[Early B.]

All other things being equal, which is better and why -- a pair of monoblocks or a dual chassis amp where the power supply is contained separately?   

[FullRangeMan]

For Solid State and Class D amps I prefer monoblocks.
For tube amps the better are one chassis w/two power transformers.

[NIGHTFALL1970]

I am curious about this as well. Is there any scientific evidence that proves one way or another?

[Speedskater]

Monoblocks with XLR inputs, each placed near its loudspeaker is better.

[toocool4]

Hard to say, i guess it all depends on implementation.

[Early B.]

Monoblocks with XLR inputs, each placed near its loudspeaker is better.

Why?

[AllanS]

I like Paul McGowan’s videos for insight into such questions.
https://www.youtube.com/watch?v=crd9YjAkZXY
The only differences that stuck with me is better channel separation and, as Speedskater alluded to, longer XLR runs than speaker cables.

[seikosha]

If nothing else, monoblocks, allow the builder to use bigger transformers than a single chassis build could reasonably accommodate.  For example, if my Quicksilvers were on one chassis, it would be huge and unwieldy amplifier.

[DaveC113]

A separate power supply presents potential issues and challenges with the required custom cable / umbilical while not having any real advantages that can't be duplicated inside a single chassis. Maybe some exceptions with a large/very complicated amp.

Monoblock amps can be placed next to speakers and then you can use short SCs, that is an advantage as resistance in SCs makes a big difference while not making much difference in ICs due to the impedances involved... generally 4-8 ohms for speakers and 10k+ ohms for component inputs.

Depending on the amp, having a power supply just for the preamp/driver section is even better than separate power supply for L/R outputs. With tubes if you can have a PS for each stage and then L/R, so 4-6 power supplies and another separate PS for heaters, that is most ideal. 

[Early B.]

Hey guys, this question is posted in "The Lab," so I'm looking for technical responses. Presumably, the primary advantage of monoblocks is better channel separation, which reduces crosstalk and thus minimizes distortion. Does a power supply in a separate chassis do this, too? If not, aside from allowing for a larger power supply, what is the benefit of a two-chassis amp?   

[Bill Baker]

Hey guys, this question is posted in "The Lab," so I'm looking for technical responses. Presumably, the primary advantage of monoblocks is better channel separation, which reduces crosstalk and thus minimizes distortion. Does a power supply in a separate chassis do this, too? If not, aside from allowing for a larger power supply, what is the benefit of a two-chassis amp?

This still depends on the build. If it’s a single power supply in a separate enclosure, you could easily run into similar issues due to a shared ground and B+. You would need a dual mono power supply to obtain the same benefits as mono blocs.
Mono blocs will give you the best separation plus being able to greatly reduce the load on the power supply allowing it to be much more efficient.
If done properly, any of these setup can provide exceptional results.

[Early B.]

This still depends on the build. If it’s a single power supply in a separate enclosure, you could easily run into similar issues due to a shared ground and B+. You would need a dual mono power supply to obtain the same benefits as mono blocs.
Mono blocs will give you the best separation plus being able to greatly reduce the load on the power supply allowing it to be much more efficient.
If done properly, any of these setup can provide exceptional results.

Thanks.

Building on the original question -- let's say I want to build the ultimate amp. We know that premium capacitors tend to be significantly larger. Do higher quality transformers and chokes tend to be larger in the same way that premium caps are larger? Will a single-chassis amp be a size limitation to achieving superior sound quality??     

[Bill Baker]

What type of amp are you looking at? Power? Tubes?  Type of power supply (tube or SS). Much easier to answer questions knowing a little more about your goals.

[Early B.]

What type of amp are you looking at? Power? Tubes?  Type of power supply (tube or SS). Much easier to answer questions knowing a little more about your goals.

I already have what I want -- a 2-chassis 300B tube amp, etc. I'm asking these questions for educational purposes.

[nlitworld]

With Chokes, size gets rediculous real quick for certain applications. I finally bought all the parts for a Tubes4HiFi ST35 and the choke power filter is bigger than the transformers. Yuge and weighs 10lbs. Granted a resistor in the circuit is probably fine enough for most applications, but I wanted balls out over the top build of that circuit. Combine the inside with film caps everywhere possible (including 3x 100uf in power supply) and even a 17x14 Hammond case will be stuffed full on top and inside.

[brj]

Monoblock amps can be placed next to speakers and then you can use short SCs, that is an advantage as resistance in SCs makes a big difference while not making much difference in ICs due to the impedances involved... generally 4-8 ohms for speakers and 10k+ ohms for component inputs.

A different analysis of interconnect vs. speaker cable length that may impact the monoblock vs dual-channel amp conversation:

https://www.empiricalaudio.com/computer-audio/audio-faqs/short-versus-long-cables

I appreciate the "all other things being equal" caveat in the original post, but I find that it's hard to realize that condition in the real world - all elements in the chain contribute to the final sound, and they have to play well together.

[DaveC113]

A different analysis of interconnect vs. speaker cable length that may impact the monoblock vs dual-channel amp conversation:

https://www.empiricalaudio.com/computer-audio/audio-faqs/short-versus-long-cables

I appreciate the "all other things being equal" caveat in the original post, but I find that it's hard to realize that condition in the real world - all elements in the chain contribute to the final sound, and they have to play well together.

I disagree with a lot of that.

Speaker cables do in fact cost a lot more for longer lengths, plus if you want to double the length you need to double the wire to achieve the same resistance but then L and C will also go up. If you're talking a high end speaker cable the difference in price is large, a heavy gauge SC may use 10x the wire of a typical IC cable.

It's really as simple as speakers are 4-8 ohms and component inputs are 10k ohms or more. If you add 1 ohm to 4-8 ohms that's more than 10% more resistance. If you add 10 times the resistance, so 10 ohms, to a 100k input that's .01% difference in resistance. Furthermore, if we're considering balanced or XLR ICs, the XLR standard was in fact developed to overcome interference issues when using very long runs of cable. Very long balanced runs of cable are VERY common in pro audio, even for low-level mic signals. It simply isn't a problem. And today's output sections for single ended cables are not as low voltage as they used to be, and we now understand how to effectively shield single ended cables, so in the opinion of many top-end component mfg'ers, running longer lengths of SE IC cable simply isn't an issue either.

For speaker/amp interactions we also have the concept of damping factor or how much control the amp has on the speaker drivers. This is simply the speaker's impedance divided by the amp's output impedance + the speaker cable's resistance. If you have an amp with very little output impedance than a long speaker cable can easily double the resistance and cut damping factor in half. The SC has real, measurable effects on speaker cone damping, and while impedance matching in components is important, the IC length and resistance is rarely an issue although capacitance can be in some situations.

I think the prevailing opinion is that shorter SC and longer IC is preferrable to vice versa, it's very rare to find anyone arguing otherwise.

[DaveC113]

Thanks.

Building on the original question -- let's say I want to build the ultimate amp. We know that premium capacitors tend to be significantly larger. Do higher quality transformers and chokes tend to be larger in the same way that premium caps are larger? Will a single-chassis amp be a size limitation to achieving superior sound quality??   

No, but WAF on a very large chassis may be more of an issue. Vintage tube amps could get to be very large. An "ultimate" tube amp will indeed have some very large caps and coils, but there are many options for packaging. My own tube amp has a separate chassis and power supply for the driver section and the output uses no electrolytic caps whatsoever and a choke-reg PS, so in total my 6w 2-stage tube amp is well over 50 lbs of stuff. And that would be just a driver for a large tube like a 211, a 211 output built like my EL34 output would be a very large amp weighing well over 100 lbs.

[rotarius]

A 12ga wire resistance is typically 1.58 ohm per 1000 feet.  Placing an amp a foot away or 6 feet away makes no meaningful difference in resistance.  You are NOT adding an extra ohm to 4-8ohm speakers.  More like .01 ohm, lol.

[DaveC113]

A 12ga wire resistance is typically 1.58 ohm per 1000 feet.  Placing an amp a foot away or 6 feet away makes no meaningful difference in resistance.  You are NOT adding an extra ohm to 4-8ohm speakers.  More like .01 ohm, lol.

It's just an example. You honestly think that I think a speaker cable might have a 1 ohm resistance?    Or maybe you're just being argumentative? I have an engineering degree and have been making the best value cables on the market for well over a decade. You seriously think I have no clue what speaker cable resistance is or what it does? 

Your statement is just plain wrong. Damping factor is definitely affected by speaker cable resistance. I'll give one example:

Amplifier output impedance: .05 ohm (typical)

3ft of 14g SC (6ft round trip), R = .015 ohm

12ft of 14g SC (24ft rt), R = .06 ohm

Speaker Impedance = 8 ohm

DF(3ft) = Zin/Zout = 8/(.05 + .015) = 123

DF(12ft) = 8/(.05+.06) = 72

The reduction of DF means less electrical grip on the speaker drivers and "looser" bass, this is absolutely audible in many circumstances. In fact, owners of vintage speakers sometimes use thinner than normal SC in order to reduce the DF of the system to what the vintage speaker was designed for. Tube amps have much higher output impedances and these drivers often have much stiffer suspensions to compensate for the fact the amps have less electrical damping of the drivers.