dissing the monoblocks

[nyazzip]

i just found an interesting website (http://www.sound.westhost.com/cables-p5.htm) that among other things, states: "Someone has managed to convince a sizable segment of the audiophile fraternity that to achieve acceptable channel separation, completely separate amplifiers must be used. Considering that it has been shown [5] that 20dB channel separation is quite sufficient for a full stereo image to be appreciated, it is nonsense to claim that infinite separation is needed or desirable.

It is not at all difficult to design an amplifier with better than 50dB separation, even using valves, and any more than this is of no audible benefit. The "cross-modulation" effect that a shared power supply supposedly introduces is drivel. If an amp is so heroically ill-conceived as to suffer from cross-modulation, then simply sticking it into its own case with a separate power supply certainly won't fix it. I might suggest that it is most ideally suited as a boat anchor, since the design is so seriously flawed that it is beyond salvation.

A common power supply is a sensible (and far cheaper) alternative, and will cause no crosstalk in itself. Most amps have a very high ripple rejection, and if they reject ripple, they will also reject any signal frequencies that happen to get onto the supply line.

In fact, the conventional power supply capacitors will filter out all but the lowest frequencies anyway, and since bass is almost invariably recorded onto disc as mono, a minor amount of crosstalk at low frequencies is of no consequence - even if it were possible by this means, which it generally is not.

Bottom Line on Monoblocks
Unless you only need a single channel amp (for a subwoofer, for example), they are a waste of money, and serve no useful purpose. You will get a slight improvement in output power, but the real difference will be inaudible in the majority of cases.

Alternatively, they are useful if you want to have the shortest possible speaker leads. The amp can be installed next to the speaker, and a very short lead used to connect the two. Then we create a problem with the low level interconnects, which will be of significant length. There is far more chance of interference and high frequency loss in long interconnects than in speaker cables, so ideally the interconnects should be low impedance balanced circuits. Sadly, most monoblocks do not offer this essential option. "

fun stuff

[Ty_Bower]

High wattage valve amps come on monoblocks because:

A) They exceed the current requirements that can be sensibly achieved with a single power transformer.

and

B) They get too heavy to put two channels on a single chassis.

[Geek]

Sorry, I disagree.

A) Power transformer magnetics allow HV at significant current to be used that are smaller and lighter than yesteryear.

B) A negates B


More like (C) some idiot magazine guru said "Thou shalt only monoblock" and it was done Yellow_Light_Colorz_PDT_16

Cheers!

[Slartibartfast]

Sorry, I disagree.

A) Power transformer magnetics allow HV at significant current to be used that are smaller and lighter than yesteryear.

B) A negates B


More like (C) some idiot magazine guru said "Thou shalt only monoblock" and it was done Yellow_Light_Colorz_PDT_16

Cheers!

How about (D), it allows you to build on a smaller footprint and also for a cleaner wiring layout underneath.


Or even (E) it is an aesthetically pleasing arrangement.

One of his arguments is that the monoblock arrangement costs more to produce. Since when has high end audio been cheap, Dynaco not withstanding?

[dhuebert]

(D) I loved how simple to build the eiClones were.

(E) They look cool sitting on the floor next to my speakers.

(F) Believe what you like as long as nobody get hurt. I believe I like mono blocks

Don

[TomMcNally]

It's defintely a size/weight thing. My stereo 300B amp weighs about 60 pounds. It's hard to move around, and it warped the bureau in my bedroom where it lives. Splitting it into two 25 or 30 pound monoblocks would have been nice.

[mesherm]

Asking what is better, two monoblocks or one stereo amp is similar to asking whether push-pull is better than single-ended. Each configuration scratchs a particular itch and has its own benefits and drawbacks. They all play music however and thats the important part.

[EWBrown]

It's defintely a size/weight thing. My stereo 300B amp weighs about 60 pounds. It's hard to move around, and it warped the bureau in my bedroom where it lives. Splitting it into two 25 or 30 pound monoblocks would have been nice.

That's definitely a Heavyweight Contender for the PPW category (Pounds Per Watt). Yellow_Light_Colorz_PDT_03 Yellow_Light_Colorz_PDT_08 Yellow_Light_Colorz_PDT_16 Yellow_Light_Colorz_PDT_05 Yellow_Light_Colorz_PDT_01

/ed B in NH

[SDS-PAGE]

The JE Labs 300B monoblocks that I built weighed at approx. 35 - 40 lbs/block. Can't imagine how much it would have weighed had I build it in stereo. Sure glad I didn't try.

My WE91A has 9 irons, three of which weigh about 35 lbs. My guess is that it weighs only 55 lbs. That's as much weight I am willing to handle on a single chassis.

[Slartibartfast]

The JE Labs 300B monoblocks that I built weighed at approx. 35 - 40 lbs/block. Can't imagine how much it would have weighed had I build it in stereo. Sure glad I didn't try.

My WE91A has 9 irons, three of which weigh about 35 lbs. My guess is that it weighs only 55 lbs. That's as much weight I am willing to handle on a single chassis.

Even the JE Labs 2A3 would be more fun to build as a monoblock system... Yellow_Light_Colorz_PDT_12

[Geek]

How about (D), it allows you to build on a smaller footprint and also for a cleaner wiring layout underneath.

That's a sweet reason for sure :)

[nyazzip]

size/weight considerations makes sense to me. for some reason it didn't cross my mind at the time i posted this; in my defense i've never actually seen or handled a high wattage valve amp in person ;D

[Gingertube]

I've built many amps as monoblocks, as a stereo (single chassis) with completely separate supplies, and as stereo with a common power supply.

It is my experience that keeping supplies for the 2 channels as independent as possible DOES impart sonic advantages.

As an example on my latest vintage 6V6G based amp which has a single power tranny I started with a 5R4 to first small cap to choke to capacitor then split the supply via separate resistors (10R) to a final cap for each channel. I found that spiltting the supply at that first cap and doing the individual channel feeds using separate chokes made a big difference. Mind you, this particular amp has been tweeked to the max, so much so, that even swapping in a vintage Mil Spec CV1071 in place of the RCA 5R4 rectifier (supposedly identical specs) gave a quite noticable improvement.

In an average design using average components you may not notice any difference between common and separate supplies (whether they are on one chassis or two). In a good design using good components I believe you will notice.

Its that old story - the more you improve an amp in any one particular area of its circuit (by design or better components) the more it will reveal any inadequacies in other parts of the circuit. Thus you get into this cycle until (hopefully) you get to point where you just sit back, listen and grin a lot.

Cheers,
Ian

Decided to edit this to add a bit more rave.
I Have also run into problems with multiple secondaries on a single transformer. I decided to solid state rectify a heater winding to run DC heaters to the front end of an amp thinking this would improve the sound -
My first impression was that this mod was real dud - it sounded much worse. A bit of sleuthing showed Heater winding SS rectifier switching noise was being injected back through the transformer and showing up on other secondaries - the real problem was that it showed up in my output tube bias suppy. A change to UF diodes and addition of a snubber for the heater winding rectifier fixed the problem. So you can get into problems with a single transformer with multiple secondaries as well. For my latest and greatest amp design (100W monoblocks using Menno VanderVenne "Super Triode" mode) I have used separate transformers for the bias supplies - Over the Top? = maybe, but having spent a small fortune on Plitron Output Trannies and Gold Lion re-issue KT88 etc. its a small additional cost.