aviel

SoundCraft spirit channel mod
« on: September 28, 2018, 11:10:05 AM »
Hey,
I have an old spirit live that i use for preamps in my recording studio. Since im not interested in a mix, and the master channel adds noise (something to do with the fx returns) i am trying to add a per channel post fader direct output. I am thinking about using the insert jack for that.

Following the signal chain, looks like the post fader signal is dc blocked by c21, so that should be a good place to steal it. I was wondering if i can reuse the insert driver also. Can someone help me a bit here? I also have a technical manual and circuit description.

Thanks!


aviel

Re: SoundCraft spirit channel mod
« Reply #1 on: September 28, 2018, 11:28:59 AM »


ruffrecords

Re: SoundCraft spirit channel mod
« Reply #2 on: September 28, 2018, 12:30:34 PM »
I am puzzled by your question. The schematic you posted already has a post fader direct out labelled  direct out.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

aviel

Re: SoundCraft spirit channel mod
« Reply #3 on: September 28, 2018, 01:23:10 PM »
Just realise the schemaitcs are a different revision from the one i have. Mine actually doesn't have direct out.. My board pcb is sc2954.
So im even more confused how to continue !

moamps

Re: SoundCraft spirit channel mod
« Reply #4 on: September 28, 2018, 02:25:22 PM »
So im even more confused how to continue !
You're on the right path, IMO.

aviel

Re: SoundCraft spirit channel mod
« Reply #5 on: September 28, 2018, 03:48:05 PM »
Thanks a lot!
So basically its so simple?
I will be glad to get the schematics for the rest of the pcbs if you have them.

moamps

Re: SoundCraft spirit channel mod
« Reply #6 on: September 28, 2018, 03:54:28 PM »
PM me your mail address.

aviel

Re: SoundCraft spirit channel mod
« Reply #7 on: September 29, 2018, 05:25:00 AM »
You're on the right path, IMO.

Thanks, also PMed you my email.

can you please explain why you connected the new resistor to the ground?  shouldnt it be connected between the previous stage and C22?

moamps

Re: SoundCraft spirit channel mod
« Reply #8 on: September 29, 2018, 12:39:38 PM »
First you need to isolate the connector from insert line by cutting PCB traces going to tip and ring pin.
Then, you should connect directly premp's output to C22 with a wire, and then the post fader signal from C21 to R34 .
The new resistor connected from ring pin to ground is used for the output impedance balancing of your new "direct"output.
You can connect it to the ground if you wish but the output signal will be then unbalanced.

aviel

Re: SoundCraft spirit channel mod
« Reply #9 on: September 29, 2018, 05:26:18 PM »
Thanks again. in that case. im not sure the insert was balanced at all, since i have tip for send, ring for return and sleeve for ground. am i correct?

I would like to ask 2 more questions  also:
1.  I was thinking about extracting 1 channel out from the console, to make it a small preamp. my main concern then is the power supply. do you have any suggestion? should i try and build something from scratch? since it's only 1 channel,  i assume i will need much much less current then the whole console.

2. i was thinking about replacing some capacitors to try and get more details on high frequencies, im looking to get a little more "defined" sound. do you have any suggestions? i mainly use it for electric guitars.


moamps

Re: SoundCraft spirit channel mod
« Reply #10 on: October 01, 2018, 03:18:58 AM »
Thanks again. in that case. im not sure the insert was balanced at all, since i have tip for send, ring for return and sleeve for ground. am i correct?
Yes. Insert is a two way connector, direct out is one way.
Quote
  I was thinking about extracting 1 channel out from the console, to make it a small preamp. my main concern then is the power supply. do you have any suggestion? should i try and build something from scratch? since it's only 1 channel,  i assume i will need much much less current then the whole console.
You need +/-17V for opamps and +48V for the phantom power. The consumption would be IMO less than 100mA so you can build it easily on a protoboard using 317/337 regulators. Or you can buy a power supply kit like this one
https://www.jlmaudio.com/shop/ac/dc-3-rail-power-supply-kit-v5-easy-mount.html?display_tax_prices=1
Quote
i was thinking about replacing some capacitors to try and get more details on high frequencies, im looking to get a little more "defined" sound. do you have any suggestions? i mainly use it for electric guitars.
Hard to say, but I prefer Panasonic FC and Nichicon Muse types for any recapping  job.

aviel

Re: SoundCraft spirit channel mod
« Reply #11 on: October 01, 2018, 06:51:43 AM »
with what capacitor in the chain will you start?

moamps

Re: SoundCraft spirit channel mod
« Reply #12 on: October 02, 2018, 08:33:26 AM »
I would change all caps in signal path at once.  :)
If the space permits I would double are values too.

aviel

Re: SoundCraft spirit channel mod
« Reply #13 on: October 06, 2018, 07:15:02 AM »
Hey,
so here is a pic of the poor transient response of the first amplification stage:



it is measured at C6, before highpass filter.
C3 & C4 are big decoupling caps, so i assume there is no point in increasing them, apart from that, what can i change in order to improve the response?
« Last Edit: October 06, 2018, 08:20:44 AM by aviel »

gyraf

Re: SoundCraft spirit channel mod
« Reply #14 on: October 06, 2018, 07:33:34 AM »
*like*
..note to self: don't let Harman run your company..

bernatvm

Re: SoundCraft spirit channel mod
« Reply #15 on: October 10, 2018, 06:42:11 PM »
Hi everybody! That seems a nice mod to try on mine, i would like to use that channelstrips into my interface :P

Mine has some problems in some channels. When I push the gain to high values it starts to make a lot of noise. It only ocurs on some channels and even without input nor phantom. Any ideas? ???

moamps

Re: SoundCraft spirit channel mod
« Reply #16 on: October 11, 2018, 02:55:20 PM »
The cause can be dirty or worn gain potentiometer or leaky capacitor 1000uF.

alexc

Re: SoundCraft spirit channel mod
« Reply #17 on: October 15, 2018, 02:57:29 AM »
I had a 'Spirit Auto' 32  - it was pretty high quality in it's day - I bought it at around 10yrs old.

32 mic line channels, each with a tape return section ...  and  a 'flip' switch  to .. well .. flip  the instrument/tape feeds  ...  both mixing to the main.

In it's day it was great - it ran 'vca automation' on all the channels and (eight) busses.  'that 2150' kind of thing with 1K faders (alps as I recall). It was a 'compressed midi' kind of data channel ... 10bit on midi ..  but only with the right receiver ... 'Steinberg SPirit Auto 32' on an Atari.

Well ... the auto got old, but the VCA faders stayed pristine till the end ...  without the auto, the faders were silent well into the '20th year'.

Then  I did a freeby for a local rock wanabee outfit   :D    Along with a nice guitar too ...  an old Aria (around 1970 orso ) diamond series in the 'Rick' style   ... but with a  spruce top and all.  Somebodies would have some fun with it!

...

As a regular Spirit 32      .....    this   32-32-8-2  inline studio oriented desk, 72 inputs to mix,   it was the cookies. 

EQ was super great for that 'price point'   and the basic perf all round was pretty awesome.

The SoundCraft analog stuff is good and you can use it all over.

...

I did measure the basics, back then  ..  it did quite well for sure ..  and I learnt a lot more about 'mix' performance all round.

My 'reference' was a Motu 2408Mk3 and Yamaha 03d back then .....  I still have both in my lounge room  ;D

« Last Edit: October 15, 2018, 04:22:52 AM by alexc »
I ping therefore I am

aviel

Re: SoundCraft spirit channel mod
« Reply #18 on: October 15, 2018, 04:40:32 AM »
well i started to play around with a single channel of my spirit:

1. started by modifying the send to be post-fader, and i sent it directly to my interface, so now i can "clip" my preamp circuit while no overloading the interface. it bring more sonic possibilities out of this channel and i like it!
2. removed 2 DC blocking caps, left the one at the output. i also replaced the voltage filtering caps on this channel and increased their value.

to be honest, i dont hear a big difference by removing DC blocking caps, neither by increasing the values.
i am open to suggestions :)


 

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