Access-312 Build Thread
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That PSU is long gone and it was just a sugestion at that time.
Don't worry about it,
you can use any 3 rail PSU.
You need +16V, -16V and +48V for the phantom power
You can buy this one with "extra aux rail" option:
https://pcbgrinder.com/POWER-SUPPLY-PSU-LM317-LM337
Don't worry about it,
you can use any 3 rail PSU.
You need +16V, -16V and +48V for the phantom power
You can buy this one with "extra aux rail" option:
https://pcbgrinder.com/POWER-SUPPLY-PSU-LM317-LM337
bxt403
Well-known member
I noticed that the Access 312 board can be converted to into a 325 circuit fairly easily (after some component value changes and removing the input transformer). This is useful when you want a pair to be used for stereo signals (where the gain switch for two modules is a double pole type: one pole per module)
I've cross-referenced with the API 325 manual's "Line or Booster Amplifier" section and it looks like the 325 has "Open" for a 6dB minimum and maximum value of 42dB @ 240 Ohm (for the column that corresponds to the output transformer's wired as two windings in series like it is on the Access 312). That means (for those who might want to wire a pair of Access 312s as a pair of 325s for stereo signals): 12dB = 39k Ohm, 18 dB = 13 kOhm, and 24dB = 5.6 kOhm, 30dB = 3.6 kOhm, 36dB = 910 Ohm). If all three secondaries are shorted (instead of the VU getting wired between the grey and violet wires); a resistance of 91K Ohm will get 12db and 22K giving 18dB) with the highest value being a short that yields 48dB. That implies that a reverse log pot (like the 25k ones available from CAPI) can be used if all three secondaries are connected in series. The other two wiring layouts don't short "SHORT" for any resistance value so I'd be reluctant in using anything by a rotary switch with resistors.
I also noticed that C3 and C4 can also be removed/ignored with the 325 layout. With a 312 layout; it looks as though they might be installed incorrectly. The capacitor might have to be connected to the input transformer's High (+) and Low (-) line inputs (and should be 1000pF w.r.t. the API 312 schematic).
I've cross-referenced with the API 325 manual's "Line or Booster Amplifier" section and it looks like the 325 has "Open" for a 6dB minimum and maximum value of 42dB @ 240 Ohm (for the column that corresponds to the output transformer's wired as two windings in series like it is on the Access 312). That means (for those who might want to wire a pair of Access 312s as a pair of 325s for stereo signals): 12dB = 39k Ohm, 18 dB = 13 kOhm, and 24dB = 5.6 kOhm, 30dB = 3.6 kOhm, 36dB = 910 Ohm). If all three secondaries are shorted (instead of the VU getting wired between the grey and violet wires); a resistance of 91K Ohm will get 12db and 22K giving 18dB) with the highest value being a short that yields 48dB. That implies that a reverse log pot (like the 25k ones available from CAPI) can be used if all three secondaries are connected in series. The other two wiring layouts don't short "SHORT" for any resistance value so I'd be reluctant in using anything by a rotary switch with resistors.
I also noticed that C3 and C4 can also be removed/ignored with the 325 layout. With a 312 layout; it looks as though they might be installed incorrectly. The capacitor might have to be connected to the input transformer's High (+) and Low (-) line inputs (and should be 1000pF w.r.t. the API 312 schematic).
Last edited:
3nity
Well-known member
Bxt403.
In fact I used a 312 PCB stuffed parts like a 325 for a poor man eq gain stage..works perfectly.
In fact I used a 312 PCB stuffed parts like a 325 for a poor man eq gain stage..works perfectly.
3nity
Well-known member
Nice build.
Love the vertical mounting of the boards.
The di is the Bo Hansen?
Cheers.
Love the vertical mounting of the boards.
The di is the Bo Hansen?
Cheers.
OK, so: I've purchased the boards, BOMs, XLR jacks, pots, knobs, buttons, screw terminals, and even an external PSU (the Collective Cases one mentioned earlier in this thread). I have my EA xformers and DOA kits from CAPI. I also have a decent amount of soldering experience and even a little time working around mains voltage thanks to about five years of guitar pedal and mic builds (including a tube one that involved swapping out a PSU board). I feel like I'm MOSTLY ready to do this thing. That said, I wanted to reach out to the DIY community and see if y'all could help me with a couple things:
1) Star ground: I've just never done it. Ideally, I'd just like some up-close-and-personal photos showing what it's supposed to look like and how people have tended to wire it. I understand the general principle, have read up on how it usually works in an amplifier (i.e. connecting a wire from the IEC to the chassis), and have even gone through the Whistle Rock ML12 PSU docs (which located star ground on the ML12 PSU PCB itself - and, sadly, seem also to have disappeared from the internet), but I would love a clear photo and diagram that shows how it should play out in this particular build. Note: I HAVE LOOKED AT OTHER THREADS TO TRY TO FIGURE THIS OUT. Hell, maybe I HAVE figured this out and am just being overly cautious. But my dumb questions include:
+ Should I star ground power and signal paths separately?
+ Wiring-wise, should I ground by soldering ground connections to a central point that's attached to the chassis - that is, use a lug terminal screwed to the chassis and solder wires to it? Or should I attach lug terminals to my various ground wires and screw them tightly against the chassis? Is either consider best practice?
Again, I recognize that these are somewhat esoteric questions and there likely isn't just one way to do it, but I want to get it right the first time! Grounding issues have been the bete noir of my DIY life, and I've become kind of neurotic about them.
2) 1U drill templates: Are they around? It seems like plenty of people have made a 4-channel version of this, and most of us want the same thing - 8 XLR punches, a star ground, and an IEC/PSU cutout on the back panel; board-spaced holes for 4 gain/P48/polarity/pad "modules" and an LED (and on/off toggle?) on the front panel. There seems to be a standard form factor for 1U chassis, too. So, that said: Has anyone made a template for the above? I recognize that I could just design one myself, but the layout thing has admittedly become the main impediment to me beginning the project - I work on computers all day, so I'm somewhat disinclined to spend a few evenings futzing with vectors and placement if I don't have to. I have actually considered picking up the Collective Cases chassis, but I already bought a Circuit Specialists 1U for this project and would prefer to just drill it and save $150+.
3) The Collective Cases PSU: Has anyone used this thing? How do you like it? Did it more or less eliminate hum? Does it obviate the need for DC filtering? And, in keeping with my first question, do I connect it to chassis ground the same way I would connect an IEC?
Any guidance on the above three concerns would be beyond welcome! This thread is already a bounty of good, useful stuff - I'm just stuck on a few things
1) Star ground: I've just never done it. Ideally, I'd just like some up-close-and-personal photos showing what it's supposed to look like and how people have tended to wire it. I understand the general principle, have read up on how it usually works in an amplifier (i.e. connecting a wire from the IEC to the chassis), and have even gone through the Whistle Rock ML12 PSU docs (which located star ground on the ML12 PSU PCB itself - and, sadly, seem also to have disappeared from the internet), but I would love a clear photo and diagram that shows how it should play out in this particular build. Note: I HAVE LOOKED AT OTHER THREADS TO TRY TO FIGURE THIS OUT. Hell, maybe I HAVE figured this out and am just being overly cautious. But my dumb questions include:
+ Should I star ground power and signal paths separately?
+ Wiring-wise, should I ground by soldering ground connections to a central point that's attached to the chassis - that is, use a lug terminal screwed to the chassis and solder wires to it? Or should I attach lug terminals to my various ground wires and screw them tightly against the chassis? Is either consider best practice?
Again, I recognize that these are somewhat esoteric questions and there likely isn't just one way to do it, but I want to get it right the first time! Grounding issues have been the bete noir of my DIY life, and I've become kind of neurotic about them.
2) 1U drill templates: Are they around? It seems like plenty of people have made a 4-channel version of this, and most of us want the same thing - 8 XLR punches, a star ground, and an IEC/PSU cutout on the back panel; board-spaced holes for 4 gain/P48/polarity/pad "modules" and an LED (and on/off toggle?) on the front panel. There seems to be a standard form factor for 1U chassis, too. So, that said: Has anyone made a template for the above? I recognize that I could just design one myself, but the layout thing has admittedly become the main impediment to me beginning the project - I work on computers all day, so I'm somewhat disinclined to spend a few evenings futzing with vectors and placement if I don't have to. I have actually considered picking up the Collective Cases chassis, but I already bought a Circuit Specialists 1U for this project and would prefer to just drill it and save $150+.
3) The Collective Cases PSU: Has anyone used this thing? How do you like it? Did it more or less eliminate hum? Does it obviate the need for DC filtering? And, in keeping with my first question, do I connect it to chassis ground the same way I would connect an IEC?
Any guidance on the above three concerns would be beyond welcome! This thread is already a bounty of good, useful stuff - I'm just stuck on a few things
vizcities said:
First thing you should do is read this thread. Thats the only thing I recomend for now.
All the info needed is here
I posted a few times a ground drawing for this project, and it's also posted on page 28, so it seems you are not reading what you should
Whoops said:
Cool - that covers the general wire routing, which I appreciate. However, I'm using (as mentioned) an external PSU with a 5-pin XLR jack. Its layout is:
Pin1 = SHELL:FG
Pin2 = COM
Pin3 = +16v
Pin4 = -16v
Pin5 = +48v
So, I guess the question is: what counts as 0v? Pin2/common ground? Pin1/floating ground? Both? Which would I wire/bolt to the chassis? And which would I connect to the boards? Also, do I still use the resistor/capacitor connection from the PSU to the chassis?
vizcities said:
Common is the 0v reference
vizcities said:
PIN1 PSU case to Chassis
vizcities said:
yes resistor/capacitor from Common (0V) to Chassis,
it's exactelly the same thing as in the layout I did
Does anyone have a PDF (or otherwise) front panel layout for the usual 4x Access 312s that includes the F2UEE push buttons? I'm finding them excessively tricky to measure vertically in a way that feels accurate/foolproof. Part of me feels like I should just cut my losses and just use "traditional" DPDT mini switches, but the "sunk cost" part of me - along with the part that doesn't want to spend $30 on new switches - wants to make these things work.
3nity
Well-known member
Let me see if I can find a PDF or distance between each ok pushbutton.
. I am building 4 whistle Rock mic pres. I have wired the PS toriod to the whistle rock ml12. The toroid is getting really hot really fast with just one pre connected. Am I not wiring this right? I tied violet to blue. Connected that to neutral side of the 120v plug and tied brown and grey together. Wired that to live Hot. What am I doing wrong?. I have number 2 on the 120 plug going to star ground. Please help. Thank you. Randy
doggy6812 said:
This thread is for the Access-312 project, maybe there's a thread for the whistle Rock mic pres. I have no idea what that project is
TillM
Well-known member
doggy6812 said:
Ask here
https://groupdiy.com/index.php?topic=56213.0
talkieparade
Member
- Joined
- Apr 12, 2019
- Messages
- 5
Does anyone know the distance in millimeters between each F2UEE push button switch (once installed in the Access PCB), from the center of one switch to another? 10mm? 12.5mm? Maybe it's more like 15mm?
I would like to purchase some chassis hardware mounts from C&K to connect their fisheye pushbutton hooks on to. They sell different chassis mounts with various spacing to accommodate different size switches.
Thanks!
I would like to purchase some chassis hardware mounts from C&K to connect their fisheye pushbutton hooks on to. They sell different chassis mounts with various spacing to accommodate different size switches.
Thanks!
