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What model is my osa preamp? Dynamic Microphones
Old 21st December 2010
Gear Addict

What model is my osa preamp?

Hello everyone,
I ran across a deal for an osa 500 series mic pre
recently. However, I can't seem to find any info on out. By the looks of it
It appears to be newer than the others I've seen.
It has a red knob for the gain and the font is in cursive,
Unlike the others I've seen with courier style print.

No model number is displayed any where on the mic

does anyone know anything about this particular osa
Old 22nd December 2010
Gear Guru
AllAboutTone's Avatar

Not to much help but its a C or A, I love the C the best, its aggressive like the 512 API
Is that a RED cap ?
Old 22nd December 2010
Gear Addict
Buss-me's Avatar

Actually I think it's an older one, like early 2000 ??, if it's the one I'm thinking of. Did you see it on Ebay??....I saw that one on there a while back.
Hard to say exactly what model it is??. I'm guessing it's more like the A model, since I believe that's the first model they came out with?.
You could try emailing Dale Epperson. OSA is no longer, but they probably still answer questions about their products.

I have both A & C models.....The C has a green knob, and the A has grey knobs.
Old 22nd December 2010
Gear Addict

The other models I've seen have two knobs for gain staging, one for input and one for output. The one I bought has only one knob controlling the gain. So, I'm still clueless. Anybody else know?
Yes, actually the one on ebay that just ended yesterday
Old 22nd December 2010
Lives for gear
axisdreamer's Avatar
I worked with Dale when he first started OSA.We made many prototypes and they had one volume knob.I would have to see a picture to tell you what transformers etc are on it. I still have nothing but the ones like your speaking of in my studio.
Old 22nd December 2010
Gear Addict

Here is a pic from the auction. I would post more, but ebay has a policy about copying photos from auctions. Ugh! Does this look familiar to anyone?
Old 22nd December 2010
Gear Head
slodk's Avatar
email for Dale of OSA

Anybody have contact info for Dale. I would like to get service on some OSA Pres.......
Old 22nd December 2010
Lives for gear
axisdreamer's Avatar
This model looks like most of mine. I have some even older than this one too.It looks like the same output transformer he uses on the newer ones.
you have a picture showing the other side of the card?
Old 22nd December 2010
Lives for gear
axisdreamer's Avatar
OK What you have here is an input transformer from an Auditronics 501 ch strip and the knob is from that strip as well. I remember when we built these in the shop.We were making alot of custom versions of the pres at this time.
The output transformer is the same ones that he used all along made by Crimson.The opamp is the same that he used too this is just an early one you have there.I don't remember how this pre sounded anymore but I know only around 5 or 6 of these were ever made with this input transformer.
Old 22nd December 2010
Gear Addict

Great! Many thanks, axisdreamer. That info is priceless! If anyone is interested, I'll post some clips when the preamp arrives.
Just let me know.

This is my first OSA purchase, so I'm pretty stoked.
Old 22nd December 2010
Gear Addict
Buss-me's Avatar

Yep that's the one.... I had contemplated bidding on it, but I was tapped after getting an old SM7, and a new car stereo .

Would be curious to hear it. Drums, gtr, voice. Congrats on winning it
Old 22nd December 2010
Gear Guru
AllAboutTone's Avatar

Looks like a older model, looks great as well.
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