Finished Build: 4 JLM BA + 2 Access 312 = 1RU Chassis

I just completed this build and everything is working like it should. It sounds great, as usual. I once had 8 Baby Animals and traded a 4 channel unit for some other gear. I did another trade on some pre's and got 4 more Baby Animals back...so they keep coming back to me!! :shock: It's cool, they are great pre's on anything.

I decided to rack the 312's in here to save on space at the studio and also having to buy another chassis from Par Metal. It took some careful planning and test printing for the front panel to make damn sure before I started drilling that it would be the ONLY time :wink:



I am using the Cinemags for IP and OP on the 312's and am using a pair of 2520 clones that I got from someone ( I believe they are of Fabio build). I still have to order 6 push button caps from Digikey.





Nothing new to me about the Baby Animals; like I said I have built 8 of them before. Except this time I am using output transformers with them. I went with the Edcor WSM600's because they are only $10-12 a piece and they are great. The first two BA's are using the JLM 1:4 trans. and 99v opamp. The other two are using Yamaha's Tamura input and some Melcor opamps I put together. I am running them around +/-17v.



Since it is such a tight squeeze in there, I wasn't able to fit a PSU. I was able to fit the JLM PSU board behind the 312's and ended up wiring that to a TRS jack for the back of the chassis. I mounted the toroid inside a Radio Shack metal enclosure and wired it to another TRS jack. So now I plug a 3 foot TRS cable to both ends and that feeds the AC power (around 24VAC) an dground to the JLM PSU board inside.









Anyway, just thought I would share.

Peace,
Adam
:guinness: :guinness: :guinness:

Great job...! How does it sound?..... :thumb:

Looks nice. Just a note - that's a shorting jack on your power supply/rack. Never plug it while the mains IEC is connected.

can someone tell me how to get the little LEDs to light up when the phantom is switched on? Also what do you use for LEDs? Something special or generic?

It nice that you can squeeze that much preamp in that little space.

[quote author="rodabod"]Looks nice. Just a note - that's a shorting jack on your power supply/rack. Never plug it while the mains IEC is connected.[/quote]

Personally, I would replace that for a more suitable connector, as Roddy says if either end gets plugged in/out whilst the unit is on you are could damage the amps.

Are you using the JLM PSU to power both the Baby animals and Acces-312 too?

Very nice and tight build......I really dig the Melcors in there!!!
I'm about to finish my 4 channels rack.

I plan on leaving the TRS cable in place once I get it to the studio so I won't have a problem shorting.

The JLM PSU is set at +/- 17v for the 312's and the 48v feeds to the Baby Animals, which have their own diodes to drop to +24v needed for the 99v.

can someone tell me how to get the little LEDs to light up when the phantom is switched on? Also what do you use for LEDs? Something special or generic?

Click to expand...

The LEDs are standard 3mm lights. Solder the longer leg of the LED (which is positive) to the front left lug closest to the front of the push button. The shorter leg (negative) will be soldered to the right front lug on the switch. See the 3rd, 4th, and 5th picture of this post to give you an idea.

Adam

Nice job getting more than 4 pres in a 1ru
Hmmm with the baby animal boards looks 8 may be possible

I third the get a new power supply connector , besides the shorting
there's is always the " someone else " plugging in " something else "
like putting 24 v into a d.i. input
it's the reason i use 4pin instead of the 3pin xlr type for external supplies

There really wasn't any room left on the back of the chassis for an XLR connector. Plus, this unit, along with all my other mic pre's, are permanently fixed in my mixing desk. All the inputs and outputs are permanently wired to my patchbay. All the switching betweeb mic pre's is done via the patchbay on the opposite side of the desk so I shouldn't have a problem with the TRS jack getting shorted.

Looks great although like most people the 1/4 on the PSU is of concern. My 2 cents would have been to hard wire it and use a grommit(I think that is what I am refering to) to keep the cable in the hole slot you drilled for it to pass through.

Looks good :grin:

But the AC/DC regs without heatsinks are only good for about 150mA on the +/- rails and 100mA on the 48v rail before the thermal protection cuts in. So they will need a heatsink. Best would be a piece of aluminium angle to the base of the case but make sure you fit the insulator kits properly so none of the regs metal tabs short to the common heatsink or angle bracket.

The 1/4 jack is not such a good idea for the power :shock:

how do they each sound ?
:guinness:

great work! I am sure they sound amazing. I am curious abot how the edcor WSM600's compare to the JLM transformer.