Ohm question

Ohm question

Postby 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!
User avatar
tcsned
Senior Member
 
Posts: 2618
Joined: Sat Mar 21, 2009 2:50 pm
Location: Blacksburg, VA

Re: Ohm question

Postby 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.
Gone are the days we stopped to decide where we should go, we just ride...
ugly rumor
Bobby
Bobby
 
Posts: 369
Joined: Thu Aug 13, 2009 6:33 am
Location: Virginia

Re: Ohm question

Postby 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?
User avatar
tcsned
Senior Member
 
Posts: 2618
Joined: Sat Mar 21, 2009 2:50 pm
Location: Blacksburg, VA

Re: Ohm question

Postby 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?
"There, in huge black letters, was 'The Grateful Dead'. It just... cancelled my mind out."-Garcia
User avatar
tigerstrat
Senior Member
 
Posts: 4628
Joined: Wed Nov 30, 2005 1:20 pm
Location: Portland,OR

Re: Ohm question

Postby 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.
User avatar
tcsned
Senior Member
 
Posts: 2618
Joined: Sat Mar 21, 2009 2:50 pm
Location: Blacksburg, VA


Return to The Think Tank

Who is online

Users browsing this forum: No registered users and 1 guest