In Reply to: If you are talking about the Sanken SAP series posted by nightdoggy on April 10, 2007 at 16:20:21:
The Sanken SAP series have two problems:1) They are only an emitter follower double. In my experience an emitter follower triple will dramatically decrease the distortion compared to a double. This is because you are decreasing the loading on the front end by a factor of roughly 100x.
2) The way that the driver transistor is wired up, it will only operate in class AB and not class A. This prevents the driver from draining off the charge from the reverse-biased output devices, also increasing the distortion.
You can read more about this on the Marshall Leach website. He tried all of the topologies and found that the triple emitter follower gave the best performance. (This was invented by Bart Locanthi in the mid-'60s for JBL and called the "T-Circuit".) I found the exact same thing in my experiments.
<< developed by Kenwood and Sanken and seem like a good inexpensive design >>
Maybe so. You can hide a lot of the problems with this output device by applying a lot of negative feedback. And I guess that if you can save $0.50 or so by getting rid of the pre-drivers, then that might make sense for an "inexpensive design". However, it is far from optimum...
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Follow Ups
- Re: If you are talking about the Sanken SAP series - Charles Hansen 19:54:56 04/10/07 (1)
- Thanks Charles - nightdoggy 03:58:25 04/11/07 (0)