jaxonmills' lsc thread (renamed)

[djw]

I have a question: Can I run my amp's 4 ohm output into my Weber attenuator set at 8 ohms? It's switchable between 8 and 16 ohms, but not 4. If I can't do that, can I use the amp's 8 ohm output while running the el84/6v6 combo? Thanks.

That's probably all good... if you check the manual, it illustrates a lot of different impedance configurations, many of which are safe mismatches. The upshot seems to be that there are not very many impedance mismatches that will really hurt the amp... it probably has to be grossly off, or run for a long time at high volume to have much of a detrimental effect (someone please correct me if I'm wrong).

As for the 4 into 8 thing, they recommend that you use the 4 ohm output with the 8 ohm speaker because with 4 6V6s, your putting out roughly 1/2 power compared to 4 6L6s. Notice that they also recommend this 4-to-8 config when you're running at 50 watts (with 6L6s)... but they also recommend you run the 4 6V6s together (i.e., using the 100 watt setting) -- most likely because of this impedance issue. With EL84s you have roughly the same equation, so when we're running just a pair of these lower-powered tubes, I THINK this means it'll sound better if you can put a 16 ohm load on the 4 ohm output. So I would recommend THAT.

I'm pretty sure it's safe to try this... going the other way (putting a 4 ohm speaker load on the 8 ohm output) is bad, I think. But going "up" seems to be safe. You can always call Mesa and confirm this, too. I'm 99% sure they don't address all of this out front because it's basically safe to ignore it, and the problem is confusing enough to explain (and compounded by channels that run at different output levels) that they just figured most users will be happy leaving it alone.

Not us, apparently...

 

[jaxonmills]

Yeah I don't know why it would be any different running my 4 ohm out into an 8 ohm attenuator instead of an 8 ohm cab, just making sure. Thanks for the quick answer.

Another question: Would it be safe to run 6v6s with EL34s (or in my case KT77s) on the EL34 bias setting? I don't see why it wouldn't be, as long as I match the inner and outer tubes.


I just tried the 6v6s in the outer sockets with the YJs in the inner sockets. I think I like it better like this. To the guy who said there was too much compression with the YJs in the outer sockets, you might like this configuration better. My strat sounds fatter on Ch 1, and my LP sounds crisper on Ch2, both of which are good things for me.

Also, I was browsing my owner's manual and noticed their description of the presence control. The presence control attenuates high frequencies and adds compression as you turn the knob counter-clockwise. They recommend setting the presence around 12 o'clock for best results, and I like this setting with my single coil guitars, but I'm trying a much higher setting for my Les Paul seeking a brighter and more open sound.

 

[djw]

Another question: Would it be safe to run 6v6s with EL34s (or in my case KT77s) on the EL34 bias setting? I don't see why it wouldn't be, as long as I match the inner and outer tubes.

I'm not so sure about this one. It's probably fine... I might be inclined to make sure I have KT77s and 6V6s with the same bias ratings. I know Charles really digs running 6V6s through the EL34 bias setting; you might ping him about this, or Mesa directly.