Enjoy the benefits of a premium membership!
Upgrade Account
-
TalkBass has been independent since 1998. Add your voice.
Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
Join free Log in
Want zero display ads or expanded classifieds tools? Compare plans.
4ohm amp with an 8amp cab..OK?
- Thread starter Hammertime3
- Start date
Absolutely. For the most part, any amp will accommodate a 4 or 8 ohm speaker load. A handful will do the 2 ohm bit but that's not a concern unless you're considering running (2) 4 ohm enclosures in parallel. What are the amp and cab in question?
Riis
True of solid state amps. Tube amps are not necessarily as flexible.
We can give an exact answer for this if we have more info about the actual amplifier and speaker cabinets
If the amp is solid state, the impedance rating is the minimum. The actual impedance of the output is much lower. The spec tells you the lowest impedance the amp can safely drive. So if you have a solid state amp with a 4 ohm minimum impedance rating, then yes you can use an 8 ohm cab. You could also use one 4 ohms cabs or two 8 ohms cabs connected in parallel.
Tube amps are different. Tube amps expect a certain impedance. For example some tube amps expect 8 ohms and some tube amps expect 4 ohms. Ideally you should show the amp exactly what it expects.
Some tube amps can be switched to expect different impedances. Some have multiple output jacks that expect different loads. For example, my Ashdown CTM 300 has an 8 ohm jack, a 4 ohm jack, and a 2 ohms jack. Only one jack should be used at a time, and the total speaker load should be exactly what the output expects. Some tube amps have switches. For example my 1987 Ampeg SVT has two output jacks and switch that allows you to configure the amp for either 2 ohms or 4 ohms.
Some tube amps are safe with an impedance mismatch. Usually the allowed range is one order high or one order low. For example an amp with a 4 ohm output might be safe at 8 ohms and/or 2 ohms. Some amps are safer if the mismatch is high and some or safer if the mismatch is low. Some can handle either. Some don't handle either safely and should always be shown the expected load.
My personal philosophy on running an impedance mismatch on a tube amp is don't do it unless you have an emergency. An impedance mismatch reduces the power the amp can make and it increase wear and tear on tubes and other internal components. An impedance mismatch may also have an impact on tone, which is why some people do it.
If you are going to run an impedance mismatch, IMHO it's best to get an expert opinion on whether the amp is reasonably safe. Also probably a good idea to consider the value and serviceability of the amp. For example if you have a highly-coveted, rare, vintage amp that has a reputation for failing with an impedance mismatch, you probably should avoid the risk and show the amp the expected load.
Tube amps are different. Tube amps expect a certain impedance. For example some tube amps expect 8 ohms and some tube amps expect 4 ohms. Ideally you should show the amp exactly what it expects.
Some tube amps can be switched to expect different impedances. Some have multiple output jacks that expect different loads. For example, my Ashdown CTM 300 has an 8 ohm jack, a 4 ohm jack, and a 2 ohms jack. Only one jack should be used at a time, and the total speaker load should be exactly what the output expects. Some tube amps have switches. For example my 1987 Ampeg SVT has two output jacks and switch that allows you to configure the amp for either 2 ohms or 4 ohms.
Some tube amps are safe with an impedance mismatch. Usually the allowed range is one order high or one order low. For example an amp with a 4 ohm output might be safe at 8 ohms and/or 2 ohms. Some amps are safer if the mismatch is high and some or safer if the mismatch is low. Some can handle either. Some don't handle either safely and should always be shown the expected load.
My personal philosophy on running an impedance mismatch on a tube amp is don't do it unless you have an emergency. An impedance mismatch reduces the power the amp can make and it increase wear and tear on tubes and other internal components. An impedance mismatch may also have an impact on tone, which is why some people do it.
If you are going to run an impedance mismatch, IMHO it's best to get an expert opinion on whether the amp is reasonably safe. Also probably a good idea to consider the value and serviceability of the amp. For example if you have a highly-coveted, rare, vintage amp that has a reputation for failing with an impedance mismatch, you probably should avoid the risk and show the amp the expected load.
