Splitting preamp signal
- Thread starter jamhead
- Start date
Ok I could be wrong, but I think it doesn't work that way. The preamp signal is basically a voltage output, not current. So splitting it will not halve the signal; the same voltage will be present at both sides of the Y. As long as the input impedances of the amps are a lot higher than the output impedance of the preamp (which is generally going to be true of consumer gear), it should be fine, meaning the preamp will have sufficient current to maintain the voltage to both amps.
Now rammisframmis can tell me why what I said was totally wrong.
Now rammisframmis can tell me why what I said was totally wrong.
D
Deleted member 133
Guest
I'll add to this by saying that in my main HT the signals are "split" multiple times between the pre-outs and the power amps because 1) I have a number of external processors, crossovers, and subs and 2) I'm running "stacks" of Koss speakers and each speaker gets an amp channel of its own, and there's two speakers per audio channel. All this without any issues - especially not when it comes to available volume! 
Jeff
Jeff
MakeMineVinyl
Well-Known Member
PaulyT said:
OK you're wrong. :laughing-lettersrofl:
Actually, you have it right. The rule of thumb about modern impedances is that the receiving end impedance should be 10 times or more the source impedance - something which is almost always the case with modern solid state gear (but something I have to pay attention to with my tube gear, which can have output impedances in the 50k Ohm region depending on the particular circuit).
If the receiving impedance does not meet this criteria, then the output from the sending device looses headroom, and will go into clipping earlier, or MUCH earlier if the load is too severe. Splitting the output from a modern preamp in two will almost surely not cause this problem, but if it gets more than that, it could be.
Preamps are ***mostly*** voltage sources, but this only true down to about 2k Ohms load, at which point they can start to act like current sources (obviously this point can be different depending on the "stiffness" of the output stage of the preamp). Power amps have a much lower point where they stop acting like voltage sources, and usually current protection kicks in before that point is reached.
Just NEVER use a "Y" adapater to sum together two OUTPUTS, no matter what component they're from. This is a recipe for at the least significant distortion, and smoke at the most extreme. You can sum two outputs if you use buildout resistors in each leg, at which point the currents sum (not the voltages technically), but this gets into DIY territory, and probably more than most people want to screw with.