Turtlerock Forum

Hey all,

After the long thread the other week about summing I'm going to give passive summing a try, so my current active summing mixer is up on the block.

I've had it for about 18 months, and I've been really happy with it. I migrated from ITB to using it, and it's a pretty clean summing amp- it doesn't colour the sound much at all, but there is a slight difference to ITB. The main advantage for me is being able to utilise my outboard and easily strap comps across the 2bus etc. For this it's been fantastic and I certainly wouldn't want to go back to ITB.
It's a great option to get into summing, as everything is organised and sorted for you. 16 inputs (the first 4 channels being assignable either mono or stereo), separate mix and monitor ouputs (with a monitor volume), an inbuilt compressor supposedly modeled on a G series SSL Bus comp, peak limiter, send/returns for strapping outboard across the 2bus, and a good sounding A/D card.
This means you can run your signals into the box, and just take a single cable via SPDIF or AES back into your converters with the mix on it.
It's also got a few other features like an external in for checking against, ability to chain with other units to deal with more than 16 channels etc. It's been discontinued, so perhaps the best source of info is here- http://www.soundonsound.com/sos/feb06/articles/audientsumo.htm
It's in perfect condition, it's been installed in the rack when I got it and hasn't moved since. Switchable 110/240v

They are discontinued, but places that still have them in stock seem to be selling them (with A/D option) for around $2k.

I'd be hoping for something around $1400 based on the couple I've seen sell on eBay in the US recently. Happy to take offers, and definitely interested in partial trades on a good stereo A/D (or potentially D/A units, or 8 channel + AD/DA etc).



I've also got a bunch of patchbays I don't need anymore.

Neutrik 1/4" 48 point bay. A few dodgy channels, so you can have it for postage + a beer!

be!@#$%^& 48 channel unbalanced bay. Bought this off Ben, didn't realise it was unbalanced which doesn't suit me. Looks to be in pretty good nick. $30 plus shipping.

How would I post you a beer??? No, I'd be interested in the slightly defective patch bay, Alistair if you've still got it? I'm in NSW.

Are you sure Alistair?

I built mayself a passive mixer using it with Manley, API & Neve Pre's which all had a great flavour and the improvement over ITB to me was enormous but after a while some things bugged me a little.

I just purchased a TL Audio A4 summing mixer which is Discrete and much better in my opinion than just dropping the volume with some resistors and slapping a mic pre on the end to boost up the volume.

You don't miss the options of having all the different pres though? What didn't you like about the passive summing? Very interested to hear your thoughts.

No matter the pre there was always a quality that was maybe caused by using a type of makeup gain that was never intended for this use. Whilst hard to describe I'll probbly go with slightly harsh/small /overly tight sounding.

The TL Audio discreate mixer seems on first use a bit more relaxed and natural.

Both a big improvement over ITB though the Slate VCC plugin has gone some way on improving things in this area. Slapping the VCC on each channel through the summing mixer really hit the spot for me. VCC in the mix buss did nothing but on an ITB mix does have a bigger impact.

Is it possible that the summing mixer you built didn't have the correct impedance to match up with a mic preamp? I know I've seen quite a few designs out there with different impedance on the outputs.

That's good to know, maybe I'll have to rethink things. I like the Sumo, I'd just like a little more control over panning etc, and the idea of being able to vary the sonics and saturation to some degree would be very cool.

The impedence could also vary with the mic pre being used also. All pre's used no matter their input impedance still exhibited the same behaviour. I think there may be some comercial summing mixers out there that are passive with there own built in makeup gain that may be designd more appropriatly though. I remember Ross Giles was makeing one himself a couple of years back.

Ok, that's good to know. Can I ask which design you used for your summing mixer? Or if it was your own design?

It was one floating around the Prodigy forum I think it was the same as the Fulcrom. Really cannot remember exactly except it had 10k resistors per channel (16 channels) and toggle switches for left and right on. The impedance I cannot exactly remember.

Copper wire no PCB.

Thanks David-
The one I was looking at was very similar, but with LCR switches. 20k input, 200ohm output impedance, with around 40dB volume drop. Should be in a good range for most mic preamps impedance wise, so it's probably nothing to do with that.