NEWS: monolith amp with Hypex amplification!

[Buckeye Amps]

it's 12% now if you have a store

Ouch

 

[pfgiv]

Ouch

One more derailment from the discussion about this amp, can you please add the option for upgraded cases in the future? Something like Nord SE

 

[pfgiv]

Two power cords are provided mainly so the stated Monolith specs offered for the amp are not impossible to reach.

Here is what the Monolith staff say:
"Given the nature of the NC502MP module and the chassis size target we were working toward, the overall assembly allowed for two power inlets so we could better position the amp to hit the targeted power numbers on all 8 channels at the same time."

"Based on testing, at full power from all 8 channels into 8ohms the amp draws ~23 Amps total from the 120VAC wall. To get to the 4ohm spec we claim, 400W, on all 8 channels we need to double that current, ~46Amps. One 20A/16A rated inlet would not handle that current. Also based on the Hypex datasheet, the NC502MP power consumption at full power is 1.2kW per module. With 4 modules in the chassis, we would need a connector to handle 4.8kW. At 120VAC line voltage, that would need to handle 40Amps."

My 2 cents:
You can see from the response above that two 20 amp circuits (one on each power cord) would be required to reach 87% of maximum power levels if all channels where running at maximum power at the same time into 4 ohms. Speaking for myself, I can't imagine going to these lengths in my setup. When the speakers are plenty loud at 5W, the need for 400W on all channels at the same time seems quite remote. Also known as - low probability for any space I wish to inhabit. At some point, you need to add reason to your audio diet.

@MakeMineVinyl @amper42 @Jdunk54nl @MaxBuck (I'm @ing you all here because you all mentioned the power cords ITT)

You don't have to use 20 amp outlets, nor do you have to plug the two power cables into separate outlets. This is only an option which can be used for those who want to be able to get all the power from all the channels which the amplifier is capable of.

Given the monoprice response quoted above, I think someone may be misinformed because I plugged in one cord, set up my new AVM70 8k, could not get it to function properly. No matter what I did, I couldn't get stereo sound. Ended up unplugging everything and tried to assess all my XLR cables to make sure none were faulty, then each input on the amp. Come to find out, 4 inputs on the amp do not work. I decided to swap the power cable from the bottom to the top, and now the first 4 inputs work and the second 4 do not.

Each power cord is needed to power 2 sets of modules. It's not really needed so you can get max power (well it kind of is in a round about way because they use two instead of one) it's needed to actually function.

Maybe this was inherently understood by most here, but I'm dumb with technical audio stuff.

 

[Mistar Muffin]

Longtime reader and lurker here. I picked up the 8125X during the recent sale and had to RMA it immediately due to audible noise from the even-numbered channels. The replacement does the same thing. I tested three different speakers, one-at-a-time and tested all 8 channels. All three speakers confirm the noise coming from channels 2, 4, 6 and 8. This is with nothing connected to the amp except power and one speaker. The odd-numbered channels are silent. I ran a long, high-gauge extension cord to another electrical circuit with no change. I briefly tested a ground lift adapter and the noise is reduced but still present. If this was an issue with noisy electricity wouldn't you expect it in all 8 channels?

At this point I don't have any hope that a third unit will behave differently.

I originally posted this issue on a different forum but am hoping the technically-minded folks here might have some guesses as to the cause.

Thanks!

 

[GXAlan]

@Mistar Muffin , are you using it with unbalanced or balanced connections? These amps need balanced connections and really suffer if you don't use a balanced signal.

I ran it through my E1DA Cosmos test setup, with a Yamaha CX-A5100 as the pre-amp. The Yamaha is a limiting factor for measurements so you cannot compare it to any other of my tests. According to Audioholics, the balanced out has a SINAD ~95 and unbalanced out is ~90 when tested on an APx585 at 2.7V.

Running 1 kHz SINAD at ~2 watts

Representative photos

BALANCED 1/2

UNBALANCED 1/2

and then running a silent signal through all 8 channels

Balanced = 111-112 dB

Unbalanced -95.3-95.5 dB

 

[Buckeye Amps]

are you using it with unbalanced or balanced connections? These amps need balanced connections and really suffer if you don't use a balanced signal.

Why though? There's no reason there should be audible hum/noise going from RCA to XLR on one of these builds

I'm not saying you're wrong. Moreso asking what causes it. Anyone ever do an internal tear down review?

 

[GXAlan]

Why though? There's no reason there should be audible hum/noise going from RCA to XLR on one of these builds

I'm not saying you're wrong. Moreso asking what causes it. Anyone ever do an internal tear down review?

My only thought is that the XLR to RCA adapter is defective. I don't remember if it was here or on reddit/avsforum, but I remember someone having a problem and then unscrewing one of those cheap XLR to RCA dongles and discovering that it was incorrectly wired where the ground was shorted with something.

I agree it doesn't make sense -- but having two in a row suggests something fundamentally wrong -- or I got lucky.

Personally, it seems like the drop in performance is high with the conversion.

Using the CX-A5100, 2 watt output
unbalanced -> Monoprice 8125X = 72.6 dB
unbalanced -> Sony TA-N9000ES 87.5 dB
balanced -> Yamaha MX-A5000 88.6 dB
balanced -> Monoprice 8125X 89.7 dB

It seems like the HypeX amps are really good, but only if you're in balanced input. A vintage 1998 Sony TA-N9000ES (which was very good at the time) does better.

The Yamaha is supposed to some sort of ground sensing transmission method on the RCA unbalanced output -- not sure what that entails.

 

[Buckeye Amps]

My only thought is that the XLR to RCA adapter is defective. I don't remember if it was here or on reddit/avsforum, but I remember someone having a problem and then unscrewing one of those cheap XLR to RCA dongles and discovering that it was incorrectly wired where the ground was shorted with something.

I agree it doesn't make sense -- but having two in a row suggests something fundamentally wrong -- or I got lucky.

Personally, it seems like the drop in performance is high with the conversion.

Using the CX-A5100, 2 watt output
unbalanced -> Monoprice 8125X = 72.6 dB
unbalanced -> Sony TA-N9000ES 87.5 dB
balanced -> Yamaha MX-A5000 88.6 dB
balanced -> Monoprice 8125X 89.7 dB

It seems like the HypeX amps are really good, but only if you're in balanced input. A vintage 1998 Sony TA-N9000ES (which was very good at the time) does better.

The Yamaha is supposed to some sort of ground sensing transmission method on the RCA unbalanced output -- not sure what that entails.

Another owner on AVS is reporting noise on all channels. Connected to a Denon.

Maybe once I'm fully awake with coffee I can think of something.

 

[Buckeye Amps]

Does anyone have pictures of the insides?

 

[Mistar Muffin]

I appreciate the replies here. I think it's important to note that I get this noise on even-numbered channels with nothing connected to the amp except power and a lone speaker. I can move the speaker from terminal to terminal and hear the noise audible from my position on the floor 6 feet away from my main testing speaker.

@Buckeye Amps If you are willing to offer analysisI can take this thing apart and take some pictures.

 

[pfgiv]

I appreciate the replies here. I think it's important to note that I get this noise on even-numbered channels with nothing connected to the amp except power and a lone speaker. I can move the speaker from terminal to terminal and hear the noise audible from my position on the floor 6 feet away from my main testing speaker.

@Buckeye Amps If you are willing to offer analysisI can take this thing apart and take some pictures.

while I have the 8250, I'm not up to the task of taking electronics apart. No one has posted a photo of the interior of either amp, so would be cool to see it.

Thanks

 

[Buckeye Amps]

I have no problem offering help from what I can see. Most likely if it is an internal issue/shortcoming it will be because of the input board design. And if so, not much insight can be had without a schematic.

But it doesn't hurt to take a peak under the hood.

 

[saxlylong]

I received my 8125x mid last week and finally had the chance to mess around with it over the weekend. I am going from an Onkyo RZ50 into the 8125x through the XLR to RCA Monoprice Premier cables to the Monolith THX-365 speakers. Like others that have posted, I fired the amp up to the sound of humming. I am not sure if there is a consensus when people use words like "noise" and "hum", but my hum is very much like a 60-cycle ground loop on all channels. This "hum" is audible from my MLP roughly 9-10 feet away from my LCR speakers and 6-8 feet from my surrounds. MLP is slightly off center. When bringing the volume up, the hum gets louder. There is also "noise" when the volume is cranked at reference that I would describe as "SHHHHHHHHH". I have always known this as "amplifier noise" and normal. It is audible at reference from a foot or so away from the speakers but not at the MLP.

I set out to try and fix the hum with research online and then spent a few hours chasing what I thought was a ground loop. After moving components around from the different electrical circuits to the same circuit, and then trying to ground the chassis with the lug, I could lessen the hum, but never get totally rid of it. I found out that the issue was the HDMI cable run from the AVR to my projector about 25 feet away. I swapped the HDMI cable with another cheap one and the hum went away. The best I can come up with was electrical interference causing a ground loop. I'm likely going to order a fiber optic hdmi cable so that there won't be electrical interference with the run.

The amp itself sounds great; considerably better than the Onkyo's internal amplifier. There is considerably more dynamics, clarity in sound, and more gain than I could possibly need to power my Monolith THX-365 speakers. Color me surprised this morning when I saw the testing above showing the loss of SINAD when converting the amp to unbalanced. On paper, the Onkyo has a better SINAD (77dB) than the test above shows (72-3dB).

Are these results repeatable with different setups? Is this a Hypex problem or a Monoprice implementation problem? Does this issue exist with Buckeye, VTV, etc? Do other amps exhibit this same problem, such as the Monolith AB amps, Purifi, or some other equivalent to the Hypex? Why is it that nobody has tested XLR to RCA loss before? I would think that many people looking for external amplification probably have a mid-grade AVR with RCA pre-outs, not a massively expensive processor.

This is certainly concerning and confusing, considering the price tag. On the other hand, my ears tell me a significant improvement. My biggest concern is spending the coin and not being able to fully unlock the potential of the amp.

 

[Jdunk54nl]

I received my 8125x mid last week and finally had the chance to mess around with it over the weekend. I am going from an Onkyo RZ50 into the 8125x through the XLR to RCA Monoprice Premier cables to the Monolith THX-365 speakers. Like others that have posted, I fired the amp up to the sound of humming. I am not sure if there is a consensus when people use words like "noise" and "hum", but my hum is very much like a 60-cycle ground loop on all channels. This "hum" is audible from my MLP roughly 9-10 feet away from my LCR speakers and 6-8 feet from my surrounds. MLP is slightly off center. When bringing the volume up, the hum gets louder. There is also "noise" when the volume is cranked at reference that I would describe as "SHHHHHHHHH". I have always known this as "amplifier noise" and normal. It is audible at reference from a foot or so away from the speakers but not at the MLP.

I set out to try and fix the hum with research online and then spent a few hours chasing what I thought was a ground loop. After moving components around from the different electrical circuits to the same circuit, and then trying to ground the chassis with the lug, I could lessen the hum, but never get totally rid of it. I found out that the issue was the HDMI cable run from the AVR to my projector about 25 feet away. I swapped the HDMI cable with another cheap one and the hum went away. The best I can come up with was electrical interference causing a ground loop. I'm likely going to order a fiber optic hdmi cable so that there won't be electrical interference with the run.

The amp itself sounds great; considerably better than the Onkyo's internal amplifier. There is considerably more dynamics, clarity in sound, and more gain than I could possibly need to power my Monolith THX-365 speakers. Color me surprised this morning when I saw the testing above showing the loss of SINAD when converting the amp to unbalanced. On paper, the Onkyo has a better SINAD (77dB) than the test above shows (72-3dB).

Are these results repeatable with different setups? Is this a Hypex problem or a Monoprice implementation problem? Does this issue exist with Buckeye, VTV, etc? Do other amps exhibit this same problem, such as the Monolith AB amps, Purifi, or some other equivalent to the Hypex? Why is it that nobody has tested XLR to RCA loss before? I would think that many people looking for external amplification probably have a mid-grade AVR with RCA pre-outs, not a massively expensive processor.

This is certainly concerning and confusing, considering the price tag. On the other hand, my ears tell me a significant improvement. My biggest concern is spending the coin and not being able to fully unlock the potential of the amp.

It was probably the CEC implementation on the HDMI cable causing the hum. This has been an issue with quite a few if you do a quick google search. I had the same issue. The ground loop originated in my coax cable hookup from my OTA antenna, then wen through the tv and into the HDMI cable to the receiver. Crazy how ground loops can travel through devices! The only way I could fix it was to remove my cable hookup and just screw it back in when needed.

That was with an older yamaha aventage 1000. I ultimately fixed it by going to a htp-1 and it no longer has that issue.

 

[Buckeye Amps]

Are these results repeatable with different setups? Is this a Hypex problem or a Monoprice implementation problem? Does this issue exist with Buckeye, VTV, etc?

I can't answer about the SINAD drop using RCA to XLR on my amps (hasn't been tested) but I can comment that audible hum/hiss/noise using RCA to XLR setups is not an issue to date with any of my implementations. Or at least not an issue anyone has reported over the last two years.

But I am curious about the SINAD drop so will be doing some testing to see how it holds up. Color me curious.

 

[Mistar Muffin]

I have no problem offering help from what I can see. Most likely if it is an internal issue/shortcoming it will be because of the input board design. And if so, not much insight can be had without a schematic.

But it doesn't hurt to take a peak under the hood.

Photos:

https://imgur.com/a/anQ463G

 

[Mistar Muffin]

I received my 8125x mid last week and finally had the chance to mess around with it over the weekend. I am going from an Onkyo RZ50 into the 8125x through the XLR to RCA Monoprice Premier cables to the Monolith THX-365 speakers. Like others that have posted, I fired the amp up to the sound of humming. I am not sure if there is a consensus when people use words like "noise" and "hum", but my hum is very much like a 60-cycle ground loop on all channels. This "hum" is audible from my MLP roughly 9-10 feet away from my LCR speakers and 6-8 feet from my surrounds. MLP is slightly off center. When bringing the volume up, the hum gets louder. There is also "noise" when the volume is cranked at reference that I would describe as "SHHHHHHHHH". I have always known this as "amplifier noise" and normal. It is audible at reference from a foot or so away from the speakers but not at the MLP.

I set out to try and fix the hum with research online and then spent a few hours chasing what I thought was a ground loop. After moving components around from the different electrical circuits to the same circuit, and then trying to ground the chassis with the lug, I could lessen the hum, but never get totally rid of it. I found out that the issue was the HDMI cable run from the AVR to my projector about 25 feet away. I swapped the HDMI cable with another cheap one and the hum went away. The best I can come up with was electrical interference causing a ground loop. I'm likely going to order a fiber optic hdmi cable so that there won't be electrical interference with the run.

The amp itself sounds great; considerably better than the Onkyo's internal amplifier. There is considerably more dynamics, clarity in sound, and more gain than I could possibly need to power my Monolith THX-365 speakers. Color me surprised this morning when I saw the testing above showing the loss of SINAD when converting the amp to unbalanced. On paper, the Onkyo has a better SINAD (77dB) than the test above shows (72-3dB).

Are these results repeatable with different setups? Is this a Hypex problem or a Monoprice implementation problem? Does this issue exist with Buckeye, VTV, etc? Do other amps exhibit this same problem, such as the Monolith AB amps, Purifi, or some other equivalent to the Hypex? Why is it that nobody has tested XLR to RCA loss before? I would think that many people looking for external amplification probably have a mid-grade AVR with RCA pre-outs, not a massively expensive processor.

This is certainly concerning and confusing, considering the price tag. On the other hand, my ears tell me a significant improvement. My biggest concern is spending the coin and not being able to fully unlock the potential of the amp.

The hum I am currently troubleshooting happens with nothing connected to my amp except power and a speaker. I mention this because I got to this point by troubleshooting a MUCH louder noise that sounds a lot like what you are describing. In my case, disconnecting the RCA->XLR cables between my Marantz AVR and the Monolith made things quiet down. I worked backwards, removing HDMI devices from my AVR until the hum stopped. It was my HDFury VRROOM HDMI cable that was adding the noise. In moving over to the HDFury, I removed the HDMI devices connected to it, one by one and traced it to my Home Theater PC. Disconnecting HDMI from the HTPC removes this noise. There are other complaints online about the RTX 3000 series of GPU adding noise to the HDMI output. Before I got too deep in trying to resolve this issue I noticed that the amp still had noise/hum from my left speaker with no inputs connected to the Monolith. It is a much quieter hum, but still audible. I only had my mains connected at this time. This is what led me to discover that the even-numbered channels had this hum.

Right now, I've paused troubleshooting the noise coming from the HTPC and am focused on just trying to make the Monolith as silent as I can with nothing connected except power. I have already exchanged with Monoprice once. If I can't fix this I will just ask for my money back.

I do plan to try a different PSU in my HTPC and perhaps wire the GPU with separate PCI-E power connectors to see if I can reduce the noise that it adds to the chain. Moving the computer and amp to the same or different circuits has no impact on this noise. Nor does using a ground lift adapter on the HTPC. I dont' think it's a ground loop, more like interference. I notice the noise coming from the speakers when using the computer seems to pitch up and down based on the activity in the PC. But, not so worried about this right now as everything is disconnected from the amp.

 

[Buckeye Amps]

I can't tell from the photos, as I think the answer would be between the back input board and the inside back case panel, but where does that bundle of black wires tied to the grounding point go? I would guess they are grounding points for the XLR connectors maybe?

Also, not sure why they are using inline filters since the Hypex modules already have filtering. I don't think that would be the issue leading to noise/hum but for me, anytime you add unnecessary components, especially when grounding is involved, you never know.

The wiring itself looks good (not a fan of the adhesive mount pads for reasons pointed out to me about my builds 2yrs ago). But the way the input board is horizontal and partially obstructed, hard to get a great look/idea what's going on with the input/output connectors.

It could just be the way they implemented their builds it makes them VERY sensitive to any ground loop or line noise. Not exactly an answer or helpful, I know, but sometimes it just happens where an issue is always present in ones setup but masked until a certain component is added and then it becomes apparent.

 

[saxlylong]

I can't answer about the SINAD drop using RCA to XLR on my amps (hasn't been tested) but I can comment that audible hum/hiss/noise using RCA to XLR setups is not an issue to date with any of my implementations. Or at least not an issue anyone has reported over the last two years.

But I am curious about the SINAD drop so will be doing some testing to see how it holds up. Color me curious.

In layman's terms: does a SINAD drop mean that the "SHHHH" amp noise floor increases? Does a low SINAD cause higher distortion at higher volume levels? As things sit, with the hum gone, the actual amp noise is not audible at my MLP. The projector fan 4 feet away and my home HVAC system are much louder.

I would be interested to see what you find about the XLR to RCA output on your amps.

 

[pfgiv]

I wonder if the problem is only related to the 8125. I do not notice any hum with the 8250, fwiw. I am running XLR to XLR