Finally upgrading my Adcom 555; the M700 looks like my choice

My Adcom 555 is the original 555 amp. It works just fine but with it being over 30 years old, its time to retire it. My Adcom preamp died not too long ago, and I updated it with the NAD 658 which has the built in BluOS so Roon is not needed. I noticed a clearer sound over the 555 pre amp when I upgraded to the NAD. My original Infinity Kappa speakers were also updated to Focal Aria 926 speakers, and I have a Denon CD player and a Dual CS 5000 turntable.

I was originally thinking of getting the NAD 298 Class D amp or the Rotel 1582 MK II Class A/B amp. However after much investigation, I think those two amps would be on the same level as my Adcom though they have different designs. After talking to Paul and doing more investigation, I think the M700’s (in black) will be the best choice for staying under $5,000.

One reviewer said the XLR connections gave a better sound compared to the RCA connection. Any truth with that?

Any comments from those who are familar with the M700, their sound and what impact on the music would be appreciated. I am not the biggest fan of Class D thought I know they have gotten better. They are known for great bass but not as good with the mids and high end.

Thanks in advance


Congrats and welcome to the forum!

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Welcome me to the community @Revelationsound

The following reviews reflect what I experienced with the M700:

The following link has the measurements

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My first “real” amplifier was an Adcom 555. I loved using it for many years and it served me well. So well in fact that I got a great credit for it on trade/buy of what I consider my first “real” set of high-end speakers – that I still run with today: Anthony Gallo Acoustics Reference 3.1s.

So, in a way, that 555 is still part of the heart and soul of my system!

Good luck with your amplifier(s) search.


Congrats on the NAD, but I believe you have a typo? The 568 is a cd player. The 658 is what you have?
Yes, you NEED balanced cables to the M700. The sound quality of the M700 is just that much better with balanced cables. The M700 gives a good, clean sound. Has a midrange smoothness at its price point that is very appealing. The M700 also images nicely and is very dynamic, to go along with the great control of the bass. Had I not lived with a full tube preamp and tube poweramp for 20+ years, I would not have upgraded from the M700 to the M1200. It was actually tough trading in the M700, as I liked them a lot, but lusted for getting more tubes in the signal path.


I upgraded my GFA-555 with M700s. I think you will be very pleased with them. I’ve since upgraded to M1200s but the M700s are fine amps in their own right.


I upgraded a Rotel RB1080 A/B 200w/ch to a Stellar 300 and the difference was amazing. I think you can’t go wrong with PS Audio and the 700’s. I’ll bet if you compare the two by living with the 700’s for 2 weeks and then switching back to the Adcom you’ll be amazed by what you were missing.


What differences did you hear between the Adcom and the M700’s?

I did the same but then switched out the M700’s for a pair of Orchard Audio Ultra’s. Great Amplifiers none the less.

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Nothing against the M700’s but if somehow you have gathered that the M700’s are technically superior to the NAD C298 then you must be doing your research in a different place than I do. The amp modules and technology used in the NAD is years newer than the ICE modules used in the M700’s. You can also buy a pair of them and use them as mono’s for $4000 though not sure why that would be necessary with your particular speaker. Your best bet to me would be to pair the two NAD pieces together. Start with a single C298 and add another later if you must or change to a less efficient speaker in the future. There is also a newer version NAD amp to be released soon.

I am surprised on PS Audio’s forum would say the NAD 298 amp which cost less sounds better than the M700. The M700 is not that old and many of the reviews have been very positive. Generally most people feel having 2 mono amps is a better design than a stereo amp. My understanding is the NAD is cleaner and does not have the gentle emulation of the PS Audio tube amps in its input stage. Being open minded, I would like to obtain more information on what made you come to this conclusion.

Never said one sounded better than the other as I have never had either in my home. I was reacting to your generalization that one amp was superior than the other two based on your research without having heard any of the three. At this point you could only be going off of reviews and the NAD has glowing reviews from all of the major publications which research would have found. Regardless of the time of their release the technology of the amp modules used in the NAD amps is years newer that is just a fact. As I told you it is possible to buy two of the NAD’s for less than your budget and use them as mono’s just like the M700’s. Same is also true of the Nuprime ST-10 mono’s also an excellent amp which I have owned and preferred to both ICE and NCore based amps. Even though this is the PS Audio forum we can and do make recommendations for other products if they could be a better fit for a persons situation or at least I do. As I’ve owned four and still own three PS Audio components I don’t have a problem recommending on of their products if I think it fits a need but won’t just because of the name on the case. In any case buy what you want and enjoy it’s your money and your system.

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Understood but you have to remember, you can’t base assumptions on a person by a couple of posts.

I’m an audio engineer for over 30 years and have worked with recording studio gear and have written reviews for magazines for years. I have been in audiophile for over 40 years and have listened to many amps, audio gear and have spoken to the people who designed them. I am aware of the pros and cons of Class D amplifiers and I like the hybrid approach of PS Audio has taken to strengthen the issues with distortion with class D. But everything is built to a price. If PS Audio could built the M700 for the same price of the NAD 298 they would do it. Smaller company’s like PS Audio have much less overhead than a company like NAD. So when they have a higher price for an amp, there are reasons behind it. I have heard other NAD amps and in its price range they provide good clean amps.

So at this point as I have not specifically heard the Ps Audio amps. So I am inquiring for those who have heard it what their opinions are. It’s also one piece in a signal chain. A Conrad Johnson amp with a average pre amp and average speaker could easily not sound as good as a better matched lower quality components.

Sorry for the rant.

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What work have you done?

I compared the Parasound A21+ and the M700’s and I preferred the meatier sound of the Parasound.