Would an impedance mismatch adversely affect my amp?

[mightyjoeyoungxnj]

Meaning, with my head at 16ohms into an 8ohm input on a cab? It's my JCM 800 and I've only played through it like this for about an hour and a half.

Any significant damage? Seems to sound fine.

-Joe

 

[Audioholic]

this type of mismatch is less safe then say putting your head at 8 ohms into a 16ohm cab imo. Though some say that you can run at 1 mismatch up or down and still be fine most of the time, I still would air on the safe side you know. It will probally effect your sound if only at least very midly

 

[mightyjoeyoungxnj]

Thanks for the reply.

I have it back to normal, matching.

I'm more worried about long term damage.

thanks!

-Joe

 

[D-Rock]

My understanding is that running an amp at a higher ohm rating than the cab it's plugged into is dangerous for your output transformer.

 

[Audioholic]

yup

some aps may be able to take it, but why take that chance? if you want to experiment with different ohms to try to get a different sound, thats kewl, but best to keep them matched evenly from amp to cab

 

[ke2]

Thanks for the reply.

I have it back to normal, matching.

I'm more worried about long term damage.

thanks!

-Joe

I would believe (note believe) that if something went wrong, it would go with a boom, if anything. Mesa states that a slight mismatch is of no danger, the manual of the MK1 reissue even encourages to experiment.

 

[blackba]

Its always best to match output impedance. As to whether it will harm your amp if you don't, it depends on the amp. Having a higher speaker impedance in the amp poses different risks than having a lower impedance to the amp. I don't really think one is better or safer. I know some on this forum like to mismatch for sonic reasons, but I prefer to match whenever possible.

Vintage Fenders for example can typically tolerate a 100% mismatch either way. If you have a 4ohm output on a fender, it can usually run down to 2ohms. If they didn't think so, they wouldn't have put an extension speaker jack on the amp....

 

[GuitarGuyLP]

I have been very interested in that topic for quite a while. Here is a link that I got from James Peters that gives a good explenation.

http://aga.rru.com/FAQs/technical.html#imp-1

Kevin O'Connor from London power also sums it up in online FAQ here

http://www.londonpower.com/faq.htm

Kevin Invented power scaling, and has written many books on amp design, and modification.

To sum it all up Marshalls are more picky then other amps. This has to do with the power amp design. This is also why Marshalls blow output transformers more then Fender, or Mesa. If you run a 16 ohm cab from the 8 ohm output it is easier on the tubes until you reach the point where the tubes can't put out any more voltage. At this point you can damage your transformer. Running a 4 ohm cab off the 8 ohm output is harder on the tubes, but you are less likely to damage your OT. But either way if you are not cranking it up to very high levels you will be OK.

 

[ke2]

I have been very interested in that topic for quite a while. Here is a link that I got from James Peters that gives a good explenation.

http://aga.rru.com/FAQs/technical.html#imp-1

Kevin O'Connor from London power also sums it up in online FAQ here

http://www.londonpower.com/faq.htm

Kevin Invented power scaling, and has written many books on amp design, and modification.

To sum it all up Marshalls are more picky then other amps. This has to do with the power amp design. This is also why Marshalls blow output transformers more then Fender, or Mesa. If you run a 16 ohm cab from the 8 ohm output it is easier on the tubes until you reach the point where the tubes can't put out any more voltage. At this point you can damage your transformer. Running a 4 ohm cab off the 8 ohm output is harder on the tubes, but you are less likely to damage your OT. But either way if you are not cranking it up to very high levels you will be OK.

And if something happens, it happens right there and then? Not two weeks later?

 

[mightyjoeyoungxnj]

Thanks for the replies guys.

I only had the amp set on 16 for maybe 1 1/2 to 2 hours total playing time since I've had it. In that time, I've only cranked it maybe once or twice for a few minutes.

When I jammed with my buddies last week, I noticed the mistake and set it to 8 accordingly.

Think I'm ok?

-Joe

 

[blackba]

Thanks for the replies guys.

I only had the amp set on 16 for maybe 1 1/2 to 2 hours total playing time since I've had it. In that time, I've only cranked it maybe once or twice for a few minutes.

When I jammed with my buddies last week, I noticed the mistake and set it to 8 accordingly.

Think I'm ok?

-Joe

You should be fine. You did better than turning on the amp with no speaker load connected.

 

[mightyjoeyoungxnj]

Thanks for the replies guys.

I only had the amp set on 16 for maybe 1 1/2 to 2 hours total playing time since I've had it. In that time, I've only cranked it maybe once or twice for a few minutes.

When I jammed with my buddies last week, I noticed the mistake and set it to 8 accordingly.

Think I'm ok?

-Joe

You should be fine. You did better than turning on the amp with no speaker load connected.

Cool, thanks man.

-Joe