Amp Tech Thread / Ask a tech Q

[Hemisaurus]

Yep, if they plug into the wall like my DOD690, or if they have a tube and use one of those 9V AC to 260V AC transformers. If they run of a battery you're pretty safe.

[liquidsmoke]

I didn't have any problems at practice yesterday and then last night I velcroed the last 3 down so I'm hoping things will stay quiet.

[bass sic]

I have a toob question. On my Egnater Tweaker 15wt I swapped out all the tubes experimenting. I put a matched set of Tung Sol 6v6gt's in and the tone improvement was very noticeable. But after about 15/20 minutes of lower volume playing the volume dropped almost all the way off. And I notice one of the tubes is glowing hot. I turn it off for a few seconds and it comes back on normal, then craps out again later. It didnt do it before the tube swap, could it be the new tube? Or fucked up amp? Ill swap tubes back later.

[The Shocker]

I have a toob question. On my Egnater Tweaker 15wt I swapped out all the tubes experimenting. I put a matched set of Tung Sol 6v6gt's in and the tone improvement was very noticeable. But after about 15/20 minutes of lower volume playing the volume dropped almost all the way off. And I notice one of the tubes is glowing hot. I turn it off for a few seconds and it comes back on normal, then craps out again later. It didnt do it before the tube swap, could it be the new tube? Or fucked up amp? Ill swap tubes back later.

No refunds! 

Bias issue? 

[Hemisaurus]

Redplating, where the plates in the tube glow red, is usually caused by some kind of bias problem, where the tube gets turned full on. Kinda like if your throttle jams open.

It's more likely to be the amps than the tubes I'm afraid, but if a tube has been allowed to redplate for a while it usually warps the plates, and so should be replaced as well. Is the tweaker one of those self bias jobs, if so tech time

[The Shocker]

I don't remember if the Tweaker's instructions mentioned biasing when changing tubes.

[Hemisaurus]

Just read them, it says if amp needs servicing or biasing, could be bad biasing causing tube failure. New tubes and a bias job might be the fix.

[dunwichamps]

could be a poor tube, bad bias supply or improper grid leaks.

[bass sic]

I'm told you can't bias this amp.

[bass sic]

I'm gonna go with bad tube, since it started right after the swap. I hope.

[The Shocker]

Bassic, you should have left those tubes alone.  

Actually, that's why I'm scared to tube swap if things are running fine.

[bass sic]

Yea, it was fine. But could always be better. Sounds fucking incredible until meltdown.

[Hemisaurus]

Are the Egnater amps cathode or fix biased?
All of the models, with the exception of the Tweaker, are fixed/adjustable bias with easy to use test points. Consult the owner's manuals or contact support@egnateramps.com for information on how to properly adjust the bias. The Tweaker is cathode biased so there is no adjustment required when replacing tubes.

So stick back in the old tubes, in the same place you took them out if poss. and see if it works.

[bass sic]

I put the stock ruby's back in and so far after an hour no issues. We will see how thetubestore.com deals with refunds. It did sound really good.

[FullCustom]

I'm told you can't bias this amp.

Everything ever can be biased.

[Hemisaurus]

Maybe he should have been more precise, it can't be biased by default.

Actually, it is biased, it's just a non-adjustable bias, if it wasn't biased it wouldn't work.

This unit, in it's default state, has a non-adjustable bias voltage.

[dunwichamps]

like every mesa I have seen. Non adjustable fixed bias, i know a fuckin weird name for it.

[Hemisaurus]

I agree with Randall whassisname about PCB's, but not giving users a chance to bias their unit is just lazy.

[FullCustom]

Randall Smith is the name. His Kool-Aid belongs with his products and nowhere else. I'll keep my bias controls thank you.

[dunwichamps]

I agree with Randall whassisname about PCB's, but not giving users a chance to bias their unit is just lazy.

I think amp companies are worrying about liability in the form of you screwing you amp up with improper bias and or having to open the amp up to bias it causing potential death. however its all dumb IMO but I do wish modern manufacturers would actually make it easier to bias shit with B+ and cathode current taps to measure bias instead of having to open up the amps to get that stuff

[FullCustom]

When I bias a Mesa I bring out two or three sets of tubes and swap them until I get the bias I want.

[dunwichamps]

When I bias a Mesa I bring out two or three sets of tubes and swap them until I get the bias I want.

sounds like a pain in the ass but not much better than an amp with just 1 bias adjust for 4 output tubes.

[FullCustom]

When I bias a Mesa I bring out two or three sets of tubes and swap them until I get the bias I want.

sounds like a pain in the ass but not much better than an amp with just 1 bias adjust for 4 output tubes.

Factory matched tude set are fine with a single bias control. Groove Tubes never setup how I want them to, sometimes they're as much as 10mA apart. I can dig around in my boxes of used junk and fine tubes matched better than that.

[dunwichamps]

i guess it will depend how well the tubes are matched, how burned in they are as well so they dont drift all over the place during initial play. Its another thing where at minimum dual bias pots should be used 1 for each half of the push pull.

[FullCustom]

I'm sitting here biasing a DSL100 and eating my lunch. The dual bias pots aren't help it. It is however doing a great job of making a set of JJ EL34 tubes unbalanced. If this was a JCM800 I would have been done with the amp before I finished my applesauce.