[Audioexcels]

Pros/Cons/Audible Differences???

I think this is an interesting subject that does not get much attention.  As many around here are diyers, of course we choose the option of building our amps as dual mono or stereo based designs.

What's everyone's take on the differences between the two?

As a nice start...most systems use a preamp of some sort.  Most system's preamp is a "stereo" based one.  So given this, where do all the virtues of the dual mono amps come from when the rest of the system from Preamp/CDP/DAC/etc. on out is ALL STEREO???  "Maybe" there is the rare few out there that have dual mono "everything"...meaning, seperate PS/Trannies in every single device including preamp/cdp/dac/etc. etc. etc...these are rare few, I'm sure.

Well...I'll let everyone have at it because I feel that with most all other components being stereo based, why would suddenly "one" component in the system be used as a dual mono design rather than a stereo type like the rest of the system???

Cheers all and looking forward to the responses!!!

[TheChairGuy]

You hit on my recipe for audio fun these days   

It is hard to find dual mono preamps, don't know why, but they are rare. 

I've had monoblock amps for the past two years now...and can't forsee looking back at anything but dual mono's in future (true dual mono's, including separate power supply windings).

I recently bought a 30 year old Mitsubishi dual mono preamp/tuner and, tired caps and all, it's the best preamp I've ever owned.  I think, in large measure it has to do with dual mono construction.  Particularly with phono, where stereo separation is limited by nature, a dual mono preamp preserves as much as it can offer. While with CD, it doesn't denigrate the superior stereo separation if offers up.

With full mono sides of my amplification now, I do hear two separate speakers producing their different halves of the performance.  There is less blending heard.  Better stereo separation and less crosstalk has obvious benefits this way.

Likewise, I have a pair of integrated tube monoblock amps(with phono as they are 45 years old)....they are fabulous as well, I have little doubt it's a function of their monoblock status moreso than any 'magic' imparted by tubes.

If you can afford it, and have room for them, monoblock amp and preamps are very good thing 

[1000a]

When you say less blending does this mean if on some tracks I hear cymbal crashes in both speakers (2 diff cymbals mind you) but in the center satge there might be a piano (I don't think a jazz drum kit is wider tham a grand piano) this kinda of thing would be lessened?

I hope this makes sense, I hear this on Barbers-Cafe Blue or is that imagining simply a product of mic placement and mixing?  It seems to me when this happens (the drums now take up the whole width of the stage and this makes no sense.

Any insight you might pass my way would be appreciatted, I thought blending was good  in the middle hol;ding the stereo image together or am I confusing to different thgings.  I am starting to eye monos and am getting curious just what I am missing.

Thanks in advance, 

[djbnh]

You hit on my recipe for audio fun these days   

It is hard to find dual mono preamps, don't know why, but they are rare.

Odyssey Audio makes a dual mono, I didn't find it on the current iteration of Klaus Bunge's site, but there's information on the Mexican Odyssey site.

[JLM]

I heard better imaging with dual monoblock amps, but I also changed power rating, amp design, and brand.  With these amps smaller sound sources do sound smaller, very much like putting on corrective lenses, the fussiness is replaced with smaller, sharper, clearer images.

Channel separation in a good preamp, even a good volume control is at the edge of hearing/testing limits.  Same for CDPs.  But a number of dual mono preamps exist and the new Shanling CD3000 is said to be dual mono from analog section on out.

Most recording/miking technics have little to do with reality.  Vocalists do their own backups.  Instruments are recorded days/months before the vocalist or in different studios.  Each artist gets their own mike.  Do you think they are in the same position during the recording as during a concert (except for classical music)?  Even if you listen to unamplified music, the hall sounds different empty than full, and the balance of instruments in symphonic pieces from overhead mikes is way different from what you'd hear sitting 5th row center.  With more simple/realistic miking, like Cafe Blue, you should hear a blend of each source from both channels.  Without blending stereo imaging couldn't occur.

But the biggest advantage I see of monoblock amps is to have the option of shorter cable runs and more importantly of having an active design where each driver gets an amp of its own.  Companies that offer monoblocks of similar design but different wattage ratings can fit that bill quite nicely.

[denjo]

Althouh the Sanders ESL amp is not dual mono, it had better separation, imaging, soundstaging than my CIAudio D*200 Monos! Power, amplifier topology or novelty of circuit design are also very important considerations.

[TheChairGuy]

Hi, 1000a.

The two best preamps I think I've owned, in terms of resolution, speed and a certain rightness were the Superphon Dual Mono (circa 1988) and this Mitsubishi DA-C20.  A couple others were excellent (actually, almost none have been bad), but these seemed to have a certain wholeness and drive that others can't match.  Both are/were dual mono's. Low level signals, remember we are only talking feeble voltages here on par with several D batteries, as these signals cross in your preamp thru common circuitry, you lose vital differnces between each side of the 2 channel performance.  They blend and bleed, they don't offer higher levels of separation as the signals are intertwined throughout.  That notion of 'imaging' will seem more correct as a result of signals that are not intertwined.

(I have owned a couple tube preamps that are/were wonderful, too, but loved for their pleasant euphony - they warmed up the presentation greatly)

With amps, monoblocking may be even more important.  Not only do you have co-mingling of high level signals, but the reserve requirements to drive your speakers in dynamic passages is so great that the use of only one power supply winding is sure to muck up the performance in some way.  The demand for the Tympani on one side one moment will mute the 'snap' of the massed strings one moment later across the aisle of the orchestra.  Two separate amplifiers, each with their own power supplies, will best be able to reproduce those two events (and all the others going on) best. 

Manufacturers that don't monoblock/dual mono-size, primarily do so for cost and speace reasons.  Simply speaking, sonically, it's a near certain way to a better performance.  But, you pay for it as it costs more to have it.

Having amps physically closer to the speakers is a lesser benefit, but a good one, too.  It's more important, however, to have lower level signals from your front end and even after the preamp to have shorter IC's.....the feeble voltages are more prone to transmission losses along long lengths and capacitance in your IC's is higher, all in all, in longer runs. 

So, dual mono amps and preamps are good, if things are equal, and keeping IC's fairly short are good, too 

When you say less blending does this mean if on some tracks I hear cymbal crashes in both speakers (2 diff cymbals mind you) but in the center satge there might be a piano (I don't think a jazz drum kit is wider tham a grand piano) this kinda of thing would be lessened?

I hope this makes sense, I hear this on Barbers-Cafe Blue or is that imagining simply a product of mic placement and mixing?  It seems to me when this happens (the drums now take up the whole width of the stage and this makes no sense.

Any insight you might pass my way would be appreciatted, I thought blending was good  in the middle hol;ding the stereo image together or am I confusing to different thgings.  I am starting to eye monos and am getting curious just what I am missing.

Thanks in advance, 

[Marbles]

True dual mono designs have two power supply's.  The power supply is one of the most important pieces of an amplifier.  The beefier the power supply, all other things being equal, the more natural the presentation and the more bass control (damping of the woofer).

[1000a]

Thanks guys

I moving in the direction of monos amps-mono pre-s, looking at the Promiteus stuff Nick is designing.

[Audioexcels]

True dual mono designs have two power supply's.  The power supply is one of the most important pieces of an amplifier.  The beefier the power supply, all other things being equal, the more natural the presentation and the more bass control (damping of the woofer).

True.  But what about an amp that uses 500VA trannies (dual mono) vs. an amp that has a 1.5KV one for stereo?

How about a dual mono amp that has 40K uf capacitance per side, and a stereo amp that has 200K total...

I'd love someone that has done actual tests of the two, in "controlled" settings, to describe what they heard, though as of now, it is good to hear everyone's response and Marbles...I agree with you...having the supply on each side/mono'd can "dedicate" the supply to each side rather than have to share it...but I still question how an overkill stereo transformer with overkill capacitance isn't the "headroom" of dual monos.

[Daryl]

Crosstalk is not a critical issue with amplifiers and so you stand only to lose by designing a componet as 'dual mono'.

Stereo separation is not affected by crosstalk in the least.

There are gains to be had when amplifiers share a power supply especially if you use like 4-10 channels.

You can end up with a power supply that is really hard to influence and all available power can be channeled where you need it.

I do kind of like the idea of a lot of monoblock amplifiers but it would be nice to be able to strap their power supplies together.

Or a bunch of monoblock amplifiers with separate power supply(s) feeding all of them.

Another way to achieve steady power supply rails is to use balanced/bridge topology amplifiers which use a lower supply voltage higher current power supply with more capacitance.

Instead of drawing power alternately from it's positive and negative rails as the signals polarity changes a balanced/bridge amplifier draws the same current from both rails simultaneously and effectively removes fundamental frequencies from the power supply rails which are the frequencies which can most easily influence them since the impedance of the filter capacitors is increasing with lower frequency.

[doug s.]

True dual mono designs have two power supply's.  The power supply is one of the most important pieces of an amplifier.  The beefier the power supply, all other things being equal, the more natural the presentation and the more bass control (damping of the woofer).

True.  But what about an amp that uses 500VA trannies (dual mono) vs. an amp that has a 1.5KV one for stereo?

How about a dual mono amp that has 40K uf capacitance per side, and a stereo amp that has 200K total...

I'd love someone that has done actual tests of the two, in "controlled" settings, to describe what they heard, though as of now, it is good to hear everyone's response and Marbles...I agree with you...having the supply on each side/mono'd can "dedicate" the supply to each side rather than have to share it...but I still question how an overkill stereo transformer with overkill capacitance isn't the "headroom" of dual monos.

i'm w/you on this.  i think the total design needs to be looked at.  a non-dual mono amp/pre can be as good or better than a dual mono, if done right.  most of my amps are dual mono, but i have a couple that share power transformers, & they are superb.  like the fisher sa300 that i just sold - it has a huge transformer.  and my almarro a205a mkll is a fantastic amp, w/the right (read: efficient) speakers...  my preamp, a modded melos ma333r, is a true dual-mono design, w/separate transformers (and even separate power switches) for each channel.  it's an absolutely stellar preamp, imo, (one piece i have no desire to try "upgrading"), but how much is due to its dual-mono construction, i really don't know.  i do know it's one of the big differences from its lesser sibling, the sha-gold-r, but that is also a fantastic preamp, imo.  and, it would be my 1st choice in preamps in the ~$1k price-range...  nice modded ma333r's usually sell for a bit more...

doug s.

[James Romeyn]

Compared to the differences in sound caused by design/architecture, it's pretty irrelvant IMO.

If you had two otherwise identical stereo amps of each type, I'd bet even then the differences would be small vs. comparing similarly priced amps from different companies.  It seems there's enough sound/performance differences based on all the other choices to just ignore this one, but I'm sure others disagree.  I previously thought just the opposite.

[DSK]

Aren't the larger toroidal xfmrs more prone to humming than (2) smaller ones?

[Audioexcels]

Aren't the larger toroidal xfmrs more prone to humming than (2) smaller ones?

That's an interesting point though don't we have these ultra-shielded trannies now out?

[kenblair]

DECWARE  "ZTPRE "  is a mono preamp and here is what the builder writes , quote - "If a guy was to build an all-out preamp with the intention of using it in a world class reference system there might be few things he would realize right off the bat. Things like - What would be the point in having monoblocks if you're going to drive them with a stereo preamp?  To keep from undoing some of the benefits of using two or more mono amplifiers, the preamp would also have to be dual mono.  That means no parts including the power supplies are shared between channels. 

He also might realize that since channel separation is the theme behind dual mono, balance controls or ganged volume pots are out.  The only way to do it right would be to use two separate volume controls.
http://www.decware.com/preamp/ztpre.htm

[warnerwh]

Being one to own quite a number of high powered amps over the years I can say that transformer hum is a non issue. In the Cinenova driving the woofers of my VMPS RM 40s the transformer is dead quiet. The transformer is 4kva btw!  I also own a Van Alstine Fetvalve 550 and you cannot hear that transformer either. Don't know the size but you can get right upto the amp and not hear it. The only amps I've had with transformer hum are a Conrad Johnson and Hafler XL600.  The ESL 600 I owned was also quiet. All these amps are 250-300wpc.

Also owned a Parasound HCA 3500 with two separate 1.4kw transformers and transformer noise was a non issue there to. My point being I suspect the qualities that cause transformer noise can be eliminated if the manufacturer does a good job and is not something we should have to be concerned about. Although I know it is an issue in alot of pieces.

Regarding dual mono amps I can say imo it's not worth looking at. I've not heard any difference that could be attributed to having dual mono.

[Audioexcels]

DECWARE  "ZTPRE "  is a mono preamp and here is what the builder writes , quote - "If a guy was to build an all-out preamp with the intention of using it in a world class reference system there might be few things he would realize right off the bat. Things like - What would be the point in having monoblocks if you're going to drive them with a stereo preamp?  To keep from undoing some of the benefits of using two or more mono amplifiers, the preamp would also have to be dual mono.  That means no parts including the power supplies are shared between channels. 

He also might realize that since channel separation is the theme behind dual mono, balance controls or ganged volume pots are out.  The only way to do it right would be to use two separate volume controls.
http://www.decware.com/preamp/ztpre.htm

He forgot to mention that the DAC/CDP needs to be dual mono also..."everything" in the chain must be dual mono to "realize" this all-out world class reference system.  You would indeed need two seperate pots for every single component in the system.

One thing uncertain about this person's statement is what others have been discussing as being, on the most part, an agreement that dual mono amplifiers do provide benefits over a stereo amplifier...

I would personally love to hear a designer's absolute very best all stereo system compared to their absolute best all mono based system...I would wager that one cannot hear the difference, but I do know engineers designing all out, to be the most reference based front ends, and doing all mono based topology...so on paper, to them, they see it as being the most that can come from a stereo system.

I personally do not see how, if an amplifier is designed exactly the same, given the same exact components necessary to fullfill the amp's needs (proper PS/trannies/etc.) that one can hear big differences...at the same time, I have to wonder if I can hear it in a listening session as I do not rule out the differences that might be heard.

But again, as you stated, why don't we see two volume pots for dual mono amplifiers?...well, aside from tube amps or amplifiers that are in seperate enclosures, etc...how about all the amps in the same enclosure using one volume/stereo pot to drive a dual mono design?  What's the difference there?