[AMPS] SB-220 Amplifiers and Garage Sales!!

[measures]

>
>Are you guys playing Rich's word games again? 
>
>Wes, the person who made the measurements, concluded there 
>was no advantage to using nichrome. Rich, despite making an 
>agreement to not "cook" Wes' data, did exactly that.
>

>Rich re-worded things. 
>
Rich did not change any measurement.  

>> Rich says:
>> 
>> > Rp was 101-ohms for a resistance-wire suppresor vs. 166-ohms for a 
>> >copper-wire suppressor.
>> 
>> Something puzzles me here. If the suppressor provided the whole plate
>> load impedance at the parasitic frequency, then the gain would be
>> reduced by only 4.3dB by lowering the parallel resistance from 160 to
>> 101 ohms. This may be enough to just stop the parasitic, but doesn't
>> appear to my mind to give enough margin to ensure stability.
>
>A lot of things should puzzle you Peter:
>
>1.) The frequency Rich selected is LOWER than the frequency 
>where the amplifier actually would oscillate. 

Wes choose 100MHz.  This is close to where parasites typically occur.  

>This makes the 
>difference larger than it really is, since Rich's suppressors lower 
>the Q most at low frequencies.
>
>2.) The suppressor Wes tested was NOT the hairpin Rich 
>recommends, it was a larger inductor made exactly the same as 
>the stock suppressor except with nichrome. If you actually use 
>Rich's hairpin, VHF Q actually INCREASES over the stock 
>suppressor when the whole system is considered.
>
100nH with a coil-inductor is the same as 100nH with a U-inductor.  

>> But in reality, the suppressor is only part of the plate load
>> impedance. As a result, the change (percentage reduction) in the load
>> that the plate sees is even smaller, so the gain margin between
>> oscillation and stable operation becomes even less.
>
>Bingo. You won't find that on Rich's web page.
>
>The entire thing is nonsense. I measured the VHF anode Q of a 
>amplifier with a pair of 3CX800's with a stock suppressor, and again 
>with Rich's nichrome. The VHF Q increased when the Measure's 
>suppressor was used.

.  Resistance wire produces a higher Q than copper or silver?
>
>That's because Rich's suppressor has less Rp, and when that Rp 
>is placed in series 

the "p" in Rp stands for parallel.  

> ...with anode lead the reactance of the anode lead 
>dominates the system.
>
jabberwocky

>Rich focuses on Rp because he can make a pathological argument 
>that "less Rp is better". 
>
is less VHF gain is better?
  
>Of course anyone who understands the system also knows the 
>exact opposite is true. When a lower Rp is inserted in series with a 
>fixed reactance, system Q increases.
>
welcome to the Rauchian world.  
>........

-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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