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Need a Preamp/Amp!

A couple days ago I powered up the amp in a different room and at different times, and I felt the hum was quieter though it can be hard to tell sometimes. I feel the hum is due to DC offset, but I'm still not completely sure.

I went ahead and ordered the CMX-2 a couple days ago, and it should arrive tomorrow. I figure it's a relatively easy troubleshooting step, and if it doesn't help I should be able to return it. I'm really hoping it works because the idea of initiating an RMA for the amp and shipping the amp back isn't too exciting (the amp is pretty heavy to lug around lol).

I'll report back with my results, wish me luck!
 
So unfortunately it doesn't seem the CMX-2 is resolving my issue :(

I guess the amp has a defect, I'll have to call Monoprice.

I'm not sure whether I should try an exchange, as I'm a bit worried a replacement unit might have the same issue. I'll also have to see what return / replacement shipping costs Monoprice will cover, since the amp is kinda heavy.

Or if I should return it and get another make/model amp, I'm open to suggestions on other options to research.
 
Being a smaller company, I'd call Monoprice and explain what you've tried to do to eliminate the problem, and see how they respond. If they don't offer to provide free shipment back, PLUS free shipment if a new unit exhibits the same problem, I'd just ask for a refund and look elsewhere. Good luck!
 
team_tsp said:
So unfortunately it doesn't seem the CMX-2 is resolving my issue :(

I guess the amp has a defect, I'll have to call Monoprice.
Click to expand...
That is really strange. The transformer in the Monoprice version of that amp is no different than the amp it was derived from, and certainly not any less well made. The only "cost cutting" is having no XLR balanced inputs.

That said, you might be better off with a different make of amp since a replacement might not work any better with your AC.
 
That's a shame. I like that amp.

I am sure Batman will help you with a halo amp.
 
Thanks for the input guys -

@Botch - I'm still debating which way to go, normally I'd be wanting to try a replacement unit, but with the amp weighing 60 lbs, it's a bit clumsy shipping it back and forth, especially if the replacement unit exhibits the same symptom. I'll call Monoprice tomorrow (since they're closed on the weekend) and get their thoughts.

@rammisframmis & @Flint - If you feel manufacturing tolerances are really tight, then I guess odds are low a replacement unit would be different :( I really wanted to like the amp too, since it seems to play clean and feels like it has unlimited power lol.

As far as Parasound Halo amps, I would be looking at the A23. I know it's not a big deal, but would it seem strange to run the 2100 preamp (part of the New Classic series) with a Halo amp? :p

Last time I spoke with @Batman, it didn't sound like he had a distributor that carried the Halo series, but I can continue discussing with him. Or I can try to buy it locally or from audioadvisor.com.

Or likewise, does anyone have experience with Parasound's New Classic amps (models 2125 or 2250)?
 
team_tsp said:
As far as Parasound Halo amps, I would be looking at the A23. I know it's not a big deal, but would it seem strange to run the 2100 preamp (part of the New Classic series) with a Halo amp? :p
Click to expand...

Those Dynaudio speakers can benefit from a very high current amp which can be pushed to its limits regularly and not fade from the task. I don't think you will get that from the Parasound New Classic amps and I don't recommend them for that reason. That said, if you were to tell me you generally keep the levels low, don't listen loud, and generally use the system for background music, I would not have recommended the Monolith amps nor the Halo amps. But, you don't give the impression that these speakers are for casual soft listening sessions.

That said, get the Halo, the A21 if the price is acceptable.

As for the idea it seems strange to use a Halo amp with the lower line preamp, that's nonsense. If I were to recommend a high end Krell amp or Bryston amp (both of which are great brands), would it seem strange to use that preamp with those big amps? It shouldn't.

The preamp is very good and doesn't need to be fancy or expensive to get the job done. The amp, especially with those specific speakers, would best service the job if it can handle constant high current, complex loads, and shine all the time. The preamp doesn't care about any of that.

So, don't think about "matching" product lines, as that has nothing to do with performance. If you can't wrap your head around it, get a Bryston or Krell amp. I recommend at least 150 watts into 8 ohms minimum for those speakers.
 
Flint said:
Those Dynaudio speakers can benefit from a very high current amp which can be pushed to its limits regularly and not fade from the task. I don't think you will get that from the Parasound New Classic amps and I don't recommend them for that reason. That said, if you were to tell me you generally keep the levels low, don't listen loud, and generally use the system for background music, I would not have recommended the Monolith amps nor the Halo amps. But, you don't give the impression that these speakers are for casual soft listening sessions.

That said, get the Halo, the A21 if the price is acceptable.

As for the idea it seems strange to use a Halo amp with the lower line preamp, that's nonsense. If I were to recommend a high end Krell amp or Bryston amp (both of which are great brands), would it seem strange to use that preamp with those big amps? It shouldn't.

The preamp is very good and doesn't need to be fancy or expensive to get the job done. The amp, especially with those specific speakers, would best service the job if it can handle constant high current, complex loads, and shine all the time. The preamp doesn't care about any of that.

So, don't think about "matching" product lines, as that has nothing to do with performance. If you can't wrap your head around it, get a Bryston or Krell amp. I recommend at least 150 watts into 8 ohms minimum for those speakers.
Click to expand...

Gotcha, yea hopefully it was apparent I was mostly joking about asking about using the 2100 with a Halo amp. :p

Usually I don't listen to music very loud, but I do like to crank it occasionally, and do want a quality amp since I took the leap of going with the C1's, and they have a relatively lower efficiency rating. However, the A21 (with MSRP at $2495) is quite a bit more than I'm wanting to spend on an amp.

Are there any other amps ~$1000 or less that are recommended? Or if the Monolith 2 seems to be the best choice, I'll strongly reconsider pursuing an exchange with Monoprice (assuming they cover at least some shipping charges) and hope for the best.
 
Yeah unfortunately the Halo line does not go through distribution so I don't have access to any of the Halo product. The only separate amps I have access to is the New Classic, Marantz, and Onkyo. Of those I'd imagine the only consideration would be New Classic and they may not be adequate?
 
Since the power transformers in all ATI amps are cranked out by machine (just like other manufacturers), one transformer is likely to be identical to the next. Try a different brand.

Just be aware that just because you might not have a DC problem, you could very well still have high distortion on your AC line. If the peaks of the AC are being clipped off and/or distorted by saturation of the pole transformer, and that distortion is somewhat symmetrical, you could still run into a buzz problem. The Emotiva gadget will not correct this type of distortion, and the only remedy is outright regeneration, which is expensive to do, and not recommended for a power amp in any event because of current limitations.

On the other hand, another amplifier brand might have a transformer which isn't bothered either way by distortion on the AC line. This is just something you should be aware of.

The AC line can be checked for distortion, but that is something a technician needs to do if you get another amp and it also buzzes.
 
It depends on the distortion. A balanced line transformer will do nothing to remove distortion which is already on the AC line - just like a balanced connection in audio will not remove distortion which is present before the balanced connection. It can filter EMI and RFI, but that's about it. Blame the stupid AC power configuration the USA is forced to contend with. Two phase 240VAC where each half is loaded differently is guaranteed to cause problems. But then we didn't have all our gadgets when the standards for power distribution were codified at the turn of the last century. Countries which use balanced 240VAC have it better, and don't have the DC problem. Think of AC power like audio, only with much more current, and you will get the picture.

Some of ATI's professional cinema amps are designed to run only on 240VAC, mostly for availability to source massive amounts of current.

Of course, many nominally 120VAC amplifiers can be re-wired to run on 240VAC, but that is certainly not an end user modification.
 
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Unfortunately I don't have much else on hand to compare the Monolith with. The only other amp-type devices I have are a 10 yr old entry-level Denon AVR and an old random Sony shelf system, neither of which make any sound unless I literally press my ear up onto their cases, at which point I can hear a minuscule hum/buzz. My SVS sub's plate amp doesn't make any sound that I can hear. But I realize all those products have very different power supply design/parts compared to the Monolith (or similar amps).

Regarding Marantz, the only stereo amp I see on their website is the MM7025. I've been trying to google information on that amp, but there seems to be very little information out there on it.

I guess I'll keep mulling over the options, hoping inspiration hits soon so I don't get stuck in analysis paralysis lol
 
rammisframmis said:
On the other hand, another amplifier brand might have a transformer which isn't bothered either way by distortion on the AC line. This is just something you should be aware of.
Click to expand...
I've been trying to follow this thread, but one of the reasons I became a mechanical engineer was that I was too smart to do civil, and not smart enough to do electrical!

Questions: is it that difficult to design a transformer that will protect against AC line distortion? Is one being better than another just a fluke - or by design?

Jeff
 
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