Balanced in phono stages preamp?

A balanced electrical interface is almost immune to spurious signal pickup: eg: hum. When using single ended interconnects I have never had a problem with noise pickup, but I have had a phono cartridge circuit pretend it's a radio. Balanced configuration makes more sense for a high gain phono input than for any other part of the system.

Actually, I do use some balanced wires, but this is because the equipment is pro sound stuff, and that's the way it is made. I have used some of this equipment single ended, and it worked fine that way also.

>>And since phono cartridges are balanced<<

This is simply not true. I'm suprised you would continue to actively propogate this myth. If anyone understands the beauty of balanced circuits and signalling, it's you. You get it.

So why pretend a two-wire device is balanced? It's not. A cartridge is floating single-ended. Balanced operation require three terminals: a common (mid-point, average, reference), a positive polarity, and a negative polarity. You don't have that with a cartridge.

Nonetheless, as I pointed out in another thread, a proper receiver can force a cartridge into balanced mode. This is done by using a center tap on the primary of a step-up transformer. The center tap connects to ground. The windings then force the cartridge to act as if it were balanced (but without the 6dB gain). I wonder how many of these so-called balanced phonostages actually do this. And how many simply connect one cartridge tap to ground and pretend?

jh

Dear Pedrillo: Jeff, Herman and Hagtech are totally right the cartridge is not a balanced device.

I was surprised at Spencer place when I read in the Atmasphere operation manual that the cartridge is balanced, it is not.

Herman, balanced it is not hype: in a fully differential well made design the distortions/noises are canceled inside the circuit ( I'm not talking here of interconnect/speaker cables ) and this subject is extremely critical in a Phonolinepreamp, could you tell us why is only " hype " ?

Hagteck, our design is real input to output balanced one, no " charlatan " seudo-balanced design.

Regards and enjoy the music.
Raul.

Raul, good to hear from you. What is this "our design" you speak of?

I agree there are some theoretical advantages to differential designs; however we both know that many balanced devices are not differential. I believe Atmasphere's are but many (most?) are not.

By hype I mean the advantages are outweighed by the complexity of the circuits, and the ability to reject common mode noise is simply not needed in the home environment. The only exception I can see where it might come in handy is the very early stages in a phono stage. Otherwise, why take an inherently single ended source, convert it to balanced, and handle it that way only to recombine the 2 polarities at the speaker? Most of those who are trying to sell balanced equipment take advantage of the fact that the average consumer doesn't understand the circuits. They tout the advantage of noise rejection (which isn’t needed) and love to point out that pro audio uses it (which isn’t relevant.)

As you may know I feel simplicity is the key to good sound. Balanced circuits don’t fit in with this philosophy. My amplifier has 3 SETs directly coupled. My phono stage has a step up followed by 2 stages of amplification with the RIAA in between. With high efficiency speakers this is all you need.

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.