API 312 Thread!

anyone know any good standoffs for pcbs?, 
found a few on mouser but they pretty expensive,  like 80 cents each,  seems exxy

laddie.music said:

anyone know any good standoffs for pcbs?, 
found a few on mouser but they pretty expensive,  like 80 cents each,  seems exxy

Click to expand...

If you are in europe Banzai musik has some pretty cheap http://www.banzaimusic.com/Hardware/

But, beware, those are "Chinese" and last time I ordered some there were several with threads missing etc.. very poor quality control but with the price compared to mouser you can order some extra and hope for the best

JP2 4-way vertical header for choosing serial/parallel connection of input trafo primaries, when applicable

anyone know what these are?  last piece (might?)  need for finishing my build...

Hey everyone.

I built 4 channels of the API boards. Works great. Very very happy with them but i have run into a big problem. Self inflicted unfortunately.

So...i have an original Univibe pedal from the 60s, for guitar...fixed it to Australian power. worked perfect in australia. brought it to europe...problem with the grounding it seems. But it works...tried to fix the grounding issue.

anyway...i plugged it directly into a DI on one of the API channels....it worked for maybe 5 minutes until i started to hear a low clicking sound in the headphones, the pres were getting warmer then blew a 47ohm resistor in my PSU. the 48v rail, and the LM317 on the same rail.

my PSU is fixed now...plugged it in...no phantom power on my APIs...then one channel worked...then the effected channel caused the PSU to start smoking again...same resistor, same rail...blew the LM317 again too.

So im trying to find out is there damage to the pcb or the DOA....what could this powered pedal plugged into my DI do? blow something on the DOA? the PCB? a resistor or cap....to much voltage into it does what?

ive searched for shorts everywhere and cant find any...unless something is blown, but where to look? nothing else is burnt like in the PSU. All the voltages on the PSU are correct, and stay correct when turned on...ive left it on (not plugged into the pres) for over an hour, measuring constantly.

im kind of a little scared to turn it back on again to fix it. i feel a bit blind not knowing where to look....because i need it for some sessions in july and dont want to destroy it further.

my PSU is the JLM powerstation....and before this incident all 4 channels were working flawlessly. pads, phasing, 48v, DI, Aux out...everything. had it turned on for 7 days, 12 hours a day tracking drums. no issues at all.

anyway....any advise would be amazing!!

thanks!!

Hey Guys

Can anyone direct me to the (or any) build docs for Fabio's reliquia312? I've searched the site high and low and cant find any. I've got some old PCB's I'm just starting to do now and cant find any docs here. Not sure what I'm missing.

Cheers and thanks

Here you are 

partslist

schematic

Beatnik - thanks, I am really grateful.

Hi guys, I'm currently designing and building a 312 style pre-amp for my college course, however I would regard myself as inexperienced when it comes to the electronics side of things. At the moment I've got a rough schematic and PCB design and I was wondering if one of you wonderfully helpful people could have a look at what I've got so far and point me in the direction of any amendments that need to be made. The circuit itself is based very heavily on Bob Schwenkler's hybrid 312.
Here are the screenshots of my design so far.

Schematic



PCB



There are a couple of things I'm unsure about at the moment.

1. Which pin of the output transformer do I use as the input and how do I connect it? Currently I'm using pin 1 straight from the 'out' of the 2520.

2. Will it be necessary for me to use the 'trim' pin of the 2520? Most schematics I've seen that use the 2520 either don't show it at all or it's just redundant.

3. Grounds, my initial instinct was to connect any ground shown in the 'Hybrid 312' schematic to the chassis ground, which I have begun to do, however I'm concerned that this will cause shorts. Whats the best way to ground everything?

4. To my understanding connections for the 15 pin terminal should be exposed in order for it to work when slotted into the rack. How would I do this in Eagle, would just drawing 15 rectangular pads be suitable?

5. I've chosen to use Lundahl transformers with the preamp, the LL1538 and LL1517 for the input and output respectively, will they be suitable in your opinion?

Any help you can provide me with would be very much appreciated. I can also upload the Eagle project files if you think that will help.

Thanks, Jack

Hello!

Could anyone tell me what the load resistor value would be for the Wally Heider modified 312 circuit?  It's a pretty low Z input with no zobel network and no decoupling caps in front of the input transformer.  Jeff Steiger's new preamp has got me really curious about this sound, the sound clips he's been posting are impressive, as is the pedigree of "the Wally Heider sound."  Electric Warrior from T-Rex is in there, for example.  I love messing with the 312 circuit!

Hey Mitsos and everybody.

I have run into an ordering problem for some parts...   
regarding the Mitsos BOM  parts    H1 and H2
2 pin vertical header for sending LED voltage to daughterboard.  (male and female)

I cannot for the life of me find male and female matching vertical headers...    and how high should they be considering it must connect but still sit above the 4PDT latching wellbuying illuminated switches..... 

Can anyone give me a mouser or idea for the right heighted vertical headers for this?   

not sure, I got some locally back then.  The switches themselves are 10mm high, so that would be the number to clear, but it might be easier to just use some solid core wire, solder it to the bottom PCB, mount everything and then solder the wire to the top PCB.  Since they're dual layer, you can solder from the top.  cheers!

I used these:

517-929834-07-36-RK
Mouser.com

They don't disconnect, but provide a little more stability than wire, to keep the switches from rotating.

This OLD thread has been so helpful.
With this new addiction to DIY and my strengthening tolerance I had to up the dosage.
Ordering PCB's wasn't doing it for me. So I broke out the Ferric Chloride and learned to etch.
Thanks to the archive of this board and all of the brilliant and curious minds I pulled it off.
4 Channels of 312 preamps. And they sound awesome. Cinemag CMMI-8 in 2 and 75101 in the others.
Pictured above them in the rack is the Whistle Rock ML-12 which started this hunger for more API's.
What a satisfying feeling to make these things by hand. The etch really adds another layer of euphoria.
Not only the fumes of poison either.

Inside

A combination of photos 1 & 2

PSU

I really like your etched logo

nice build

Thanks, monkey