SS CCS and distortion

[Globulator]

Notice the resistors in the plate circuits of the HMV and ImPasse?😀 It's all part of "competent design."

I noticed you using them in your phono amp project too!

 

[keantoken]

Hey everyone.

Is there a thread dedicated to SS CCS's for use in tube circuits that I can read?

Thanks,
- keantoken

 

[SY]

There have been a few. The best treatment of bipolar CCS is in Morgan Jones's "Valve Ampliers," 3rd edition. The MOSFET cascodes are covered in general in Walt Jung's articles in (I think ) march and April 2009 AudioXpress and my ImPasse article in February '09, same mag.

The basics can be summed up while standing on one foot: the gain of a triode voltage amplifier is mu times R_L/(R_L + r_p). R_L is a fixed resistance, r_p varies with current. If current is fixed, r_p can't vary. If the load impedance is VERY large compared to r_p, the gain equation reduces to mu, which is a more constant parameter. So the minimum distortion a triode can have is with a CCS load.

 

[keantoken]

Sounds a lot like a transistor.

Thanks,
- keantoken