[BUILD]CAPI 2-ACA-Bo~Official Support Thread

[pacemaker]

ok nice !
i know mouser carries them but they're pricey,
if i remember correctly, you're cheaper than mouser !!! 
thnaks for these info jeff,
i think i will order the PCB,2623'S,L-brackets and caps today,
can't wait to install the ACA on my tascam, i hope it will boost my mixes !!!!!!

 

[pacemaker]

order just made for half of the kit,
please send me the BOM soon !!!!!!!!!!! 
thank you very much for all these amazing projects jeff ,
need to find some work and money totest your new VP312DI !
best regards,
francois

 

[sintech]

Progress report:

First mix today, for the 40 channel Trident MTA with Classic 2bus summing in buckets of ten, having spent the last three week installing into my studio space.

And the results are very pleasing indeed, massive headroom, infinite punch, great solid tone, no smear, it's a Big Boys 2-bus for sure.

Worth every penny spent., and would highly recommend it as the best way to bring a mid range console to life.  Massive thanks to Jeff

Scored a nice 200 segment plasma for the 2 buss metering.. schweeet

 

[haima]

the new board is looking (and apparently sounding!) great!  8)

 

[pacemaker]

Hi Guys,
while looking at the 2-ACA block diagram,
and reading this thread,
i noticed that the insert points are before the fader,
On my tascam M3500, the fader and summing amps are before the insert points,
wich are unbalanced,and the insert return goes to the balancing boards,
mayeb i'm studid but someone explain me
the benefit of having the inserts before the fader ?
best regards,
francois

 

[hobiesound]

Hi Guys,
while looking at the 2-ACA block diagram,
and reading this thread,
i noticed that the insert points are before the fader,
On my tascam M3500, the fader and summing amps are before the insert points,
wich are unbalanced,and the insert return goes to the balancing boards,
mayeb i'm studid but someone explain me
the benefit of having the inserts before the fader ?
best regards,
francois

that way you can fade out your mix without messing up the threshold on your buss compressor.

as far as i know that's normal on every mixing desk....

greetings,

Thomas

 

[pacemaker]

ok,
nice answer,
so my Tascam M3500 might not be a decent mixer..... :
hope to receive my 2-ACA soon !!
thanks for your reply,
best regards,
Francois

 

[pacemaker]

Hi guys
i have received my 2-ACA,
i am now trying to install it in my tascam M3500,
i've read and read the thread and studied schematics,
But i have a problem with the summing resistor,
All the summing resistors in my tascam are 22K ,
so after reading the thread,
i guessed i have to changed the summing resistors on the 2-ACA
to 22K and adjust capacitor to achieve same cutoff frenquencies
according to the gainchart xls file linked in the thread,
i'm not sure to understand if i need to add a 22K resistor before the ACA input
or if i need to change R2, R7 and C2,C6 on the 2-ACA pcb,
Any help would be greatly appreciated,
here are some links to the M3500 schematics:
http://img512.imageshack.us/i/tascamsummingamp.jpg/
http://img4.imageshack.us/i/tascaminputa.jpg/
http://img299.imageshack.us/i/tascaminputb.jpg/
http://img825.imageshack.us/i/tascambalancedpcb.jpg/

Hope someone could help,
Francois

 

[jsteiger]

Francois,

I would start with changing R10 and R15 to 22K. Also, C11 and C15 should be changed to 100pF or maybe 82pF. It is just the feedback components of the ACA that you will change.

Cheers, Jeff

Edit: see two post below for correct values.

 

[pacemaker]

ok cool,
thanks for the reply,
so i guessed it's R10 and R13 not R15,
from 28K to 22K and i will change caps to 100pf,
i was also curious about the mult output on the ACA ,
what did you used it for ?
Regards,
francois

 

[jsteiger]

ok cool,
thanks for the reply,
so i guessed it's R10 and R13 not R15,
from 28K to 22K and i will change caps to 100pf,
i was also curious about the mult output on the ACA ,
what did you used it for ?
Regards,
francois

Wait, hold on a second! I spoke too soon earlier. I just dbl checked the schematic. I should never fully trust the memory anymore.  :-[ I would recommend changing R10 and R13 from 28K to 13K. C11 and C15 from 47pF to 100pF. The values on the schematic give you a -3dB knee @ 121K and the new values will be 122K (for feedback). Close enough I think! The original gain structure is -2dB after the ACA section. The 13K should give you that with 22K bus R's.

I do not use the mults after the ACA for anything myself. It was easy to add so I did. The mult from the Booster section can be used for a control feed or what have you.

 

[pacemaker]

Ok jeff thanks for your reply,
unfortunatly i don't have 100pF neither 13K available,
I have 56pF and 200 pF and a 10K,12K 15K etc resistors,
I can use the gainchart calculator form bob schwenkler
to achieve same cutoff frequency,
but i don't know how to calculate the interaction with my 22k summing resistors
to achieve -2dB level,
can you explain me a bit or help finding the correct combination ?
best regards,
Francois

 

[jsteiger]

See figure #3 here. http://danalexanderaudio.com/ApiInfo/api2520_02.jpg

Original Rf is 28K and Rs was 47K. Just make sure the end result is the same. Then use Bob's calculator like you say.

 

[pacemaker]

thanks for the link,
so the formula is gain=Rf:Rs
and with Rf 28K and Rs 47K the result is 0,6 or -0,6 right ?
so as the tascam summing resistors are 22K
i'm stuck with the 13K resistor to achive same gain
right ?

 

[jsteiger]

thanks for the link,
so the formula is gain=Rf:Rs
and with Rf 28K and Rs 47K the result is 0,6 or -0,6 right ?
so as the tascam summing resistors are 22K
i'm stuck with the 13K resistor to achive same gain
right ?

Yes, correct. Time to place an order at your local electronics supply house. 

I'm sure you could temporarily get by with a 12K to just get her going.

 

[pacemaker]

yeah............
but my local electronic shop only have crappy ceramic disc cap,
and i'm not sure to find 1% metal film,
Time for a mouser order ! ;-)
Thanks for the great support !
i'll keep you informed and post pics in the thread
best regards
francois

 

[jsteiger]

...Thanks for the great support !

Haha! It's only good if it works!    Otherwise...crappy support! 

BTW, any C0G would be fine for the feedback cap.

Let us know how things go!

Cheers, Jeff

 

[wolfgang]

12kfor Rf should not be a problem! Difference to 13k is only about 0.7 dB!!!


regards,
Wolfgang

 

[gar381]

Hi Guys

I needed a Classicapi 2-ACA for this nice old late 70s 8 channel Tangent 802a
to make a nice old school small GREAT sounding remote mixer out of this old
war horse. (interesting and fun project)

The Classicapi 2-ACA PCB was physically to BIG to fit in the space
so I modded a Classicapi JLS Inv-ACA PCB into a 2-ACA
buy doing some creative mods with a little help from Jeff...
(THANKS my friend) to the JLS PCB and using
4--  2623-1-CF trafos.

I added some P&G 8000 series faders , 10 - Barnett Ind.
7 LED VU meters and changed lots of caps and opamps.

This $50 ebone mixer now sounds like a $5000 mixer..... GREAT!!!!

BTW..Rs for this mixer = 10k
       I used for Rf  6.2k
       and Cf 150pf

I'll post a thread in the next few days in the lab on all the FUN
I had Modding this old BAR board.  I am VERY pleased with the
results.

GARY

 

[jsteiger]

Nice work Gary! She is a sexy looking old gal indeed.