Music Reference RM Mono?

I am using an RM10 MKII (35 watts) with my Merlin VSMs (89db, smooth, high impedance)in an 18x12 ft room. Listen to jazz at moderate listening levels (I think)- it plays plenty loud with 35 watts. I was wondering if I would get any significant improvement by buying another and running them as monoblocks with 70 watts given the type of music I listen to and the size of my room. Any Music Reference lovers try the monoblock congifuration? Better? In what way? I'm think another 3db is volume isn't going to make any difference to me, but....
I'm think another 3db is volume isn't going to make any difference to me, but....

That's what Roger basically told me. My room is 18.5 x 14.75, and we listen to the same type of music. I'm even light loading mine and do not notice any side effects. There is plenty of oomph.

Roger did mention there might be some improvement in separation, but he didn't seem to think it would be revelatory.
My feeling, rightly or wrongly, is that well designed stereo amps do, for all practicle purposes, separation as well as monoblocks - with much of the theoretical advantage being more part marketing than real improvement, except in the case of poorly designed gear with poor cross talk performance. Of course, you do need monoblocks for high power tube applications - got to put all those tubes somewhere:) I too am using light loading, can't here much (any?) difference so if it is easier on the tubes, less distortion and more linear output, why not. Roger's repsonse to me had nothing to do with mono versus stereo, simply said I might (might) get more bass output if I went with the RM200, he was not leaning towards a move to the mono option - but, I have not heard it, so....
One of the best things about mono's is that they are much lighter and you don't need a crane to help you move high power SS class A or Tube amps around. For lower power though, stereo will serve most folks well, except for the few that have associated equipment and listening skills that will easily reveal the marginal increase in benefits from monos, such as power supplies, and channel separation.
I have no experience with the RM10s, but I had a similar situation when I went from a single Monarchy SM-70 Pro to using two as monoblocks, driving 90dB Von Schweikert VR-1s in an 18x14 room.

The monoblock configuration was better in every way. The best way to describe it would be "effortless". The additional headroom makes for better bass, more vivid midrange, and smoother highs, all without changing the fundamental sonic characteristics that I loved in the Class A SM-70s.

I believe that the reason for the difference is that the two channels don't have to compete for the power supply. As for you, the ability to play 3dB louder was a non-factor for me, and I think that most of the monoblock advantage would remain even if the monoblocks only made the same power as the stereo amp channels.

For me, it was revelatory. I'm guessing monoblock RM-10s would produce the same results.

I sort of feel that way too (I do use Atma-sphere monoblocks as well, in the colder months:), and also us various Quicksilver monoblocks). My hesitation with pulling the trigger is that like Clio9, the manufacturer was very hesistant to make any such claims for the benefits of going mono; which gives me pause since it would be an easy sale for him. Boy.....
I think Roger is a scholar and a gentleman, having owned one of his EM7s at one point. However, I'm guessing that amp designers don't necessarily have the same priorities as we crazy audiophiles, hence his very practical answers to your and Clio09's questions.

If you're already using monoblocks, then you already have a pretty good idea what the answer is for you.

The RM-10 power supply is overbuilt by a factor of 10x. I have to imagine the two channels can coexist just fine with something that overbuilt. Also, with Roger's custom written application for an EL-84 circuit (that generates 35 watts where others struggle to attain half that) the amp is designed to run effortlessly in stereo mode. I just cranked out Machine Gun and Hear My Train a Comin' from Jimi Hendrix Live at the Fillmore and there was no hint this amp was struggling.

The RM-10 was designed to be efficient, reliable, and affordable. IIRC, the main reason for it's existence was to drive Roger's Quad ESL 57's. If there was ever a speaker that required RM-10 monoblocks to drive them, I'd have to think the ESL 57 would qualify.

Like Pubul57 I figured RM-10 monoblocks would just be plain better, but Roger shot straight with me so I'll defer to him. I'm sure some amps are designed to be monoblocks or work better in bridged mode. Perhaps the RM-10 does in certain applications, but I have easy to drive speakers with a smooth impedance curve so perhaps mine isn't the best scenario.

BTW- I also own a set of VAC monoblocks. They're sitting in the closet right now. I'm not even tempted to pull them out even though the weather has cooled quite a bit of late and the extra heat would be beneficial.
Anthony, I sometimes wish Roger did not put that darn mono swith on the unit:) Oh well, I think I might manage to leave good enough alone (for now). Now if I could get my hands on some NOS Mullard EL84s......
I have NOS Telefunken EL-84's and tried them in the RM-10. Roger's stock tubes were just as good sonically, and quieter to boot. I've never heard the Mullards, but for the cost I'll stand pat.
His stock EL84s are Ei? When I bought the amp he was "raving" about the Genalex Reissues, you might want to give them a try in 10,000 hours - $100-120 for a matched Quad from Jim McShane, a bit more from Roger.
Roger commented that he's had to return the last couple of batches of the Genelex reissues. I'm waiting for him to give the okay on the new batch he's testing. Nothing against Jim, but I'd prefer to buy from Roger since it's his amp.
I think that the speaker’s impedance has everything to do with whether 1 or 2 RM10’s are needed. I initially tried 1 RM10 to drive my Totem Mani’s (notoriously difficult load) and then went to a 2nd RM10. The extra 3db headroom was a blessing with my Mani’s, even though I typically listen at low volume levels. When I used the RM10 with my Quad 63’s I noticed no difference between stereo or mono block.

Regarding tubes, I used Amperex for both the EL84’s and 12ax7’s. I found that the Amperex added a little “sweetness” that the EI’s didn’t display.
Agree with Jaffeassc, speaker impedance curve would play a big part as to whether stereo or monoblocks would be needed.
Well, since the Merlins are 8ohm, 6.5 min (VERY EASY TO DRIVE)I feel that much better with sticking with 1. I like and believe in the idea that, other than power output, fewer power tubes sound better than more output tubes in the circuitry. Along with my belief that lower powered versions of any circuit will sound better than hiogher powered versions - unless you need the power.
Anthony, can you hear any difference between using the 4 ohm and 8 ohm taps with your Audiokinesis speakers?
Yes, it's more linear, especially noticeable in the lower frequencies. Not sure if this is due to lower distortion or the fact there is less stress on the tubes and the amp operates more efficiently. In some ways it appears to have more balls which is evident in transient attacks. You would not think this to be the case since it loses about 25% of it's power, and a little more with my speakers since they operate at around 10 ohms on average. Pretty incredible design is all I have to say. A local friend of my has an early RM-9 and the RM-10 is much cleaner at about 25% of the rated power of the RM-9.
Good, so I am not hallucinating:)
Not unless I am too:)
Hi Pabul57. Firstly, Happy New Year and all the best for 2011.

You have a wonderful system there sir.

To be candid here: I doubt the addition of another RM-10 into the system will reap much of a difference [if any] with the Merlins.

Your tube choice will have a much bigger influence in the the RM-10 [or any other el84 based amplifiers for that matter]

While I do think the new Genelex EL84's re-issues are quite a capable example of a decent el84, they do sound very similiar in tone to the older EI's.

Voicing the RM-10 with tubes.
Jaffeassc's choice of old stock Amperex tubes in the RM-10 is spot on IMHO, in both the front end as well as the outputs.

RE: NOS EL84's.

Simply put, the el84/6bq5 is a wonderful sounding tube, regardless of new old stock or current production... it's all about "tone" with this pentode.
I have been collecting el84's [as well as amplifiers employing that tube] for over 30 years.

NOS Mullards el84's are certainly a good example of the breed and are probably the most distinctive of the type. However they are way overated [and overpriced] IMHO. If you want a bloomier midrange then a good choice perhaps.

The telies have a wider bandwith at the frequency extremes,a livelier tube per say but drier sounding in most circuits.

Amperex [Holland Production] are very very good at everything.
The pre 60,s D getter versions in particular....they are perhaps the best of the Amperex family. Fabulous bass power,depth and definition,a vivid midband thats articulate and 3 dimensional. Possesessing a top end that floats above the sound field and seems to go on forever. However, these are quite rare today [read expensive here] . The later O getter examples from the 60's are very close in character, much less expensive and easier to acquire. No current production example will get you here.

THE HOLLY GRAIL of the el84?

My vote would be none other than the common GE 6bq5 [round plate version only] These just tell the truth regardless of the circuit there employed in. They are in a league of there own! Neither the nos Mullards nor the Telies can capture the air,the breath and magical tone of the GE.
The best news is: There are still an abundance of them out there [for the time being] and one shouldn't have any problem sourcing a quad for little money, somewhere around $100.

All the best in your quest.

Ecclectique. love your note, and I think you are right about
looking at tubes rather than going mono. I will have my eyes
out for some NOS to "play" with. I never heard any
type of Amperex tube I did not like. Since posting, I've
been listening to a lot of music through the RM10 (with my
Lightspeed Attenuator)and it clear to me that Anthony
(Clio9) and Roger Modjeski are right, stick with a single
stereo amp in my situation. I am going to give the GE a try
when I can find them from a trusted tubemongerer. Ooops!
found them at Brent Jesse $80 per pair, not bad. Well get

Cheers! Paul.
These are the original 1960s grey oval plate GE tubes. These are not the round plate?
Hi Pubul57. Yes Sir, the grey oval plates are the tube I was referring to.

All the best.
Great. Thanks. Nice that the RM10 does not need too many tubes!
Go Ravens!
The GEs are in the mail. Clio9, you sticking with the Ei 12ax7s? Roger and Sal seems to advise that.
Yes, for now I am. Roger is testing a new batch of the Genelex reissues and if he makes them available I may try a set of those.
Hey Pubul57. Did you get those ge oval plates yet?
No, not yet. What price should I be able to get a quad for? I take your $100 price was for a matched pair?

Will you please send me an PM I have questions about Rm-10 and VSM.


Jim, I regret to inform you that Paul recently passed away. As a friend and fellow RM-10 owner Paul and I have had many conversations about this amp and his speakers. I will send you an email and perhaps I can assist you.