Timeline for What's the difference between bass and guitar heads?
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| Feb 26, 2016 at 4:27 | comment | added | Todd Wilcox | @DietrichEpp My understanding is that current will not be limited enough at the output and the transformer and tubes will be overheated by excess current, possibly to the point of damage or destruction. That is borne out by warnings in instruction manuals provided by amp manufacturers. It's possible the warning are based on an overabundance of caution, but I've never heard of an overly low load impedance being described as anything other than very, very bad. | |
| Feb 26, 2016 at 4:22 | comment | added | Dietrich Epp | @ToddWilcox: I think we're getting at different phenomena here. My point is that because tubes have high output impedances, it is relatively safe to use a tube amp to drive a low-impedance load, even below the amp's nominal rating, because the current will usually be limited by the output impedance (not counting that speakers are highly inductive). Your point is also correct, that they are not designed to do this, and as a result the tone may be inferior. High impedance loads can cause problems with tube amps because the power tubes will basically be driving the inductance of the xformer. | |
| Feb 26, 2016 at 0:26 | comment | added | Todd Wilcox | @DietrichEpp You've got that backwards. Power tubes have high impedance outputs which is then lowered using an output transformer. But there are limitations to how low the impedance can be practically made with a transformer, so it is rare to have a tube power stage with an output impedance below 4 Ohms. Solid state designs, especially those based on cascaded bipolar junction transistors, can in some cases be made to have arbitrarily low output impedances, below 2 Ohms. I didn't think of that in my answer, but impedances should always be checked, regardless of design. | |
| Feb 25, 2016 at 21:58 | comment | added | Dietrich Epp | I'd like to elaborate on this: one of the reasons why guitar amps powering bass cabinets is safer is because guitar amps with tube output sections are less likely to be damaged by low speaker impedances. If they were solid-state, they'd fry much more easily when hooked to low-impedance speakers. | |
| Feb 25, 2016 at 16:41 | history | edited | Todd Wilcox | CC BY-SA 3.0 |
added 3 characters in body
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| Feb 25, 2016 at 16:25 | history | answered | Todd Wilcox | CC BY-SA 3.0 |