Access-312 Build Thread

[Deepdark]

here it is:

 

[dacapitan]

Is it possible to use the Pad on this pre for +4db line level signal? Does any one know what db the pad is?

 

[Harpo]

Is it possible to use the Pad on this pre for +4db line level signal? Does any one know what db the pad is?

Possible, as long as the source can drive this load.
Pad in dB is LOG(R8/(R8+R9+R10))*20 (you fill in your fitted corresponding resistor values in ohm...)
With BOM parts values -1x.922dB (when you fill in the corresponding resistor values in ohm, you know the value of the 'x' representing 2nd digit ...  )

 

[dacapitan]

Thanks for your reply Harpo - I used the standard BOM values which gives me -18.922db. I must admit that I am still a bit confused - i know my audio interface output is +4dbu and 100ohms balanced but I am unsure how it all ties together to determine whether it's ok. any help to try explain would be much appreciated

 

[soundsactive]

mine has been cranking fairly well for a while now and i LOVE IT!

a recent problem started up that i was curious if anyone else encountered. when all 4 of my pres are sending phantom power, the voltage drops to 45v. the PSU is the universal PSU for DIY parts supply. should i worry about this or is that still fine to power all 4 mics? thanks!

 

[Eliani]

So I'm rushing into this project to get a 4 channel Access 213 mic-pre working.

I've ordered Collective-Cases PCB's and 19 inch Rack.
I ordered all the parts from mouser taking in regard I will be using Ed Anderson transformers, and 10k rev log pots.
PSU: Fabmodules 2448 + toroidal transformer ordered...

I guess we'll see where this get's us!!

 

[fnhscar17s]

kind of a random question long time lurker, has anyone had success integrating the whistlerock DI if so how should i wire it up. Trying to go for spec 3124 with di on each channel. I just noticed actually you cant get the whisterock DI anymore but i could make a passive that is the exact same i have the schematic i was just wondering how i should wire it.

Eliani... watch out if you used the mouser list that was posted earlier in this thread there were parts missing and some incorrect values and layout footprint... good thing i had my dial calipers to check before checking out i will post an updated BOM once i place the order if anyone needs it.

 

[IndietownRecording]

What gauge hook up wire are people using?

 

[Deepdark]

What gauge hook up wire are people using?

22ga is fine

 

[IndietownRecording]

Thanks. One more question. I see that the a popular power supply being used is the Fabmodules 2448 + toroidal transformer. If I use this one, are people putting these in their own separate case, or sticking these in the same case as the pre's? If the latter, what size case (depth) would be best?

 

[Deepdark]

Thanks. One more question. I see that the a popular power supply being used is the Fabmodules 2448 + toroidal transformer. If I use this one, are people putting these in their own separate case, or sticking these in the same case as the pre's? If the latter, what size case (depth) would be best?

I used the 2448 psu from 5fish audio. Works great. If you make a 4 pre Inside one box, be sure to have a chassis of more than 11in deep, if not, you'll not have enought space to put a good distance between the api cards and the psu, and it will results in hum and buzz into the closest board. I had to put the psu into a separate box because of that. If you have a chassis of 17in deep, no trouble. If you make a dual, then you should be ok. Another thing you could do if you want to stick with the psu Inside the same box, is to use toggle switch instead of the push button switch. This way, you could put your 4 boards side by side, as far as possible from the psu and hard wire the toggle switch. You should use shielded wire to be sure to not introduce noise and hum.

 

[dandeurloo]

You could use this PSU.

http://collectivecases.com/?product=psu-cc-psu1

 

[phelar]

Hi Neil.
Theres Yes you can use that.
What you have to do is change 2 resistors and 2 caps and youre set.
R5 is 20K, C7 is 120pf and R4 should be 220R and C6 should be 250uf/6v.
Thanks

Is 470uF on C6 gonna mess things up?

 

[dandeurloo]

470uf will work.  You just really want to use a high grade audio cap.  That cap is in the audio path to filter out the DC.  I have used ELNA SILMIC II's.  They are physically big but they can be made to work with a little rigging, they sound really great.

http://www.mouser.com/Search/ProductDetail.aspx?R=RFS-25V471MJ6%235virtualkey55500000virtualkey555-RFS25V471MJ6%235

 

[phelar]

470uf will work.  You just really want to use a high grade audio cap.  That cap is in the audio path to filter out the DC.  I have used ELNA SILMIC II's.  They are physically big but they can be made to work with a little rigging, they sound really great.

http://www.mouser.com/Search/ProductDetail.aspx?R=RFS-25V471MJ6%235virtualkey55500000virtualkey555-RFS25V471MJ6%235

I´ve got the Elna to
I gonna use my preamps in a summing box and i dont really need the gain switch. My plan is to set them to +45 db(the loss in the passive summing network) with just one resistor. Must be the same as using that same gain stage on a switch?

 

[Whoops]

Is it possible to use the Pad on this pre for +4db line level signal? Does any one know what db the pad is?

yes, to pad the input for line level you will need around 40dbs attenuation

replace R8 , R9 and R10 for this values and match R9 a d R10
R8 - 150R
R9 - 7,5K
R10 - 7,5K

or

R8 - 470R
R9 -  4,7K
R10 - 4,7K

PADs explained here, worth a reading:
http://www.uneeda-audio.com/pads/

 

[jaybot]

Hi im new here but need a bit of help with the 312 access board,im just used to building kits ect as you wwill see☺

Im using cinemag cmmi-8pca for input and cinemag cmoq-2s for output.these were suggested to me

Jumpers are set for high ratio.

Is res 4 10k. And res 5 100r?

Res 6/7 i have at 9.76k is that right?

Where on the board is RC located? And what is its value supposed to be?

Is cap 1/2 220pf/35volt?

Is c6 really anywhere between 100 to 470uf/10/16 volts?

Is c8 22pf correct? It says zobel network,how do i do this or is it already setup  on the board?

C4 is 100nf but theres 3 pin holes wich combination should i use?

C3 is 100nf combined with diode 1N4007 how do i connect these together? 3 pin holes there aswell ☺

Where is RC located on the board? And should the res value be 150k?

Anyones help would be greatly appreciated!!!! 
Thanks so much!!
Jaybot

 

[Whoops]

Hi im new here but need a bit of help with the 312 access board,im just used to building kits ect as you wwill see☺

Im using cinemag cmmi-8pca for input and cinemag cmoq-2s for output.these were suggested to me

Jumpers are set for high ratio.

Is res 4 10k. And res 5 100r?

Res 6/7 i have at 9.76k is that right?

Where on the board is RC located? And what is its value supposed to be?

Is cap 1/2 220pf/35volt?

Is c6 really anywhere between 100 to 470uf/10/16 volts?

Is c8 22pf correct? It says zobel network,how do i do this or is it already setup  on the board?

C4 is 100nf but theres 3 pin holes wich combination should i use?

C3 is 100nf combined with diode 1N4007 how do i connect these together? 3 pin holes there aswell ☺

Where is RC located on the board? And should the res value be 150k?

Anyones help would be greatly appreciated!!!! 
Thanks so much!!
Jaybot

I think all that answers are replied in this thread.
Read the full thread and copy to a word doc the most important info and then you have a compilation of all the info

good build

 

[Whoops]

mine has been cranking fairly well for a while now and i LOVE IT!

a recent problem started up that i was curious if anyone else encountered. when all 4 of my pres are sending phantom power, the voltage drops to 45v. the PSU is the universal PSU for DIY parts supply. should i worry about this or is that still fine to power all 4 mics? thanks!

The voltage drops when all the 4 mic pres are powering 4 condenser mics?
or it drops when you turn the 4 indicidual phantom power switch on without condenser mics connected?

Whats the DC voltage you measure at the 48V regulator input with no mic connected?

 

[Whoops]

Thanks. One more question. I see that the a popular power supply being used is the Fabmodules 2448 + toroidal transformer. If I use this one, are people putting these in their own separate case, or sticking these in the same case as the pre's? If the latter, what size case (depth) would be best?

I always use the PSU's inside the box, this is because I hate when I move around with equipment to have to bring with me several external PSU boxes, prefer to have everything in one.

For the hum inducted by the transformer, I rotate the toroid while I listen to the preamp that is closer, I mark the position where the toroid induces the least amount of noise, I then stick one of this shielding sheets around it:

https://www.don-audio.com/trafo-shield

It works great