Balanced in phono stages preamp?

All right, everyone, a little lesson about why all phono cartridges are balanced and how balanced operation works. Cartridges are balanced as they have 2 wires per channel, neither of which has to be tied to ground for it to work. Proof? invert the phase of one channel of your cartridge in your system and see if it hums (it doesn't).

Hagtech, the ground is the tone arm itself. Have you ever wondered why the phono is the only hookup in your system that requires an extra wire for grounding (else it hums)? This is the result of trying to operate a balanced source in single-ended mode. Other examples include tape heads on tape machines, the light pickup on a laser head, most microphones and nearly anything with a transformer-coupled output.

You don't need a 'center-tapped transformer' to 'force' the cartridge to be balanced. Any differential input will accept the cartridge without any such work! I've been doing this now for nearly 20 years with my cartridge and we've been building phono sections like this for 18 years. It works.

All of your recordings were made in the balanced domain. All of them. They only get converted to single-ended in playback- if you allow that to happen. For a long time, you had no choice- now you do. The benefits are lower noise with less gain stages (blacker background lower distortion wider bandwidth) from the phono preamp, and less buzz/humm/RF from the pickup wiring. There are no tradeoffs if executed properly- often the signal path is simpler!

Herman, single-ended/balanced has nothing to do with sound in space, quite simply the analogy falls apart and becomes a logical fallacy. SE/balanced has everything to do with how recordings are made and played back: that is where we need to be focused.

Have you ever wondered why the phono is the only hookup in your system that requires an extra wire for grounding (else it hums)? This is the result of trying to operate a balanced source in single-ended mode.

That is simply not true. It is not required. A cartridge connected to a single ended input sometimes will hum with the ground connected and sometimes without. Sometimes the ground connection makes no difference. After playing records for almost 40 years I have proven this to be true.

While it may be true that balanced equipment might have been used in the recording process, the groove in the disc is not balanced. Balanced has 2 signals of opposite polarity per channel so a stereo signal would require 4 separate signals. There is no medium (tape, vinyl, digital, etc.) that provides these balanced signals so all sources are single ended. Why even imply that vinyl is balanced?

Dear Herman: Our design is the Essential 3150 Phonolinepreamp that you can follow at this link:
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1166047312&openflup&49&4#49

The Essential 3150 is fully diferential input to output and has two gain phono stages with out step-up transformers.

Ralph, I understand your cartridge balanced explanation but it is not clear to me, how a coil/inductor can be balanced?

Regards and enjoy the music.
Raul.

>>Proof? Invert the phase of one channel of your cartridge in your system and see if it hums<<

You're kidding, right?

>>Balanced is hype<<

There is more to balanced circuitry than is obvious to the casual observer. One significant advantage is PSRR. Or the way it interacts with a power supply. Think holistically for a moment, everything is inter-related to everything else. I can walk through an example here.

What is the best type of regulation? Many will say shunt. Why? Because it offers a lot of line rejection and can be made very fast. It is also class A. What is better than shunt regulation? What if (pretend it is possible) instead of reacting to a load variation, as a shunt regulator does, that you could know in advance what the variation will be? What if the regulator acted precisely at the same moment and without phase delay to a load transient? And without feedback. Would that not be better? Imagine correcting the supply rail perfectly in response to the music. Well, that is basically what a balanced differential stage does. One way to look at it is a single-ended stage mated with a shunt regulator. You can actually run it that way. There isn't any other topology out there that can top that.

Now take it even further. You can add passive line regulation (no feedback). In a balanced phonostage I once designed you could take a variac on the ac line and crank it up and down (simulating line disturbances), and the dc output level from the amplifier doesn't budge. Yes, the power supply rails move in response to the variac, but the output doesn't. Well, at least not at a 1Hz variac rate. The point is, there are tricks you can pull with differential topologies that you can't use anywhere else. It ain't hype. Unfortunately, there is a big price to pay. It takes double the number of devices. Cost goes way up.

jh

Atmasphere, agreed. The notion that balanced circuits are more complex that single-ended is a myth. In fact, balanced operation in comparison gives you twice the voltage (+6 dB) than single-ended, which in many stages would allow you to eliminate one gain stage (or several, with multiple stages)! Also, a symetrical circuit presents supply current variations in opposing polarities, so cancellation takes out and supply demands are drastically reduced. Balanced circuits are more elegant from an engineering standpoint, etc. As a final bonus, the signal-to-noise ratio improves by +3 dB (not +6 dB). You can definitely notice that.