NEWS: monolith amp with Hypex amplification!

[joeliu2003]

We found the issue.

The M8125/M8250 was designed to be driven by a balanced input signal, and no provision was made for an unbalanced input. Certain cables and adapters used to connect between unbalanced (RCA) sources and the M8125/M8250 can result in a low level buzz in even numbered channels. We have devised a hardware fix with will eliminate the problem which can be retrofitted to units in the field using only a Phillips head screwdriver. We anticipate the fix to be available in the coming weeks.

If you are not using an XLR to RCA adapter, there should not be a noise issue and the product performs as it should.

@MonolithGuy just wanted to confirm that new units (ordered today) have the indentified fix implemented? I just ordered an 8125 that I will be using with the monoprice RCA to XLR cables. Please confirm.

Thank you for the amazing resource this forum is!!

 

[MonolithGuy]

The current units in our warehouse do not have the fix applied yet. They will in the very near future. We are working the logistics of this out.

Here is a picture with the "fix" installed. As you can see, it's a pretty simple fix

 

[joeliu2003]

The current units in our warehouse do not have the fix applied yet. They will in the very near future. We are working the logistics of this out.

Here is a picture with the "fix" installed. As you can see, it's a pretty simple fix

Oh yikes - so you are currently sending units out without the fix in place?

Feels like a stop ship should happen....anyways....do I need to refuse the unit being sent to me so it can have the fix applied?

I'm planning to use with unbalanced input from a Marantz Cinema 50 -- so assuming my setup would exhibit the issue on the even channels.

Planned on using the monoprice RCA to XLR cables.

Joe

 

[DWG]

I'm curious what this fix is? Centered in the green box is an "L" shaped bracket. Also that it is three months later, does the current product shipping have this fix? I am considering the 8250x

 

[mhardy6647]

Looks like a shield(?).

 

[DWG]

@MonolithGuy Maybe Hobie can answer this

 

[2000b5]

@MonolithGuy is it right that we can use the same rack ears as the HTP1? Any pulse on when the ears will be back in stock and if the amps are shipping with the mod done yet? I’ll be buying the 8125x and will likely be starting with an unbalanced signal path.

 

[Blackdevil77]

Will we see an ASR review of the 8250? I'm sure it will do well, but I'd love to see the actual test results.

 

[DWG]

The Monoprice site has some nice detailed Audio Precision test reports, although not quite as thorough as Amirs. Also this site has detailed reports of the NC502MP multichannel amp provided by Buckeye. Since they both use they same modules similarily configured, my guess is they would measure about the same.

Last month Monoprice had the 8250 on sale so i pulled the trigger. I also pulled the trigger on the Parasound A52+ (a five channel amp) which was also on sale. Compared the two for a month. Both had oodles of ultraclean power, that I believe would meet almost anybody's requirements. I ended up returning the Parasound because size and weight (at 62 its getting hard to move heavy amps and speakers around) and the fact that the 8250 has eight channels (although I am currently only using five).

One note on the 8250. As discussed on the last few pages of this thread, with speakers connected and no input cables installed, I was getting a very slight hum/hiss in the even number channels. Speakers are 88dB sensitivity KEF IQ7 speakers. I had to place my ears close to the speakers to hear this. Once I connected XLR cables between my pre/pro and the amp the noise disappeared. I have not opened the case of the amp to see if Monoprice added their shield (see post#282) to eliminate/reduce noise. This is nitpicking but If you are concerned about this and are using very high sensitivity speakers and RCA/XLR adapters you might want to consider alternatives.

Note two and this is my theory and I have no facts to back this up. @mhardy6647 mentioned the fix in post #282 looks like a shield. I agree. The shield separates the power supply from the input signal that arrives via a 16 connection ribbon cable. It seems to me noise from power supply components are finding their way into the ribbon cable and finding their way to the amplifier output at a very low level. Balanced XLR cables will cancel this noise out where an unbalanced cable wont. I'm not sure why Hypex would use a ribbon cable in lieu of shielded cable or twisted pair, but it is what it is and i dont think this should be an issue for most users.

Anyway, small imperfections aside this is a great amplifier and I can eagerly recommend the NCXXXMP based amplifiers available from the various manufacturers.

 

[Blackdevil77]

Of course I just missed the sale. I’ll be keeping an eye on it for when it goes on sale again. The next time it does, I’ll snag one

 

[DWG]

FYI. I believe the 8125 (lower powered amp) is currently on sale for $1499. It may have all the power you need.

 

[Blackdevil77]

FYI. I believe the 8125 (lower powered amp) is currently on sale for $1499. It may have all the power you need.

I'm definitely gonna need the 8250. I currently use 300 wpc Crown DCi amps and those hit the limiters when cranking the system on the surrounds. I definitely don't want to feed them less.

 

[dumpingg]

The current units in our warehouse do not have the fix applied yet. They will in the very near future. We are working the logistics of this out.

Here is a picture with the "fix" installed. As you can see, it's a pretty simple fix

Oh yikes - so you are currently sending units out without the fix in place?

Feels like a stop ship should happen....anyways....do I need to refuse the unit being sent to me so it can have the fix applied?

I'm planning to use with unbalanced input from a Marantz Cinema 50 -- so assuming my setup would exhibit the issue on the even channels.

Planned on using the monoprice RCA to XLR cables.

Joe

Any updates on if the currently shipping units have the fix or not?

 

[Mistar Muffin]

One note on the 8250. As discussed on the last few pages of this thread, with speakers connected and no input cables installed, I was getting a very slight hum/hiss in the even number channels. Speakers are 88dB sensitivity KEF IQ7 speakers. I had to place my ears close to the speakers to hear this. Once I connected XLR cables between my pre/pro and the amp the noise disappeared. I have not opened the case of the amp to see if Monoprice added their shield (see post#282) to eliminate/reduce noise. This is nitpicking but If you are concerned about this and are using very high sensitivity speakers and RCA/XLR adapters you might want to consider alternatives.

I'm not so sure this issue is even nitpicking. I think there's a reasonable expectation that gear at this price point not introduce power-supply interference into the signal path, even if using balanced cables negates it. Especially when the noise is only introduced on half of the channels. It's been a while since I have looked at the @GXAlan measurements but I seem to remember the XLR connection significantly reducing, but not eliminating the 60hz noise on even-channels. Even though the noise gets reduced to likely-inaudible levels by balanced cables I would think any continued mismatch in channel measurements would invite fair criticism.

I just followed-up with @MonolithGuy over email about the DIY repair kits. My unit just had its 6-month birthday and I am still only able to use half of my channels. I am just not in a place where I can drop three or four thousand dollars on a pre-pro with balanced outputs. I am tempted to buy some stainless steel angle brackets from a home improvement store and affix them as shown in the December photo. I know there are many of us that would appreciate an update.

 

[GXAlan]

I'm not so sure this issue is even nitpicking. I think there's a reasonable expectation that gear at this price point not introduce power-supply interference into the signal path, even if using balanced cables negates it. Especially when the noise is only introduced on half of the channels. It's been a while since I have looked at the @GXAlan measurements but I seem to remember the XLR connection significantly reducing, but not eliminating the 60hz noise on even-channels. Even though the noise gets reduced to likely-inaudible levels by balanced cables I would think any continued mismatch in channel measurements would invite fair criticism.

I just followed-up with @MonolithGuy over email about the DIY repair kits. My unit just had its 6-month birthday and I am still only able to use half of my channels. I am just not in a place where I can drop three or four thousand dollars on a pre-pro with balanced outputs. I am tempted to buy some stainless steel angle brackets from a home improvement store and affix them as shown in the December photo. I know there are many of us that would appreciate an update.

That is correct. I also ran my unit to a speaker and had higher buzz on half of the channels. Subtle, but weird. I ended up returning mine, so I haven’t followed the issue.

ATI is a world class builder of amps, so I am surprised it has taken this long for your to get yours fixed. MonolithGuy did reveal in a YouTube interview that he is dealing we a new diagnosis of cancer, so Monolith probably isn’t the highest focus right now.

The Monolith prices are even lower than Buckeye amps, so in a way, it would be nice to know that this is the best it gets and you have extra noise for cost savings or there is a simple
Fix and you have max performance AND cost savings.

 

[DWG]

I'm not so sure this issue is even nitpicking. I think there's a reasonable expectation that gear at this price point not introduce power-supply interference into the signal path, even if using balanced cables negates it. Especially when the noise is only introduced on half of the channels. It's been a while since I have looked at the @GXAlan measurements but I seem to remember the XLR connection significantly reducing, but not eliminating the 60hz noise on even-channels. Even though the noise gets reduced to likely-inaudible levels by balanced cables I would think any continued mismatch in channel measurements would invite fair criticism.

I just followed-up with @MonolithGuy over email about the DIY repair kits. My unit just had its 6-month birthday and I am still only able to use half of my channels. I am just not in a place where I can drop three or four thousand dollars on a pre-pro with balanced outputs. I am tempted to buy some stainless steel angle brackets from a home improvement store and affix them as shown in the December photo. I know there are many of us that would appreciate an update.

Apologies @Mistar Muffin if my earlier remark came across as insensitive. Using the word "nitpicking" was probably a poor choice of words and I didn't fully consider how this issue was affecting others. For me, the noise on even numbered channels was almost inaudible (maybe my new unit has the fix). Once XLR-XLR cables were attached to my pre-pro the amp became dead silent. If only four channels of your amp are usable I feel bad for you. I hope the manufacturer makes good for you and others dealing with the issue.

 

[danstahl]

@MonolithGuy is it right that we can use the same rack ears as the HTP1? Any pulse on when the ears will be back in stock and if the amps are shipping with the mod done yet? I’ll be buying the 8125x and will likely be starting with an unbalanced signal path.

Same question for me. The description says its easy to rack mount but I can't actually find rack ears for this to be mounted with .

 

[dumpingg]

Just a note for the crowd here. I just purchased a B-Stock M8125X unit from Monoprice. I was told by tech support at Monoprice that all the B-Stock units have the shield retro fix mod installed. However the new units still do not. At present the M8125X new and B-stocks are on sale. Also, there is a 20% off coupon code MP20 on the monoprice homepage that works. So the B-Stock M8125 was $1088 plus tax.

When my M8125X arrives I will verify that the shield is in place and post an update here.

 

[dumpingg]

I am happy to report that the B-Stock M8125X did in fact have the shields already installed. Also testing so far (at least in my setup) does not reveal any hum issues. And my setup includes RCA to XLR adapter cables.

 

[kalexan9]

Just a note for the crowd here. I just purchased a B-Stock M8125X unit from Monoprice. I was told by tech support at Monoprice that all the B-Stock units have the shield retro fix mod installed. However the new units still do not. At present the M8125X new and B-stocks are on sale. Also, there is a 20% off coupon code MP20 on the monoprice homepage that works. So the B-Stock M8125 was $1088 plus tax.

When my M8125X arrives I will verify that the shield is in place and post an update here.

How do we go about getting the mod installed for the new units? I just got a new unit delivered.