Review: Symphonic Line RG-4 mkIII Amplifier

Category: Amplifiers

This is a review of the Symphonic Line RG4 Mk III mono-block 150W/ch power amplifiers. I bought these amps used & I’ve had them for 1 month now. As many of you might know Klaus Bunge at Odyssey Audio is the official U.S. importer of the Symphonic Line products. Not much is written about the Symphonic Line amps in the U.S.A. except an article written by Dick Olsher in Stereophile’s November 1992 issue wherein he reviewed the RG7 amplifiers. Apparently, Mr. Olsher was quite awed by that amp. Plus, I have not seen any consumer reviews though I know that several people own the RG4, RG10 & Kraft 250 monos. I found this to be quite frustrating when I was making up my mind to buy these amps. I hope that this review will shed a positive light on this wonderful product that might help some other person make an informed decision in the future. Before I proceed with the review I must warn you that this review is long (!!). First, I will provide a little bit about the remaining equipment, set-up & room dimensions.

My Room Setup & Dimensions:
My audio room is located in my converted attic area & is quite asymmetrical in shape - the listening portion is 17’X19’ with a 9’ ceiling. There is also a knook which is 11’X6’ with an 8’ ceiling. So, speaker placement is quite important otherwise the left speaker might not have an interacting side wall whereas the right speaker will. I have experimented with speaker placement per the Cardas website but I found that the math did not work out for my room owing to the knook. I adapted his calculations for a modified speaker placement wherein the distance to the rear wall is less than the distance to the side wall but found that this did not work for me - soundstage was constricted tightly between the 2 speakers compared to my present position wherein they are separated 7.5’ center-center & 62” from the rear wall. I must also add that the vertical wall is really vertical for about 6’ & then it slopes towards the ceiling.

Symphonic Line RG4 Mk III details:
These amps are rated at 150W/ch into 8 Ohms & run in class A/AB mode. I’m not sure at what point in the power output curve they switch to class-AB from class-A. In the Symphonic Line product line-up these amps are 1 position below the flagship Kraft 250 class-A monos. Per the manufacturer, they are stable down to 1 Ohm. These have a wonderful & unique chrome finish on all sides including the bottom. Scribed on the front plate in the chrome finish are the words “Symphonic Line” & “RG4 MK III”. They accept only RCA inputs & have 1 pair of WBT speaker binding posts. Presently, they are sitting on top of a granite slab, which in turn is directly on the carpet. The future plan is to put them on individual amp stands. They weigh between 50 & 60 lbs & have heat sinks along both the left & right sides. They have an IEC connector for the power & a red LED above the power switch informing you that the unit is on/off. Inside, each amp has a 750VA transformer with 100,000uF of capacitance. I believe (from word of mouth) that the amps can supply a peak/transient current of 120A but I’m not sure over what time period. The damping factor is in the region of 800 continuous implying that the amplifier’s own output impedance is very low (in the 0.01 Ohm range). It is no wonder that the bass is so phenomenal! Frequency response is from 1.5Hz – 600KHz. The input stage is FET, for high input impedance, while the output stage is BJT/bipolar devices – 8 power output devices/channel. They’re priced at $8500 new but can be obtained for a fair price pre-owned when & if they come on sale in the used market, which is few & far between I found. The Symphonic Line website is but the details are sketchy at best.

The Listening Tests:
I listen to a fairly wide range of music such as classic rock, soft rock, blues, modern progressive jazz like Larry Carlton/Lee Ritenour etc, classical jazz like Charlie Byrd, Ella Fritzgerald, Stan Getz, Thelonius Monk, classical like Mozart etc & a tiny bit of opera like Maria Callas. I find that the system sounds best after 45 minutes of warm-up (no surprise there!).

To test the bass speed & tracking I played Police “Zenyatta Mondata” LP, Patricia Barber “Nardis” & “Like JT” tracks, Dire Straits “Communique” CD & “Love Over Gold” CD, Eagles “Hotel California” track. In each case the bass was very well defined, deep, fast & tight with no added boom or fuzziness or wooliness. In the “Nardis” track the percussion solo caused the sound of the percussion instruments to move from left to right & back again several times. I suppose that the artist had a wide range of instruments to play that probably spanned the arc of both arms. This is an absolutely incredible track for testing bass speed & tracking & I recommend it heartily for those of you who have not heard/tried it. However, I must warn you that it is a relentless test that lasts almost 9 minutes! I have read 2 comments about the RG4’s bass - one from the folks at MSB Technology & the other from Marc Mickelson during his review of the Clayton M70 in Sept. 1996 - & in each case they said that it was the very best bass they have ever heard! Being an owner of the RG4s I can now see why they remarked so - the bass is truly magnificient. The amps always seem to have full control on the speaker with natural detail & effortless power.

To test the midrange & high frequencies, I played “Tin Pan Alley” from Stevie Ray Vaughan’s Couldn’t Stand The Weather LP. The drum snap at the start of the track came through crisply & with great definition. SRV’s robust & charismatic voice comes through with great emotion. From my listening position the sound is “holographic”/3-D in that the speakers seem to disappear in the room & all I hear is the artist’s voice coming from the center as though he is standing right in front of me. There is great synergy between SRV’s guitaring and the bass guitar - both are clearly audible without the bass overpowering the lead guitaring. In some amps, I’ve heard too much bass in that there is too much bass boom, which tends to overpower any other music being played concurrently. Not so with these amplifiers – each instrument has its own space. Yet another favourite track of mine is “Downstream” from Supertramp’s Even in the Quietest Moments LP. Rick Davies’ voice is just left of center & is a higher pitched voice (compared to, say, SRV). This track is quite soulful & the amps are able to reproduce his voice with great emotion helplessly drawing me into the music. It’s as though he is baring his soul & you can “see” it right in front of you. Still another track that displayed the amps great high & midrange is “From Now On” from the same Supertramp LP. The tracks starts with a piano solo that is the main theme of the song & as the keys are struck, I could hear the key hitting the string & then the tonal decay as it hung in the air until it completed faded. I think that J.D. MacRae described it very well in his Audiogon review on the Plinius SA-102 & I’ll borrow his words (J.D., I hope that you don’t mind!) – “I liken it to watercolor painting. If a painter starts with a brush stroke in the middle of a white sheet of paper and continues to wash that first stroke down the paper with water, the result will be a fine line where they took the first stoke. Continuing the wash decreases the color until almost transparent but always with some original tinge left. … the piano key hitting even the shortest string begins with a sharp point of color, fading off into several subtle shades and hues of the original color”. I also played Patsy Cline “Greatest Hits” & George Michael “Ladies & Gentlemen” CDs. These 2 CDs are an incredible test for high frequency extension & vocals esp. with Patsy Cline’s voice & almost any track from either album can be used as a test. Once again these amps proved that they are absolutely great - no grain whatsoever in the HF (because I felt no listening fatigue even after 3 hours of spinning both vinyl and CDs), seemingly limitless high frequency extension & they seem to draw me into the music with a voice presentation that was almost live concert-like. I was completely taken in by these amplifiers’ ability to communicate the air & space around both the instruments and the artist’s voice.

I also found these amps (& perhaps the system) to be somewhat sensitive to the quality of the recorded material. For example, I played a number of tracks from Heart’s “Brigade” CD & found that many of those tracks had a lot of sibilance. Fortunately or unfortunately I was not able to find this “feature” on any of the other material I played so I have just one data point. As I test these amplifiers over time it is possible that I will discover more material in my collection with this “feature” (?).

I did all my listening at a moderate volume (still too loud, my wife said!). “Moderate volume” is a fuzzy term but if this helps any – most of my listening was done with the volume control on the CAT set at the 8 o’clock position. FYI, at 9 o’clock the music is louder & anyone in the bedrooms below will surely be jiving or will be cursing me. At the 10 o’clock position the sound pressure level is at the upper limit of my ears & I’m not even dreaming of the 11 o’clock position anymore! The amps showed me that they have incredible detail & transparency even at this moderate power output level – there is a rich & full palette of sound. From what I heard I will never run out of 150W/ch anytime soon.

In conclusion, I remain amazed with the ability of these amplifiers. They are not only beautiful to look at but they also sound simply superb. Size-wise they are on the smaller side compared to some of the competition in that they are 18”WX8”DX8”H but they have a “big” sound. In my system, these amps present the music as though you are seated in the 1st row of a live concert – I like it this way. I have heard a number of amplifiers such as the McCormack DNA-125, Krell FPB600, Rowland Model 10, the Audio Refinement 125W/ch, Aloia ST-15.01, Clayton M70 & I would say that this amplifier is at par with the Clayton but exceeds all others except the Krell. However, the Krell-Symphonic Line comparision is not even fair as the Krell clearly belongs to another class. The Symphonic Line RG4 Mk III monos have rich warmth: liquid trebles & emotional midranges. They have tight, fast & deep bass exerting full control on the speakers. They have the ability to draw you into the music urging you to spin disc after disc, LP after LP. I feel that this is great compliment to the amplifier and its designer. I was informed by the Ken Stevens (of CAT) & by Klaus Bunge (ODAV) – I believe that both are or have been owners of Symphonic Line amps - about the tremendous synergy between the CAT pre & Symphonic Line amps & I can confirm to you personally that everything that I have heard and read on this synergy is absolutely true. This is a very worthy addition to my audio system that gives me no “buyer’s remorse” whatsoever. In the end, I find that it is all about music & these amps allow the music to flow unobstructed never imparting any of their own sonic signature & once I’m captivated by the music, I forget that they even exist in my system.

Associated gear
The equipment is:
· Music Hall MMF5 TT with the stock Goldring 1012GX MM cartridge.
· Harmon/Kardon HD7525 CDP - this is my trusty-rusty CDP which has an 18-bit built-in DAC, analog & digital outputs (of which I’m using the analog L&R outputs) & a captive power cord. I have DH (large) Cones under the CDP chassis. Even though the unit is 7 yrs old, I feel that it has great sound. So far I have not been tempted to upgrade it.
· CAT SL1 Signature Mk III tube preamplifier with Sovtek 6922 & Electro Harmonix 12AX7 tubes. Since the manuf. insisted that the design is optimized for Sovtek 6922 tubes, I have tried to stick to them. No further isolation for the CAT per manuf. recommendations + I’m using the stock power cord.
· Symphonic Line RG4 Mk III mono-block power amplifiers, which are the subject of this review. More details on the amps follow.
· B&W DM 604S2 3-way, 4-driver floor standing speakers in black ash, which was the only colour available when I bought them (much to my wife’s dismay!). Speakers are on 3 brass spikes each.
· Interconnects & cables used: 1m Groneberg TS Premium between TT & pre, pre & power. Tara Labs RSC Master Gen II between CDP & pre. Tara Labs Prism biwire speaker cables. In my opinion, the B&Ws are known to be on the bright side so I have tried to limit the brightness by avoiding silver speaker cables. ESP Essence power cords, for the power amps, connected to the Juice Bar & a Silver Audio Power Burst connecting the PS Audio Juice Bar to the wall outlet.
· Lovan Soverign 2+2 audio rack.
· 1 Richard Gray Power Co. 400S into which the CDP & TT are plugged & 1 PS Audio Juice Bar into which the pre & power are plugged. Note that the Juice Bar does not have any filtering of any sort – just like I want it.

Similar products
I have heard a number of amplifiers such as the McCormack DNA-125, Krell FPB600, Rowland Model 10, the Audio Refinement 125W/ch, Aloia ST-15.01, Clayton M70.
Interesting and thorough review (if I may say), Bombay -- incidentally, we had near-identical electronics (mine: CAT III->Ultimate, RG4 III)!
My musical tastes are classical, but I also listen to some mentioned above (D-Straits & others) and can confirm your experience -- albeit, with different speakers. To add to your impressions:
1) SPEED. As one friend put it: "...this guy's (i.e. Mr Gemein) is making the music sound faster than it really is."
2) Macrodynamics: you can't relax unless you're listening to Vivaldi -- QUIETLY. If the recorded volume goes up, so does the reproduced one -- fast. I've noticed these amps run out of steam (slightly) with the huge Avalons of old, at high volume -- over 13:00 hrs on the CAT.
Also, I can mostly confirm the 1 ohm stability without modification, having operated the RG4 with AudioExklusiv full-range stators that boasted a ridiculously unstable, NASDAQ-type, impedance of 1,0 -- 31,0 Ohm.
I used different power chords -- although the ones supplied are S-Line's second-to-top aftermarket product anyway...
Also, they are very well serviced, it seems (I never had a problem).
Finally, I found that best sound (in classical) was to had with +24 hours...
I enjoyed these amps a lot. They match magnificently with Mr Steven's pre and I have noted elsewhere that, rumour has it, Mr CAT used to (still does?) voice his pre's with Kraft 250 among others including his own, of course.
If my experience can be of interest, don't hesitate to mail me. Cheers!
(BTW, in case you're wondering, I changed my RG4 for Kraft 250!)
Very good review and follow up. I am glad my friend told me to read this on Audiogon.

Symphonic Line is a great manufacturer and should be better known among audiophiles for the sound it produces with its "solid state" amps.

As a reviewer mentioned, Symphonic Line amps can serve the music, and the most notable signature they have is the fact that they have no signature at all. They get lost in the system. As Robert Green wrote in his review on RG-1 amp in TAS: "if only the source was as good as this amp".

There are couple of things I would like to add. Bombaywalla writes that Krell "belongs to another class". It may have more low bass extension than RG-4, but midrange is not nearly as good, RG-4 will have better speed, Krell has its own sound which will never disappear in your system (Kraft 250 will have as much bass or better as a big Krell and Kraft 400 is just a bass champion).

People always argue about what is better, tube or soild state components, and , by virtue of the superiority of the tube's midrange and more transparent representation of the recorded material, many writers refer to the better sounding solid state amps as a "tube like" sounding. The fact is that Symphonic Line has neither solid state nor tube sound. It simply amplifies your speakers by letting you hear the rest of the system and music you are playing.

My suggestion to the Bombaywalla: turn on your amps and never turn them off. They will improve over time and in two-three weeks the sound will change so much that they will sound like you have never heard them before. The power switches on RG-4's are on the back not only for cosmetic reasons, but also for practical ones. You should turn them on only once. There is no standby mode.

I have had Kraft 400's for about 10 years and owwned RG-4's before them. My preamp is CAT Sl-1 Ultimate. Before that I had several older CATs. At one point I had my 400's on for over three years!!!(I don't change my speakers very often). If you have never had them on for more then a couple of days, you have never heard them at their best. And you can turn your CAT on and off without any problem. You wouldn't damage your amps.

I hope that my comments were not too long. My best regards to both individuals who wrote about Symphonic Line.

Bye for now.
Great review and comments. I have the RG4-MK2. When auditioning to drive Apogee Divas, I compared them with several top amps of the time (late 90's). They never failed to impress. The Divas are a famously difficult load (not as bad as some other Apogees) but the RG4 has no difficulty with them. The Divas are in the boxes and now I drive KEF 102.2. Still sound great. As mentioned, the base is tight and never lacking. Mid range is flawless. A very satisfying experience.