Weber Bias Rite, Reverend Hellhound, and ?

[that_brianm_guy]

OK, I'm new to biasing amps.

Got a Bias Rite, hooked it up to the Reverend Hellhound, measuring 490 on the plate voltage. Flip the switcj to IK, which, according to the web site "This will show you the tube’s idle current (bias) in milliamps (mA)."

the reading is 17.0

check the other tube, VP is 483, IK is 18.7


according to the Reverend Hellhound manual http://www.reverendguitars.com/reverend/archive/manuals_tech/hellhound_manual.html
"Use set with current draw rating of 46 to 49, or in the manufacturer’s middle range (for example 4,5,6 on a scale of 1 to 10). Amp has NO bias adjustment - install tubes and use."

These are the tubes that came with the amp - and the amp sounds fine, btw. I just thought I'd check.

I happen to have a brand new set of matched 6L6s - pop 'em in, and plate voltage is 495 and 485, and IK is 20.8 and 18.2

The readings for IK are nowhere near what I expected - which is between 46 & 49.

What is going on here? What am I doing wrong?

I did the same thing with a Marshall, and got IK reading of 8.1, when I was expecting 30 ma or so... so I think I'm using the Bias Rite incorrectly, but I can't figure out what else I could be doing.

Suggestions?

[sundaypunch]

Your readings are ice cold for a 6L6. At 70% MPD it should be in the 43-44 mA range. I don't think the amp would have much gain if your readings are accurate.

There isn't much you can do wrong when using a Bias Rite. Maybe someone here can tell how how to check that your Bias Rite is giving you the proper reading. You also could call Ted Weber and pick his brain.

[HeeBGB]

Check it with a meter and make sure the reading between the Bias Right and the meter coincide first! If they don't I would suspect something other than the amp. If they do coincide then the amp is biased cold.

You could also try this http://www.compu-bias.com/ A friend of mine has one and it is OUTSTANDING!

[that_brianm_guy]

Your readings are ice cold for a 6L6. At 70% MPD it should be in the 43-44 mA range. I don't think the amp would have much gain if your readings are accurate.


The Hellhound manual says I should be seeing between 46 and 49, and that there is no bias adjustment to be done - just install the tubes and go.

I'm going to check a third amp, see if the IK readings are off.. if three amps come up wierd, then something's wrong with the Bias Rite.

[fullerplast]

The Hellhound manual says I should be seeing between 46 and 49, and that there is no bias adjustment to be done - just install the tubes and go.

I'm going to check a third amp, see if the IK readings are off.. if three amps come up wierd, then something's wrong with the Bias Rite.

When you check your other amps, like you did the Marshall, do you know specifically what they were biased to? You are using the Marshall as a "reference" but do you know for a fact that it has been properly biased to begin with?

I suspect that your BiasRite is fine, and the Hellhound is simply conservatively biased, like most off-the-shelf new Fenders. To be sure, you'll need to measure using a different method.

If it is correct, then you'll need to either tweak the bias circuit or buy tubes from somebody that will sort them for you by current at your operating plate voltage.......or if the amps sounds good as is, you could just play and be happy.:)

[Blue Strat]

The Hellhound manual says I should be seeing between 46 and 49,

No, it means that the "test readings" from your tube dealer should be 46 to 49, which in itself, is VERY misleading since no 2 tube dealers measure tubes the same way. Those readings in your amp would represent 80% of idle power dissipation which is WAY too high.

70% is also too high. That number represents a "theorerical" maximum that tubes should be set for. 50 to 60% is more often the "ideal" range.

That said, 18mA is on the low side, but fine if the amp sounds good.

8mA in your Marshall is way low. Since it's adjustable, try increasing the bias to closer to 30mA.

[that_brianm_guy]

some more results with the Bias Rite

70s silverface Champ, single 6v6, VP of 361, IK of 51.5 - very hot!

1963 brown Deluxe - with a Sovtek 5Y3 rectifier, VP of 400 and 384, IK of 31.8 and 30.8

with a NOS Philips 5Y3, VP of 380 and 367, IK of 23.3 and 23.0

So, I'm thinking the Bias Rite works fine. (and the marshall above was damaged in transit, but that's another story)

Back to the HellHound - the tubes in there now are EH 6L6GC,. The codes on the tube box are "lp: 40" and "Gm: 4,9000"

what do those mean, and what should I be looking for in order to get a tube that biases warmer? The amp could use more gain to my ear. Even with the gain on full, it's too clean.

[Occam]

I've been using 70% for years and never had a problem...maybe I'll try 50-60%...what kind of tonal change should I expect with something like this?

[valen]

I came accross this thread because I just got a Bias-Rite myself and have the same problem. A low cathode current reading . My 1966 Vibrolux Reverb measures 440 v and only 10 ma. I masured my Mesa Tremoverb Dual Rectifier and it measured 420 and 14 ma. That does not sound right to me.

I have the "head-only" Bias-Rite and use my Fluke meter with it. I set it to a low VDC setting as suggested on the Weber site. The Bias-Rite is supposed to do the scaling for you.

[allynmey]

+1 on the Compu-bias from Mission amps! Just insert the tube connector, fire the amp upand view Plate Voltage, Cathode Current, and Watts dissipated. All at once! You can watch 2 tubes at once also on the digital display. Much better than a Bias Rite. I've had both of them!

[Player1]

I too have been using 70% biasing for years with no problem and no premature tube wear. While radio tube manuals would frown on this
rock n roll amps thrive for the 70% rule.

Just my thoughts and experience.