Monoblock amplifiers - any significant (dis)advantages? - Page 2

stvnharr · 9th October 2012, 12:21 PM

Quote:

Originally Posted by stratus46

You're asking - no, begging - for a nasty ground loop. Why would you want monoblocks and then connect the output grounds together via the power ground? The signal grounds should come back together via the RCA cables at the preamp. Any slight ground variances due to signal currents won't make an iota of difference as the output ground is 'floating'.

Please remember that any voltage drops in a cable happens in both conductors. 'Ground' (earth if you will) is not the same at the load as it is at the source. You MUST obey Ohm's law. You can try to force your way with ground straps or larger gauge wires but there is always resistance whatever you do. Don't fight it, work within the limits.

G²

Did you read my post on how the LF board is designed?
It's relatively easy to check for ground loop noise by just connecting mains earth to star earth, and seeing what happens. I've used LF amps for years, and find no ground loop issues with connecting mains earth to star earth.

Rhythm Willie · 13th November 2012, 11:41 PM

Just noticed this thread, I have "monoblock" amps made in a mirror pair.

I have connected the chassis to star earth as I had a bit of noise in my "Soraya" boards, due to the fact that I had a large Mundorf silver/oil input cap fairly close to the board and therefore the output inductor. Dead quiet now. I did'nt have to do this on my original 100+n amps.

I tried this after I noticed that Hugh had done it on his commercial "Soraya", no problems at all.

andyr · 14th November 2012, 12:04 AM

Quote:

Originally Posted by Rhythm Willie

Just noticed this thread, I have "monoblock" amps made in a mirror pair.

I have connected the chassis to star earth as I had a bit of noise in my "Soraya" boards, due to the fact that I had a large Mundorf silver/oil input cap fairly close to the board and therefore the output inductor. Dead quiet now. I did'nt have to do this on my original 100+n amps.

I tried this after I noticed that Hugh had done it on his commercial "Soraya", no problems at all.

Then again, with my Soraya monoblocks (each module is in a custom-built case with 2 Lifeforce 55 modules plus an active XO), the star earths on all 3 modules are connected together but the chassis is not connected ... with zero noise.

But then, I only have the standard input caps.

Regards,

Andy

gingertube · 14th November 2012, 01:58 AM

Rod Elliot to the rescue: "How to wire a power supply".
Power Supply Wiring Guidelines

Note the dotted box with the label "loop breaker" in Figure 2. That is "ground loop" breaker.

The connection (or otherwise) of the 0V to chassis ground is what the guys have been talking about above.

I prefer to have a direct connection but that can introduce ground loops. If you have a ground loop problem (causing hum) then add in the "loop breaker".

Rod's "loop breaker" is covered here:
Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
It breakes the ground loop without compromising safety.

There, everything (and more) that you ever wanted to know about earthing and power supply wiring. Thank You Rod.

Cheers,
Ian

Bob Richards · 14th November 2012, 03:46 AM

If grounding techniques are done exactly right, there should be no real difference. The whole "monoblock" thing is in my opinion a gimic.

andyr · 14th November 2012, 03:58 AM

Quote:

Originally Posted by Bob Richards

If grounding techniques are done exactly right, there should be no real difference.

On the contrary, AFAIAC ... as the chassis should be connected to mains earth (for safety reasons), if signal earth is connected to chassis then it will be "infected" by hash on the mains earth line. Hence I do not connect signal earth to chassis.

Quote:

Originally Posted by Bob Richards

The whole "monoblock" thing is in my opinion a gimic.

If you mean by that statement ... having a separate PS & power trannie for each channel is no better than when both channels share the one PS/power trannie then IME, you are wrong.

A pair of mono Naim 135s always sounded better than a single stereo Naim 250 ... because each channel had its own dedicated PS. This is also the case with the amps I use.

However, if you are saying that a 'stereo' amp which has a PS+power trannie for each channel is no better than the same thing in 2 separate 'mono' boxes ... then I would agree with you. Except of course, the 2 monoblocs will enable you to locate the amps directly behind the speakers - so reducing considerably, the length of speaker cable required ... which is definitely a benefit.

Regards,

Andy

probbo · 14th November 2012, 09:07 AM

I second Ian's suggestion to follow Rod Elliott's guidelines for grounding, which I used when assembing my NAKSA70 in 2010.

Peter

Bob Richards · 14th November 2012, 07:01 PM

Assuming grounding is done right, I would expect having separate power supplies in a stereo poweramp for each channel to make about as much audible difference as using Jenlabs $12,000 speaker wire compared with 14AWG wire you bought at the hardware store. Any time you do comparisons, you have to look at any other variables that may be at play. Not everybody is knowledgeable and experienced enough to see some of the variables. Don't always believe what you think. It turns out that we are able to fool ourselves.

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13th November 2012, 11:41 PM	#12
Rhythm Willie diyAudio Member Join Date: Aug 2009 Location: Williamstown, South Australia	Just noticed this thread, I have "monoblock" amps made in a mirror pair. I have connected the chassis to star earth as I had a bit of noise in my "Soraya" boards, due to the fact that I had a large Mundorf silver/oil input cap fairly close to the board and therefore the output inductor. Dead quiet now. I did'nt have to do this on my original 100+n amps. I tried this after I noticed that Hugh had done it on his commercial "Soraya", no problems at all.

14th November 2012, 01:58 AM	#14
gingertube diyAudio Member Join Date: Oct 2004 Location: Adelaide South Oz	Rod Elliot to the rescue: "How to wire a power supply". Power Supply Wiring Guidelines Note the dotted box with the label "loop breaker" in Figure 2. That is "ground loop" breaker. The connection (or otherwise) of the 0V to chassis ground is what the guys have been talking about above. I prefer to have a direct connection but that can introduce ground loops. If you have a ground loop problem (causing hum) then add in the "loop breaker". Rod's "loop breaker" is covered here: Earthing (Grounding) Your Hi-Fi - Tricks and Techniques It breakes the ground loop without compromising safety. There, everything (and more) that you ever wanted to know about earthing and power supply wiring. Thank You Rod. Cheers, Ian

14th November 2012, 03:46 AM	#15
Bob Richards diyAudio Member Join Date: Feb 2011 Location: Portland Oregon, USA	If grounding techniques are done exactly right, there should be no real difference. The whole "monoblock" thing is in my opinion a gimic.

14th November 2012, 09:07 AM	#17
probbo diyAudio Member Join Date: May 2011	I second Ian's suggestion to follow Rod Elliott's guidelines for grounding, which I used when assembing my NAKSA70 in 2010. Peter

14th November 2012, 07:01 PM	#18
Bob Richards diyAudio Member Join Date: Feb 2011 Location: Portland Oregon, USA	Assuming grounding is done right, I would expect having separate power supplies in a stereo poweramp for each channel to make about as much audible difference as using Jenlabs $12,000 speaker wire compared with 14AWG wire you bought at the hardware store. Any time you do comparisons, you have to look at any other variables that may be at play. Not everybody is knowledgeable and experienced enough to see some of the variables. Don't always believe what you think. It turns out that we are able to fool ourselves.