OSA pres....

E-Rock · Post by **E-Rock** » Thu Mar 16, 2006 10:39 am

I've been thinking about adding some more pres to my rig. We spent last weekend in a cabin, recording for two days. (fun shit, who needs a studio!!)
Anyway, we were lucky enough to get our hands on a pair of old API pres that had been racked. They sounded GREAT!
So, I've been thinking about adding the "API" sound to my rig at home. The OSA seem really cool for the money. I was wondering if anyone has had any time with them?
Thanks!

Leopold · Post by **Leopold** » Thu Mar 16, 2006 11:57 am

Lots of opinions on these and the RED mics on here do a search and you'll find a few things, also check out the seventh circle audio kits might be what you want if you can build them yourself.

Eddie

jrepro · Post by **jrepro** » Thu Mar 16, 2006 2:49 pm

OSA does not = API While one is interchanageable, they do not really sound the same. API is a completely discrete opamp while the OSA has IC chips inside the little black box. If you were to change the Opamp out to a API, change the input transformer to Jensen 115K you would be much closer.

API rocks! If that is the tone you like, buy API. I am not saying OSA is bad at all. Just that it is not the same tone as API.

JRE

kayagum · Post by **kayagum** » Thu Mar 16, 2006 3:08 pm

Nathan posts here on occasion, and his store sell them.

Read his opinion/review here:

http://www.atlasproaudio.com/nathanslowdown.html

thearnicasync · Post by **thearnicasync** » Fri Mar 17, 2006 11:54 am

jrepro wrote:OSA does not = API While one is interchanageable, they do not really sound the same. API is a completely discrete opamp while the OSA has IC chips inside the little black box.
JRE

This is interesting. I had the mp1-c, and when it showed up, I called about the ic in there. It wasn't in the product photo, so I was kind of pissed.

According to the builder (can't remember his name), the ic's aren't actually in the audio path, for what that's worth.

Maybe they've changed. Maybe it matters even if it isn't in the audio path.

BTW, the Mp1-C is rad. I sold it as it was my only really great pre, and it was way too 'vintage'-sounding for that purpose. I very much with I had it again, for electric guitars...never had anything since that comes close; not api not a12, nada. All great, but not nearly as colorful...

kb

jrepro · Post by **jrepro** » Fri Mar 17, 2006 12:37 pm

Well there is a opamp that drives the meter. That is not in the audio path. But the opamp that looks like the API 2520 package is in the audio path. From what I remember looking at the schematic of the opamp, it had two IC based chips inside the box. API has all discrete components inside the packaging. I looked to see if I could find the schematic again, but could not. So I only have my memory to back me up on this for now.

If Nathan stops by, maybe he can confirm this. I looked around on the OSA page, and nothing states that it is or is not discrete. This also leads me to believe it is IC based. When a company uses discrete componenets, this becomes a huge selling point.'

NONE THE LESS.....OSA preamp still are good preamps. They do have a thick vintage tone as well. I am pretty sure that Dale set out to make a great sounding preamp in the API style. I do not think he set out to make a API clone.

Joe

I'm Painting Again · Post by **I'm Painting Again** » Fri Mar 17, 2006 1:20 pm

APIs..the new 512c's anyway also have ic's in there..two I think..though I dont think they are in the audio path..they may be used for metering on the little led meters they have..API has extremely good build quality..they are based around the proprietary 2520 discreet opamp (which actually is an integrated circut of sorts)..they use a custom transformer(i think) which is not labeled with any identifying marks that I can see..each module is also shielded with a metal plate on one side which I guess is to control the magnetic fields the psu and transformers can create..

I've not experienced the OSA but never heard anyone really say they don't sound "good"..I'm sure they are not exactly the same as their api counterparts but they should hopefully be in the ballpark at least..

jrepro · Post by **jrepro** » Fri Mar 17, 2006 2:20 pm

Under the cover of a 2520 opamp:

Mostly API used Jensen 115K 1:10 ratio transformers. At some point they also used Reikenbach, which I think was an earl partner of Deane Jensen. (not positive). At some point API also used a 1:7 ratio input which was equivalent to the Jensen 110K transformer. Both sound excellent.

jrepro · Post by **jrepro** » Fri Mar 17, 2006 2:24 pm

The OSA also uses a "custom" wound input transformer. You are correct that the Mu can is to shield the outside world from getting in. Because the mic level is so low (-40db) the amp has to increase that to about 0 or +4db. So any little noise in the low level circuit gets amplified along with the mic. This can helps to keep out extra noise.

The IC in the upder left is for metering just like on a API 512 card. The black box in the uper middle is OSA opamp. It is under that cover that I recall the schematics showing more IC based opamps instead of what the picture about looks like...

thearnicasync · Post by **thearnicasync** » Fri Mar 17, 2006 3:01 pm

Interesting stuff. I didn't realize there were ic's in the box...that's kind of funny. Like marketing a proprietary box full of non proprietary amps.

Thanks for that info.

Has nothing to do with that discussion, but I'm getting a whole lot less snotty about ic's, lately. I played with some Quad 8 model 441 eq's...nothing but NE 5532's/4's and OP275's inside. I LOVED that eq...I want a dozen. No transformers, either...

funny, i guess...

why did i spend all that money?

jrepro · Post by **jrepro** » Fri Mar 17, 2006 7:20 pm

Nothing wrong with IC's! They just do not sound the same as Descrete opamps. Not better or worse.

E-Rock · Post by **E-Rock** » Mon Mar 20, 2006 10:19 am

Whoa, I come back on Monday and find a bunch of info! Thanks y'all!!!

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