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

[Dan Martin]

I can second that this is a fine transformer. I've had one for years and
have found it a very useful and flexible shop accessory whether used for the
390A or not. For my own 390A audio I take the diode load on the back panel
and feed it into a quality preamp and 200 watt stereo power amp. Solid
state, yes. A bit heretical, I know. If you're hard core about this, build
up a 6V6 amp in push-pull and it would be marvelous. Old Dynaco preamps and
amps are available,too. With some loving care and tidying up they would
serve well and keep the straight-through tube lineage. With my preamp
switched to mono and feeding some Yamaha Studio Monitor speakers a whole new
meaning is brought to the term "AM". Using an arrangement like this on an AM
oldies station is great, not to mention what some of the higher achieving 
AM-ers are doing out there on our ham bands.

I think the 2-3- discrete components needed for this tie-in is pretty common
knowledge but Chuck describes it on his website and everything needed can be
easily mounted right on the diode load terminals. Fast and easy.

Dan


----- Original Message ----- 
From: <chuck.rippel at cox.net>
To: <r-390 at mailman.qth.net>
Sent: Thursday, December 27, 2012 1:35 PM
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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