PS Audio Stellar S300 amplifier + PSB Synchrony One speakers = some distortion around sustained volume of 75-80 dBs? suggestions to resolve?

Hi, long-time Copper magazine reader, first-time PS Audio owner… :wink:

I’ll cut to the chase with a provocative summary of my situation, but please read the context that follows before responding:
I wonder what is going on with the distortion I’m sometimes hearing with my PS Audio S300 stereo amplifier. It’s kind of like the amplifier runs out of gas at a certain point, and collapses into some distortion at the edges of the music; distinct separation of instrumentation starts to struggle, and soundstage sort of flattens.

To be 100% clear: The S300 is my favorite amplifier of all the ones I’ve auditioned, including: Outlaw Model 2220 monoblocks, McCormack DNA 0.5 Deluxe Edition stereo amplifier, N.E.W. A20.1 high bias class A power stereo amplifier, and Audio Research D240 stereo amplifier. The PS Audio Stellar S300 is the most pleasing of all those. (Though the Audio Research D240, admittedly, “SLAMS” with bass dynamics like a MOFO compared to S300 which is much more polite, despite all its other myriad charms. However, the Audio Research D240 falls short in so many other areas, it’s still no contest.)

… Except for this one thing: the bottoming-out distortion after driving this system at loud-ish volume in the 75-80 dB range with the S300 amplifier … So I’ve boldly just ordered a used pair of PS Audio M700 mono amplifiers, to see if wattage and headroom and whatever other advantages of the M700 vs. S300 will more than cover for the sensation of “running out of gas” I sometimes hear with S300.

I have been experimenting with compiling a pleasing home-away-from-home stereo system, so I’ve been auditioning a handful of amplifiers and other components over the last few months …

I feel settled on:

  • source: WiiM Pro Plus streamer + DAC (digital high-resolution streaming such as Qobuz and my own FLAC/WAV downloads and rips from CDs; I’m trying to keep it simple and not go down the rabbit holes of acquiring source components for optical discs and vinyl disks)
  • pre-amplifier: Audio Research LS2 MkII (I think it’s marketed as a “hybrid” tubed pre-amp; it’s got one tube in the main signal path, and two others in the phono pre-amp section; I do crave some of that tube warmth … )
  • speakers: PSB Synchrony One tower speakers (note that these are 4 Ohm speakers, and they go down to around 30 Hz)

The amplifier component had been the most un-settled of this system … until I inserted the PS Audio S300 stereo amplifier. Then I felt that the system was nearly exactly where I wanted it to be … except for this distortion that creeps in over time when I’m playing at higher volumes - which for me is around 75 dBs, with up to 82 dBs at peaks, measured at approx. 1 meter from speaker.

When all of these components are working well together, the “synergy” is amazing. I wrote recently on a Facebook group (specifically about the PSB speakers, but really I was describing my entire system including PS Audio S300): “I’m mystified by how rich and full the bass is, how holographic and real the midrange is, and how tempered and smooth the highs are.”

The room dimensions are 12 feet deep (measuring the dimension spanning from my listening seat to the speakers) by 20 feet wide by 7 feet tall ceiling. there is an opening to the right (when sitting and facing the speakers) that is 25% bookshelf, and 75% open space into the adjacent dining room, which is perhaps 12’ x 12’ or so.

The triangle among my listening position and the speakers is approximately 8 feet from each speaker, and about 6 feet between the two speakers.

So here is the key question, even as the PS Audio Stellar M700 mono amplifiers are en-route to me, arriving early next week:
Will the M700 mono amplifiers be more compatible with my PSB Synchrony One speakers, so that this occasional “bottoming out” or “running out of gas” effect with the S300 stereo amplifier is reduced or hopefully eliminated entirely?

Is there anything I should be watching for within the amplifier (either S300 or M700) when this effect is heard, such as checking the lights through the grates of the amplifier case? It has NEVER gone into protection mode while playing music at any volume, or anything like that.

Do I need to check with my electrician to install a dedicated (e.g., 20 amp) circuit for this system (okay, I am running this in my parents’ old house that was constructed in the 1950s)? (I know PS Audio has a range of power conditioner products, but I’m not ready to go into that rabbit hole yet, for a “home away from home” system that I intended to be fairly streamlined.

I don’t have anywhere close to unlimited funds, so I’d appreciate the most bang-for-buck feedback suggestions first/primarily. Then see how those help and go from there.

PSB Synchrony One speakers specs shown below to help others answer my question …


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Just curious, have you tried moving the chairs to see if you don’t run out of gas as easily? Good luck with the m700s. Folks here say they are a step up from the S300 (which I own).


The Synchrony Ones don’t appear to be that difficult to drive and the S300 is certainly within PSBs recommended input specs. At the sound pressure levels you mentioned I wonder if the amp is generating more than a handful of watts.
How long are your speaker cables?
Did you search to see if any other S300 users on this forum have a similar problem?

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Well, that’s certainly an easy thing to try. I’ve just moved the two armchairs out of the room.

While I’m at it, I’ve also moved the speakers out about 1 foot in each lateral direction, so that the triangle with the listening seat is now 8 feet all three ways.

I’ll give this experiment a try over this weekend to see what the change sounds like.

Out of curiosity, what’s the hypothesis behind your suggestion? In other words, can you articulate what impact you think having those chairs next to (and/or the 70s-era Sears console stereo between) the speakers is having?

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I am using an S300 to drive a pair of Maggie 1.6QRs (purchased in 1998), which have a slightly lower sensitivity (86dB at 2.83V). At those SPL levels, I do not observe any of these effects. In fact, I would say the system really starts to “come on” at those levels.

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Speaker cables are about 15 feet long. (12 gauge; I cut them myself and put spades on the ends.)

I did search and read through all of the S300 threads I could find on these forums, and didn’t notice anyone else having a similar problem.

I did buy my PS Audio Stellar S300 used from The Music Room, so it’s possible that the unit I have is faulty somehow. (But I don’t want to go to that conclusion until after I try a bunch of other experiments first, if nothing else resolves the issues.)

Another idea: Could it be that at a certain point in a listening session at higher volumes, the room reflections of the sound waves are somehow “stacking on top of each other”?

I certainly do notice that S300 comes alive as volume goes from very low to louder. Ever since I got my S300 about a month ago, there’s been a sweet spot around 65-70 dBs that this system sounds great and doesn’t get to that overwhelmed place that I’m trying to sort out and resolve with this thread.

By the way, I think I’m about 30 minutes into my “move the speakers away from the damn furniture” :wink: experiment, and even at 80 dB -ish volume the distortion / overwhelmed phenomenon I’ve been experiencing does seem to be noticeably reduced (improved), if perhaps not quite fully resolved.

E.g., I’m listening to the 2019 mix of Beatles Abbey Road at 96/24 on Qobuz right now, and it’s sounding fully dynamic and not distorted at 80 dBs -ish as I type this. (I LOVE the way S300 controls the bass on these speakers, conveying the subtlety and nuances of the drums and bass instruments while still pushing enough air to get the bass feeling into my torso.)

Photo below shows how precise and scientific I got with moving the speakers, as evidenced by the measuring tape on the floor in front of the speakers. :smiley:

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Try putting some rugs on the floor in front of the speakers. It could be floor (or wall or ceiling) reflections causing the issue.


Might be absorbing certain frequencies and throwing things off balance. Just a guess.

If the low cabinet must stay in front of the window, consider putting your electronics in or on the cabinet and shortening your speaker cables by 8 or 9 feet.
I used to have Synchrony Twos, their sound was enhanced by pulling the front baffles from the front wall like you did and using extra port plugs purchased from Lenmark to adjust the bass output.
Congrats on working out the issue with distortion.

Unrelated to your distortion issue…

While you’re at it, try changing the distance between the tweeters of your speakers to 80" rather than 8’.

Listen to see if you hear a better presentation in terms of depth/width of field and center imaging.

Good luck solving your issue.


80 inches is within a few inches of where these speakers were apart from each other originally, before I started moving things around today.

But you’re right - the imaging / soundstage is more cohesive when they’re somewhat closer, versus 96 inches apart. I guess an equilateral triangle configuration isn’t ideal for my listening space.


Yes, the equilateral triangle configuration didn’t work for my setup either. After building the right synergy with electronics, electrical conditioning, speakers, cables, vibration control and cabinets, paying attention to listening position and reflected sound waves was the final step to maximize my sonics.

I improved sound by moving my listening position further away from the back wall (better bass) and diffusing reflected treble/upper midrange by hanging a tapestry on my back wall and louvering my blinds to help with window reflections.

Yes to consideration of window reflections.

I’ve long-noticed that every configuration of this evolving system sounds better with the curtains drawn behind the speakers … but during the day it’s just too lovely to look out the open window while listening to music, that I’ll temporarily concede a bit of audio quality in favor of the overall audio-visual experience. :slight_smile:

I’m slightly embarrassed (but also grateful) that my first post here started as a “help me with this Stellar S300 amp that seems to be distorting” quickly turned - with your generous feedback and suggestions - into a fruitful room treatment and furniture positioning thread instead.


Just out of curiosity could it be possible that there is something other than the amp or the room causing the issue? You said your pre has tubes, could the tubes be going bad? How old is your ARC pre? Sometimes ‘vintage’ gear could have problems that might cause what you’re hearing. Have you plugged your DAC directly into the S300? Does the problem still exist? Have you tried swapping cables? A bad or loose cable could produce some of the effects you are describing.


Yes, throughout the course of evolving this system over the last several months, I have done most of those suggestions.

I haven’t checked on the pre-amplifier as a factor, because the prior amplifiers I had connected to the Audio Research pre-amp didn’t exhibit the “runs out of gas” phenomenon as the S300 has, with - ironically - the exception of the Luxman R-115 receiver that started this whole journey of upgrades … that Luxman sounded gloriously warm at around 55-60 dBs, but would quickly crap out and get fairly tinny and harsh at around 70 dB and up (this was with Pioneer Andrew Jones tower speakers, before I got the PSB speakers) …

However, I have not done every single one of your suggestions as rigorously and methodically as I could.

Therefore, those are all still really good ideas of things I could try with more scientific rigor …

According to FedEx, my pair of used Stellar M700 amplifiers will arrive tomorrow, so I’ll make a point of un-seating and re-seating all the connections in the system before I fire those up.

And two days after that, I have a Pangea audio rack and a pair of isolation tables (for each of the M700s, after reading the Stereophile review’s observations on stacking the M700s, versus side-by-side and isolated) that are arriving on Tuesday, so after I get those setup I’ll once again re-check and re-connect all the cables again as part of putting the gear into the rack.

For the moment, though, I’m just enjoying this current system at slightly lower volume (more like 70-72 dBs) where it’s performing very well with Billie Eilish’s Happier Than Ever album in 24-bit / 44.1kHz via Qobuz streaming.

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Well, a few significant changes have been made to my system, since my last update on May 11th.

The pair of M700 amplifiers arrived a few days ago, and I’ve been listening to them stacked …

… Until this afternoon, when I received and setup a Pangea audio rack and some isolation platforms for the amplifiers. Now the M700s have some space between them, and hopefully these isolation platforms are adding some benefit as well?

So with these changes, I’ve been starting to run through my audition playlist of music I know very well on Qobuz.

Early impressions of the M700s in this system, compared to the S300:

  • Any limitations I had experienced with the S300 seem to be completely gone with the M700s.
  • None of the audible artifacts of “running out of gas” I heard with the S300 are present with the M700s. (It’s as if with the S300 in my system, I was regularly bumping up against a ceiling limit, and needing to dial the volume back to restore order … while with the M700s, the ceiling seems out of my reach no matter how much I turn up the system - no distortion artifacts at any volume with the M700s, and nothing else has really changed with the room, etc., beyond moving the furniture, etc., that I already did above.)
  • Dynamics are crazy-wide. I have to be a little more careful about turning up the system too much during quieter passages, then getting thrown back in my listening seat when some loud passage hits me with a wallop.
  • Soundstage is more distinct overall, and more well-balanced all the way from side to side (and height, too).
  • High frequencies are brighter, compared to the S300, which I was not expecting (I expected a more similar sonic signature between two amplifier models of the same Stellar family). Yet the brightness is definitely pleasing and not “shrill” or anything like that. My ears welcome the somewhat brighter, more natural sounding reproduction of cymbals and other higher frequency instruments of the M700s!
  • Bass is perhaps a little more taut than the S300, which had what I guess I might call some more “bloom” in the bass notes. However, turning up the volume more seems to compensate for this and brings more bass into the room, so this may just be another way that I’m hearing the wider dynamic range of the M700s in this context?
  • Each M700 unit feels significantly heavier than the S300. How is that possible? The PS Audio product pages of M700 and S300 say that a single M700 weighs the same as an S300 (“13 lbs [5.9 kg]”). Adding to the confusion, one of the amps came with a combo “Owner’s Reference” manual for both “Stellar S300 and M700 Amplifiers,” and page 8 claims that “Weight S300 and M700” is a mere “8 lbs.” My arm muscles disbelieve that the M700 and S300 weigh the same!

In summary, the M700s improve as remarkably versus the S300 as so many others have already said many times already on these Forums. Yet the S300 is still a worthwhile amplifier, just probably best for a smaller room than this 20 foot by 12 foot by 7 foot ceiling room I’m in (note: plus openings on either side where sound pressure can escape). Or maybe the S300 would have been perfectly fine for this listening room if I’d been pairing it with higher sensitivity (or otherwise differently spec’ed) speakers?


Congrats on the new to you amps! Now you can put the chairs back. I’ve wanted to upgrade my S300 for a while but the budget is a bit strained. Enjoy!

Oh, I wish I could simply move the chairs back!

I just tried again – I moved the chairs back next to the speakers, and the effects of the chairs on the sound resumed.

I put my hands onto different places on the chairs while they were next to the speakers, and I can feel the bass frequency vibrations through them. So it really does seem like the frame of the chairs underneath the upholstery and cushioning are somehow resonating with certain frequencies in certain ways that are audibly unappealing and antagonistic to the sounds of the music.

Thus, I quickly moved the chairs away again, to keep the sound quality optimal.

This also means the reply I marked as “solved” for this thread remains valid and appropriate. (Though if I could mark two replies as the solution, it would be moving the chairs PLUS upgrading to M700s!)

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Maybe some isolating feet and vibration dampening sheets for the chairs! :roll_eyes:
(Now I think I’ll start a new thread on acoustically neutral chairs. I think mine might be on the warm side. Perhaps metal frames instead maple might brighten things up.)

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