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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
pbnaudio's avatar
pbnaudio
1,617 posts
 
Al,

"When the RCA input is used in those cases the unused signal pin on the XLR connector is simply grounded, via either a jumper inserted into the XLR connector"

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. 

Second one being that the non inverting amplifier is connected to ground via the volume control, which means that a varying resistance ( depending on Volume control setting ) is inserted between signal ground and the inverting amplifiers input.

Our preamps are configured so that when a RCA input is selected the inverting amplifiers positive input is connected to signal ground via a relay AFTER the volume control.  

Good Listening


Peter


almarg's avatar
almarg
9,670 posts
 
Thanks, Peter. Regarding the first point, yes, a provision that an RCA input is to be used in conjunction with a jumper inserted between pins 1 and 3 of an XLR input likely reflects a grounding approach in the design that is non-optimal at best.  Such as pin 1 being connected to signal ground, or signal ground and chassis ground being common.

Regarding the second point, my comment addressed the inputs of power amps, that do not provide a volume control.

Best regards,
-- Al

atmasphere's avatar
atmasphere
12,412 posts
 
How much potential sonic performance would I lose by using my SE preamp into the unbalanced inputs of a fully differential amp? e.g., my UV-1 preamp into the SE input of an Atma-sphere amp, or using this preamp with a Pass Labs amp.
If using our amps, the difference essentially amounts to the sonics of the cable, as that comes into play when running single-ended. The amplifier input really doesn't care because the voltage amplifier in our amps is a differential amplifier. It simply amplifies what is different between its inputs. If one side is ground it still works the same way.


lowrider57's avatar
lowrider57 OP
5,418 posts
 
@atmasphere , thanks, that's the answer i was hoping to hear.

"my guess would be that finding a fully balanced preamp providing sonics that are as much to your liking as those of the UV-1, for a comparable price, would be a tall order if not impossible"
Al, that is quite true.
lowrider57's avatar
lowrider57 OP
5,418 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.






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