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blown speaker?

Posted: Sun 04/12/20 1:41 pm
by sruffinc
I'm running a 20 watt heritage greenback in my 18 watt tmb. Recently I had been pushing more high gain pedals into the amp and getting a good sabbath/guns n roses sound. Then tried a brand new OCD v2 that sounded harsh. Also tried a keeley 1962 and same sound. Kinda like the bass frequencies are overwhelming the input and it sounds like hard clipping. Sounds ok with no pedals, but bass frequency doesn't seem to hold together like it used to. Assumed that the 20 watt greenback would take it. I only run the amp volume at 2. Can excess gain damage the speaker? Even at low volume?

Re: blown speaker?

Posted: Sun 04/12/20 2:42 pm
by zaphod_phil
No, not at all. That's a guitar amp speaker, not a hi-fi tweeter. You may need to tweak some cap values to reduce your amp's harshness. Maybe start by changing the EL84s' cathode cap to around 1000uF to 2200uF.That usually helps deal with low-end nastiness, by stabilizing bias voltage on the big low notes.

Re: blown speaker?

Posted: Mon 04/13/20 11:17 am
by sruffinc
Thanks, that's very helpful and good to hear.

For my own education, can bias voltage drift over time? Wondering if that is why my amp seemed to sound differently than before. Or maybe it was always there and I just didn't realize it because I had not been pushing the amp with pedals?

I also was thinking it might be the set of ANOS EL84s I've been using. Maybe they are worn out. The bass frequencies used to seem much tighter.

I have a set of new JJ EL84s but they are definitely harsher than the ANOS EL84s. If I did go with the new JJs, would the larger EL84 cathode cap also help tame their harshness?

Re: blown speaker?

Posted: Mon 04/13/20 11:42 am
by zaphod_phil
In theory it should work with any/all power tubes

Re: blown speaker?

Posted: Mon 04/13/20 12:15 pm
by JMPGuitars
sruffinc wrote:
Mon 04/13/20 11:17 am
I have a set of new JJ EL84s but they are definitely harsher than the ANOS EL84s. If I did go with the new JJs, would the larger EL84 cathode cap also help tame their harshness?
JJ EL84s are generally not good. They range from mediocre to dangerous in my experience. I like their tubes in general, but more than 90% of the EL84s I've purchased from JJ were bad.

Re: blown speaker?

Posted: Mon 04/13/20 12:20 pm
by sruffinc
JMPGuitars and zaphod_phil, thanks for the help. I'll try the larger cathode bias cap and shelve the JJs.