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Old 19th January 2004, 02:59 AM   #1
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Default Inverting X circuit

There are comments about the excel about x configuration, especially in aleph pages,

In this same website, there are comments about the excel of inverting power amp, especially in the gainclone threads.
So an idea of questions comes in my mind. I dont really understand why inverting power amp is said to excel the normal one. Fig 1 is the normal X amp, while A1 and A2 is a "Normal Current Gain".

Let's pretend that we can make an inverting current gain (or inverting feedback) that is as good as the normal one. Our main focus here is Q1 and Q2. A1 and A2 is an "Inverting Current Gain " . If this inverting current gain (or inverting feedback) is applied to X schematic, so it comes to Fig 2.

1. Will this work at all?
2. X is coming from the crossing of input and feedback between the 2 differential transistors. But inverting current stage results in fig2, which has no crossing at all. Is this still can be classified as x circuit?
3. The DC problem with aleph-x is somehow related to "positive feedback", at least that is how I understand it from the GRollins tracking approach. With Fig2, there will be no positive feedback, since the input and output is applied to the same differential transistor. Will this eliminate the DC problem in x circuit?
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Old 19th January 2004, 03:16 AM   #2
tiroth is offline tiroth  United States
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Default Fig. II

No matter how you slice it, its the same. You could invert one half of a 2-stage amp, or as your drawing capitalize on the the negative output of the diff. pair. I hesitate to call this bridged b/c there is a single shared input stage, but in the basic concept you could say it is bridged (w/ a simplified input stage).

This is distinct from X conceptually, even though it is only a couple of different wires. The feedback is coming from a totally different place.
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Old 20th January 2004, 03:07 AM   #3
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Thanks for the info.
I DO really want to understand this X esstentials, and takes merit of its excel, both in sound reproduction and distortion elimination.
Is there anyone have the "RIGHT" X schematic for ordinary 3 stages class AB amp? How does the input-feedback connections will be?
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