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previous: Randall Aiken Done properly, the FET input scheme... -- 10/3/1999 6:31 AM

Re: More info on cascodes and diff stages

10/4/1999 2:30 PM
kg	Re: More info on cascodes and diff stages Yeah yeah, I know--silicon in a guitar amp! I guess I'd better add a bunch of heater windings and switch all of my diodes over to tubes. And the DC heater supply for the signal tubes is going to be a bitch to regulate with vacuum. I'll need a bigger case, more sockets, and larger trannies to cope with all the losses. Seriously, I really don't have a bias against SS. It's all about using the best tool for the job. For example, rectification is one place I really can't justify the tube route... the only benefit I can see (and admittedly it IS a big one) is the turnoff characteristics of the vacuum diode. Then again, some ultrafast soft recovery silicon with proper snubbers attached can be VERY VERY quiet as well. Cheaper, more efficient, smaller, simpler. SS devices make way better CCS's too, as well as series pass elements. I mean, you CAN use tubes here, but you've got to worry about Vh-k, not to mention the drop across the element itself. In my case, the SS jfet has the benefits of huge gm, a huge input impedance, and absolutely no microphonics. It is also optimised for lowest self-noise. I must admit though that the tube is far more beautiful. Especially when lit up! Randall, the g didn't show up because it was inside of less-than greater-than. Use the square ones instead! [g] Ken

10/4/1999 2:30 PM

Re: More info on cascodes and diff stages

Yeah yeah, I know--silicon in a guitar amp! I guess I'd better add a bunch of heater windings and switch all of my diodes over to tubes. And the DC heater supply for the signal tubes is going to be a bitch to regulate with vacuum. I'll need a bigger case, more sockets, and larger trannies to cope with all the losses.

Seriously, I really don't have a bias against SS. It's all about using the best tool for the job. For example, rectification is one place I really can't justify the tube route... the only benefit I can see (and admittedly it IS a big one) is the turnoff characteristics of the vacuum diode. Then again, some ultrafast soft recovery silicon with proper snubbers attached can be VERY VERY quiet as well. Cheaper, more efficient, smaller, simpler.

SS devices make way better CCS's too, as well as series pass elements. I mean, you CAN use tubes here, but you've got to worry about Vh-k, not to mention the drop across the element itself.

In my case, the SS jfet has the benefits of huge gm, a huge input impedance, and absolutely no microphonics. It is also optimised for lowest self-noise.

I must admit though that the tube is far more beautiful. Especially when lit up!

Randall, the g didn't show up because it was inside of less-than greater-than. Use the square ones instead! [g]

Ken

Replies:

Randall Aiken Thanks for the tip, Ken. It is har... -- 10/5/1999 7:24 AM
Carl B. Constant Current Source: How about a Current Limiting Diode? -- 10/5/1999 6:36 PM