egnater vengeance....

I posted a thread on the tech section because I was having some bigtime feedback on the gain channel. Not good feedback. I turned the gain boost switch off and the gain knob down past noon and it went away but also neutered the amp. I retubed it with some mesa 6l6 gc's and put a ruby high grade in the PI slot and that fixed it. Wish I knew what preamp tubes were responsible for what because I would like to swap out a couple more maybe. I have an at7 as well as some mesa 12ax7's and one more ruby HG. Still a little noisy but the squealing is no more. I'm using my mode 4 cab which is extremely dark so first impression is the amp is dark. The amp was worth the price for the clean channel. It's a fender twin type clean which is what I prefer. Anyway still fucking with it and waiting for my cable for the footswitch. So far I like it. Will hook it up in stereo later....and this amp has a ton of options...plus you can run about any combination of power tubes you want as long as you keep them paired up....1 and four-2 and three slots....
 
So you got the feedback squeal fixed? I saw your thread. I was simply going to add that I would buy 2 or 3 new 12ax7s to always have on hand for things like this. I personally love tube rolling. Get a JJ, Tung Sol, and a Chinese or New Sensor one. Love how these Egnaters can handle different power tubes.

Have you done the pencil tapping test?
 
Got my cable in and got the foot switch hooked up. Was having issues with the loop until I discovered a cable was halfway out of the return. Anyway it’s all set up and nasty as fuck. Definitely has some mids on the gain channel. Have not tried my other cab yet but damn this amp is dark sounding. I do like it though. Not really sure what you could compare it with. The clean channel is the surprise with this one. Just a stellar clean.
 
Damn. Getting ready to play pre amp tube roulette and thought I would recheck the bias. If you remember I couldn’t get a reading on one pair of power tubes…well the bias was set so high my meter was getting an OL reading. Started decreasing the bias and the first reading I got was over 120…damn. The bias on the other set increased also after adjusting the one set. Anyway they are both reading around 62 now. The chart said between 60-70 for 6l6’s but I’m tempted to go lower. Going to pull the 12ax7 hg out of the pi and put in a at7….any other recommendations? The switch inside the chassis drops v1 out and replaces it with a solid state whatever. I tried it and never noticed anything sound wise so I plan on doing nothing to v1 for now. I have some background noise but after adjusting the bias it decreased some.
 
Not noticing anything but I'll leave the at7 in the pi and not fool with any of the others for now. I think I will drop the bias to see if that affects the noise anymore. Any chance of hurting anything by having a cold bias?
 
The bias point for 6L6GC tubes is a matter of personal taste and tube life. Fender recommends 60mv for safety and tube longevity, but some say 68.3mv is the sweet spot for 6L6GCs. Others recommend 50-55%, and Leo idled his 6L6GC amps at 50-55%.

I just read the above quote. I'm at 62mv...so what exactly would 50-55% be? The Eggie manual says to bias 6l6's at 60mv-70mv....I'm fine with how it is now but was just curious.
 
JackBootedThug said:
The bias point for 6L6GC tubes is a matter of personal taste and tube life. Fender recommends 60mv for safety and tube longevity, but some say 68.3mv is the sweet spot for 6L6GCs. Others recommend 50-55%, and Leo idled his 6L6GC amps at 50-55%.

I just read the above quote. I'm at 62mv...so what exactly would 50-55% be? The Eggie manual says to bias 6l6's at 60mv-70mv....I'm fine with how it is now but was just curious.
Click to expand...
You need to know the plate voltage to know where you're at on the bias. Otherwise it's a complete crapshoot.
Measure it from pin 3 to ground on the power tubes. Set your DMM to DCV. Ground the black probe on the chassis and put the red probe on pin 3 of any power tube.
From there use the formula:
(Plate Dissipation / Plate voltage) * desired percent

Quick example:
Measured Plate Voltage: 480 DCV
6L6GC Plate Dissipation: 30 watts
Desired percent: 65% (Personally I like to be between 65-70%, but depending on the amp it can go colder or hotter)

30/480 * .65 = .041 or 41 milliamps

Keep in mind that the plate voltage will change slightly as you adjust the bias. So it's a good idea to go back and remeasure the plate voltage after setting the bias and make any minor adjustments as necessary. Also good to go back an recheck the bias after a week or so and adjust for any minor drift as the tubes settle in.
 
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