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Why Single-Ended?

I’ve long wondered why some manufacturers design their components to be SE only. I work in the industry and know that "balanced" audio lines have been the pro standard (for grounding and noise reduction reasons) and home stereo units started out as single-ended designs.

One reason components are not balanced is due to cost, and it’s good to be able to get high quality sound at an affordable price.
But, with so many balanced HiFi components available these days, why have some companies not offered a fully-balanced amp or preamp in their product line?
I’m referring to fine companies such as Conrad Johnson, Consonance, Coincident, and Bob Carver’s tube amps. CJ builds amps that sell for $20-$39K, so their design is not driven by cost.

The reason I’m asking is because in a system you might have a couple of balanced sources, balanced preamp, and then the final stage might be a tube amp or monoblocks which have SE input. How much of the total signal is lost in this type of setup? IOW, are we missing out on sonic bliss by mixing balanced and unbalanced?

lowrider57
lowrider57's avatar
lowrider57 OP
3,018 posts
 
It is correct that some manufactures use a jumper pin from 1 to 3 when a input are configured with two options - XLR and RCA. IMO there is several issues with this. First one being that pin 1 of a XLR should have Chassis ground (earth) potential - not signal ground which is what the inverting amplifiers input needs connected to when only feeding the non inverting amplifier to get a balanced output.

When using a SE input to a differential amp, I thought the ground was tied to pin 1 of the XLR input and to the chassis. What are the consequences of also being tied to the safety ground?

I was offered a Pass amp at a great price, but don’t know if I should use a SE pre with their fully-differential design.






pbnaudio's avatar
pbnaudio
1,534 posts
 
Lowrider,

In order to prevent ground hum most have 2 different grounds, one being Chassis Ground (earth, safety ground) which should also be connected to pin 1 of all XLR connectors both in and outputs.   Typically Signal ground is isolated from chassis ground with a dual diode in reverse parallel and a resistor - or something similar.  Signal ground should not be present on pin 1 of the XLRs

I have  referred to this paper before - it contains some very useful information about grounding 

https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf


Good Listening

Peter

lowrider57's avatar
lowrider57 OP
3,018 posts
 
@pbnaudio , Thanks, I’m familiar with the Whitlock paper, probably time for me to read it again.
Typically Signal ground is isolated from chassis ground with a dual diode in reverse parallel and a resistor - or something similar. Signal ground should not be present on pin 1 of the XLRs
Peter, your components are magnificent. I like the toggle between balanced and RCA on the back of the amps.

I appreciate the info provided by yourself, Ralph and Al. It makes me realise that the design of an amplifier needs to be examined carefully before making a purchase. It’s easy to check for a balanced signal, or for fully-differential by reading the specs, but how an amp deals with safety and signal ground is not always disclosed. Atma-Sphere states clearly that their amps use a star grounding topology.

atmasphere's avatar
atmasphere
7,068 posts
 
^^Just FWIW, star grounding is nice but the real issue is how the chassis and circuit grounds are handled!
wolf_garcia
4,650 posts
 
I have a balanced preamp and XLR inputs into my power amp, but the amp inputs are likely not balanced at all (Jolida 502p). Thus when I hooked up a pair of balanced Mogamis to replace whatever the unmarked weird green XLRs (that sound fine by the way) are that came with my preamp, the Mogamis sounded awful…weirdly since I’ve used Mogami balanced cables in pro audio for years. I can now assume the Mogamis just didn’t mesh with the "unbalancing" of the amp inputs, so back they went to Guitar Center (I tried). I use Mogami Neglex for my turntable "din to RCA" and they’re much quieter than the stock Linn cable they replaced, so Mogami is still OK by me. I use an AQ balanced cable to the amp now, and it works fine. Note that when I was recording songs by "folkie" artists for a cable TV interview show we had in Maine years ago, I did notice that high quality XLR mic cables all around sounded somewhat better in my headphones than el cheapo cables…so there’s that.
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