[sdiy] Debugging Hammond filter circuit

[Donald Tillman]

On Apr 24, 2010, at 7:10 AM, Ian Fritz wrote:

> At 01:15 AM 4/24/2010, Donald Tillman wrote:
> 
> 
>> Wow, this is a truly awful patent.   There are mistakes in the schematic, the resistor reference designators start from R142 for no reason, the plot has no tick marks or units, there are no voltages or levels specified...
> 
> Right.  I'm pretty rusty on designing transistor amplifiers, but doesn't the base need some kind of DC bias connection?


Yes, that's R152, providing DC bias and negative feedback from the collector to the base.  It's hard to tell because the dot connecting R152 to the collector was omitted.   (That was one of the mistakes I was referring to above.)

There are lots more mistakes... For instance, there needs to be a high value input resistor on the CONTROL SIGNAL INPUT.

I say, connect the circuit between a Stratocaster and a Marshall stack, and have fun with random parts substitutions...

  -- Don

--
Don Tillman
Palo Alto, California
don at till.com
http://www.till.com