Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. The sunn still shines online!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  

Channel jumping inputs fender to Matchless

4/28/2005 8:38 PM
Channel jumping inputs fender to Matchless
1.) What happens when i daisy chain inputs?  
or channel jump the channels from different  
amp designs?  
a.) Does the impedance get mismatched?  
because the two amps have different  
circuits and are different designs?  
b.) Does it change the Frequency Response?  
c.) Does it load down the inputs?  
example: guitar goes in fender normal input#1  
jack.normal input#2 jack goes to a  
Orange amp input jack#1 with a daisy  
chain cord.  
input jack#2 of orange amp another  
daisy chain cord goes to a Matchless amp  
input jack#1  
2.) The Signal parallels off to the other amp but  
is there any REFLECTED load current or voltage  
when channel jumping?  
3.) Does anyone know any cool Channel jumping  
path ways?
4/29/2005 12:58 PM
Mark Lavelle

Sounds like you're asking for some serious ground loop problems (at the very least)!
4/30/2005 5:57 AM
Wild Bill

2.) The Signal parallels off to the other amp but  
is there any REFLECTED load current or voltage  
when channel jumping?  
Not sure what you mean by "reflected" - if you mean interaction it depends on the specific input circuitry of each amp. Not every input circuit is the same.  
Guitar inputs are of a high enough impedance that daisy chaining one or two will probably not load things down appreciably, causing signal loss. However, if one amp has a parasitic ultrasonic oscillation running around the input stage then daisy chains can couple it to the other amps. That's because there's no isolation by a simple daisy chain setup.  
I have a foggy memory that says daisy chains with solid state inputs are VERY prone to ultrasonic oscillations! Wish I could remember more specifics.  
In any case, I doubt if you will get any major tone differences. The input circuitry DOES isolate the tone/gain stages! The most you will get with a bunch of amps chained is some input signal loss but with all those amps cranking how could you tell? :)  
We're talking a little loss of gain due to loading. I would say there's NO frequency response changes but if I did there will certainly be someone with bat ears who will jump in and say I'm all wet but what's the chances of having a whole audience with such bat ears in a club at once? Vivid mental image, though... :)  
---Wild Bill
4/30/2005 12:34 PM

1.) So it does Reflect the signal if the input  
stage has a oscillation and will pass it  
along in the daisy chain  
2.) Reflect the voltages and current from the  
input stage from the first input channel  
and then its daisy chained reflecting its  
voltages and current to every amp
4/30/2005 7:27 PM
Wild Bill

There virtually is no current at the input - it's a voltage amplifier.  
"Reflect" implies bouncing back. Actually the voltage is constant along the path and loaded down by the impedance of the load. That's not much with a high input tube grid but it does drop a bit with each additional input load put on the line. The guitar voltage goes in one amp, is loaded by the input circuitry and continues on out jack #2 to the next amp, where things get repeated.  
Think of your signal path as a long bus bar - each amp input is like a resistor hanging off the bus to ground. More resistors, more voltage drop. Or daisy chained power bars, with a light plugged in at each interconnect point.  
An oscillation will flow along that bus and appear at every point, just like any voltage. The signal is not reflecting out the jacks, just passing through since the jacks are in parallel.  
As Yoda would say: "Reflection? There is no reflection!" :)  
---Wild Bill
5/3/2005 12:24 PM

If i Y Cord 2 amp channels whats the difference in impedance from a Y cord to 2 amp channels and Daisy chaining 2 amp channels the impedances are both different  
1.) Y cord impedance going into 2 amps channels?  
2.) Daisy Chain inputs going into 2 amp channels impedance?  
3.) Im looking at it in a impedance way Y cord VS Daisy Chaining input channel impedances?
5/3/2005 5:09 PM
Geoff Gross

You sound like you are using RF type terminology. In RF, you get reflected power when there is an impedance mismatch.  
In audio, as wild bill said, we typically deal with voltage amplifiers, at least in preamp stages. They have high input impedance, so impedance matching is kind of a moot point. If both inputs have a 1M impedance, then you've got 500k if they're in parallel. That's fine for guitars, you wouldn't be loading them down too much.  
Don't worry about characteristic impedance of guitar cords. Audio frequencies are so low that we don't really talk about them as transmission lines as they do in the RF world. I suppose if you had a really long cable you could think of it as a transmission line, but I think you would be getting into the hundreds of feet before you'd see t-line effects. We just worry about the capacitance from the center conductor to the shield, and we try to keep that to a minimum.  

  Page 1 of 8 Next> Last Page>>