Cascoded designs for old Pass circuits

[vossie]

There is a lot to be said about cascoded transistor configurations in the audio circuits. I have recently been looking to implement this into the Aleph design to see if any benifits could be had. The folded cascode configuration could change the whole circuit so I was thinking more of the straight forward drain-source connected cascode setup to start off with. I see Nelson uses the folded cascode configs in his patent for susy, have any of you tried
this on the coutput stage of any of the Alephs? Nelson, any comments - I'm sure we could better the X circuit presented elsewhere on this forum much by using cascodes??

Vossie

[Nelson Pass]

It would be a little tough to use folded cascode on the Alephs, as they have only two stages. You can fold-cascode the input stage so as to render the output stage a unity current cascode, but this would necessarily result in the full output current having to flow through the input differential pair. This is do-able, but gets pretty far from the original design.

If you want to cascode Alephs conventionally (as opposed to folded), you can cascode both the input and output stage. While this gives you some voltage losses in the output stage, it works very well.

[jam]

A few hints from thse Master?

[vossie]

"If you want to cascode Alephs conventionally (as opposed to folded), you can cascode both the input and output stage. While this gives you some voltage losses in the output stage, it works very well."

I tried the conventional way on the symilator but it seem like I get distortion at around cross-over which is barely noticable in the audable frequency range but becomes more prone when at 30kHz and up. It is easilly detected when feeding square signals. Does the sound familiar - is there something I'm missing? Will post a diagram later with results.

Vossie