NEWS: monolith amp with Hypex amplification!

[Mistar Muffin]

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.

Doesn't the fact that I get humming without any inputs connected negate any concerns about these inputs or a ground loop being the cause? Is there any fault in that logic?

 

[Jdunk54nl]

Doesn't the fact that I get humming without any inputs connected negate any concerns about these inputs or a ground loop being the cause? Is there any fault in that logic?

Ground loop could still be the cause. You have it plugged into a power outlet. Even plugging into another outlet may not fix a ground loop issue since they are still all tied together at your breaker box.

Is there any way you could try it at a different location? Office? Neighbors? etc?

The reason I suggest the above is due to it being slightly weird that this is happening across two different amps. So it seems it is either something with your home electrical or something wrong with the design of the amps. So need to rule out your home electrical somehow.

 

[PJ 1]

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

Yeah, same here. Sorry to hear the problems they are having with ground loops. I have had the 8250 connected to my 8805 with XLRs for about a month. Plugged and unplugged several things into the same 20 amp breaker as the HT with zero issues. I do have some (what I think) are quality HDMI, XLR, and speaker cables from Blue Jeans Cables but nothing else special. I would suggest tagging "MakeMineVinyl" to see if he knows why things are the way they are with these amps. He's been pretty helpful in many amp discussions in the past and might have suggestions that work.

 

[Mistar Muffin]

Ground loop could still be the cause. You have it plugged into a power outlet. Even plugging into another outlet may not fix a ground loop issue since they are still all tied together at your breaker box.

Is there any way you could try it at a different location? Office? Neighbors? etc?

The reason I suggest the above is due to it being slightly weird that this is happening across two different amps. So it seems it is either something with your home electrical or something wrong with the design of the amps. So need to rule out your home electrical somehow.

What about a battery backup, like a UPS? I could disconnect from the mains and run on battery output. Still strange that the amp would only hum on one channel on each module, though...

 

[Buckeye Amps]

What about a battery backup, like a UPS? I could disconnect from the mains and run on battery output. Still strange that the amp would only hum on one channel on each module, though...

Or just disconnect everything else on that circuit and only have the amp plugged into the power outlet.

 

[Mistar Muffin]

Or just disconnect everything else on that circuit and only have the amp plugged into the power outlet.

I went with the UPS, as I had one on-hand. I stole it from my 3D Printer. The hum is still present when connected to the UPS while running on battery power. Interestingly, and possibly most-importantly: the hum still only exists on the even-numbered channels.

Questions for experts: What the heck could Monoprice have done, design-wise, that would only allow the hum to exist on one channel per nCore module? I have tested two amps and both display this behavior so I lean towards a design flaw. Even in the case of dirty power I would expect the hum to come from all channels.

If it is a design flaw I'm a bit surprised I'm the only one seeing it. Admittedly, my initial testing was with some very sensitive speakers (Klipschorns). But I have since tested with less-sensitive bookshelf and surround speakers and can hear the hum (with no inputs connected) from only the even-numbered channels. It's very strange.

 

[peng]

I went with the UPS, as I had one on-hand. I stole it from my 3D Printer. The hum is still present when connected to the UPS while running on battery power. Interestingly, and possibly most-importantly: the hum still only exists on the even-numbered channels.

Questions for experts: What the heck could Monoprice have done, design-wise, that would only allow the hum to exist on one channel per nCore module? I have tested two amps and both display this behavior so I lean towards a design flaw. Even in the case of dirty power I would expect the hum to come from all channels.

If it is a design flaw I'm a bit surprised I'm the only one seeing it. Admittedly, my initial testing was with some very sensitive speakers (Klipschorns). But I have since tested with less-sensitive bookshelf and surround speakers and can hear the hum (with no inputs connected) from only the even-numbered channels. It's very strange.

Your logic seems right! With nothing connected except the power cord and speakers then unless your speaker are the active type there should be no ground loop. Now you mentioned only the odd number channels hum, it gets even weirder and it would seem more likely there is something wrong with the amp (likely internal wiring related) itself. You should try to get a replacement and see what happens.

 

[Buckeye Amps]

Your logic seems right! Will nothing connected except the power cord and speakers then unless your speaker are the active type there should be no ground loop. Now you mentioned only the odd number channels hum, it gets even weirder and it would seem more likely there is something wrong with the amp (likely internal wiring related) itself. You should try to get a replacement and see what happens.

This is his second amp having the same exact issue fwiw

 

[GXAlan]

This is his second amp having the same exact issue fwiw

I think my measurements show that this isn’t the case for all amps. My serial is in the low 100’s and was ordered about 2 weeks ago. I haven’t decided if I am going to keep it yet.

But two in a row suggests that
A) there is a batch of bad assembly at ATI. I would imagine that they are tested before shipping
B) there is a batch of bad hypex modules
C) there is something else we haven’t identified yet

@Mistar Muffin , you should reach out to ATI directly. They probably would like to know? What are your serial number ranges?

@Hypexsales , do you have any contact to the engineering team to address this?

@MakeMineVinyl , as a general amplifier expert with confidential employer who once mentioned that you work for a company focused on reliability, do you have any input?

 

[Buckeye Amps]

Just for clarity, was not at all trying to imply this is a systemic issue.

 

[GXAlan]

Just for clarity, was not at all trying to imply this is a systemic issue.

No worries. Even though you are a “competitor”, I don’t think anyone thinks you are being unfair.

Two in a row does suggest that there is a “systemic” issue as opposed to a random failure, but it could be a systems error on the user/owner’s behalf. Either way, it’s not just two amps. It’s 8 modules total, which is really weird.

 

[Mistar Muffin]

I contacted Monoprice this morning and have set up another RMA. By the time the third unit arrives I will be past my 30 day return window but I decided to roll the dice anyways. If the issue persists I will expect Monoprice to make it right, return window be damned.

Dylan has been completely fair and helpful in his feedback. If anything I think I was the first one to suggest this might be a systemic issue, although I referred to it as a "design flaw".

If I was on the other side of this, I would agree with @GXAlan that the most likely explanation would be operator error. My hope that by testing with only power and a single speaker I have eliminated any possibility of that. For the curious here was my testing methodology.

1) Connected amp to power ONLY
2) Connected left Klipschorn to Channel 1
3) Turned on amp
Result: No Hum

4) Moved left K-Horn to Channel 2
Result: Hum

5) Tested remaining channels by moving left K-Horn between terminals
Result: Hum in Channels 2, 4, 6, 8

6) Repeated test with right K-Horn, to eliminate issue with speaker wire or specific speaker
Result: Hum in Channels 2, 4, 6, 8

7) Repeated test with modern, less sensitive Klipsch surround, RP-240S.
Result: Hum in Channels 2, 4, 6, 8 (audible from the floor in front of my equipment and this speaker is hung at the ceiling line)

8) Repeated test with surround back, a Klipsch bookshelf, RP-150M
Result: Hum in Channels 2, 4, 6, 8 (audible from the floor in front of my equipment and this speaker is hung at the ceiling line)

9) Returned to using left K-Horn on Channel 2 for further tests
10) Added ground-lift (cheat plug) to amp
Result: Hum reduced, but still present on Channels 2, 4, 6, 8

11) Removed cheat plug
12) Added ground wire between outlet cover screw to ground terminal on back of amp
Result: Original Hum in Channels 2, 4, 6, 8

13) Removed extra ground wire
14) Ran high-gauge extension cord to another circuit
Result: Hum in Channels 2, 4, 6, 8

15) Brought in an APC battery backup (UPS), fully charged and connected to mains
16) Connected Monolith to battery backup and powered it on
Result: Slightly louder Hum in Channels 2, 4, 6, 8. Not surprised that the UPS power is slightly noisier. It's not a high-$$ UPS

17) Yanked UPS from mains, silenced UPS alarm and tested each channel.
Result: Hum in Channels 2, 4, 6, 8

Not sure what other testing I can do. I feel fairly confident that this is a hardware issue with the unit. Either back-to-back defects or a systemic issue. I can't explain why no one else is reporting this. Maybe I got the only two units with this defect. I do note that most people seem to be gravitating towards the 200w unit, however. The 8125x has 0 reviews on Monoprice. I tried to add one of my own and it never appeared on the site. Imagine that.

 

[Krusty09]

hey,

so ch's 1,3,5,7, no hum?

 

[Mistar Muffin]

hey,

so ch's 1,3,5,7, no hum?

Dead silent.

 

[Jdunk54nl]

Dead silent.

Are these new or refurbished units?

 

[Mistar Muffin]

Are these new or refurbished units?

Both units were brand new.

 

[Jdunk54nl]

Both units were brand new.

I was hoping for the opposite. that could have helped explain the issues....

 

[peng]

Dead silent.

Really sounds like there is something wrong with the internal interconnections/wiring such as ribbon cables. If there is a bad batch modules or just random bad modules or another other components, the probability with channels 2,4,6,8 would be extremely low. This being the 2nd unit, did Monolith say anything about what was the problem with the 1st one. Did the first 1 one hum the same way and also the 2,4,6,8 channels?

 

[pfgiv]

I will be past my 30 day return window but I decided to roll the dice anyways. If the issue persists I will expect Monoprice to make it right, return window be damned.

These units have a 5 year warranty, so if they keep sending you units that do not work, that's on them for 5 years.

I would maybe try taking the unit to another home/apartment (depending where you live), with one speaker, and see if you can recreate the issue.

Actually, read more into what you wrote, and the switching of all those speakers and always only giving you issues with the even channels, probably would be no different anywhere else. Def seems to be an issue with the units.

 

[Krusty09]

if its a board problem it would need to be a ch2 problem on all boards since its 2nd ch is wired most likely to the even ch and ch1 to the odd. that would suck for them. that's a real problem.