[James Tanner]

Hi FM,

I guess I am not understanding what they feel the advantage of the unshielded XLR cable is over a standard single ended cable?- except maybe the they like the XLR connector better?

james

Shielding the cable increases its capacitance. Nordost also has unshielded cables, this is what they say:

Nordost cables are not shielded because shielding increases the capacitance of the cable by a factor of 55% or more when applied in the conventional manner. If the capacitance of the cable is increased high frequency information is rolled of and you don't hear all of the musical information.

Hi All,

I have looked into this further and below is a short email I recieved from Jim Hayward who is the most qualified person I know when it comes to the understanding of cables and how they work.


Hi James,
 
I've attached my first article on cables.

You can see that I chose a practical length of 10 meters (35 feet) of the best and worst interconnect cable samples that I had.

In terms of their capacitance, the impact on frequency response when being driven by a high output impedance passive pre-amp and the low output impedance Bryston BP-20. 

·   The frequency response results were terrible when using the passive pre-amp with higher capacitive interconnects.

·   The frequency response results were excellent when using the BP-20 with higher capacitance cables. 

Why? 

The output impedance of the BP-20 was very low.  Therefore, the attenuation in the audio range was infinitesimal even when using the worst interconnect with the highest capacitance.

Cheers,
James Hayward.

[KeithA]

I remember reading Mr. Hayward's articles in Audio Ideas Guide. I agree that he knows what he's talking about and many times, made technical topics easy to read.

Keith

[Gary Listen]

James,

Regarding balanced and unbalanced lines, does Bryston use "phase splitters" in the analog output stage to create the balanced output signals in the BCD-1 and SP-2, or are the balanced signals created in the digital domain?  Also, if a balanced signal is input into the SP-2, does the SP-2 convert the balanced signal to an unbalanced signal for its internal gain stages?

Thanks

[brucek]

Also, if a balanced signal is input into the SP-2, does the SP-2 convert the balanced signal to an unbalanced signal for its internal gain stages?

The SP2 only enjoys unbalanced inputs........ there are no balanced inputs to this processor.

brucek

[alexone]

...the pro-version of the sp2 has one digital xlr input instead of the two toslinks.

 but i assume gary was talking about analog xlr ins and these are indeed not available in a sp2.


 so we have to wait for the sp3 .


 alex.

[Gary Listen]

I do have the SP-2 pro model with the AES/EBU balanced digital input.  However, I don't use it with my BCD-1.  The player sounds better in my system using the unbalanced analog outputs.  I'm sure part of the reason for this is the player's over-sampling of the signal for processing.  To my knowledge, the SP-2 does not have that capability.

The reason for my question is this.  If a digital processor takes an unbalanced signal and converts it to a balanced signal with a phase splitter, the signal is subjected to an additional active stage and puts more circuitry in the signal path.  If the preamp converts the balanced signal to an unbalanced signal for processing, another active stage is added to the signal path.  After the unbalanced signal is amplified by the preamp, it must convert it back to balanced with another phase splitter.  If the preamp's balanced output is then sent to a power amp's balanced input, it's converted again to unbalanced with yet another active stage.  This results in unbalanced/balanced/unbalanced/balanced/unbalanced conversions that add additional electronics to the signal path.  I think that is why some unbalanced components sound better than some balanced components.

I would be interested in knowing how the SP-3 will handle this.

[Phil A]

...the pro-version of the sp2 has one digital xlr input instead of the two toslinks.

 but i assume gary was talking about analog xlr ins and these are indeed not available in a sp2.


 so we have to wait for the sp3 .


 alex.

Yes - I have the pro version of the SP1.7.  I owned a Proceed PMDT transport at the time I ordered the unit and it sounded best using that output.  As a transport only, it had toslink, RCA coax, BNC coax and balanced.  I already have a coax to toslink converter (or vice versa) and I'm currently using that with the SP 1.7 on a new digital TV tuner I just bought.  So I figured it left me an option I would not have with the regular non-pro version.

I also find that I prefer the Bryston as an analog preamp vs. use of its DACs.  They are fine for Dolby Digital but with a good analog source (like the BCD-1) it really shows what it can do.

[James Tanner]

James,

Regarding balanced and unbalanced lines, does Bryston use "phase splitters" in the analog output stage to create the balanced output signals in the BCD-1 and SP-2, or are the balanced signals created in the digital domain?  Also, if a balanced signal is input into the SP-2, does the SP-2 convert the balanced signal to an unbalanced signal for its internal gain stages?

Thanks

Hi Gary,

Answer from Engineering:

Hi James;

Bryston uses input buffers on our amps and preamps, regardless of whether the signal arrives balanced or unbalanced.  The buffers have gain, reducing the gain requirements in following stages, and in fact reducing overall distortion in the amp or preamp.  They also, in the case of the preamps, allow lower-value volume and balance controls, reducing noise.

In electronic balancing the common-mode noise that arrives on the cables is cancelled when the signal is converted to single- ended, so this is a necessary step .

cwr

[vegasdave]

So with a Bryston preamp, driving long cables is no problem, and it's like a direct connection. True?

[James Tanner]

So with a Bryston preamp, driving long cables is no problem, and it's like a direct connection. True?

True, as an experiment a number of years ago we ran 1/4 mile of balanced cable from one of our preamps before we could measure any rolloff.

james

[vegasdave]

Wow. That's impressive!

[James Tanner]

James,

Regarding balanced and unbalanced lines, does Bryston use "phase splitters" in the analog output stage to create the balanced output signals in the BCD-1 and SP-2, or are the balanced signals created in the digital domain?  Also, if a balanced signal is input into the SP-2, does the SP-2 convert the balanced signal to an unbalanced signal for its internal gain stages?

Thanks

Hi Gary,

Answer from Engineering:

Hi James;

Bryston uses input buffers on our amps and preamps, regardless of whether the signal arrives balanced or unbalanced.  The buffers have gain, reducing the gain requirements in following stages, and in fact reducing overall distortion in the amp or preamp.  They also, in the case of the preamps, allow lower-value volume and balance controls, reducing noise.

In electronic balancing the common-mode noise that arrives on the cables is cancelled when the signal is converted to single- ended, so this is a necessary step .

cwr

Hi Gary,

Follow up answer from Engineering.

Hi James;
 
Bryston does use a phase splitter output circuit, in the form of a pair of discrete op-amps driven in opposite polarlty.  This produces an output of twice the Voltage, to reduce the requirement for gain in the following components.  It is done entirely in the analog domain.  Bryston's balanced input stages use differential amplifiers to both convert the signal to single-ended, and to mathematically cancel any noise picked up on the cables.
 
cwr