#88756  by tcsned
 Mon Nov 01, 2010 7:58 am
I uses a Hiel Talk Box and just switched from my Mesa Mark IV with an 8ohm 1x12" speaker to my Mark III with 4ohm 2x12" - the Talk Box is rated at 8ohms. Will it risk blowing up if I plug it into the 4ohm output of the amp (goes through to the 2x12)?

I used an A/B pedal on Saturday and ran the Talk Box into the Mark IV but would rather not have to set up an extra amp just for an effect I use a couple of times a night.

Any thoughts?

Thanks!
 #88808  by ugly rumor
 Tue Nov 02, 2010 9:00 am
Tom,

As you described, there is no danger to your amp or speakers, or talk box. you will notice a diminished response (lower volume) with the box in series (8 0hms + 4 ohms = 12 ohms resistance, or more accurately, impedance). In parallel, you have 8 + 4 divided by 2, or 6 ohms, during talk box operation. You'll be fine!

Lower impedance hurts the amplifier, not the speakers. I have always considered running less than a 4 ohm load to constitute amplifier abuse. Excessive current (wattage) is what hurts the components.
 #88813  by tcsned
 Tue Nov 02, 2010 9:34 am
Thanks! The talk box bypasses the speaker cab when it is engaged so it's either or not both together. The signal path is:
amp 8 or 4 ohm out -->talk box (8 ohm) --> 2x12 cabinet (4 ohm)

since they both need to run out of a single output am I better off running out of the 8 ohm or 4 ohm output of the amp?
 #88817  by tigerstrat
 Tue Nov 02, 2010 10:03 am
My Mark III has three Speaker Outs: one labeled 8 ohm and two labeled 4 ohm ... is that different from yours, tcs?
 #88818  by tcsned
 Tue Nov 02, 2010 10:07 am
tigerstrat wrote:My Mark III has three Speaker Outs: one labeled 8 ohm and two labeled 4 ohm ... is that different from yours, tcs?
mine's the same - I thought about running the speaker cabinet out of the 4 ohm and the talkbox out of the 8 ohm but since the talk box is only active when engaged I was worried about plugging something into power where the power has no place to go.