Nelson Pass said:
Well, the - line isn't SEPARATELY driven as it would be with an active solution. But the - line has the same signal on it as it would if it were, just that the signal level would be half that of the active solution (providing the active solution is separately driving both lines at the same level).
So for example if you had an unbalanced output driving the line with say, 1 volt, and you converted to balanced by driving the second line with the same signal only inverted, you'd measure +1 volt on the + line and -1 volt on the - line.
If you converted to a balanced output using the passive solution, you'd measure +0.5 volts on the + line and -0.5 volts on the - line.
And not to be too much of a stickler here, it's not the line that rejects the noise. That's done by the differential input. What balancing does is help keep common-mode noise common.
If an interference field impinges upon each line identically (and techniques such as twisted pairs helps assure that they do impinge identically), if the impedance of each line with respect to ground is the same, then the voltage induced across each line will be the same in terms of magnitude and polarity and subtracted out at the differential input.
If the impedances are not the same, then the voltage induced across each line will be different, and the differential input will amplify the difference between the two.
Yup. Though I wouldn't call that "educated." Mislead would be more like it. And unfortunately in this industry of ours, it happens all too often and is looked upon (sadly quite rightly in many respects) as a technological backwater.
But hey, rightly or wrongly, it's still a lot of fun.
se
Why add more circuitry to convert unbalanced to balanced when the preamp in question already does this? If you feed the balanced output of the preamp to the balanced input of a power amp, you are good to go.
You could go to http://www.jensen-transformers.com/ln_in.html and get one of those if you absolutely must have the unbalanced to balanced conversion prior to your preamp.
But for the record, I wouldn't bother.
Erik
You could go to http://www.jensen-transformers.com/ln_in.html and get one of those if you absolutely must have the unbalanced to balanced conversion prior to your preamp.
But for the record, I wouldn't bother.
Erik
Bob2 said:
Unfortunately, at an input, it's not such a simple matter as it is with an output.
At the input, it's not just a matter of balancing the impedances of the two lines, but also of providing a differential input so that any common-mode noise on the lines can be rejected (which is the raison d'etre of balanced interfaces in the first place) and depending on the existing input circuit could involve much more significant changes in the circuit itself rather than just tacking on a few parts.
So without a specific circuit to work from, there really is no generic answer as with outputs.
se
Banned
Joined 2002
Nelson Pass said:
Well no, you wouldn't see anything on the - line if you analyze it simply as drawn. That's because as drawn, it's not terminated. There's no load so the - leg is an open circuit with respect to ground.
Tie a load resistor across the two output terminals and then let me know what you see.
se
Peter Daniel said:So I new there was a price to pay after all.
Until you get around to plugging it into the component that it's going to be feeding. Until then, it's not going to be of much use anyway.
Basically, on the plus side, you're not contributing additional non-linearities due to active circuitry.
On the minus side, you don't get the 6dB of voltage gain you can with an active circuit so your signal to noise ratio will be a wee bit higher with the passive solution.
In other words, the common-mode voltages due to induced noise on the line will be of the same magnitude regardless of whether you go the active or passive route, so the higher the absolute signal level, the better the signal to noise ratio.
se
Re: HUmmm
You may well hear a difference. The question is, will it be an improvement? (Then again, you may not. Or you may think you hear a vast improvement simply because you built the thing. I can't be the only one who's fallen for that.)
I can't see how adding more circuitry between the CD player and the Aleph P 1.7 would do anything beneficial. It would add a bit more distortion to the CD player's output than you had before.
I'd rest comfortably knowing that the Aleph P can do a wonderful job converting a single-ended input to a balanced output without adding anything else to what is a neatly simple circuit.
Erik
JasonL said:
You may well hear a difference. The question is, will it be an improvement? (Then again, you may not. Or you may think you hear a vast improvement simply because you built the thing. I can't be the only one who's fallen for that.)
I can't see how adding more circuitry between the CD player and the Aleph P 1.7 would do anything beneficial. It would add a bit more distortion to the CD player's output than you had before.
I'd rest comfortably knowing that the Aleph P can do a wonderful job converting a single-ended input to a balanced output without adding anything else to what is a neatly simple circuit.
Erik
Banned
Joined 2002
Re: Re: HUmmm
But that arrangement has no benefit whatsoever with regard to the line between the CD player and the Aleph P in terms of rejecting any noise that may be induced into that line.
Running unbalanced from the CD player to the Aleph P, the induced noise will be differential, rather than common-mode which means the Aleph P will simply amplify it and pass it on down the line.
And since the noise is differential, the fact that the Aleph P's output is balanced is irrelevant. It will feed the noise to the amplifier as a differential signal as well which means it will not be rejected by the amplifier's differential input.
se
eLarson said:
But that arrangement has no benefit whatsoever with regard to the line between the CD player and the Aleph P in terms of rejecting any noise that may be induced into that line.
Running unbalanced from the CD player to the Aleph P, the induced noise will be differential, rather than common-mode which means the Aleph P will simply amplify it and pass it on down the line.
And since the noise is differential, the fact that the Aleph P's output is balanced is irrelevant. It will feed the noise to the amplifier as a differential signal as well which means it will not be rejected by the amplifier's differential input.
se
Banned
Joined 2002
Re: Re: Re: HUmmm
Why don't we consider CDP and Aleph P as one unit. A player with Aleph as a buffer and the line between them very short (in my case 10"). So maybe the chances of noise pickup are very slim. I've seen this length of cables inside the players and preamps alone.
And one could assume that the line from preamp to the amps is more noise sensitive (in my case is more like 10 ft long). So there is still advantage in having balanced outputs on the preamp in terms of rejecting any noise that may be induced into that line.
Steve Eddy said:
Why don't we consider CDP and Aleph P as one unit. A player with Aleph as a buffer and the line between them very short (in my case 10"). So maybe the chances of noise pickup are very slim. I've seen this length of cables inside the players and preamps alone.
And one could assume that the line from preamp to the amps is more noise sensitive (in my case is more like 10 ft long). So there is still advantage in having balanced outputs on the preamp in terms of rejecting any noise that may be induced into that line.
Banned
Joined 2002
JasonL said:
No, that's not quite what I was saying. What I was addressing was the notion that simply because the Aleph P has a balanced output that this will amoeliorate the fact that the interface between CD player and the Aleph P is unbalanced as seemed to be implied by the post I was responding to.
How much if any noise you may ultimately hear depends on any number of factors. I'm simply saying that all else being equal, balanced interfaces will result in less noise than unbalanced interfaces, irrespective of whether or not there's any actual audible noise to begin with.
In other words, I'm not insisting that any interface must or even should necessarily be balanced in order to provide a satisfying result. Only the end user can decide that for themself.
se
Re: Re: Re: Re: HUmmm
That's fine.
As I explained to Jason, I'm not insisting that a balanced interface is the only way to go. Ultimately I'm just trying to explain what it is that they are, and what it isn't that they aren't.
se
Peter Daniel said:Why don't we consider CDP and Aleph P as one unit. A player with Aleph as a buffer and the line between them very short (in my case 10"). So maybe the chances of noise pickup are very slim. I've seen this length of cables inside the players and preamps alone.
And one could assume that the line from preamp to the amps is more noise sensitive (in my case is more like 10 ft long). So there is still advantage in having balanced outputs on the preamp in terms of rejecting any noise that may be induced into that line.
That's fine.
As I explained to Jason, I'm not insisting that a balanced interface is the only way to go. Ultimately I'm just trying to explain what it is that they are, and what it isn't that they aren't.
se
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