Access-312 Build Thread

[thesystem]

well, that makes sense. I think I'm going to go for the post xformer way.
thanks

 

[buildafriend]

you mean with 2 different output pots? i don't think that's what I want. So, to make my choice I'd like to know the difference
[/quote]

I mean one gain pot(pre transformer) and one output level pot(post xfrmr). That would give you both worlds.

 

[soundsactive]

ok so i have been reading a lot about transformers and still have no idea how to source a power transformer. i know i need a small torodial for a whistle rock audio PSU for this api312 clone project, for 120v in and 30v out to the 4 channels. it needs to fit within a 1u rack.

i've been searching on digikey and mouser and just don't really know what i should be searching for, other then transformer and height. what are the series output ratings?  i'm sorry for asking such a isolated question from this build, i'm just a bit lost and all the articles i have been reading are going over my head.  :-[

 

[buildafriend]

http://search.digikey.com/ca/en/products/VPT30-830/237-1326-ND/2090064

or

http://search.digikey.com/ca/en/products/VPT36-690/237-1327-ND/2090065

 

[1sound]

Hey guys!    I'm kind of in the early planning stages of this build and had a quick question.

Anyone try to build a compact 8 channel 1U (say 8" deep) version of this?  Looked around but saw mostly 2U or 4 channel 1U's.  It's for my new portable recording rig (the old one is kind of beer, whiskey and blood soaked compliments of a last minute bar recording gig / brawl event for a "friend") so space is at a real premium.

If not, can anyone think of any less than obvious problems they've had when putting these particular boards in close proxmity to each other? Any necessity of faraday shielding in between channels (there's just barely enough space in the enclosure unless my measurements are out to lunch).  Parasitics?

Power is going to be externally shared with a universal console style switching supply.


Thanks in advance!

 

[frazzman]

Not going to happen, you won't have enough space internally to house 8 of the boards, let alone the lack of rear panel real estate to house 16 xlr sockets. it would make more sense to build in 2ru and mount boards sideways

Hey guys!    I'm kind of in the early planning stages of this build and had a quick question.

Anyone try to build a compact 8 channel 1U (say 8" deep) version of this?  Looked around but saw mostly 2U or 4 channel 1U's.  It's for my new portable recording rig (the old one is kind of beer, whiskey and blood soaked compliments of a last minute bar recording gig / brawl event for a "friend") so space is at a real premium.

If not, can anyone think of any less than obvious problems they've had when putting these particular boards in close proxmity to each other? Any necessity of faraday shielding in between channels (there's just barely enough space in the enclosure unless my measurements are out to lunch).  Parasitics?

Power is going to be externally shared with a universal console style switching supply.


Thanks in advance!

 

[sr1200]

Im going to respectfully disagree with it 'NOT' happening.  It can be done, but its gonna be a HEAVY unit.  You would have to do 3 things.

1 get a case thats atlest 12-14" b/c youre going to have to do 4 front 4 rear in order to keep them away from the PS. (if youre doing that internally also) 

2 youre going to have to wire the switches instead of mounting them to the board.  I would suggest something VERY small.  You have approx 1 7/8" per channel (for gain and 3 switches) leaving about an inch for a power switch on the FP.  You can also do the focusrite HI/LO layout which leaves more room per channel (kinda) If you need help organizing the FP I'd be glad to help.

3 youre NOT going to be able to do 16 XLR's (and honestly if you're using a DAW, theres no reason to do that anyway unless
you're using an analog console to sub mix before going in to the interface) do the 8 XLR ins, then do either a staggered 1/4" TRS line out or do a DB25 line out. 

That being said, i would also like to +1 doing it in a 2U anyway... when you see the mess wiring all the components is gonna be, you're going to wish you did.  I did a 4ch, and wired all the switches (wanted toggle switches instead of ueee push buttons and it was UG-LEE!)

 

[buildafriend]

Not going to happen, you won't have enough space internally to house 8 of the boards, let alone the lack of rear panel real estate to house 16 xlr sockets. it would make more sense to build in 2ru and mount boards sideways

Hey guys!    I'm kind of in the early planning stages of this build and had a quick question.

Anyone try to build a compact 8 channel 1U (say 8" deep) version of this?  Looked around but saw mostly 2U or 4 channel 1U's.  It's for my new portable recording rig (the old one is kind of beer, whiskey and blood soaked compliments of a last minute bar recording gig / brawl event for a "friend") so space is at a real premium.

If not, can anyone think of any less than obvious problems they've had when putting these particular boards in close proxmity to each other? Any necessity of faraday shielding in between channels (there's just barely enough space in the enclosure unless my measurements are out to lunch).  Parasitics?

Power is going to be externally shared with a universal console style switching supply.


Thanks in advance!

Yeah just make a 1u  wth 4 pres and then build another. Maybe use different parts in the second one like metal film resistors in one and carbon  comp in the other. use  all classic API in one and cinemag in the other. One orange drop caps and one WIMA caps...

 

[1sound]

Hey guys!

Sorry for the delay and thanks for the replies.  I'm really set on something that's uniform in construction and in a 1U (because it will physically fit).    No variations of component types, trannies.  Just cookie cutter style.  If I need more variation, that's what my mics are there for to begin with.

My remote rig is something that absolutely has to be as compact as possible because of some of the places I record in (think really small clubs where you get a tiny table to sit at with someone else and they're having dinner too for example - it's just a reality there).  So I want "the right gear" there but usually don't have enough room though I've always made it mysteriously work.  And I've never needed more than 14-16 in so.

Anyway, I know it's going to be a "heavy" unit so the average flimsy 1U type of chassis is out.

The universal PS already exists, is external, and supplies a variety of voltages so it can power most of my rack; not to just this unit, but to everything I've got.  I understand the "complexities" and constraints of working with that.  It's on the bench right now but when it's 100% sorted, I'll share, just incase anyone is interested.

No XLR's here either because as 1200sr said, it doesn't really make any sense (coiming in and going to DAW via completely isolated and separate patchbays actually).  DB25's made the most sense there for me too.  Nice and compact.

And no power switch on the front so all the real estate there is available to me for this.  Would like to squeeze in a 10 segment dip for VU per channel though...  yeah, right...  Well... maybe..  There's almost enough room...

Thanks for the offer to help with FP layout btw.  Think I have that almost sorted as well (and will share).

I was also planning on wiring the switches up off board so that "jumble" is no biggie for me either as I've dealt with that in the past with orderly and neat results.  Coming from guitar amp design/building land, I've never been big on mechanicals being mounted on PC boards.  Just too many failures when you're dealing with people who are a bit "rougher" on their gear.  And parts replacement is usually significantly easier.  You guys ever see pot "keys" busted off along with a bent shaft and snapped PC board inside?  Could have been a pot and a few wires redone.  Now it's a whole PC board.

To me at least, those things seemed pretty obvious but thanks for keeping me in check too since I didn't really say anything about the application or how much I'd thought about it.  But it is all in the details there, isn't it?

However, what I was really wondering about, is if anyone had encountered oscillation or wierd crosstalk issues that I might encounter just by having these specific boards operating in close proximity to each other.  Things like that seem to happen when you get into spacial density like that.

Or if no one's seen problems like that yet (because they've stuck with the standard and pretty spacious physical layout), is anyone still building this where they haven't put it in the case yet and feel like just physically moving the boards right next to each other to see if anything odd starts happening?  I'd be willing to express mail a few pints to ya!

cheers!

 

[sr1200]

My 4ch unit has the boards REALLY close.  Since i have my PS in the same unit, i didnt want the torriod "talking" to the other kids in the sand box so to speak.  As far as metering goes, you can do a 5seg LED per channel (same as i did) the 5fish LED VU will fit vertically inside a 1U and there should be enough room to do 8ch with this.  I'll mock up a FP for ya at some point today.

 

[andia]

I plan to add an output attenuator to my access 312 pres and have a little question that bugs my mind:

I plan to do the attenuation with a t-pad attenuator after the output transformer. the t-pad has an impedance of 600ohms. the output transformer as it is wired no has an impedance of 300ohms, if I see it right. (ea2503)
my question is, do these have to be matched to have the same impedance or can I just put the attenuator after the transformer?

thanks,

andi

 

[sr1200]

i have an 8ch layout for you but it wont accept the file as an attachment, i will post it tomorrow when i can upload it to my server.

 

[jsteiger]

...I plan to do the attenuation with a t-pad attenuator after the output transformer. the t-pad has an impedance of 600ohms. the output transformer as it is wired no has an impedance of 300ohms, if I see it right. (ea2503)
my question is, do these have to be matched to have the same impedance or can I just put the attenuator after the transformer?

Just put the t-pad right after the output transformer.  That's how all of my VPxx preamps are. It will work a treat.

 

[tskguy]

Ok what the heck are you guys using for c6? I actually order a 1500uf 6.3v electro and noticed that 3nitys latest bom says to use 100 to 470 uf and 10 to 16v??? Im using the EA transformers. I understand its part of the gain stage but not sure whatdifferent values would change in terms of sound....

Eric

 

[3nity]

It doesnt really matter and it will not affect the sound at all.
I updated it later just to follow more of a traditiona API schematic.
Thanks

 

[soundsactive]

@buildafriend - thanks for the quick solve! i really need to dive into transformers more, they are still a mystery to me!

 

[thesystem]

I plan to add an output attenuator to my access 312 pres

I'm planning on doing the same, what t-pad attenuator will you use and how do you wire it?

 

[jsteiger]

I plan to add an output attenuator to my access 312 pres

I'm planning on doing the same, what t-pad attenuator will you use and how do you wire it?

T-pad = http://hairballaudio.com/shop/product_info.php?cPath=27&products_id=65

If you get the PCB, the pads are labeled. It's super simple.

 

[andia]

I plan to add an output attenuator to my access 312 pres

I'm planning on doing the same, what t-pad attenuator will you use and how do you wire it?

T-pad = http://hairballaudio.com/shop/product_info.php?cPath=27&products_id=65

If you get the PCB, the pads are labeled. It's super simple.

yes, I'm also going with jeffs t-pads...

 

[thesystem]

I plan to add an output attenuator to my access 312 pres

I'm planning on doing the same, what t-pad attenuator will you use and how do you wire it?

T-pad = http://hairballaudio.com/shop/product_info.php?cPath=27&products_id=65

If you get the PCB, the pads are labeled. It's super simple.

yes, I'm also going with jeffs t-pads...

Cool, thanks!