Dual Mono Balanced Differential Design vs. Monoblock Design

Cam -- Mon, 08/16/2010 - 13:56

I'm in the process of moving from my Simaudio Moon Evolution i-7 integrated amplifier to a separate pre-amp/power amp set up. The initial plan (to save money) is to use my i-7 integrated amp as my pre-amp (since the pre-amp in the i-7 is basically the same as the Moon Evolution P-7 pre-amp) and buy a separate Simaudio power amp.

The most affordable amplification in the Simaudio line up are the 400 watts channel Moon M400 monoblocks at $6,500 for 2. The stand-alone version of the i-7 amplification section, a dual mono design with 150 watts per channel, is $9,000.

When I asked Simaudio about the difference between these two amps, they told me they are different amplification designs. The 400M monoblock is basically a stereo amplifier in bridged mode to get it up to 400 watts output at 8 ohms whereas the w-7 is a "dual mono balanced differential" design.

Can someone help me understand the difference (including pros and cons) of these two Simaudio amp designs?

Robert Harley -- Wed, 08/18/2010 - 13:22

Bridging configures a stereo amplifier to function as a more powerful single-channel amplifier. Bridging changes the amplifier’s internal connections so that one channel amplifies the positive half of the waveform and the other channel amplifies the negative half. The loudspeaker is connected as the “bridge” between the two amplifier channels instead of between one channel’s output and ground.
Dual mono refers to the fact that each amplifier channel is completely independent, and shares no circuitry with the other channel. Balanced differential means that each channel contains two audio signal paths, one of the + phase of the balanced signal and one for the - phase. A dual-mono, balanced differential circuit is much more expensive to implement.
Do you have a dealer that will let you take home both amplifiers before deciding?

Cam -- Wed, 08/18/2010 - 20:27

Thanks Robert.

I'm considering using my Simaudio Moon Evolution i-7 integrated as a pre-amp and the Simaudio Moon 400M monoblocks as my power amps when I move up to new speakers (considering Revel Ultima Studio 2s or Vandersteen Quatro Woods). The Simaudio Moon 400M monoblocks are acutally MUCH less expensive than the Moon Evolution P-7 or P-8 dual mono power amps and have a much higher power output, so I was wondering why that would be and trying to understand if the 400M's bridged design was inferior to the P-7/8's dual mono design.

I am in the process of buying new speakers and am happy with my i-7. However, I really liked the Vandersteen Quatro Woods when I auditioned them (driven by the Moon 400m's and the new Moon pre-amp). However, the high pass filter needed to use the Quatros doesn't work with my i-7 integrated (there's no pre-out/main in jumpers, just line outs from the pre-amp) so I'd need to add separate power amplifiers to make it work. This set me down the path of potentially buying new amplifiers (specifically the 400Ms).

The other speakers I'm considering are the Revel Ultima Studio 2s (the Salons are too big for my listening room/living room). I heard them driven by my i-7 and they sounded great but I heard that the Revels like power and thought maybe they would also benefit from an upgrate to the 400Ms. If I go with the Revels (I'm doing an in-home audition with them in a few days) then I will try them with the 400Ms after I break them in to see what the difference is vs. my i-7.

Thanks for your clarification above on the amplifiers!

TOGA -- Thu, 08/19/2010 - 22:17

Hi Cambasky, Your set up in the future is highly similar to my last set up. Long time ago, I used i7 integrated amp to drive my Revel Salon2. At moderate
sound level it make a lively and good bass, compared to Mark Levinson 326s/436mono. But at higher level, i7 sounded stressed while Levinson saperate
still maintain performance at such high level. next I purchased Moon P8 + Moon W7M mono to drive my salon2 and sold Levinsons. Surprisingly, they are not
sound very musical at all. it sounds cold, not even tiny bit of warmth. music lack power and punch despite 500wpc rating. Then I learned that Moon P8 or P7
has very low gain of 5dB while CD playey I used does not provide high output level. Volume range of my P8 always in the 58-68 range to make them sing.
   Way to fix for me ? I can use Moon's Andromeda CD player which has higher than normal output level. But I just love my Esoteric player, So I bought new
preamp. new ARC tube preamp and paired it with Moon W7M, Now I got fuller body and much better dymamic and weight.
    Also dont plan to use MOON's preamp to drive power amp from other camps, Moon s own amp has higher gain to compensate their preamp's low gain.
When I use P8 to drive other power like Mcintosh MC402, Pass's XA160.5, 350.5. which have normal gain of around 26dB, this time pushing P8 volume to
70-75 to make the same sound level. and it doesnt sound powerful anyway. My conclusion is that Moon P8 and P7 should be used with source which provide high output level like their own Andromeda and SuperNOva, even new 750D didnt make P8 sing. and P8/P7 not quite able to drive other amplfiers rather than MOON's. It's quite suprised to me that just remove Moon's Andromeda from P8+W7M system, then all that super powerful sound is gone.
      Hope this helps.

Cam -- Fri, 08/20/2010 - 08:05

Thanks TOGA,
It's great to get feedback from someone who was using the same system as me! I had the same experience yesterday in a dealer when I tried the i-7 as a pre-amp with the Moon 400Ms - I had to crank up the volume to 55-65 to get some good sound. But I forgot to check the input configuration - my i-7 has confirgurable inputs that allow me to adjust the gain from +0 to +10dB for each input source to equalize the volume from different source equipment. With my components at home now, and my Marantz 11S1 SACD player, I have the gain set to +7dB and I get great volume and sound at a volume setting of 40-45.
I'm going to have a home audition of the Studio 2s in a few days so it'll be interesting to see how the i-7 manages with them. I'll take your advice and try then at different volume levels to see if/where the i-7 starts to stuggle with them. If that's the case, I'll take your advice as I start to upgrade amplification in my system. I wonder how Macintosh would sound with the Revels?
Thanks for your advice!
Cam

TOGA -- Fri, 08/20/2010 - 12:00

Dear Cambaskey,
What you adjusted in sub menu of i7 is not actually a gain adjustment, it's just for matching level between each source. Setting a lot of +
will make you feel like you dont need much volume, but amplification gain will always be 5dB, despite Moon says 9dB in its spec. Regarding amplification for Revel, until now I really don't know what kind of sound the Revel make. Sound character changed with changing in anything before them. Don't know about
Studio2, but for Salon2, C46+MC402 doesn't provide much power, also Pass' XP10+X350.5 But frankly, Pass has a lot more transparent and more detailed sound than Mc. Mc is nice at low volume for background music. For my Salon2, there're only 2 set up that I feel have enough power for them. First one is Moon Andromeda+P8+W7M. but as soon as I removed Andromeda out, most of the powerful feeling is gone, it's like get out of E63AMG to Honda's VTEC engine. The second that make very powerful and tight bass is Esoteric+Pass XP20+XA160.5, despite of 160w rating. But again XP20 while has very very good bass, it is way too grainy and hard compare to my ML 326s, Moon P8, ARC Ref5. Until now, What I enjoyed most is Esoteric+ ARC Ref5 + Moon W7M or Pass XA160.5. Krell EVO600e is really interesting for me too, as it has high input impedance to suit my tube preamp. If you like warmer sound I think Moon is really not for you. for me MOON's sound is equivalent to Theil CS3.7 sound. which is transparent, and clean. But not a bit of warmth.

Cam -- Mon, 08/23/2010 - 15:54

Interesting, thanks TOGA. Indeed, the Moon P8 spec claims a gain of +9dB - where did you see measurements of only +5dB?

The ARC claims +6dB (single ended output) or +12dB (balanced output). I definitely can see that, if you're using the balanced outputs on the ARC you are getting a much higher gain than the P8!

I am using a Marantz SA-11s1 SACD player - not sure what the output level is on that. Anyway, I take it it will all come down to some serious listening and I'm looking forward to it!

Thanks for your input!

Cam

Robert Harley -- Mon, 08/23/2010 - 19:51

All preamps produce an additional 6dB of gain when using the balanced outputs. It's the nature of a balanced signal.

TOGA -- Tue, 08/24/2010 - 12:22

Hi Cam,
I read from John Atkinson measurement from Stereophile reviews. Both P7, P8 actual gain is only 5dB instead of published 9.
I still curious how could they happy using P8 to drive amplifiers from other manufacturers.
P8 is really transparent preamp, soundstage is one of the best, distortion seems very low. I just like warmer tone and
more gain, pity gain is not adjustable. Unlike my Levinson 326s.
Toga

Cam -- Fri, 08/27/2010 - 14:33

Thanks for your input TOGA - it's great to learn from the experience of others like yourself in these forums!