How is your DIY Summing box treating you??

[Sammas]

Im about to tackle a balanced 16 channel passive summing box with DB-25 connectors... just wondering how yours turned out? How's it sound?

Any words of wisdom before i setup to the plate?

I'm thinking about getting a pair of JLM 99v's for makeup gain, either that or using my soon to be complete Gssl...

 

[smilinfu]

NYCDAVE?s posts on the subject are full of information and are indispensable. Read them a bunch of times it helped me a lot. :thumb:

I used them as a starting place but then breadboarded different summing resistor values until I got something that sounded best for my purposes. About an hour of experimenting that was very educational and well worth it for the sound. I think is was 5 or 10K going unbalanced into stereo JFPs. Everything was LRC switch able.

I just used 8 channels and noise was definably an issue, 16 will be even worse.

I would like to do another one (I use it as an effects returns), this time I will definitely go balanced. It was not to noisy for most thing, but it was enough to knock it out for certain applications. Probably a better layout may have helped this. Good grounding and shielding seamed to make a big difference. It was very susceptible to hum from transformers and such, so leave space for yourself to play with and don't be to put off if it is noisy while it is sitting on the test bench.

The JFPs worked great for a while, very full sound, but they run hot, and I think I blew something inside as they as very distorted now. Will probably try something else next time.

Beware that this will make you start dreaming of building your own console.

 

[Ian MacGregor]

I have designed a PCB for a balanced 16 channel passive summing box. Mine also uses DB25 connectors for audio in. I used the standard Tascam wiring diagram, so we hook it up directly to our Bro Tools via HD192s. As far as the sound, the engineers who have tried it now will not mix without it. Most of the guys mix in Bro Tools, then at the end, instead of bouncing, they split their mix up into 8 stereo stems and run it through the summing box. Usually the mix changes enough that they need to tweak.

We've been using Seventh Circle Audio N72's for makeup gain and they sound great. We immediately notcied increased stereo width. We also took the time to do several proper AB tests with digital summing. The analog always won out. The analog does not have the extended low end that the digital has. This may have to do with the transformer coupled mic amp we are using for gain.

Definately find New York Daves info about the summing box. Very valuable.

Ian

 

[Helsing]

Ulysses and I got the Folcrom into a production a few years back. Good to see folks building their own around here. Its so incredibly simple but makes such a big difference.

At the TapeOp convention last year Trina Shoemaker talked about how on lower budget projects she would do all the mixing at home on pro tools and then rent an SSL equipped studio for a day or two for summing tracks at unity.

Ulysses and I thought this idea might be dead and gone long ago but perhaps its just taking off.

Helsing

 

[strangeandbouncy]

I built a 8 stereo balanced resistive network into our patchbay, thanks to invaluable info and advice from NewYorkDave. I normally use my 10 channel Sony MXP2000 as a sub-mixer for our rather small 32Channel SSL 4000E. Great combination btw! Now I sometimes use my passive mixer instead/as well! I use either some Helios mic-pre's or perhaps Focusrites for the make-up, depending on how warm or clean I want it. I am thinking of building some unity gain buffers so i can mix sources. I love to add the lead vocal AFTER everthing else has been combined ssl stylee. Sony is good for this, but Passive with Helioses RULES! so much detail in the vocal. easy-peasy does it! - Does get a bit noisier though.


ANdy P