Balanced XLR to SP1.7

musicology · « **on:** 13 Mar 2005, 09:22 pm »

I want to connect a cd player to my SP1.7 by XLR but there are no XLR inputs only RCA.

How do I get around this and maintain sound quality?

I know that there are XLR - RCA cables but do they degrade the sound quality?

Thanks

nicolasb · « **Reply #1 on:** 14 Mar 2005, 09:58 am »

It probably would degrade it, but not by very much - balanced connections are better at rejecting interference than unbalanced ones, and converting XLR to Phono effectively reduces the signal volume by 6dB. There's no active "conversion" involved, just one wire connected to another.

Btw, a standard XLR to phono cable is wired phase-to-signal, ground-to-ground, but I reckon it's better to use a piece of "balanced" cable and wire it phase-to-signal, antiphase-to-phono-ground, and leave the cable shielding wired to the XLR ground - that way you retain most of XLR's ability to reduce ground loops....

Levi · « **Reply #2 on:** 14 Mar 2005, 03:25 pm »

I think the pro version of the SP1.7 has a digital XLR input. I have not seen an analog XLR input verson. Maybe on the next update on the SP1.7

James Tanner · « **Reply #3 on:** 14 Mar 2005, 03:32 pm »

Hi Musicology,

Balanced cables have nothing to do with 'quality'. Assuming the Balanced cable and the Single ended (RCA) cables are of similar construction and quality the difference is one of noise rejection only.

Balanced cables make sense when you want to elimiinate 'noise' (RF etc.)from the outside world from affecting the noise floor of your system. Your cables are 'antenna's' for these electromagnetic waves and Balanced lines have the ability to reject the noise through 'common mode' cancellation. The longer the cable the more important this noise cancellation is. Most people have their sources close to the SP1.7 so balanced inputs become much less of an issue.

Balanced circuits must have a 'sending' and 'receiving' section in order to be considered 'differentially balanced'. There are poor ways to balance a circuit and there are better ways to balance - we use fully discrete Class A operational amplifiers in our products. Many others use IC's or transformers.

james

dan_lo · « **Reply #4 on:** 14 Mar 2005, 07:40 pm »

Hi James,

According to what I understand since you have the signal + and signal - , when you combine them you have double the voltage, which means less amplification. This leads to a better THD in the power-amp.

Your power-amps manual says that you have 3db better THD when used in balanced mode.

If this is correct, It means you have better performance using balanced cables, even if you use short runs.

Did I understand correctly ? If not , please correct me.

James Tanner · « **Reply #5 on:** 14 Mar 2005, 08:43 pm »

Hi Dan,

The specification refers to the noise levels between unbalanced and balanced inputs, 110dB unbalanced, 113dB balanced.

The signal level is expected to be higher when using balanced inputs on the amplifier, so the gain of the amp is reduced to compensate. The minimum noise specification is slightly better as a result.

There is no reason to avoid using the balanced inputs, even on short runs but the differences are small.

james

dan_lo · « **Reply #6 on:** 15 Mar 2005, 03:22 pm »

Thanks James,

While we are on the subject. If we use the DAC in the B-26DAC, is the output signal on the balanced connections or the unbalanced ?
Alternatively - is the following chain possible :
CD--(digital connection)--> BP26DAC --- (balanced connection) --> 4BSST

James Tanner · « **Reply #7 on:** 15 Mar 2005, 03:29 pm »

Hi Dan,

The DAC output is available on both the TWO - RCA outs and the Balanced XLR out.

james