Info about classic (voltage summing) and modern (current summing)
- Thread starter r2d2
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r2d2 said:
I am always willing to pontificate about summing technology.
I was not aware of that particular nomenclature-distinction.
I googled the neve 75 and it appears two use two different summing technologies "virtual earth" (what some call current***), and transformer windings (stacked I ASSume) that some call voltage summing.
Virtual earth summing is widely used and well understood. Using individual transformers is quite expensive for the task and I guess in theory does not suffer from the insertion loss associated with virtual earth.
I stopped using transformers for mic preamps in the 70's so I am not going to use one per bus stem inside a large console (I'm cheap). I guess if you have too much money you could use them.
FWIW modern digital domain combining is cheap and loss-less (in fact you end up with extra signal, or extra resolution if summed signal gets scaled down.)
JR
**** "current summing"... I had an interesting dance with the patent office back in the 1980's when I tried to patent my (lossless) current source summing bus structure. By summing together the output from synthesized current sources I avoided the insertion loss/noise gain inherent in typical virtual earth summers. Unfortunately for me the wet behind the ears patent examiner didn't understand the difference between "current sources", and "currents" flowing in typical VE summer. I couldn't afford to pay an expensive patent lawyer to educate him about basic electronics from my slender personal bank account back then. :'(
JohnRoberts said:
Hello John ,
many thanks for your post!
i asked to the actual neve 75 series desk manufacturer
some audio sample about the 2 summ option of the console
unfortunately no reply at now........
(.... a little bit no serious i.m.h.o. from a company that manage that pro type of "product"....)
about your patent office issue , seem really that they have to back to school ....
...also seem that they are the same as many politics ......
(.."entertainement" department of big corporations...)
i understand that transformers are the expensive way to manage sound ,
it could then say that the sound difference between the 2 option of summ
would be like the vintage 80 series neve consoles , and something like a modern ssl ic desk,
for example the duality ?
more thanks for post!
R.
It may be a way offer two different "sound" choices, but if both are well executed the sonic differences should be subtle, if at all..
I suspect the actual differences could be characterized with good high resolution bench test equipment.
JR
PS: Being asked for sound samples is not a common request. Perhaps they could tell you studios or recording that used that desk.
I suspect the actual differences could be characterized with good high resolution bench test equipment.
JR
PS: Being asked for sound samples is not a common request. Perhaps they could tell you studios or recording that used that desk.
I can measure things that I can't hear, and can't hear things I can't measure..r2d2 said:
Ears are useful to confirm that I measured everything important.
JR
Sometimes, ears ear things that do not exist, though...r2d2 said:
ruffrecords
Well-known member
Both mixing methods are very similar in theory. How well they work in practice depends a lot on the implementation. JR and Steve DOve can both give chapter an verse on the pitfalls of VE summing/
At Neve, back in the 70s, the passive mixing bus bars were contained in a custom aluminium extrusion which consisted of a number of U shaped channels. Holes were drilled in the bottom of the U and bus feed resistors were fitted through these holes. Inside the U channel, the bus resistor was soldered to a length of one hole wide Vero strip (I kid you not) that ran the length of the channel. When this assembly was complete a flat aluminium cover was fitted over the top of the Us so each signal bus was completely and separately screened. The bus bar was fitted right underneath the routing modules that fed it and connected to it by short single unscreened wires.
Cheers
Ian
At Neve, back in the 70s, the passive mixing bus bars were contained in a custom aluminium extrusion which consisted of a number of U shaped channels. Holes were drilled in the bottom of the U and bus feed resistors were fitted through these holes. Inside the U channel, the bus resistor was soldered to a length of one hole wide Vero strip (I kid you not) that ran the length of the channel. When this assembly was complete a flat aluminium cover was fitted over the top of the Us so each signal bus was completely and separately screened. The bus bar was fitted right underneath the routing modules that fed it and connected to it by short single unscreened wires.
Cheers
Ian
I know you're not kidding, having had to troubleshoot the (in)famous Barclay Studios custom board; it took me one and a half days to find an interrupted mix bus, for a broken joint. I don't know who at Neve designed this arrangement, but I think it's unworthy of a major manufacturer.ruffrecords said:
The "classic" summing hardly qualifies for voltage summing. It's current summing, albeit a different one than VE; I certainly wouldn't want to use the term "voltage summing" for it. Only an editor of advertising department can have the audacity to do so.r2d2 said:
True voltage summing can be done only by putting in series floating voltage sources, which generally implies transformers, and cannot reasonably be extended to multi-channel/multi-bus, for reasons of cost, bulk and performance.
The differences between classic and VE are well-known. Both provide similar level of performance and require slightly different optimizations. The advantages of VE, particularly with the availability and affordability of VLN devices, outnumber those of "classic", the only justification for the latter being nostalgia.
Hi all,r2d2 said:
I am the owner of Burbank Audio Systems, and we are the manufacturers of the Custom Series 75 console.
I would first apologize for not responding sooner, but don't get to spend too much time in the forums, and must have missed R2D2's email.
The question regarding the difference between 'voltage' and 'current' summing has already been covered very well, and I would never presume to state a preference - this would be a subjective opinion, and should be left to the individual.
As to sound samples, I don't believe these would necessarily serve the purpose, and would recommend sitting down in front of a console and trying it out with source material that you are familiar with.
The CS75 does have both buss architectures, and you can switch between them on a channel by channel basis, or the whole console together. There are the aforementioned transformers on the 'voltage' summing busses, all Carnhill/St. Ives. And yes, it does increase the manufacturing cost, but is the only way to stay true to the method.
And with regard to our use of the BA283, the 3055 is also available in a TO220 package, which is what was used with a suitable heatsink.
If you have any further questions, please feel free to email me: [email protected]. Unfortunately, I can't predict when I will next have a few moments to check the forum.
BTW thanks to everyone else's input!
Bruce
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