fs: scully 280 stand-alone germanium mic/line amp - w/ psu

[themagicmanmdt]

hey everyone -

i found this last week that i had an extra scully 280 electronics unit that doesn't work with my machine - it's a different year - so, I decided to make it into a stand-alone preamp.

all germanium transistors
(no op amps)
dates to '70, made in USA, built by hand
XLR, transformer balanced all the way - UTC xfmr mic in, Freed xfmr line in, UTC xfmr line out. the mic pre actually goes through the line transformer, too - that's three transformers in the signal path made of nickel! sounds huge. hi-fi.

mic preamp has ~55db gain, line amp has ~25db of gain

(the trick is to use the mic preamp for quieter stuff, and use the line amp for condenser and high output mics that don't need a ton of gain. this works perfectly.)

the VU meter also works properly and is fully calibrated. two cracks in the meter glass, though. that's the only bummer.


i've also wired and added a phase switch and a -20db pad on the front for the mic input.



so, i put some TLC into it. i own an 8 track and am getting a 4 track, so I've got tons of these mic pres already, and decided to make this usuable for someone who wants the scully sound. i built a to-spec PSU in where the oscillator card sits. this PSU is removable if, one day, post-apocalypse, we need the electronics for a tape machine.


$325 shipped and paypal'd.

local pickup in austin TX would chop off the shipping fee.


and, for the record, i can do these scully preamp power supply and phase/pad mods if need be. but, i won't do a lot of them, as us tape machine owners need the electronics more than just preamps!


pm or reply

marshall

[telepathy]

photos?

[themagicmanmdt]

give me a day; working tonight; plus, major allergy sick. not fun. :/

[themagicmanmdt]

[themagicmanmdt]

re-evaluated the market - price drop to $325 shipped via fedex

black saturday something or other

[themagicmanmdt]

Last post and bump to say, hey, trades, anyone?

[Fenris]

The beige 280's usually have silicon transistors. However, I have a pair of beige 280's with germanium transistors, so either they were swapped or some of the early beige ones used germanium. The germanium transistors are in metal cans shaped like a little top hat. Silver or possibly black.

Did you put the 20 dB pad before the mic transformer? I thought about reducing the gain by switching out one of the two transistors in the mic preamp section.

[themagicmanmdt]

totally. this one had germanium. lil' silver cans. not the black mini button silicons.

yeah, -20db is before the input transformer.

it's not really an 'amount of gain' thing i deduced from the cards, but the way the whole input card is biased. the first transistor is what saturates. it's biased by NFB (as well as a little feed forward), so it's already at a delicate operating point, and seemed like it would need some deconstruction of the stage to change it... one day, maybe, but it would sound totally different.


and, had it on ebay.

sold!

so i think. hasn't paid yet.

[telepathy]

oh yeah, was wondering what happened with this. still interested if the buyer turns out to be deadbeat ... or if you feel like assembling another one!