Gareth's Advice on Upgrading the SC600

Founded in 1973, Soundcraft first made its mark with the launch of the Series 1, the first mixing console in a flightcase.

Moderator: GJC Designs

Gareth's Advice on Upgrading the SC600

Postby Anthropic » Fri Apr 04, 2014 9:04 pm

Hi Gareth!

Thank you for moderating such an incredible resource. I've enjoyed countless hours reading this forum and learning as much as I can from the master technicians here.

After reading several of your previous posts, it seems that when you were designing the Soundcraft 600, the company forced you to compromise with certain portions of your design to reduce costs.

As a 600 owner, I was wondering if you could possibly advise me of any modifications that could be done to it to increase its performance beyond its already-fantastic level (that don't involve trace-cutting, or other similarly destructive/fiddly work)? For example, are there any Op Amps or transistors that can be switched, capacitors changed/enlarged, resistor values changed to enhance sound quality?

Thanks for any info you can offer!

Best,

Dan
Anthropic
Analog Enthusiast
 
Posts: 7
Joined: Wed Apr 02, 2014 10:02 pm

Re: Gareth's Advice on Upgrading the SC600

Postby Gonecat » Mon Apr 07, 2014 6:24 pm

I am on a similar quest and although I am a near total amateur I can at least share a bit of what I have learned thus far, and you can research and fact check from there if you want. I imagine (and hope) someone like Gareth will come along and cut what i say to shreds - that's how you learn the fastest :-)


Check out the "Issue" number printed on your channel strips. Certain 'mods' that people do today were apparently "done" on later versions (either v7 or v9) - Though I've had a hard time identifying what factory mods were done on those later versions, you might have better luck.

My SC600 is pretty dern quiet, but people often say the Eddie Ciletti grounding-mod is a must-do. Easily found on the Goog.

Power Supply - re-cap it if it hasn't been done.

Transistors - for the channel strips there are a few that are recommended (but still not super easy to find) including: 2SA1316, 2SA1016, 2SA1085, Renesas 2SA1084. For the stereo mix you can try a National LME49720.

IC's - you'll need a PSU that can hang with the additional current some chips may require, and it seems you'll need to add some bypass caps so they don't oscillate.

Recapping the channel strips with good caps (seems Nichicon and Panasonic are top choices) appears to be one of the best and most effectual mods you can do. Also adding small bypass caps so you retain more top end. Lots of posts out there about this.

As an aside, just cleaning the pots, switches and contacts has cleared up nearly all probs i was having and improved things all around.

Sure hope something in here helps, I'm always the one asking the questions and not answering them, so I thought I would try my hand at it :-)

Please keep the forum apprised of your findings!!
Gonecat
VU Meter Specialist
 
Posts: 46
Joined: Mon Jan 27, 2014 8:59 pm
Location: Los Angeles

Re: Gareth's Advice on Upgrading the SC600

Postby Anthropic » Fri May 02, 2014 11:39 pm

OK, here's an update:

I replaced all of the electrolytic capacitors. For the first 2 caps in the Input channels, I used 220uF Panasonic FC's. All 2.2uF signal path caps were replaced 47uF/50V Panasonic HD's. Finally, any other signal path caps were replaced with either 470uF/25V Elna Silmic II's or 470uF/25V Panasonic FR's (depending on where I could fit them).

I also replaced all of the power rail caps (usually 47uF/25V) with 470uF/25V Panasonic FR's- which is where I've run into a problem- at least as far as the bus/output modules go. On power up, each C37 cap popped and smoked, along with the 10 Ohm resister right in front of it (I think it's R9 or R10). Being that their capacitance was upped 10 times, I'm thinking that the current rushing in overheated the cap(s). Just to be sure, I checked to make sure the polarity and voltage rating of the caps was correct. It was. So, now I'm trying to figure out exactly how to solve the problem. None of the channel strips or Master module had any failures (despite also possessing enlarged PSU decoupling caps). I'm thinking that I need to either decrease the value of the caps back to the original specs, or replace those 10 Ohm resisters with either higher resistance and/or higher wattage. Anyone have any guidance they can offer?

Thanks!

Dan
Anthropic
Analog Enthusiast
 
Posts: 7
Joined: Wed Apr 02, 2014 10:02 pm

Re: Gareth's Advice on Upgrading the SC600

Postby ric3xrt » Tue May 06, 2014 6:51 pm

I'm following Just bought a 500 32Channel Going to pick it up next week
ric3xrt
Analog Enthusiast
 
Posts: 16
Joined: Sat Apr 05, 2014 4:43 pm

Re: Gareth's Advice on Upgrading the SC600

Postby Anthropic » Mon Jun 09, 2014 11:00 am

UPDATES/SUGGESTIONS:

1. I found the culprit causing the burning resisters in the MASTER section: a backwards IC chip. The socket had actually been installed backwards by the factory, so I desoldered it and corrected it.

2. The burning resisters in the OUTPUT channels seemed to be caused by my "upgrading" certain 2.2uF caps to 47uF or higher. This seemed to draw too much current and overstressed certain resisters (see warnings below).

3. Unless you want to change the response of the EQ's (or something like that), don't bother replacing any of the non-electrolytic caps- the original manufacturer used high-quality (i.e. low distortion dialectrics like polypropylene or polystyrene) caps in the necessary (audio path) positions, so they've already done what you want to do!

4. Anyone doing an electrolytic capacitor "upgrade" or replacement should heed my warning to NOT increase the values of the following electrolytic caps (as it will have the negative consequence of burned resistors, or an improperly-functioning "clip" LED on the input channels). Just replace them with the same values as were there originally (I used Panasonic FR or EB caps):

- MASTER SECTION (R.H.):
C4, C10, C20, C33, C41, C54, C55, C56, C57, C104, C110, C120, C133, C141
And, if you're replacing OpAmps, remember that IC13 on the Right Hand
Master Section is the SOLE TL071 in the whole mixer. Don't accidentally
replace it with a TL072 or the Talkback won't work.

- MASTER SECTION (L.H.):
C6, C18, C30, C42, C54, C66, C73, C74, C75, C76, C77, C78, C79, C80

- OUTPUT CHANNELS:
C11, C16, C37, C38

- INPUT CHANNELS:
C22, C23, C27, C29, C30

5. I had a problem with only the LEFT master channel outputting. I traced the problem to the Master Fader, so I took it apart and cleaned the whole thing thoroughly. That didn't correct the problem, so I ordered a new fader from MOUSER (approx. $35). That did the trick and now I have no problems.


Good luck! Mine's all done and sounds great. It was a tedious project, but I'm happy to have a fully functioning console now. I'd definitely suggest purchasing a Hakko Desoldering Pump and Hakko Soldering station. Both worked wonderfully and greatly decreased the time it took to complete the project. Despite how well my tools worked, I was often faced with lifted solder pads and traces from overheating the boards while desoldering. All I can say is work fast, heat the legs of the part first, and don't touch the board with the desoldering iron until the solder is melted around the part already. Regardless of my care in desoldering, I still had many lifted solder pads and traces. Luckily, it's not too difficult to ensure the circuit is complete by using bits of wire or scraping a little bit of the solder mask off over the trace and soldering to that.
Anthropic
Analog Enthusiast
 
Posts: 7
Joined: Wed Apr 02, 2014 10:02 pm

Re: Gareth's Advice on Upgrading the SC600

Postby Jim Williams » Mon Jun 09, 2014 11:20 am

If larger psu bypass caps are causing part burning, something else is amiss. I use 1000 uf/25V psu bypass caps on 600 inputs. I also remove all the electrolytic coupling caps past the mic preamp. The low cost mylar box EQ caps sound poor, Wima FKP or MKP are good subs.
Jim Williams
Audio Upgrades
Jim Williams
Yacht Rocker
 
Posts: 371
Joined: Mon Jul 14, 2008 9:58 am
Location: beautiful Carlsbad, CA

Re: Gareth's Advice on Upgrading the SC600

Postby Anthropic » Mon Jun 09, 2014 11:57 am

That's what I was thinking too, Jim (regarding the PSU bypass caps). I added C29 and C30 in my "Do not enlarge" list for the INPUT channels just as a precaution. I believe I have a number of input channels where I upped C29 and C20 to 1000uF and they're fine.

The real problems were the 2.2uF/50V "decoupling" caps sprinkled around the OUTPUT boards. I think I had 47uF's in there and I was getting smoke from the 10 Ohm resisters. I replaced those larger caps with 2.2uF's and all of the problems went away... Maybe it was "luck" or something, but that was the only change I made to cause the smoking resisters to stop doing so.

Also, does the 600 have mylar caps in the signal path? I remember checking the schematics for film resisters at critical points (like the inputs to channels, etc.) and it seemed as though each one I checked was already a polypropylene or polystyrene. I guess I didn't look deep enough into the circuit to see the mylars.

Thanks for the advice Jim.
Anthropic
Analog Enthusiast
 
Posts: 7
Joined: Wed Apr 02, 2014 10:02 pm

Re: Gareth's Advice on Upgrading the SC600

Postby Anthropic » Mon Jun 09, 2014 12:03 pm

Also Jim, I know you do incredible upgrades to the OPAmps, etc. of the SC600 (obviating the need for almost all electrolytic caps), but are you saying that it is possible/advisable to remove all electrolytic coupling caps in the signal path (after the mic preamp) of a non-Jim Williams-upgraded 600?
Anthropic
Analog Enthusiast
 
Posts: 7
Joined: Wed Apr 02, 2014 10:02 pm

Re: Gareth's Advice on Upgrading the SC600

Postby Jim Williams » Mon Jun 09, 2014 1:20 pm

The 2.2 uf caps across the power rails is a short stop fix. I remove those and replace them with .1 uf mono ceramic caps. You should add .1 uf's from the rails to ground to stabilize the opamps. Adding small feedback caps across the feedback resistors without them also will stabilize replacement opamps. You should do that in the EQ sections. 22 pf works well.

072 opamps are low open loop gain devices, modern low offset opamps will work without coupling caps. LME National parts and BurrBrown OPA1642's are good swaps. The BB parts draw 1.8 ma, same as the 072's but are far lower in noise and will drive 600 ohm loads. Change the sweep EQ resistors from 6.8k to 3.32 k will allow hi mids to sweep to 22k hz. Change the low mid EQ caps to .022 and .047 uf and low mids will sweep down to 50 hz. Change the 6.8k tuning resistors to 3.32 k to restore the upper sweep range.
Jim Williams
Audio Upgrades
Jim Williams
Yacht Rocker
 
Posts: 371
Joined: Mon Jul 14, 2008 9:58 am
Location: beautiful Carlsbad, CA

Re: Gareth's Advice on Upgrading the SC600

Postby Anthropic » Sun Jun 15, 2014 10:33 pm

Thanks again Jim. And, forget what I said about not replacing the film caps in the SC600. When I posted that, I was thinking of the Otari MX-50 I was re-capping at the same time. Otari was the one who put the good film caps where they need to be. Sorry about that...
Anthropic
Analog Enthusiast
 
Posts: 7
Joined: Wed Apr 02, 2014 10:02 pm


Return to Soundcraft Recording Consoles

Who is online

Users browsing this forum: No registered users and 2 guests

 
Mr Patchbay sells patchbays, tt/bantam cables and more