Zen V4.0

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The one and only
Joined 2001
Paid Member
I am more concerned about noise with the Zen,
as they have poor psrr and are often coupled with
sensitive drivers.

I have not seen a big need for absolute regulation
as such, although it can't hurt as long as it is well
bypassed, preferrably with a couple mega-farads ;)

For you newbies:

psrr is power supply rejection ratio, the ability of the
circuit to ignore the ripple and other noise on the
power supply rail.
In the Zen V2.0, the conclusion section states that this circuit can be operated balanced, giving twice the output.

Can be balanced operation be obtained by using two amp sections, using the inputs of each section as the +/- inputs of one channel, and connecting the +/- of a speaker to each of the two outputs?

Will this eliminate the need for the capacitors at the output, as the DC on each speaker terminal would be the same?

Is it infact this simple?

Thanks in advance.

Understanding Balanced operation

This is my understanding (a very weak understanding, my apologies) of balanced operation:

* A source presents two lines. The pos. line (arbitrary sign) carries the signal + noise and the neg. line only the noise

* When this balance signal is presented to difference amp only the signal is amplified and the noise common on both lines is ignored.

* When a balanced source is presented to two sections of the Zen V2.0, the pos. section will amplify the signal + noise and present it at the output and the neg. section will amplify only the noise and present it at the ourput. Since the noise amplified to the same level is presented to both terminals of the speaker it has no effect and only the signal ends up being converted into sound.

The two questions I have are:
1. Even though the two sections of the Zen will effectively reject noise, is this truly a difference amplifier?
2. The two sections together present only the signal to the speaker terminals without the noise. This is the same amplification as one section with the addition of noise. If this is true how does the power output of two sections of the Zen double the power output? I'm sure I am missing something here.


Account Disabled
Joined 2002
I'm not quite sure what you're asking, but you're understanding of balanced operation isn't quite right.
When you have a balanced system, you're not talking about just signal and a "return" ground anymore, you actually have two <i>phases</i> of the same signal referenced to ground- one phase will be going positive, and one will be going negative. The input section looks at the <i>difference</i> between the voltage on both the lines, and amplifies that difference. What happens when you have noise riding in on those two phases is that the input amplifier sees the same signal on both lines (since they are so physically close, induced noise will be virtually the same) and since it is the same on both lines, it will not amplify it, rejecting the noise but amplifying the original signal.
I believe (could be wrong here) that when the zens are run balanced, you use the balanced output from your preamp to drive them differentially. Since each amp is amplifying noise, then that noise appears as a common signal in phase at the speaker (which is driven across the two amps outputs). Since it is the same voltage level and phase at both amps outputs (assuming they are well matched) it can't cause a current to flow through the speaker- just like connecting both terminals of the speaker to only the + on a battery-there is no potential difference, so no current flow. On the other hand, since the signal coming into the two amps is exactly out of phase, it will appear amplified and out of phase at the output terminals, and will be double the voltage across the speaker. If the amps can push double the current, you will get 4 times the output of one amplifier.
Hope this helps.
Account Disabled
Joined 2002
I drew something up to explain it better.


  • balanced.jpg
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