During the work for Sokrates I have become a real fan of differential circuits because of their striking advantages namely
- no hum, buzz, click, pop and less masking of the signal because of greatly decreased ground noise
- less cross talk
In total differential designs result in a much cleaner signal.
Ground noise, ground loops and grounding techniques are always blamed when it comes to noisy signals. However, ground noise and loops are virtually unavoidable in HiFi installations and so the noise will always contaminate the signal of single-ended circuits although that might not be obvious right away.
So instead of blaming the inevitable, what about using the proper technology to render the issues harmless ?
Differential circuits and signal transmission simply leave no opportunity whatsoever (if done properly) for ground noise to combine with the signal because ground is not used as a signal return path like in single ended designs. Instead there is a third and dedicated wire not carrying all the dirt that is to be shunted to ground.
Anyway, this passion has now been re-ignited by an article in Linear Audio Vol 5 by Bruno Putzeys about analogue differential signal processing.
During the recent years I have missed all this notion about chipamps although they really come with a set of nice features such as overload protection, thump-free start up/shut down and thermal sensing and tracking. This is all good instant stuff, just add water.
Although there are already about one zillion designs out there, some of them are simply overdone and others are missing basic but essential stuff like proper supply bypassing, let alone the PCB layout. Also, what I have not come across so far (without looking too hard especially in the deep dark bowel of the usual suspect forums), are differential designs (and I hope there are no good reasons for that).
As a result of all this I have designed three different configurations to cover the typical use cases. The buffers are always LM4562.
There is a single configuration for small woofers, midrange drivers and tweeters: