[Amps] Parasitics & Filament Sag

[Joe Subich, W4TV]

Tony writes: 
 
> Obviously Rich's suppressors work. Some just can't seem to 
> admit that part and want to argue the technical differences 
> in what they COULD do if they chose to MODIFY or FIX the 
> conventional one versus what he has done and does do with his.  

Rich's suppressors work but not for the reason that he claims. 
Nichrome is not a magic bullet and "low Q" or "Low Rp" is total 
nonsense.  

The instructions for the SB-220 (and any dual 3-500Z amplifier) 
show three of his suppressors in series!  Since there is not 
enough room for the three suppressors between the tubes and 
the RF choke, they must be installed in a "zig-zag" manner  
that completely changes any resonances in the anode circuit.
The change in anode circuit resonance is more likely to be 
responsible for the elimination of the parasitics than the 
nichrome!  

A standard method for taming "unruly" amplifiers has been  
adding parasitic suppressors in the cathode (input) circuit. 
In the old days that was generally two or three turns of bus 
wire on the body of a 22 Ohm 2 Watt resistor.  It did not have 
the dissipation problems that the anode suppressors faced ... 
and it was probably more effective than a second suppressor 
in the anode line.  

For years Rich has been making magical claims for his nichrome 
suppressor and labeling any argument for which he could make 
no rebuttal as barnyard waste.  It is time to view the claims 
for what they are - patent medicine at best and fraud at the 
worst.  

That his suppressors work in some cases is not in doubt .. but 
anything that perturbs either the anode or input circuit of an 
RF amplifier can "fix" a parasitic problem if it changes the 
feedback circuit or effects the anode resonance.  It is just as 
likely that an unruly amplifier can be stabilized by simply 
cleaning up other construction or design flaws. 

What is at issue here is the intellectual dishonesty of claiming 
magical powers for michrome ... and using Wes Stewart's test 
results (without his permission and in violation of his copyright) 
to claim the very thing that Wes disproved. 

If you want to use resistance alloy in your suppressors, that's 
fine.  However, understand what it does and how it works.  Don't 
expect it to be the magic cure-all for every other design problem. 

Using resistance alloy instead of fixing the circuit issues is 
no different than changing the material used in a tube chimney  
instead of moving the tube a sufficient distance from the wall 
of the chassis.  It is a band-aid that may help when other 
solutions are not acceptable. 

73, 

   ... Joe, W4TV