Stellar M700s arrived 3 weeks ago


#1

I received the M700s on Monday, April 3rd.

The casework is well done. No gaps, raised edges or screws akilter. They are a nice clean design and very unobtrusive looking. I really like having two sets of speaker binding posts. It makes bi-wiring much easier.

My system

Amp: Krell KAV-3250 (250 watts x 3 channels), used to drive the main speakers and a passive subwoofer.

Speakers: Krell Resolution 1 (main), Nelson-Reed 1204 passive sub (4 12" woofers). The processor is set to crossover to the sub at 40 hz.

Preamp: Krell S-1200U home theater processor. Yea, I'm a Krell guy, maybe something to do with watching Forbidden Planet when I was young.

CD Player: Sony BDP-S5000ES Blu-ray player

Analog: Music Hall 7.3 turntable with an Ortofon Bronze cartridge

Phono Preamp: PS Audio NuWave Phono Converter. I love it.

Power: PS Audio P10 and Powerplant Premier.

Power cables: PS Audio Statement and Plus (xStream, I think), which I believe are some of the earliest power cables PS Audio came out with.

Interconnects: PS Audio xStream digital interconnect from Nuwave Phono converter to processor. Pure Silver Sound Octet with locking RCAs from preamp/processor to amps.

Speaker Cables: Pure Silver Sound Octet bi-wired from amp(s) to speakers

Environment

My system is in is a combined home theater and stereo room. This family room is open to the kitchen behind it, as well as having open hallways to the living and dining rooms. The family room/kitchen space is approximately 18x28'. The ceilings are 10'. Internal walls are 2"x4" studs with drywall.

Initial impressions

After the initial hookup, there was a hum coming from the speakers. I wouldn't say it was loud, but from the listening position, it was obvious. I was not able to reroute any cables, as that would require taking apart the shelves. I didn't want to do that until I decided whether I was going to keep the M700s.

My solution was to use cheater plugs. This removed most of the hum. I could only hear it when I had my ear within 6" of the speakers. I'm concerned that putting cheater plugs would affect the sound quality to some extent.

The initial sound was thin, though there was good detail. No point in going into any more detail at this point.

Burn-in

The M700s have been on continuously since the afternoon of April, 3rd. For the most part I have been playing music 24x7. I've also used Purist Audio Design System Enhancer burn-in CD during the past few weeks. I would say the units have in excess of 400 hours of time on them during which they were actively playing music.

There was a two day period when I switched back to the Krell amp so I could compare the sound more closely, and a few other times where I switched back to the Krell for a few hours.

Concerns

One of my concerns is that the speakers may present a difficult load for the M700s. I don't know how this might affect the sound. From the M700 literature, they can handle a 4 ohm load, and be stable with 2 ohms for musical transients. I found a Stereophile review of the speakers. From the measurements section, most of the audio band is well below 4 ohms, and even dips below 2 ohms at one point. Offsetting this load is the subwoofer, which is powered by the third channel on the Krell. Anything below 40 hz (not sure how the rolloff works, whether it's 6 DB per octave or something else) goes to the subwoofer. Here is a link to that review:

http://www.stereophile.com/content/krell-resolution-1-loudspeaker-measurements

Listening Impressions

Most of my listening was done with analog (vinyl). When I listened to digital it was done with CDs, I don't have any hi-rez recordings. I feel my system has noticeably higher resolution when listening to vinyl. The downside is the deficiencies of vinyl, such as surface noise, pops, and somewhat restricted bass, along with everything else the analog chain offers.

Overall, these amps are more dynamic than the Krell, so recordings sound more alive. On some songs, singers will harmonize with themselves. It is much easier to hear this with the M700s. I can hear two or more distinct voices, rather than a suggestion of this with the Krell. Comparing the M700s to the Krell, there is greater clarity on vocals. The Krell sounds slightly muddy in comparison.

For the high end, cymbals, and the upper range on the piano through the M700s, it doesn't seem quite as natural as with the Krell. Maybe that is due to the additional clarity, and I need to become used to it.

When a female vocalist goes into her upper range and sings more loudly, it becomes hard sounding, sometimes to the point of being unpleasant. This happened on the Barbra Streisand album Guilty. On the last song, Make It Like A Memory, Barbra starts out singing and it sounds wonderful, but then 2-3 minutes in, she goes into a higher register and sings much more loudly, when this happens, her voice becomes hard, brittle and has a glassy sound to it. This is when listening to vinyl. When listening to the CD, it seems like the dynamic range isn't as great, so her voice doesn't become nearly as unpleasant. The odd thing is that the CD is supposed to have greater dynamic range than vinyl, so I would expect the CD to have even more of a problem with this. When I listen through the Krell, I'm not hearing nearly as much of that hard glassy tone in her voice, either on vinyl or CD.

The M700s produce a more developed soundstage than the Krell. It is wider and deeper. I can hear details I couldn't hear before. Things that were only hinted at with the Krell, and more clearly audible with the M700s.

Vocals, both male and female, are more present and physical with the M700s, as compared with the Krell. I would call vocals more vivid and lifelike with the M700s.

I made some changes to see if I could address the hard sounding vocals. I removed the stock power cables that came with the M700s, and used two xStream Plus power cables. I tried with and without the cheater plugs. The hum was still present, though to a much lesser degree with the cheater. I need to work on that and see if I can get rid of the hum completely. With the Plus power cables, the loud vocals became less hard sounding. However, they still didn't seem natural. I wonder if there is something going on with the M700s, maybe increased distortion (regular or TIM) of some kind, when they are trying to reproduce the higher range in vocals or piano when loud. I don't hear this hard sound when the singer/piano isn't hitting their notes as loudly. I did clean the stylus on the cartridge to make sure it wasn't due to contamination. The cleaning had no effect.

Other material I listened to (on vinyl unless otherwise noted)

Mannheim Steamroller's Fresh Aire III - The Sky has a piano that echos throughout the song. It sounds good, but still that hard sound is there slightly. When listening through the Krell I can relax into that song and just enjoy it. As a side note, I never enjoyed this song until I listened to the vinyl version. It has a dreamy quality to it. Listening through the M700s, I just can't seem to completely relax during this song. It sound good, but it just doesn't pull me into the song, due to that hardness.

Crosby, Stills, and Nash's Daylight Again - Southern Cross sounded exceptional through the M700s. The chorus behind the singer built a huge expansive wall of voices that was wonderful. I've never heard this song sound this good. This song doesn't really have any hard percussive sounds and has a warmer sound in general, so that might be why it sounded so good to me.

Dire Straits first album - In The Gallery, it has some nice cymbal accents throughout, which are beautifully reproduced. Again, I wonder if it is because the cymbals aren't hit very hard. This is their only album I enjoy from beginning to end.

Dan Fogelberg's Wild Places on CD - Forefathers, compared to the Krell, the sound was much more expansive with many details on the mix, which the M700s brought out, which were not nearly as clear through the Krell.

Heart's Little Queen - Love Alive starts out with acoustic guitars and Ann Wilson singing. Her voice sounded much more present as compared to the Krell, where it seems a bit buried in the mix.

Al Stewarts's Year Of The Cat, MSFL release - On The Border sounds very spacious. Al's vocal is very clear and natural. The percussion, guitars, and lyrics combine to create a song that is shimmering and slightly hypnotic.

Supertramp's Crime Of The Century, MFSL release - School is outstanding. There are many details during the opening that are much clearer through the M700s. When the little girl lets out a scream just before the song starts cranking, it made me jump. The soundstage is wall-to-wall throughout the song.

Bruce Springsteen's Born In the U.S.A - I'm On Fire is a very simple track, guitar in the right channel, wood block (I assume) and cymbals in the left, and Bruce's vocal in the center, along with bass drum. There is also a synthesizer playing as a wall of sound behind everything. It's a haunting song. Through the Krell it doesn't quite have the same emotional impact.

Judy Collins' Colors Of The Day - Farewell To Tarwathie had the largest soundstage of anything I listened to. I wonder if Judy's vocals were recorded in a church. There was a very natural spaciousness and reverb to her voice, and the dynamics of how she sang the different verses drew me into the song.

Conclusion

I very much enjoyed the M700s. Visually, they are very clean looking. It's also nice that they don't get very warm. After an hour the Krell gets almost too hot to touch. I live in the Southwest, and during the Summer, they would bring the room temperature up by 5 degrees or more.

Soundwise, the M700s are very clean sounding. I would not say they are lean, but I think the Krell has a little more "meat on the bone". Acoustic guitars through the Krell provide a little more of the body of the instrument than do the M700s. However, this is at the expense of resolution. Perhaps this will change as they break in further, or perhaps it's a cabling, speaker or some other issue. The M700s provide a clarity that the Krell can't quite muster. The Krell is over 15 years old, so maybe some of its deficiencies are due to its age.

I am concerned about the hardness when vocals or instruments increase in volume during a track. I don't know if this will go away over time, or if cables, speakers or some other component is a factor. I wonder if balanced interconnects would make a difference in this regard. I do dread going down this path, as I fear I will get on the upgrade merry-go-round and not exit it for awhile.

There were times when I was listening and I couldn't completely relax into the music. It could be because I was trying to be analytical about the amps, and that got in the way of just enjoying the music.

At this point, I am planning to keep the M700s. I will continue to listen and make a final decision in the next week.

Lastly, since going through this process I now have more respect for the reviewers of stereo equipment. Critical listening takes discipline and staying focused, which I don't think I could muster. Not to mention putting it into words in the form of a coherent review.


#2

Thank you for that very detailed review!

Are you cheating the earth ground on the M700? I do not recommend you do this. Can you run balanced cables to the M700? If so, it will likely remove your ground loop unless the loop is further up the chain. The Stellar amps also sound better with a balanced input. Let us know, we’d like to help you resolve the ground loop.

Thanks for writing!


#3

Hi Darren,

I am using a cheater plug on the AC cord. So, unless that is what you are referring to, I think I am ok. The manual mentions a cheater plug as a possible solution.

Regarding the hum, it is only happening with the turntable connection. I think I found the issue. The ground wire connection to the Nuwave phono converter from the turntable had gotten knocked loose. When I reconnected it, the hum was down to a very low level. I would need my ear within a foot to hear the hum. However, when I removed the cheater plugs, the hum went up in volume. It went up a small enough amount, that the hum is no longer intrusive when listening to vinyl. I can still hear it from my listening position if I don’t have a record playing. What this allowed me to do is compare the sound with and without the cheater plug. I found that they do make a difference. Removing them has lessened that hard sound I referred to in my review. I can still hear a little bit of it, but it is noticeably less bothersome.

So, at this point, I think I will order a couple of power cables from you guys, so I can remove the ground pin and get the hum down to what it was with the cheater plugs, and avoiding the negative effect of the cheater plugs. Your power cables still allow the ground pin to be removed, correct?

I am so sorry I didn’t see the disconnected ground wire. It would have made the review easier. I will go back through the recordings I have commented on in my review and see if I can tell a difference. I should be able to do that in the next day.


#4

Hi RJ,

I was not aware that we had stated that in the Stellar amp manuals. We will be updating the manuals and correcting them.

The switching power supplies depend on a very low impedance path to earth ground in order to perform the way that they are intended to. It can dramatically affect sound quality.

Glad to hear that you were able to remove some of the hum! Just keep in mind that we recommend running balanced cables to your preamp for the best possible performance.

Thanks again for the review!


#5

After getting the hum down to a lower level without the cheater plugs, I re-listened to the tracks I listed in my review. I think there might be a slight improvement, but it’s hard to tell.

Darren - Should the balanced inputs on the M700s have shorting wires? I see on my Krell that two of the pins on each balanced input are shorted together. Might this make a difference with the hum I am hearing?


#6

Hi RJ,

I doubt the shorting pins will remove the hum but it wouldn’t hurt to take the ones that are in the Krell and insert them into the M700’s just to see. Could you try this?


#7

Hi Darren,

You were right, putting the shorting pins on the M700s didn’t make a noticeable difference.

I’ve got a set of balanced cables on order. I expect they will show up by the middle of next week. Hopefully they will address the hum issue.

Regards,

RJ


#8

Hi Darren,

I re-read through the manual regarding ground loops and hum issues. You are correct, it does say not to use cheater plugs on the amps. I mis-read it, which was a mistake on my part. I would suggest that in a future version of the manual, maybe the text which says “You should not remove or defeat the ground pin of your M300 or M700 for any reason.” should be put into a bold font, so other customers don’t miss it like I did.

Regards,

RJ


#9

Does this mean that those of us with older wiring, without a 3rd wire ground need not apply ?


#10

Welcome, drumnman2!

It looks to me for the unit to sound its best you would need to establish a good ground path.


#11
drumnman2 said

Does this mean that those of us with older wiring, without a 3rd wire ground need not apply ?

If you don't have 3-prong outlets, it is time to change some of them. It is easy enough to do, shut the power off at the breaker, remove old outlets. Wire in new ones. If house is to code, there should be a black (hot), white (neutral), and the metal box acts as the ground. Otherwise there will be a third wire a green one (ground).

If you aren’t comfortable doing this, order some audiophile quality outlets like those PS Audio sells. (You can get a 5 pack for a discount) and hire an electrician.

Or you could buy some 2 to 3 prong adaptors, attach the green tail or the round loop to the screw on the cover. That is the same as a cheater plug, where you don’t connect the ground wire or loop. We usually clip the ground wire, or remove the tab.

I would start with the listening room, and anywhere else you have HDTVs or stereo gear. Then go to a local hardware or Home Depot type store and buy some decent 3-prong outlets, maybe hospital grade, and do the kitchen and bathrooms.

What have you been doing all these years?


#12

Thanks, I have already done what you suggested. I have moved to an upstairs room which does have the 3 prong grounding outlets but there is no green ground wire. I was unsure if just the metal box would be a sufficient ground. I am using a different brand class D amp there now with no problems.


#13

You can get inexpensive testers to determine if an outlet is properly rounded, like this: https://www.amazon.com/Electrical-Receptacle-Outlet-Ground-Tester/dp/B0012DHVQ0/ref=sr_1_5?ie=UTF8&qid=1493596696&sr=8-5&keywords=electrical+ground+tester

[edited to correct “expensive” to “inexpensive.” They are just a few bucks.]


#14

The box ground is typically very good. Often the boxes are grounded with metal conduit which serves as the ground. The three prong outlet needs to have a ground wire running from it to the box to be properly grounded.


#15

Elk, I think when you screw the outlet to the box it is grounded. They have the separate ground screw if you are using Romex.

The little tester recommended above are usually available at any local hardware store. Drumnman 2 should get one just to be sure.

I have had one for so long, it slipped my mind. It is probably in the drawer with the multi-tester;-)


#16

The bet thing to do is to connect a ground wire to the grounded box and properly ground the outlet by connecting it to the green grounding terminal on the three-prong outlet (the picture is of a GFCI and the ground screw on the outlet is hard to see, but the installation is the same):

grounded-outlet.jpg


#17
Per Darren Myer's suggestion, I ordered a set of balanced cables to see if it would address the hum issue. I ordered a cheap set through Amazon. FWIW, they were well rated. They cost less than $8 a pair. HA!
The addition of the balanced cables eliminated the hum. To hear the hum now, my ear needs to be within an inch of the speaker, when listening to CDs. When listening to vinyl, my ear can hear a soft hissing with within 2-3 inches. I think this is from the NPC. So, I would say the hum problem is resolved.
My listening experience was significantly improved. I wonder if this was due to the lower noise/hum, which allowed more details to emerge and remove the distraction from the hum. Maybe balanced cables reduce the distortion?
Everything improved, I could hear more of the ambiance of the different recordings and how they were put together. Vocals had more presence. There was a small improvement in the impact from drums. It all added up to a significant improvement.
The downside is that I am still hearing some hardness and glassiness/graininess in vocals when they are loud. This was something I noted in my original review. This is still present. I don't hear this with my old amp. As an aside, my old amp improved with the balanced cables as well.
I also feel that the bass is lacking some impact. With my old amp, I could feel the impact in my gut, from bass drums and bass guitars. With the S700s, I can hear the bass, but I don't feel the impact. My speakers are a difficult load, with some of the low frequency spectrum being near 2 ohms, and sometimes slightly below. I wonder whether this might be affecting the S700s ability to drive the speakers in this region. Also, above 6khz, the load is around 3 ohms, which might affect be difficult to drive for the S700s.
For most music, the S700s sound great. They are very detailed, and create a clear soundstage. I'm very impressed with them. However, there is enough of a problem with the other areas I've mentioned that I can't completely enjoy all my music. So, for this reason I am returning the S700s.

#18

Is this due to power or M700 not able to handle impedance dip or something else ? Whats the expert opinion ?

Would a BHK 250 solve the problem ?

@RJ, if you using power conditioner with the M700, you might want to try directly to the wall. In my experience with other class D amp, for some reason they don’t work well when plugged into power conditioner.


#19

Yes, I used the P10, as well as a Powerplant Premier. Neither seemed to make a difference. I don’t recall using a wall outlet, but I may have. If I did, there was no difference.

Unfortunately, the M700s were shipped back last Thursday, so I cannot try your suggestion.

Overall, I think they are great amps. They just didn’t quite work in my system. Others have posted glowing reviews. I am curious to see what the review magazines say.

It was great fun to be a part of the beta program. Many thanks to PS Audio for allowing me to participate!