4312- A Lab Project

[fum]

Hey there,

Things have been quiet, so I thought it was time to spice things up a bit :grin:

I'm just finishing up this project, and would like to start by thanking lots of people who made this possible. It's a long list, and it shows an extreme credit to the people who hang out here. I sat back and looked at this project, and almost every piece of it was contributed by different people who frequent this forum. So here's the rundown:

Power Supply- SSLTech

PCB help- jrmintz

Discrete Opamp PCB's- fallout

Output Traffos- tommytones

Switches- wilibee (rescued from a parted out QE console)

knobs- maxwall

Graphics- mcs for the scale-o-matic, plus extra thanks for his putting up with my odd graphics questions as I tried to get crap to import properly

Stepped Attenuators- PRR, SMG, and St Domingo for helping me with the calculations

Thanks Guys!

And now, for the pics:

 

[Flatpicker]

Nice work! :thumb:

 

[Bauman]

GREAT WORK! :thumb:

Any music thru it already??

:sam:
FAbio

 

[CJ]

Holy crap that looks good.
Not worthy. Head bowed.

Hey, speakin of Head Down, whatever happened to the Chef?

 

[peter purpose]

He's got his head down.

Very tasty Jon.. :guinness: :guinness:

 

[fum]

thanks guys.

I want to know what happened to butta?? haven't seen him round in ages

ju

 

[peter purpose]

He's brown bread.

 

[jrmintz]

Hi Jon,

Nice work! I love those blinky switches.

:green: :green:

 

[kiira]

Dang. That's gorgeous! What are those cute push button switches? I want some. Are those series stepped attenuators on the front?

Kiira

 

[daArry]

very nice arry :thumb:

 

[fum]

[quote author="kiira"]Dang. That's gorgeous! What are those cute push button switches? I want some. Are those series stepped attenuators on the front?

Kiira[/quote]

The switches can be bought through DigiKey still, but these were rescued as assemblies from a Quad Eight Console. They are sold under the E switch name I believe

I've still got some assemblies, but mounting them did involve machining some square stock so that they sit in the right position (involves drilling and tapping).

And yes, those are 12 position Alpha stepped attenuators, using 1% resistors.

Regards

ju

 

[fum]

[quote author="Bauman"]GREAT WORK! :thumb:

Any music thru it already??

:sam:
FAbio[/quote]

Ok, gots some music through it today. Had to chase down a shorting problem that was causing the negative rail to pull too much current. (it would regulate for a while, and then get too hot, and stop regulating.

Got all four channels tested out, put it in the studio, compared it to my BA312, and my initial impression as follows:

Similar in sound, but has more gain. Could it be the higher rails? (I'm running at +/-18V, whereas the BA312 is in a lunchbox running at +/-16V)

Oh, or it could be I'm running 3 windings of the output traffo instead of two ( will have to check the BA card to see how they wired it).

In either case, it sounds real good. At present, I'm a fan of the API 312 pre (or at least the BA version, which is all I've worked with to date), so having these done and integrated into the studio is making me smile.

Next project will look almost identical, only it will be a 4 channel Quad Eight pre. We'll see how I feel about the 312 when it's done :green:

Regards

ju

 

[cayocosta]

Really nice, Ju.