|
|
Post by gouge on Jul 7, 2015 2:41:36 GMT -6
I didn't want to derail the 500 series blender thread so started this one.
I've got a bunch of Jensen jt-123 transformers that the Jensen schematic specifies for their stereo to mono summer. Or I have a box of 20 or so mci output transformers that I think are also 600/600.
But what would others do?
Lots of options one of which is resistor based using a couple of high grade resistors.
I guess active also. Any sample kits around?. For me I'd be wanting transparent.
What would you do?
|
|
|
|
Post by svart on Jul 7, 2015 14:10:44 GMT -6
The easiest would be a pair of summing resistors, just like you'd use in a summing box.
The jensen schematic shows two 15K resistors as the summing device and the transformer for level conversion and balancing to a mic preamp.
An active design would also use the resistors and an amp to gain up to replace the loss.
|
|
|
|
Post by gouge on Jul 7, 2015 17:42:34 GMT -6
Which schematic are you looking at svart?
I'm looking at as080
|
|
|
|
Post by jsteiger on Jul 7, 2015 17:57:55 GMT -6
What are you trying to combine? The simplest way is to use 0.1% precision R's and nothing else because nothing else is required.
|
|
|
|
Post by gouge on Jul 7, 2015 18:16:43 GMT -6
Usually it's 2 snare mics or 2 tom mics. Sometimes 2 cab mics for bass.
So I'm talking post pre line level. I currently use the console. The groups are a pain because I loose panning ability. Aux requires some extra patching which is no problems but of late I've been feeling I prefer going direct to the converters and use the console for mixing and monitoring.
Resistors would be fine as well. What values would be suggested for 2 channel.
Either way I'd prefer passive to suit remote tracking as well.
|
|
|
|
Post by gouge on Jul 7, 2015 18:32:51 GMT -6
I found a circuit that suggests 1k.
For the purposes I'm talking about here, would crosstalk be an issue. If so is that why one method or the other would be preferred.
|
|
|
|
Post by jsteiger on Jul 7, 2015 19:47:50 GMT -6
I use 300Ω in the control room module to sum stereo to mono. 1k is also fine. I would make sure they are precision or matched very well.
|
|
|
|
Post by gouge on Jul 7, 2015 21:33:23 GMT -6
Thanks Jeff. :-)
|
|
|
|
Post by svart on Jul 8, 2015 6:57:10 GMT -6
The value depends on what the driving impedance and the receiving impedances are. Lower resistor values are better from a noise standpoint, but the lower the value, the more power the driver circuit wastes and can trigger other issues with heat and distortion. Also, the higher the summing resistor value, the better the crosstalk specs (which might not be that important since you're summing anyway..) but drops the driving ability of the channels being summed.
For line level(and impedance) I would use more like 4.7K to 10K for summing resistors. They are a good balance between impedance, crosstalk and current drive requirements.
If you went higher to say, 47K, you'd get even better crosstalk specs but you'd need to turn to active summing to achieve usable levels and current drive abilities again.
|
|
|
|
Post by EmRR on Jul 8, 2015 7:04:22 GMT -6
If you are mixing two signals together, what crosstalk would be an issue?
|
|
|
|
Post by svart on Jul 8, 2015 10:01:29 GMT -6
If you are mixing two signals together, what crosstalk would be an issue? Probably doesn't mean much but why not do it the right way anyway? |
|
|
|
Post by EmRR on Jul 8, 2015 11:59:14 GMT -6
You are joking, right? I am.....I guess I blinked first!
|
|
|
|
Post by gouge on Oct 23, 2015 6:27:04 GMT -6
Finally did this.
Ended up using 1k .1% as I had access to them. Also tied a 20k across the hot/cold summed output.
Rane white paper suggested 20k resistor. Will try it on guitar or snare tomorrow.
|
|
