Mk IV 8 Ohm Vrs 4 Ohm

[kingster]

Anyone use the Mk IV with an 8 Ohm output instead of the 4 Ohm that it is set up for? Mine blows fuses and I thought maybe the 8 Ohm would lighten the load on the amp.?????

 

[scottywompas]

I have a combo which runs at 8ohms. Are you using a head with a cab?

I don't think running 4ohms is possible into only 1 speaker. At least Ive never seen a 4 ohm speaker.

Mis matching the Ohms could cause problems.

Scott

 

[6L6C]

With the 4 ohm jacks you are supposed to have (2) 8 ohm loads. Whether it is two 8 ohm speaker cabinets each connected to each 4 ohm jack or two 8 ohm speakers each connected to each 4 ohm jack.
An of coarse the 8 ohm is for 8 ohm jack (do use the a combination of the 8 & 4 ohm jacks).
What speakers do you have and how are they wired (if cabinet with two or more)

 

[kingster]

scottywompas,
Jeez - You are correct. It is 8 Ohms, and says so on the combo speaker. I have 2 external cabs each with (2) 8 Ohm speakers wired in parallel, producing 4 Ohms. I run the 8 Ohm output from th Mk IV to the 1st 4 Ohm cab, and the 1st cab directly into the 2nd 4 Ohm cabinet. The cabinets run in series produce 8 Ohms. I know it sounds weird, but I think I did it so I could distribute the sound easier, and weight considerations.
I measured the resistance into the Mk IV and it is in fact approx. 8 Ohms (9.2 actually). So my first issue of running a 4 Ohm amp is moot. But I still have the question about fuses. I saw another post about fuses with the Mk IV and thought it may be something known and can be corrected.
I love the amp enough that I will buy a second one for live use, which ideally should be the case anyway.
I hate to be dead in the water in the middle of a song on a live stage. Embarrasing to say the least. Unprofessional as well.
Thanks for your response. It made me actually get off my butt and verify what I thought I was talking about.
kingster

 

[NoGlassNoClass]

scottywompas,
Jeez - You are correct. It is 8 Ohms, and says so on the combo speaker. I have 2 external cabs each with (2) 8 Ohm speakers wired in parallel, producing 4 Ohms. I run the 8 Ohm output from th Mk IV to the 1st 4 Ohm cab, and the 1st cab directly into the 2nd 4 Ohm cabinet. The cabinets run in series produce 8 Ohms. I know it sounds weird...
...I measured the resistance into the Mk IV and it is in fact approx. 8 Ohms (9.2 actually). So my first issue of running a 4 Ohm amp is moot.

So you are running the combo's speaker AND an 8-ohm load of extension cabs? You should plug the combo speaker into one 4-ohm jack and the ext cabs into the other 4-ohm jack.

Something seems odd about your 9.2 reading...typically an 8-ohm speaker (or multiple speakers wired for 8-ohm total) will show a DC resistance between 5.7 and 7 ohms. Check your wiring, and the speakers themselves to see if there is a problem.

You could also rewire your cabs with the speakers in series to give a 16-ohm load each cab, and parallel the cabs...that way if a speaker fails in one of the extension cabs you will still be showing a 16-ohm load to the amp. Might lose some volume in the event of a speaker failure, but safe for the amp.

 

[JAZZGEAR]

Anyone use the Mk IV with an 8 Ohm output instead of the 4 Ohm that it is set up for? Mine blows fuses and I thought maybe the 8 Ohm would lighten the load on the amp.?????

Uhhh? The 8 Ohm jack is the default connection :shock: