[sdiy] sort of OT: Ward Airline phono input test: success!

[John L Marshall]

It may not be an RIAA phono input.

It is likely a crystal phono input with a higher voltage input and little 
equalization.

AGC usually does not work on the audio portion. A detector produces DC that 
is fed back to the intermediate frequency amplifiers with variable mu 
pentodes.


Take care,
John
www.sound-photo.com
www.antenna-farm.com

----- Original Message ----- 
From: "Travis Shire" <tshire at charter.net>
To: "anthony" <aankrom at bluemarble.net>; <synth-diy at dropmix.xs4all.nl>
Sent: Monday, November 05, 2007 5:25 PM
Subject: Re: [sdiy] sort of OT: Ward Airline phono input test: success!


>
>> So I cleaned up that neat looking Ward Airline radio's chassis, changed
> some
>> caps and plugged my guitar through a hotrodded Peavey Hotfoot into the
> phono
>> input of the radio. It's weird, it actually sounds like the AGC is 
>> working
>> even when you're running it through the phono input - I got LOTS of
>> disortion but not extra volume from the Hotfoot. It does sort of make
> sense
>> though since the only preamp stage between the 6V6GT and the phono input
> was
>> a 6AV6 hi-mu triode/dual diode - all sharing a common cathode. I'm pretty
>> sure the diodes are for the AGC since there's a 6AL5 that I'm pretty sure
> is
>> being used as the detector here (since this is an AM/FM radio). Hooking
> the
>> amp straight through sounded nice and clean, but not much break-up since
>> there was only 1 triode gain stage.
>>
>
> The phono input will have RIAA EQ...you don't wanna use that. Strip it and
> redo it with a more guitar friendly circuit. You'll only need a cathode
> follower if you choose to use a Mar$hall type tone stack. If you just want 
> a
> high cut control, you can run that right off a plate (after coupling cap).
>
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