[HBR] HBR-11/2000. Comments?

[SGT Brian Ford]

Why not a 6sn7 or 6sl7 for audio output?  those are
pretty common and cheap.

Keith.

--- N2EY at aol.com wrote:

> In a message dated 7/23/06 9:21:02 PM Eastern
> Daylight Time, Tuchueh7 at cs.com 
> writes:
> 
> 
> > Progress to date 
> > on the test chassis (6AR8 mixer-6EH7 if): I was
> able to stabilize it 
> > somewhat 
> > by using resistive loading of the input and output
> transformers, and 
> > reducing 
> > the cathode bypass cap to .001 (if freq = 530kcs.)
> Still evidence of 
> > regeneration; narrow nose BW and excessive gain. 
> > Now I try capacitive bridge neutralization. 2.7
> mmf neut. cap. and 1500 mmf 
> > cap on the bottom of the input IF trans. gives me
> a fairly stable IF amp 
> > w/out 
> > the resisitive loading and normal value of cathode
> bypass. At this point, 
> > trace goes south on the old TEK 454a necessitating
> some down time to fix it. 
> > Looks 
> > like neutralization is the ticket!!! 
> 
> It strikes me as odd that a single stage of 6EH7 is
> so hard to stabilize. Two 
> stages can be fussy but a single stage was no
> problem for me when prototyping 
> the Type 7. 
> 
> One trick was the use of unetched PC board material,
> with a copper flashing 
> shiled across the socket and all bypasses soldered
> direct to the PC copper.
> 
> 
> 
> > Next item on the agenda is the audio amp and B+
> supply built on a separate 
> > chassis
> > from the HBR. I got some nice solid walnut boards
> to house the amp/B+ 
> > chassis 
> >and
> >a six inch commercial PA speaker. I have found that
> I need lots of loud 
> clean 
> >audio
> >for hamming around.
> 
> Why such a small speaker? If you like audio, why not
> a 10 or 12 incher, in a 
> nice big wood cabinet?
> 
> Some time back, in the search for cleaner audio, I
> went to an all-triode 
> audio chain. Power stage is a pushpull 12BH7. Gives
> me a couple of clean audio 
> watts at much less distortion than a single-ended
> pentode - without negative 
> feedback. Power consumption is about the same as the
> 6AQ5 it replaced, and I have 
> a much wider choice of output iron.
> 
> 73 de Jim, N2EY
> 
> 
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>  
> 
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> 
> 


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