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Buckeye Nc502mp Review (6 Channel Amplifer)


The SM for the TX-RZ810 is available and you can search for it.

The volume control IC has the following specs:

Maximum output voltage: Min. 3.8 Vrms, Typ. 4.2 Vrms, that's for RL=10kΩ

For DAC, the chip used is the AK4458, same as Denon/Marantz (those made before the spring of 2021).

I could not find any review on it with measurements, but based on the datasheets for the volume control chip and the DAC chip I think you should have enough voltage to take advantage of the NC502MP's rated output.
Oh wow I've checked every piece of documentation and couldn't find that. I was originally concerned as i was using an old peavy cinemacoustic to run some subs and had to crank the gain.

I guess now i have to put in an order!

Thanks also to @Rottmannash for that!
 
Anyone see anything that looks off here? I figured I’d ask you experts before sending it back to exchange for an amp with nc252mp modules. Thanks.
 

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I'll add in (as I have been working with him): I replaced both NC502 modules with brand new ones. Both the original modules and the new ones worked fine on my test setup and even on my personal setup.
How very strange? Appears to yet be a ghost or two in the Hypex modules
 
If you replaced the modules in the amp enclosure, and having eliminated an effect outside of the amp, then I would investigate the items in the box you did not replace. Maybe there is a stray strand of wire where it doesn’t belong, or a defective connector with an insulation leak.

I certainly cannot believe that there’s something about the 502’s design that would cause such a thing, and you’ve eliminated a production/execution issue by replacing the modules.

Here’s a pic of the interior of my 502 if you want to make a comparison. But I’m betting the issue won’t be visible at this level.

Buckeye-502-interior.JPEG


Rick “even a weird ground loop caused by a flaky internal case ground” Denney
 
I looked over all the wiring when I hade it back in my possession and tested it on two different systems I have.
 
I looked over all the wiring when I hade it back in my possession and tested it on two different systems I have.

I know something similar happened to someone with the 502 but not yours. Regardless, I think you can ask Hypex tech support about this as I do believe the design of the 502MP (probably has to do with the specific switching frequency of that model) likely make it prone to interference (even harmonic resonance..) between the amp's output filter and the speaker's crossover network. If I am right, the fix could be quite simple, and Hypex should know how obviously. I think it would be extremely rare for such interaction to result in some weird noise with only certain speakers. Did you hear back from him if the ferrite cores fix it?
 
He did try the ferrite cords and shorter speaker wire runs.
What's even more strange is the amp works fine on his Front LCR speakers
 
His speakers are probably wonky. When in doubt, buy new!
 
He did try the ferrite cords and shorter speaker wire runs.
What's even more strange is the amp works fine on his Front LCR speakers

Yep, same with the other member's, again it wasn't a Buckeye amp. His also got the NC502MP modules replaced but the issue persisted, he eventually got the NC500 and problem solved. I would love to discuss such issue with Hypex but the won't talk to me because I am not a dealer. They will talk to you though.
 
Yep, same with the other member's, again it wasn't a Buckeye amp. His also got the NC502MP modules replaced but the issue persisted, he eventually got the NC500 and problem solved. I would love to discuss such issue with Hypex but the won't talk to me because I am not a dealer. They will talk to you though.
I am messaging them soon here to see their thoughts
 
One has to wonder if the particular combination of amp and speakers is resulting in some sort of resonance with the amp's output filter, and/or perhaps modulating the switching noise in the tweeter or whatever down to the audio band.

Vexing.

Kudo's to @Buckeye Amps for all the help in troubleshooting, module replacement, and ultimately amplifier swap to keep a happy customer! And to @Hcg76 for helping work through the issue without throwing the manufacturer under the bus. Both seemingly rare attributes these days.
 
One has to wonder if the particular combination of amp and speakers is resulting in some sort of resonance with the amp's output filter, and/or perhaps modulating the switching noise in the tweeter or whatever down to the audio band.

Good to know I am not the only one mentioning the "resonance" scenario. If it was me I would try to prove it by doing a quick experiment, that is to just de-tune it. Not a fix, just to trouble shoot.
 
Good to know I am not the only one mentioning the "resonance" scenario. If it was me I would try to prove it by doing a quick experiment, that is to just de-tune it. Not a fix, just to trouble shoot.
Yah, I guess it was the other thread a few days ago that I suggested sticking a 1-ohm resistor in series at the amplifier outputs to de-Q the circuit. But realistically how many audiophiles have a box of resistors lying around? Would be an interesting experiment. Hopefully Hypex will dig into this.
 
What would resonate? I’m curious but a bit out of my depth.

In my simple ham radio mind, oscillation happens at the tuning point of an RLC network, with the resistor providing the damping by lowering the sharpness of the resonance (Q). The speaker provides the R and (possibly) the C, and the amp/wiring provides the inductance, one supposes. Adding resistance as Don suggests would reduce the Q and presumably damp the oscillation to some extent. (And also reduce overall gain, so the comparison would need care, it seems to me.)

Putting ferrites on the speaker wire should add inductance and choke RF frequencies, it seems to me. But if this is an oscillation in the audible band, wouldn’t the speaker wire need to be coiled through the ferrite to create higher inductance and lower the frequency? Of course, that would change the frequency response. Plus, the ferrites are probably clip-on beads designed to choke common-mode RF from a shield, and not big enough to loop wire through them.

But reading back, the ferrites did affect the phenomenon, and that reinforces that even that simple choke inductor at least influenced the problem, which in turn does point the fickle finger of fate to oscillation.

Does the person have the ability to extract the audio from the video so that it can be more easily posted? Or record a new sample using, say, audacity in a computer?Looking at waveforms would be interesting.

A usually reliable poster on another forum reported that his 502 lost something when driving speakers that presented a capacitive load up high (no data obtained or reported, of course). I wonder if that could be related.

Rick “sensing a learning opportunity” Denney
 
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His speakers are probably wonky. When in doubt, buy new!
I’d highly doubt them being wonky. I have hooked up my surround speakers, JTR Noesis 110HTs to my Cherry 5 channel amp and my Buckeye amp with nc252mp modules. They have absolutely no weird sounds coming out of them except beautiful sound. Stumped on the 502 amp though as it seems I’ve tried everything… I’ve been trying to upload a video for anyone who wants to hear the noise but apparently the website won’t allow uploading videos?
 

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Just get some 24 GA speaker wires and the 1 ohm will take care of itself. ;)
 
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