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Luke's basic amplifier tests


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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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Small update on the Hypex amps: according to them all amps are tested at the factory and run through a burn-in period there. I suspect that this step was skipped because the amps were on back order already (I waited 2 months to get my amps in mid 2020 due to the pandemic), but of course this is nothing but a speculation from my side right now. I voiced the same thoughts to Hypex and waiting for their take on that. Will keep you posted

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I've recieved an answer and they suspected this phenomenon was caused by bad contact of the speaker connector on the amp. I had the amps stored on a shelf in the warehouse for a few months, so it makes sense that there was some dirt build-up and corrosion-like effects (humidity never exceeds 60% there thou, so it's only minor), since the amps were unpacked. Running a higher current through the connector seems to literally clean it, which reduced the distortion. The more you know..!

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  • 2 weeks later...
On 1/3/2021 at 9:32 AM, peniku8 said:

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.

Sorry for the late response. I thought I would get an email notification if anyone replied to me, but the setting changed for some reason. 


I tried on v1.41. v1.42 had a lot of problem with master/slave syncing (no sound on the slave speaker occasionally). v1.44 broke the EQ. 

Originally I said the soft limiter didn't work because I set it at 400W and the amp still power cycled at loud ULF passages. Upon further testing (using 5W limit instead) I see the limiter does work. 

Nice testing on the behavior of the limiter BTW!

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1 minute ago, lowerFE said:

Sorry for the late response. I thought I would get an email notification if anyone replied to me, but the setting changed for some reason. 


I tried on v1.41. v1.42 had a lot of problem with master/slave syncing (no sound on the slave speaker occasionally). v1.44 broke the EQ. 

Originally I said the soft limiter didn't work because I set it at 400W and the amp still power cycled at loud ULF passages. Upon further testing (using 5W limit instead) I see the limiter does work. 

Nice testing on the behavior of the limiter BTW!

I didn't get the amp to power cycle at 10Hz, however it did so below 10Hz. REW starts its measurement sweep one octave below the start frequency (and does a fade-in or w/e) and the amp would shut off at the 5Hz input. But I'd not go with Hypex amps if I wanna get sub 10Hz, I'd probably want something with a bit more power. Even 400W at 5Hz probably produces no meaningful output 😅

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16 hours ago, peniku8 said:

 Even 400W at 5Hz probably produces no meaningful output 😅

Sure it does, you just need a few hundred cubic feet of volume for the sub cabinets!

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On 1/20/2021 at 5:11 PM, peniku8 said:

I didn't get the amp to power cycle at 10Hz, however it did so below 10Hz. REW starts its measurement sweep one octave below the start frequency (and does a fade-in or w/e) and the amp would shut off at the 5Hz input. But I'd not go with Hypex amps if I wanna get sub 10Hz, I'd probably want something with a bit more power. Even 400W at 5Hz probably produces no meaningful output 😅

 

On 1/21/2021 at 9:39 AM, Ricci said:

Sure it does, you just need a few hundred cubic feet of volume for the sub cabinets!

Or a floor resonance.

And for that matter, I believe that audibility thresholds for content at the frequency extremes within typical audio program can be much lower than audibility thresholds for pure sine waves.  Pure sine waves are actually extremely unnatural sounds and may be one of the worst possible "test signals" for assessing human hearing.  Real sounds almost always have lots of THD, and audio programs almost always have additional THD---because it sounds better (in moderation).

The tricky thing is that the audibility of ULF is probably very dependent on the quality of the rest of the bass response.  And as we know, rooms small enough for ULF reproduction to be practical tend to have major problems higher up in the spectrum.  In hindsight, @Bossobass Dave may have found a decent formula for good ULF: small footprint floor-to-ceiling stacks of subs placed in at least two corners and Linkwitz Transform via very broad stroke EQ.  I'm told his room had an impressive 5 Hz floor resonance, but another factor may have been the quality of the response of his systems above the ULF.

I have no idea where the actual thresholds may be for systems with "ideal" responses.  My frequency response optimization is probably a bit too coarse in frequency resolution below 20 Hz.  I have plans to enhance the DSP capability so I can process with high res all the way down to single digits.  That improvement could be transformative.  I do have a very mild floor resonance at 5.5 Hz, and curiously I don't always notice it, even with the same content!  It also depends on what the rest of the frequency response is doing.  I'm finding the same is true for other "felt" bass.  So audio can facilitate or mask tactile sensation and visa-versa.  Amazing!

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On 1/2/2021 at 6:09 PM, SME said:

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.

SME, did you ever resolve the issue with the 16A outputs and the Hypex amps? I thought I read someone had done a simple mod on the amp inputs to filter out the rf noise that causes the issue. Commercially the only one doing RF filtering on the inputs that I know of is March Audio, I'd rather get a Buckeye NC252/NC502 based amp for max bang for buck.

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I'm not using any Hypex amps.  I'm just reporting on others' experiences.  If the inputs can be modified to accommodate the Motu 16A and related products, that's good news for those willing to go through the trouble.  I'm not aware of other amps that had this problem with the 16A thus far.

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On 1/7/2021 at 5:24 PM, jay michael said:

Added a follow up video to my previous comparison between the K-10 and CVR 3002. More subs, higher power and load.

Jay I ran through your videos, thanks for posting those!

Did I miss where you address the noise floor on the CVR (perhaps, I skipped around)?  I know earlier in this thread there was discussion as to how dead quiet the NC500 Hypex modules are, I can confirm, I have two  NC500 monoblocs in my living room on a pair of Martin Logan electrostats, dead quiet.  I'm still working on a NC502MP module amp enclosure install I have here (I need a hand to finish it).

If I buy a CVR 3002, will I hear any hiss or buzz in my speakers?

Thanks!

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On 3/15/2021 at 8:41 PM, maglito said:

Jay I ran through your videos, thanks for posting those!

Did I miss where you address the noise floor on the CVR (perhaps, I skipped around)?  I know earlier in this thread there was discussion as to how dead quiet the NC500 Hypex modules are, I can confirm, I have two  NC500 monoblocs in my living room on a pair of Martin Logan electrostats, dead quiet.  I'm still working on a NC502MP module amp enclosure install I have here (I need a hand to finish it).

If I buy a CVR 3002, will I hear any hiss or buzz in my speakers?

Thanks!

Good luck with the amplifier build. I too will have 502s (6 channel amp - 3 modules). Will be using them alongside the nc500s for the surrounds. These modules continue to provide clean power with efficiency. 

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I finished a 6Ch amp build made from two Hypex FA123 yesterday. It's a lab amp for speaker testing, so it has all connections on the front. It's not the prettiest and already has a bunch of scratches, but hey, at least it's got cable management..!


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On 3/15/2021 at 6:41 PM, maglito said:

Jay I ran through your videos, thanks for posting those!

Did I miss where you address the noise floor on the CVR (perhaps, I skipped around)?  I know earlier in this thread there was discussion as to how dead quiet the NC500 Hypex modules are, I can confirm, I have two  NC500 monoblocs in my living room on a pair of Martin Logan electrostats, dead quiet.  I'm still working on a NC502MP module amp enclosure install I have here (I need a hand to finish it).

If I buy a CVR 3002, will I hear any hiss or buzz in my speakers?

Thanks!

Sorry I didn't specifically take not of that, but I am going to play around with them again tomorrow so Ill try to get a sense for you. The fan's are quite noisy, to use in a theatre or listening room you would have to look at fan mods for sure. 

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