[floresjc]

Can anyone give me a quick rundown on why/what situations having balanced connections on a pre/pro and amp would be wanted? I've been looking very heavily at the Wyred4Sound amps, and they all have balanced inputs. I don't know if its important to take advantage of them by searching for a pre/pro that has balanced outputs, or if I can just use the regular connections and choose from a wider variety of processors. I would assume that at least some Salk owners, given the wide variety of gear people are using, have experience in this.

I'm in the process of searching for a processor to decode the new HD audio formats that come on Bluray and has HDMI switching. If anyone can recommend one, that would be great.

[R Swerdlow]

Can anyone give me a quick rundown on why/what situations having balanced connections on a pre/pro and amp would be wanted? I've been looking very heavily at the Wyred4Sound amps, and they all have balanced inputs. I don't know if its important to take advantage of them by searching for a pre/pro that has balanced outputs, or if I can just use the regular connections and choose from a wider variety of processors.

Balanced connections are commonly used in recording studios for microphones with long cables.  Long cables (30 feet or more) carrying low voltage signals can pick up noise induced by electromagnetic interference (EMI) or radio frequency interference (RFI).  Balanced connections and the differential circuits required on the preamp and amp can cancel out this noise.  I'm not sure what voltage levels are involved with microphones, but I think it is much less than the typical standard line level of about 0.2-0.3 volts in home systems, as you would get from the analog audio outputs of a CD player.  It may be more like the low voltages, about 5 millivolts, from a moving magnet phonograph pickup.

Read about it here: http://en.wikipedia.org/wiki/Balanced_audio

It seems that balanced connections are fashionable for preamp to amp connections, and many higher priced examples feature these as a sought-after feature.  The voltage levels between preamps and amps are higher, roughly in the range of 0.2 to 5.0 volts.  So it is likely that interconnects at this level are less prone to EMI induced noise, especially if they are less than 30 feet long.  I think that standard RCA interconnects between a preamp and amp are fine, unless you have an unusually noisy environment with high levels of EMI.

This subject, like so many in home audio, has become controversial.  I have no doubt that others will chime in with opposing opinions.

If any one knows the approximate voltage levels from a low impedance microphone, please tell us what it is.  And also, why are there never balanced interconnects coming from a phonograph pick up?  They put out the lowest voltage signal found in home audio.  If they don't require balanced interconnects, why do some people think they are of benefit at the much higher voltages found between a preamp and amp?

[floresjc]

Great explanation. The first thing that hits me is that if this is for long runs of 30ft or more, why is it even necessary on a preamp-amp connection. In most cases, they will be about 1ft apart on a rack, seemingly negating the need for extra noise rejection. I can think of very few setups where people have the preamp a long distance away, with the amp sitting right next to the far away speaker.

[Gord_Toronto]

The Blue Jeans web site has this artical on what are Balanced and Unbalanced wire systems.  I found it to be very informative.  When you get to the bottom of the artical it states that Balanced is always better and to use it whenever it is possible


http://www.bluejeanscable.com/articles/balanced.htm

[TomW16]

Balanced circuits require additional circuitry to cancel noise picked up in the interconnects.  So the question is, do the additional balanced circuits outweigh the noise rejection offered?  Sometimes yes and sometimes no.  It will depend on the level of "noise" in your area that your interconnects are exposed to, the design of your interconnects (i.e. sheilding) and how long your interconnects are.

Cheers,
Tom

[R Swerdlow]

I did a little searching to find a range of ouput levels for typical microphones http://www.shure.com/ProAudio/Products/WiredMicrophones/index.htm

Phono pickups (typical values)
Moving coil            0.5 mV  (1 thousand mV = 1V)
Moving magnet       4.0 mV

Microphones        1.3 – 3.2 mV

Line level            0.32 V  (100 times stronger than a microphone)

Home audio preamp (B&K Ref 50)
Input sensitivity       0.09 V
Max output             8.0 V

Home audio amp (B&K Ref 200.2)
Input sensitivity       1.4 V (unbalanced)
                            2.8 V (balanced)  (1000 times stronger than a microphone)
Voltage gain           28 dB

Microphones put out about as much signal as typical moving magnet phono pickup.  This is about 1% the voltage of any typical line level source such as the analog audio outputs from a CD player.  And it is 0.1% the input sensitivity of at least one home audio amp where I could find the relevant specs.

Now some will argue that balanced connections between a preamp and amp will insure protection against EMI induced noise.  Yes this is true.  But is it worth the extra cost to buy a preamp and amp with the differential circuits required for balanced connections?  The voltages involved between preamps and amps are 100 to 1000 times larger than those in microphones.  They are 100 to 1000 time less sensitive to induced noise.

I'd rather spend my money on one of Salk's nicer veneers  .

[R Swerdlow]

So far, I've presented reasons, based on signal strength levels, why I believe balanced connections in a home audio system are not worth it.

To be fair, I did learn one tidbit of info about it's benefits.  If the entire audio signal chain has differential circuits and is connected with balanced cables on all electronic devices in the chain, it will provide 3 dB of greater dynamic range.  This means from a sound source like a CD player (or DAC) through preamp and amp.  Providing this only between a preamp and amp will not accomplish this.  3 dB extra headroom is not insignificant, but it will cost a premium.

I am still curious why there are no turntables or pickups with differential circuitry and balanced connections.  The signal levels from pickups are as weak or weaker than from microphones.  Was it never done years ago because no one thought balanced connections were needed in home audio, or is there something inherent in these pickups that prevent using that design?

[avahifi]

If the entire audio system is done completely balanced, which requires a four channel DAC analog filter and audio circuit set, a four channel preamp, and a four channel power amp (or two stereo power amps) maintaining balanced operation from input to output, summing the signal at the speakers, then in theory, all common mode distortion in the system will cancel, providing superior musical operation, depending upon how much distortion was there to cancel.  This is usually only possible with a DAC source where both plus and minus left and right signals are available from the source, depending upon the DAC chip set in use.

We actually have tried this with positive results.  Of course it essentially doubles the cost of the audio system.

However, in our case, the audible improvements alerted us that since the process was better sounding, then there must be distortion components in the audio chain that were being canceled that we had not yet addressed.

This sent us on a serious effort to discover the remaining weak links in the audio chain we produce and fix them if possible.  The result was significantly improved performance for several of our products, resulting in only minimal improvements when those improved components were once again tried in a full balanced system.  This made the thought of actually doing a full balanced system not cost effective at all.  But the exercise sure was helpful in putting up red flags that we were not as good as we had thought we were and helping us make things better.

Regards,

Frank Van Alstine

[R Swerdlow]

Frank - I was hoping that someone with your experience would speak up.  Thanks.

[Nuance]

Great info, Frank.  Thank you. 

[TomW16]

This sent us on a serious effort to discover the remaining weak links in the audio chain we produce and fix them if possible.  The result was significantly improved performance for several of our products, resulting in only minimal improvements when those improved components were once again tried in a full balanced system.  This made the thought of actually doing a full balanced system not cost effective at all.  But the exercise sure was helpful in putting up red flags that we were not as good as we had thought we were and helping us make things better.

Awesome job Frank.  I was wondering if the fully balanced idea would ever come to fruition but it sounds like you used it as a benchmark to improve your product line.