Bridging / Wiring in Series 2 X1000's

Is wiring two X1000's in series the same as bridging them? if not please explain what the difference is.

I also understand how 2 standard mono channels (with a +ve and ground output) can be bridged together to provide double the peak to peak voltage and double the current (ie. 4 times the power) using the +ve outputs of 2 such amps amplifying an in-phase and out-of-phase signal to create a +ve and -ve output to the speaker.

What i dont understand is how the increased peak to peak voltage is achieved when there is already a +ve and -ve (ie. balanced) output (ie. a -ve output instead of a ground output) such as in the X1000. The literature says you need floating inputs such as are created by the array interface so I know it is to do with the floating inputs and i have been reading the X1000 back engineering thread here which is kinda sinking in but mostly going over my head :) I understand that the signals are not always automatically referenced to ground but instead sometimes to some other figure that is cancelled at the outputs. So more accurately, i guess the question should be this...... in an array of X1000's can the voltage swing of the array exceed the voltage swing of a single X1000 ie. ~145V between +ve and -ve outputs? If so, where does the extra voltage come from / or more correctly how are the amps wired to each other to produce it?

In the interest of keeping things simple, when using 2 X1000's in series / bridging them, how are the inputs and outputs from each amp connected to each of the inputs and outputs of the other amp to achieve this? ie. how do u wire two X1000's in series or bridge two X1000's?
Simple explanation

The X series amps have floating internal electronics. This means that their "position" is not fixed. If you say are 6 feet tall, you are this tall whether you stand on the ground or whether you stand on top of a mountain. This means that a floating voltage output can reside on top of another and not really worry about it. An example of a floating voltage source is a battery. Hook two in series, and you have twice the voltage. Connect one terminal to an achorpoint and you have fixed that point, but the relative voltages still remain intact.

There are probably several ways to hook such beasts up, and I encourage you to check with Pass labs, but the basic principle is the same as that for batteries.

Your question on how to do this when the outputs are alread balanced is insightful, but remember that when everything is floating, it does not much matter whether it is balanced or not. It is however very important to thread carefully when deciding what to hook up where as the input voltages will be the ones that anchor output voltages.

I strongly suggest that you buy a Pass X-4000 if that is indeed what you need. You will gain lower output impedance etc and have less trouble deciding how to get it to work. If you ask Pass Labs kindly, they will probably do it for you as the design is scalable :)

Then again, you can always do what I am doing and build a a Pass X-100 ...

Thanx Petter that has cleared some things up for me ...... i am asking this as i plan to build a diy amp based on a hybrid X series / aleph circuit with balanced operation rated for between 50 and 100W in 8ohms ...... and i want to be able to (at a later point in time) wire them in series to get more power / channel. So i am trying to get as wise as i can b4 i start cause i know i am gonna pay for it thru the nose if i dont :)
Since posting this topic, I have received an email from Mr. Pass explaining that as I suspected, due to the balanced operating mode of the X1000, it is already effectively operating in bridged mode and by nature you cant bridge a bridged amp :) which is where operating multiple X1000's in series comes in, while as we all know, wiring multiple amps in parellel gives an increased current capacity into lower ohmage loads, wiring the X1000's in series gives an increase in output voltage so you get more power into the same ohmage load.
I have just received another email from Mr. Pass regarding the X1000 in series operation and from what i can gather, because of the fact that everything is conpletely floating, you connect the balanced floating inputs from the array interface to each amp in the array and then connect their outputs to each other like you do when you connect multiple batteries to create higher voltage...... ie. for 2 amps, use the +ve output on one amp as the positive line to the speaker\s, the -ve output on the other as the negative line to the speaker\s and connect the unused +ve output on one amp to the unused -ve output on the other amp.

[Edited by AudioFreak on 10-19-2001 at 11:58 PM]


2000-12-31 9:31 am
I have withdrawn my earlier post on the topic as I may have not been totally correct (I wish it was the last time that happened) but I am still not too convinced about this business of putting amp in series.
If I understand this correctly the two output voltages are added and for that you should have perfect time domain response from both the amps and although it's only at the most 20kHz I wonder how significative that may be.
For parallel connection absolutely must have amps of matching impedance and some type of splitting buffer for each input to compensate for unequal input impedance.

If anyone out there feels like I should be burned at the stake for these statements please jump right into the discussion.