Re: [Harp-L] Running amps in Tandem?

[Greg Heumann <greg@xxxxxxxxxxxxxxx>]

Buck - there are many ways, and each has advantages and disadvantages.

1) Daisy-chain as you suggested in your post
2) “Y-Cable” to split mic’s signal into 2
3) A/B/Y box to split mic’s signal into 2
4) Line out from Amp A to Amp B


#1 is the least efficient as it will run the signal through multiple resistors and therefore rob the most tone from the element. 

#2- works fine but the mic will see both amp’s input impedance in parallel. If both amps have 100K input impedance, the mic sees 50 ohms. If they both have 1Mohm inputs, the ic sees 500K. If the two input impedances are different, the actual formula is R1*R2 / R1+R2. Crystal and ceramic elements are much more sensitive to drops in input impedance than dynamic elements (like modern vocal mics, or vintage Shure controlled magnetic or controlled reluctance elements. )

#3 - these boxes are available in 2 flavors - passive and active. Passive means it works exactly like the Y cable, except that you can switch from one amp to the other or both with a tap of your foot. Active boxes actually “receive and rebroadcast” your mics signal - so it only sees the input impedance of the active box. Note that you could ALSO run your mic through any pedal that you like while it is ON- and it will have the same effect of isolating your mic from what’s downstream. In other words, if you go mic to delay pedal to Y cable or passive ABY box, you’ve solved the impedance dropping problem. 

#4 - Many amps have line out circuits. These are electrically isolated from the mic so once again too-low input impedance is not a concern. However this usually adds to the overall gain of the system - you will get more volume but you probably have to turn both the 1st amp down from the max you set it at when playing it alone in order to avoid feedback.


/Greg

http://blowsmeaway.com
http://facebook.com/blowsmeawayproductions


When responding to this email, please include the copy of our previous conversations.



> 
> List,
> How does one run 2 amps in tandem (if that's what you call it)? Let's say 2 Champ type amps. Run the mic into amp #1 and run a cable out of the #2 input and into amp#2's #1 input?? I have never tried this.
> How is this done? Or am I a'll wet' on this?
> Regards,
> Buck Worley 		 	   

> 
>