DIY Mic Pre Kits, Lunchbox Mic Preamp Kits, Power Supply Kits

That transformer wiring is for 120V 50Hz right?

Yes... this is for 120V wiring... i.e. parallel the 2 primaries together. (RED and BLACK WIRES)

A/C is already scary and the big red letters on the diagram make it scarier!

So just to be clear, when looking at the back of the A/C plug, the left side is the black wires and the right side is the red wires and the top center is connected to the enclosure, right? What happens if you put this inside a plastic housing? How do you connect the ground?

Well, I want people to take seriously working with AC voltages.

This not "circuit-bending" where you just have 9V batteries powering kids toys and you just poking wires wherever you want "just to see" if it will create new sounds. Noooohhhh, noooo noooo..... we're not doing "circuit bending" here... whatever that means!!!

We're doing real DIY electronics project here, so it's important you understand this fact. And if you open any electronics textbook, Chapter 1 is usually about SAFETY.



Yes. The top center is the ground connection.

Well, any pro gear out there is usually racked in a metal case/rack. Show me a pro gear racked in a plastic case. Even Behringer have metal rack gear for their cheap stuff.

I would recommend a steel/aluminum case rather than plastic. Primary reason being 1) you can ground the case (safety), (2) it does a better job of shielding against EMI/RFI noise, which results in a quieter preamp.

I'm with you 150%. I was really just voicing my inner fear of A/C. I've been zapped a few times in my day and I have a healthy respect for it.

owel, apart from needing to connect the primaries and secondaries in series, is this the same for 230volts?

also, where it says to connect the wires together, is that just twisting them and soldering to the same point? then with a heatsink slipped over the twisted wires?

what do i do about the ground? solder a wire to a bolt, which is then drilled into the chasis?

similarly what do i do about a ground for the XLR? leave that pin? the cable only has two wires

with two channels, do i connect the outs of pre one to the outs of pre two and then run the outs of pre two to the power supply, with two sets of wires connected to the solder points on pre two?

also, what is RGA and RGB (i think?) for? they are empty right now

sorry for all the questions, i tried to get them all in one go as im wiring it myself now

thanks!

Same guide for 230V, except connect the red and black wires in series.



Twist them both, solder, tape with electrical tape, then apply heatSHRINK if you have any.



Solder the wire to a terminal (lug nut terminal I think they're called), then put the terminal in between the case and bolt.



What cable? The two inner conductors in the cable goes to pins 2 and 3. The shield (or ground wire) goes to pin 1.



Please restate question. I do not follow.



You can safely ignore them. They're meant if you want to use a reverse log potentiometer instead of the 12-step selector switch.



Hey no problem. Good questions..

the cable is this:

http://www.maplin.co.uk/Search.aspx?cri ... 0T&DOY=4m7

im guessing just a seperate piece of hookup wire for the ground then?

and sorry for being unclear with the second question. basically, since i am running two channels off of the same power supply, i was wondering how these two channels would be connected to said power supply.

ie. 'daisychained' together with just one channel connecting directly, or both channels connected to the same solder points on the power supply.

thanks!

No no no..



Wire the red wire to pin 2, and the white wire on pin 3.

The shield (outer braid), twist them and wire them to pin 1. This is the ground wire.



While daisy-chaining will work, I made the PSU kit with an extra set of holes on the output. So just wire all the preamps back to the PSU.



I prefer this approach, though daisy-chaining will work too.

ok brilliant, thanks a lot owel, im just sourcing some bolts now.

would you be able to post a picture/some info on the lug nut terminal please? not heard of that one. thanks!

I found the correct term. It's called a "ring terminal"

right! i am about to get to work wiring, but before i do i have constructed a crude diagram just to make sure i have everything correct:



let me know what you think of that

also, are we to connect it all up and power in the mains to adjust the trimmers BEFORE we connect the channels? then once the trimmers are correct, we connect the preamp channels?

one last (STUPID) question, when connecting the shield on the xlr cables, im to take the insulator sheild, unwrap it a bit, then twist it to solder for a ground?

anyway, im nearly there (fingers crossed) thanks so much owel

Tom

you're in the UK, right? So you're using 220/230V ???

Your primaries are wired wrong in your diagram. From the PDF it says...

http://rocky.digikey.com/WebLib/Amveco- ... ormers.pdf



The RED and BLACK are tied together, and not wired to anything else.
The YELLOW can go to the IEC, and THE VIOLET can go to the DPDT switch.




Yes. Though I don't see any problems if you've already connected to the preamp before you adjust the voltages. But just to be safe, adjust the voltage then connect to the preamp.



Yes.

amazing, thanks so much owel.

one last question if thats ok??

to extend the wires on my trafo so that they reach the front of the case, do i solder one wire to another and then tape that joint?

cheers!

Yes, twist the wire so it's mechanically secure, then apply solder to permanently fuse the 2 wires, wrap with tape, and even secure with heatshrink tubing if you've got any.