K-10. Might be a good option for people looking for some decent performance at a good price point. Maybe you will find it interesting. Ill have this set up for a couple more days so if you're quick and send me a request for ideas for further testing I can try to accommodate 

 

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4 hours ago, jay michael said:

Hey guys. While not as rigorous as the excellent testing in this thread I put together a little vid doing some light testing and listening comparisons between the chinese CVR branded 3002 amplifier up against a Powersoft K-10. Might be a good option for people looking for some decent performance at a good price point. Maybe you will find it interesting. Ill have this set up for a couple more days so if you're quick and send me a request for ideas for further testing I can try to accommodate 

 

Thank you for sharing. Hadn't heard of this brand before. Any thoughts on sinbosen compared to these CVR (if you happen to have experience with sinbosen)? 

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20 minutes ago, klipsch said:

Thank you for sharing. Hadn't heard of this brand before. Any thoughts on sinbosen compared to these CVR (if you happen to have experience with sinbosen)? 

I have no experience with the sinbosen sorry. 

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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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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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I can't recall where, but I have read that many brand new electronic components (capacitors among some things) do have a break-in process, but it is very rapid, essentially done after the component has been charged for a few seconds.  Distortion of 0.1% isn't exactly high---*it* might be slightly audible in an amp depending on the particular nature of it---but if the problem vanishes after pushing it briefly, it doesn't seem like anything of much practical concern.

However, this does suggest that Hypex is not testing the finished components at their specifications before shipping them.  I'm rather surprised, as this doesn't seem like a difficult or expensive thing to do.

Unrelated to this, I know that Hypex amps will not accept a signal from the Motu 16A audio interface (or others in the same family) that I use together with a PC for many channels DSP.  Something about how the 16A analog outputs are driven just doesn't jive with the Hypex amps.  I don't really understand it, but it was reported on in detail here among other places.

Lastly, IIRC someone I know managed to get a Hypex amp (one with builtin DSP, I believe) to go unstable (i.e. noise at full blast) by feeding it high-level ultra-low frequency signals.  I believe he first implemented the ULF boost via the built-in DSP and later used an external DSP, and both caused the unit to go bananas.  I'll see if he wants to come onto the forum and share his experience, so you can hear about it first hand.

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Interesting RE hypex. I use 3 of the nc500 amp modules to drive my 3 danley SH50s. One of the few amps where I can stick my head inside the horn and it is dead silent. Literally zero audible "hiss" in a ~34 dB noisefloor room inches from the compression driver.

Other class D, like Pascal and ice modules, the "hiss" would be audible from 13 feet away. (e. g. from D-sonic amplifiers I've tried). 

I am interested in the newer self contained hypex modules to see/hear how they compare (e. g. Compare the original 500NC VS the 500mp or 502mp)

 

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1 hour ago, SME said:

Lastly, IIRC someone I know managed to get a Hypex amp (one with builtin DSP, I believe) to go unstable (i.e. noise at full blast) by feeding it high-level ultra-low frequency signals.

Mine power cycled when I tried to get it to output 20V into 4R at 10Hz (FA123).

1 hour ago, klipsch said:

I am interested in the newer self contained hypex modules to see/hear how they compare (e. g. Compare the original 500NC VS the 500mp or 502mp)

The FA123 I have consists of a NC122MP, NC100HF and MP-DSP Main plus MP-DSP Digin.

You can see better measurements than I could ever take of the NC252MP amp here:
https://www.audiosciencereview.com/forum/index.php?threads/buckeye-6-channel-amplifier-review.18579/

I think this one is very interesting and much cheaper than combining their other offerings:
https://www.hypex.nl/product/ncas500mp/174

This plus the dsp board is way less than the full FA253 (almost half the price). Dunno if it's available to non OEM customers thou.

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That's some very interesting results. Did you find out whether maxing out one channel is enough to break in all channels? 

I'm the person that SME mentioned on Hypex amp experiences. It does some things very well, but some things are shockingly rough around the edges that I'm amazed they released a product with flaws like this. 

For example if the total gain on all filters exceed +24dB, the DSP crashes and sends full scale noise to the amp channels. Luckily, it spared the tweeter channel, and luckily the DSP recognizes the crash and doesn't go crazy after a restart. But this is still really bad. 

It is also possible to crash the DSP with a strong enough input signal. I suspect it is because I tripped the +24dB gain limitation because I had +20dB of boost due to Linkwitz transform, and I raised the master volume to +6. So when a -2dB or louder ULF signal hits the DSP, it gets boosted to +4, and since I had 20dB of ULF gain, I trip the +24dB gain and the DSP crashes and sends loud noise to the channels. 

This kind of bug should never happen on a commercial product.

I can also get my FA503 to power cycle when exceeding its power limits. I'm disappointed the soft limiter doesn't work. My previous ICEpower amp never power cycled no matter how hard it was driven. The soft limiter actually reduced amp power output with a stronger input signal. I'm sure that saved my speakers from blowing up during some extended loud parties.

@klipsch On the FA503's, Hypex actually did a pretty smart thing. It actually seems to turn the amp off when there is no signal to the DSP, and therefore the speakers are dead silent with no hiss. But there is actually a hiss, and if you feed it a silent/very quiet signal, the hiss is apparent.

While the Hypex are technically excellent amps, it really sucks on the usability aspect. I haven't even talked about the excessive heat combined with a low maximum temperature, or how the DSP/amp takes 5 seconds to wake from sleep, or there's a very loud click every time it wakes/sleeps that I can hear from another room. For my next speakers I will use Pascal L-Pro modules instead. I hope they have much better usability behavior than the Hypex. I wish I could get my hands on OEM DSP plate amps with Pascal amp modules. If not I'll build my own plate amp.

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9 hours ago, lowerFE said:

That's some very interesting results. Did you find out whether maxing out one channel is enough to break in all channels? 

I'm the person that SME mentioned on Hypex amp experiences. It does some things very well, but some things are shockingly rough around the edges that I'm amazed they released a product with flaws like this. 

For example if the total gain on all filters exceed +24dB, the DSP crashes and sends full scale noise to the amp channels. Luckily, it spared the tweeter channel, and luckily the DSP recognizes the crash and doesn't go crazy after a restart. But this is still really bad. 

It is also possible to crash the DSP with a strong enough input signal. I suspect it is because I tripped the +24dB gain limitation because I had +20dB of boost due to Linkwitz transform, and I raised the master volume to +6. So when a -2dB or louder ULF signal hits the DSP, it gets boosted to +4, and since I had 20dB of ULF gain, I trip the +24dB gain and the DSP crashes and sends loud noise to the channels. 

This kind of bug should never happen on a commercial product.

I can also get my FA503 to power cycle when exceeding its power limits. I'm disappointed the soft limiter doesn't work. My previous ICEpower amp never power cycled no matter how hard it was driven. The soft limiter actually reduced amp power output with a stronger input signal. I'm sure that saved my speakers from blowing up during some extended loud parties.

@klipsch On the FA503's, Hypex actually did a pretty smart thing. It actually seems to turn the amp off when there is no signal to the DSP, and therefore the speakers are dead silent with no hiss. But there is actually a hiss, and if you feed it a silent/very quiet signal, the hiss is apparent.

While the Hypex are technically excellent amps, it really sucks on the usability aspect. I haven't even talked about the excessive heat combined with a low maximum temperature, or how the DSP/amp takes 5 seconds to wake from sleep, or there's a very loud click every time it wakes/sleeps that I can hear from another room. For my next speakers I will use Pascal L-Pro modules instead. I hope they have much better usability behavior than the Hypex. I wish I could get my hands on OEM DSP plate amps with Pascal amp modules. If not I'll build my own plate amp.

What firmware version did you experience these issues with? I'll try to replicate this today with my amps running 1.44 which I updated to yesterday. I didn't quite understand your remarks about the soft clip limiter; you say it doesn't work but then you say it reduced output power, isn't that exactly what it's supposed to do? It certainly worked when I tried it, but I haven't monitored the signal so I'm not sure if it was a gain reduction (soft limiting) or a peak reduction (hard limiting). I will run a signal to the amp and loop the output back into my interface to listen back to what it's doing. I'm just sad that you can't change the limiter's attack and release times, it's instantaneous, which doesn't make sense since loudspeakers are not linear devices.

The amps have a signal detection and automatic turn off functions, like most HT subwoofers do. My FA123 didn't mute the output signal while it was on and I could hear the noise from a distance of about a foot of the 94db/w/m tweeter. Not an issue there, but certainly audible on an unpadded compression driver (that was with an input signal connected thou and the input gain at around 0db, not sure if the noise came from the amp even).

The Pascal amps look higher power but also more expensive (their website was down so I checked a store which had like two modules listed?), to the point where I'd probably consider going Powersoft instead. The digiMod like is certainly on my list of amp candidates for active PA speakers. Not sure about their noise floor, maybe it's not good enough for a HT setup where you want inaudibility of the noise floor on unpadded compression drivers, if that's even achievable, but I don't need multi KW modules on tweeters.

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Report on the soft clip limiter: test set to 25W 4R (10V in theory), generator at 1kHz

-Protect light starts flickering around 11V (30W) but it won't go any higher than that (long term)
-attack time was ~5ms when overdriven by 10db followed by a gradual roll off to the target over 50ms
-when overdriven by 20db it stays in hard clipping for 30ms then ramps down to the target in less than 1ms
-even 20db hot the target is undistorted
-10Hz sinve was butchered a bit but didn't look too bad
-distortion just below limiter as expected (between 0.001 and 0.003% in my sweep)
-3db into limiter 2.5%THD@20Hz; 0.4%@100Hz; 0.04%@1k; 0.004%@10k
-10db into limiter the values multiply by 3, values stay the same for 20db+

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20Hz tests with 3 +10db low shelves at 50Hz which means +30db at 20Hz:

-23V unclipped baseline @ 0db reference
-+10db no issues, just clipping
-+20db no issues, just clipping
-+25db amp shuts down after a few seconds, output muted
SCL engaged at 125W4R:
-22V unclipped baseline @ 0db reference
-nothing changes except the clipping output signal turns into a "clean" signal
Master input was at +4db on the amp and I raised that to +14 for signals over 20db into clipping because I ran out of output on my interface

Overdrive tests:
-SCL set to amp specs (125W@4R)
-Clean at 125W (100Hz)
-no issues at +3db
-no issues at +6db
-no issues at +9db
-test repeated at 20Hz and 10Hz, no issues

-amp goes into protect at 5Hz, but doesn't complain at -1db

@lowerFEmaybe all your issues were solved in a firmware update?

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14 hours ago, lowerFE said:

 

@klipsch On the FA503's, Hypex actually did a pretty smart thing. It actually seems to turn the amp off when there is no signal to the DSP, and therefore the speakers are dead silent with no hiss. But there is actually a hiss, and if you feed it a silent/very quiet signal, the hiss is apparent.

 

Interesting. I do not have FA503s. I have the nc500s https://www.hypex.nl/product/nc500-oem/50. I have also had the nc400s (borrowed).  There is zero audible hiss with any signal. 

I am interested in the newer 502 https://www.hypex.nl/product/nc502mp-oem/77 or 252 for other channel duty.  Potentially similar high SINAD and clean power. 

The nc400s were the same as the nc500 (no audible hiss) and clean power. 

The Pascal L pro modules had audible hiss that annoyed me during quiet movie passages, soft jazz music, and other genres with similar sonic qualities. The X Pro and M pro were slightly better, but I ultimately sold my D-sonic amplifier that used the X pro modules. For inefficient speakers, the X pros may be a good fit.

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On 1/2/2021 at 12:40 AM, SME said:

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?

Thanks SME. I'm just editing a follow up to the previous video. This time I was able to run the cvr up to 48 volts driving 4x 21sw152 at a 2 ohm load. No appreciable difference between it and the k10. I have no illusions that the cvr can hang with the k10 all the way to max power, but it can drive 4 21's on a 2 ohm load to pretty fun levels very well. Ill post the vid when its ready

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52 minutes ago, jay michael said:

Thanks SME. I'm just editing a follow up to the previous video. This time I was able to run the cvr up to 48 volts driving 4x 21sw152 at a 2 ohm load. No appreciable difference between it and the k10. I have no illusions that the cvr can hang with the k10 all the way to max power, but it can drive 4 21's on a 2 ohm load to pretty fun levels very well. Ill post the vid when its ready

I'd love to test this amp with my loadbank. I'd also love to test if it'll explode being driven at max after a while like my Sanway did.

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18 hours ago, peniku8 said:

I'd love to test this amp with my loadbank. I'd also love to test if it'll explode being driven at max after a while like my Sanway did.

Yeah someone really needs to do some proper bench testing for sure. I guess they beefed up this model already, the 3302 has more power apparently

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