[R-390] R-390 600 ohm audio solution

[Tom Bridgers]

I agree 100% with Cecil.  Particularly his comment regarding feedingan external amp from the R-390A's diode load connection.  I personallyhave handled the AF output this way more times than I can rememberfor my R-390A's.
And finally, thanks for sharing your thoughts with the list, Walt.  I foundthem useful, interesting and worth considering.Best,-Tom  KE4RHH


> From: chacuff at cableone.net
> Date: Thu, 27 Dec 2012 15:02:27 -0600
> To: kr4hv at numail.org
> CC: Chuck.Rippel at cox.net; r-390 at mailman.qth.net
> Subject: Re: [R-390] R-390 600 ohm audio solution
> 
> No waste of time Walt...
> 
> A good exercise.
> 
> While there are many solutions to matching modern speakers to our boat anchors...the 70v line transformer being one of them...and one that has been discussed here before as a decent option...all that has been pointed out is that the Hammond seems to be the top choice for someone looking for the best quality that can be had with today's offerings and it is reasonably priced...and the least likely to suffer core saturation.
> 
> Outside of that the best option of all is to feed an external tube amp from the diode load...that provides the most flexibility for tailoring the audio to ones liking.
> 
> Hang in there Walt...this is a great group....vast knowledge here!
> 
> Cecil
> K5DL
> 
> Sent from my iPad
> 
> On Dec 27, 2012, at 2:16 PM, "KR4HV" <kr4hv at numail.org> wrote:
> 
> > To all: Please disregard my previous posts regarding line to voice coil
> > transformers for use on military and BA equipment. While they work fine for
> > me, they may not meet the standards of the group.
> > 
> > Sorry to have wasted your time with my posts..
> > 
> > Walt
> > KR4HV
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > -----Original Message-----
> > From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
> > On Behalf Of chuck.rippel at cox.net
> > Sent: Thursday, December 27, 2012 1:36 PM
> > To: r-390 at mailman.qth.net
> > Subject: Re: [R-390] R-390 600 ohm audio solution
> > 
> > The R390A has an audio output of 600 ohms which means it will not work 
> > well at all into an 8 ohm loudspeaker.    The very best choice is to 
> > purchase a Hammond model P-T119DA 600 ohm primary/8 and 4 ohm secondary
> > audio transformer currently priced at $26.20 from Antique Radio Supply. 
> > The late Fred Hammond and I had a phone conversation one afternoon talking
> > about some shared issues with our Collins 20V-2 transmitters and I mentioned
> > that no one made any 600-8 ohm audio transformers.  Fred answered that he
> > had a personal, wide frequency design used when Collins was building 75A-4's
> > in Canada and would that work?  He sent a sample, its as big as your fist
> > and is rated something like 30-20,000 cycles, easily 10W has a 600 ohm
> > primary with secondary taps at 8 and 4 ohms.
> > 
> > You don't have to use 70v line transformers, etc.....  This works
> > wonderfully and is a direct solution.  I've linked the product directly,
> > below:
> > 
> > http://www.tubesandmore.com/products/P-T119DA
> > 
> > ---
> > No  trees were killed to deliver this message.  However, a large number of
> > electrons were terribly inconvenienced.
> > 
> > Chuck Rippel
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