Einstein 50 Bias Question

[spyeman]

Got my Einstein 50 and it is one hell of an amp, loving the second channel, and pissing of my neighbors big time heh heh, well I thought I would throw my favorite Winged C EL34's in there, and when I went to research it on the web, two things were kinda bizarre - one, the Diezel instructions suggest one remove the fuse when biasing, I did that and my readings went all over the place, it didn't seem to work, then I saw on the instructions that the recommended bias level for the EL34's was 60-70 - WOW, never been past the mid 40's on my EL34's, so I have the following questions -

Does removing the fuse affect the readings, so that a 60-70 reading without the fuse is really a lower reading with a fuse?

and, assuming the answer to the above is no (fuse in or out has no affect), then is this 60-70 Ma correct, good Lord, that's making me piss my pants just typing it!!!!

Thanks in advance........

 

[Anonymous]

What type of bias tool are you using?
A Biasrite (my bias tool) with the octal tube holders does not require one to remove the fuses. This is what I use. After inserting the tubes into the octal tube holders, plug them into the tube sockets, bias and you are done.

Check to see whether you need to remove the fuses to bias your amp.

If you are using a simple meter, it may be worth your money to order a weber Biasrite. It will be the best investment you can make for your amp.

 

[petereanima]

then I saw on the instructions that the recommended bias level for the EL34's was 60-70 - WOW, never been past the mid 40's on my EL34's, so I have the following questions -

"60-70" is meant for a PAIR, not for a single tube!

 

[eddiespaghetty]

Hi,

yes, you have to remove the fuse, when you use a voltmeter. 80-70 is for the pair, as mentioned above. I had to play a bit around carefully with the plugs to get the right measure-point, but after a couple of tries I had the correct mAs.

ed

 

[spyeman]

Thanks guys, I've self biased most of my amps, and I have a bias rite equivalent (the tubes with the octal test socket are too tall to fit in without pulling the chassis, and since there are bias pots right there, trying to use those). Like Eddy, I agree, it's hard to get a stable reading on your meter, it bounces all over the place, but I think I have that worked out - question is, when I put in my test/reading needles, one in the black, one in the red, am I getting a read there for one, or for two tubes??? The Diezel tutorial shows a picture of this, and a reading of 65 on the meter, so I'm guessing it's for the pair? Thanks

 

[spyeman]

Okay, I went back and read the Diezel tutorial a little more carefully. I see the biasing is clearly set up for pairs, so with only two tubes in the 50, and using the "inner" testing slot, I'm obviously getting the correct pair reading. What was weird is that when I first dropped in the Winged C's, they were reading at 35, which seemed close to normal to me, and I'mjust not used to biasing anything up to 70 lol. I did run them up to 50 last night, and of course was nervous as hell they were going to blow up, red plate, etc., but no issues. Okay, tonight I move em up to 70.

Saw a few people in my search who like the JJ KT77's, think I will give em a try as well, what the hell.

Thanks all, I think I have it now.........I will say when I moved from 35 to 50, the clean channel did seem to warm up a bit, but who knows, maybe just my imagination....

 

[Duolos]

I could be wrong with what I am reading and how I am understanding what you are saying but 70 mA is not high. If you are used to a single tube mA reading then I agree that 60 to 70 mA is very high but that 60 to 70 reading is per tube pair. I would park it at 65mA personally. I run all 34 type stuff there and it works beautifully.

 

[Fishfinger]

I borrow your topic a little, hope you don't mind.. As I ordered a new pair of 6550:s to my Einstein, the forthcoming biasing operation made me think how "hot" to set the bias. At their website Diezel suggests 80 to 100 mA for 6550 for Einstein. For my understanding soundwise "hotter is better" but tube longevity vill decrease. So, have anyone noticed how drastic is the difference from 80-100 mA for age of tubes?

 

[spyeman]

Man, I don't know, I put the tubes up to 65 on the meter, and they looked like they were ready to blow, blue color everywhere, but what was really concerning was the plates were glowing (is this red plating?) not entirely, but along the entire length on the sides of the plates, obviously being heated up by the central element in the center of the tube (obviously no tube techie here), most of the plates looked okay, the inside bottom of the tubes looked fine, tremendous heat coming from the tubes, felt like more than typical, I just don't know, I've had 25 different amps, and the tubes never quite looked like that - I played for a couple of minutes without issues, does this sound normal?

 

[spyeman]

Well, screw it, I pulled out the chassis, and using the Bias Rite, after having biased them at 65 per the bias pots, guess what - the first tube I tested was at 138. Holy smokes, I knew it wasn't right, but 138, how the hell did it not blow. Reset em to 40. Amp sounded great. Needless to say, I wont be using the bias pots in the future. It's nice that the chassis is very easy to pull out and return. Putting this in the past....