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previous: Andrew Hi Steve,Do you int... -- 3/31/2000 8:36 AM View Thread

Re: Route 66 PS Questions (and UL questions)

3/31/2000 9:13 AM
Steve A.
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Re: Route 66 PS Questions (and UL questions)
Andrew:  
 
    I hadn't even thought about that but I'm glad that you brought it up... I thought that the Route 66 output section looked a lot like the Vox AC30- especially the AC30/4 design with the EF86's that Ted B. has shared with us- only with the two KT66's using fixed bias instead of four EL84's using cathode bias...  
 
    As a matter of fact when you compare the two designs (ignoring the Vib/Trem channel of the AC30/4) they are almost identical except:  
--the Route 66 has a rather unique two knob tone stack, while the AC30/4 runs the signal from the EF86 through a .01uF coupling cap and optional 220pF(?) cap en route to the Volume control ahead of the PI  
--the AC30/4 uses a 250kA cross-line cut control (with 0.01uF cap) ahead of the EL84 grid stoppers.  
--the PI uses the exact same resistors except for the plate resistors, and with the non-inverting input on the Route 66 connected to ground instead of to the Vib/Trem channel on the AC30/4.  
 
    Lots of people here have been building amps without NFB and they haven't mentioned their amps being particularly unstable but it would be something to watch out for!  
 
Steve Ahola  
 
P.S. BTW with the design similarities between the two amps it seems like it would be a *killer* mod to be able to switch out the Route 66 tone stack and engage the treble-cut control instead for a boosted mode... or better yet, wire in a 6 position tone switch like on the second channel of a Matchless DC30! And that would be for only one of the channels... wire up a second channel preamp like the AC30 Top Boost! It would be interesting to see how the KT66's would compare to plain old 6L6's, and to cathode-biased EL84's...

 
Replies:
SpeedRacer re- UL, stability and nfb.. UL uses... -- 3/31/2000 6:37 PM