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Post subject: Re: Economy Biasing
Posted: Thu Mar 15, 2018 10:06 am
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Well why does Erotubes state in writing on their website the following?

Congratulations! By owning a bias probe you’re not at the mercy of a tech anymore and you are now in control of your tone.

There are two different kinds of bias probes, one type that uses a resister in the circuit and measures in millivolts and the second type that does not use a resister and measures directly in milliamps. Ohm’s law states that “one volt equals one amp” so the measurements are the same. Our probes measure directly in DC Milliamps so you will need to set your multimeter to the DCA mode (DC Amps, NOT VOLTS!) and if the meter is not auto sensing then select the 200mA scale. If you have purchased one of our “Cheap Multimeters” then you will find this setting right between 3 to 4 O’clock. Insert the black plug from the probe into the “Common” input and the red plug into the positive input which is usually marked mA. DO NOT CHANGE THE FUNCTION SWITCH ON YOUR MULTIMETER WHILE IT IS HOOKED UP TO THE AMP! This will blow the fuse in the meter and you will need to replace it! Make sure the meter is set properly and the probe is plugged into the meter before you plug the probe into your amp.

Remove one of your power tubes and plug the probe in. Place the tube into the top of the probe. If you had to remove the amp from the chassis then make sure that you have plugged the speaker back in. You must have a speaker load on the amp when you are adjusting the bias! Turn on the meter and then turn on the amp leaving it in the standby mode for about a minute, then switch to the play mode. Your meter will read out the plate current in milliamps. Turn the trim pot to adjust the plate current to the desired setting. Wait about 5 to 10 minutes with the amp in the play mode and do a final bias adjustment after the tubes are hot. Congratulations again! You have just biased your amp!


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Post subject: Re: Economy Biasing
Posted: Thu Mar 15, 2018 12:03 pm
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strayedstrater wrote:
If we all demanded the "best" instead of "good enough".........Squiers and Epiphones wouldn't exist.

Sorry, got to correct you there.

Epiphone started in 1873 making fiddles, lutes and mandolins, later Banjos. The company started producing guitars in 1928. The company wasn't acquired by CMI (who also owned Gibson) until 1957.

Epiphone was RUINED by Gibson and now everybody thinks Epiphone means "knock-off Gibson". The truth is, the company had their own rich history and produced guitar models that were never produced by Gibson including the Casino (see The Beatles) and Sheraton (see John Lee Hooker).

Even after being ruined by Gibson, Epiphone had a line of guitars called "Elitist" which are easily as good or better than Gibsons. Only a few Elitist models are still produced, you can see them HERE.


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Post subject: Re: Economy Biasing
Posted: Thu Mar 15, 2018 12:17 pm
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Blue Notes wrote:
Well why does Erotubes state in writing on their website the following?

Congratulations! By owning a bias probe you’re not at the mercy of a tech anymore and you are now in control of your tone.

There are two different kinds of bias probes, one type that uses a resister in the circuit and measures in millivolts and the second type that does not use a resister and measures directly in milliamps. Ohm’s law states that “one volt equals one amp” so the measurements are the same. Our probes measure directly in DC Milliamps so you will need to set your multimeter to the DCA mode (DC Amps, NOT VOLTS!) and if the meter is not auto sensing then select the 200mA scale. If you have purchased one of our “Cheap Multimeters” then you will find this setting right between 3 to 4 O’clock. Insert the black plug from the probe into the “Common” input and the red plug into the positive input which is usually marked mA. DO NOT CHANGE THE FUNCTION SWITCH ON YOUR MULTIMETER WHILE IT IS HOOKED UP TO THE AMP! This will blow the fuse in the meter and you will need to replace it! Make sure the meter is set properly and the probe is plugged into the meter before you plug the probe into your amp.

Remove one of your power tubes and plug the probe in. Place the tube into the top of the probe. If you had to remove the amp from the chassis then make sure that you have plugged the speaker back in. You must have a speaker load on the amp when you are adjusting the bias! Turn on the meter and then turn on the amp leaving it in the standby mode for about a minute, then switch to the play mode. Your meter will read out the plate current in milliamps. Turn the trim pot to adjust the plate current to the desired setting. Wait about 5 to 10 minutes with the amp in the play mode and do a final bias adjustment after the tubes are hot. Congratulations again! You have just biased your amp!



Well, if you've bern following the arguing going on between the people who have posted on this thread, there's "bare minimum biasing, just good enough that your amp and tubes will most likely run safely", and then there"s "check everything and then you can be absolutely sure your amp and tubes are running safely".

Buried in all the back and forth, you may have missed something I hinted at:

You've made a good start in learning how to bias. I consider it mostly adequate. I've done it that way myself. I don't feel like you need to immediately buy a different probe and immediately re-do the bias.

If you continue to buy relatively inexpensive current production tubes, maybe you never need to get more advanced than you are. You're already a notch above most tube amp owners.

But there is more to biasing. If someday you decide to spend hundreds of dollars on a sweet pair of NOS Holy Grail tubes, it would be best to learn how to measure plate voltage.

There's "good enough", and then there's "the best you can do".

"Good enough" is great as a beginning. And it's possible to always be satisified with good enough.

Stratele52 and Shimmilou may come off as disparaging your efforts. But they're really trying to encourage you to take the next step.


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Post subject: Re: Economy Biasing
Posted: Thu Mar 15, 2018 12:37 pm
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ghost_of_strings wrote:
strayedstrater wrote:
If we all demanded the "best" instead of "good enough".........Squiers and Epiphones wouldn't exist.

Sorry, got to correct you there.

Epiphone started in 1873 making fiddles, lutes and mandolins, later Banjos. The company started producing guitars in 1928. The company wasn't acquired by CMI (who also owned Gibson) until 1957.

Epiphone was RUINED by Gibson and now everybody thinks Epiphone means "knock-off Gibson". The truth is, the company had their own rich history and produced guitar models that were never produced by Gibson including the Casino (see The Beatles) and Sheraton (see John Lee Hooker).

Even after being ruined by Gibson, Epiphone had a line of guitars called "Elitist" which are easily as good or better than Gibsons. Only a few Elitist models are still produced, you can see them HERE.


I am aware of Epi's history. And Epiphone Japan models, and Elitists.

And I'm aware that Squier has made some outstanding guitars.

It was an aside, a minor point, an example. I probably should have said that if everyone demanded only the best, they'd buy Fender Custom Shops and Gibson Custom&Historic models, and not "settle" for Fender American Standards and Deluxes, or Gibson USA models.

Or not buy anything from Fender or Gibson. Only boutique brands.

Whatever.


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Post subject: Re: Economy Biasing
Posted: Thu Mar 15, 2018 2:22 pm
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Blue Notes wrote:
How many others here use a single bias probe to bias your amp? I got one from Eurotubes, and must say I couldn’t be happier with the results.

My amp has two 6V6s, and all you have to do is pull one out, and plug it back in through the single bias probe with your volt meter, turn on your amp, and it shows you your bias in milliamps.

Image


Here is something I had found on the Gear Page and I tried it and it did work. The last time I had checked my plate voltage on my 69SR with it, the screen resistor, popped and split in half, I dont think it was the probe, but one never knows.
Keep in mind if you go this route I am not responsible for any issues ::
mud

Just some info on the cheaper bias probe from eurotubes, it got me thinking since I have one, I thought that with out a doubt if I switched my probe while the amp was off or in standby to dcv high voltage setting 1000, that the probe should read plate voltage, and it did, gave me 425 for jj 6v6 in a fender deluxe reverb reissue. They don't tell you that it will also read plate voltage, then I put the amp in standby again, and switched my meter to dc amps 200 is fine, and I set my bias accordingly. With all of this I let the amp sit in the on and standby on for about 10 minutes for each reading, this way I knew it was settled out. You must make sure you do not switch your meter while the amp is on, the power can be on but you must switch it to standby mode first before you switch, if you do not you will could blow your meter or cause awful popping sounds to come out of the amp. So again make sure your in standby mode FIRST then switch to and from your DC Voltage or to Dc amps to do the baising. DC Voltage for Plate Voltage, DC Amps for Bias setting. Just to make sure you understand I am talking about the cheap 25 dollar probe from Eurotubes. You don't need the more expensive one to get your plate voltage, and the great thing is your not in the amp poking around! Hope this helps! If doing this is wrong which I feel it isn't I would love some feed back. To get my bias where I like it I use formula and ears, I take

Plate Voltage x milliamp reading for example 22 milliamps is 0.022 then I divide all of this by the tube spec wattage, 14 for jjs

that will tell you what percentage dissipation you are at, i tend to try to stay just under 70% as I like a little bit more clean headroom.

Plate Voltage x Milliamp / tube wattage = % of maximum plate dissipation for that tube.

thanks


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Post subject: Re: Economy Biasing
Posted: Thu Mar 15, 2018 5:05 pm
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That’s pretty cool there mud, I’ve been wondering if Measuring plate voltage was possible with my probe.

When you turn the bias pot, it effects not only plate current, but it also changes the plate voltage.

So my question now is, which setting does one go with? the plate voltage, or the plate current? Because changing one effects the other.

:? Needless to say, I’m a bit confused here.


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Post subject: Re: Economy Biasing
Posted: Thu Mar 15, 2018 6:11 pm
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No worries Blue Notes, the Plate voltage only varies by a few volts when adjusting bias. You can stick with the initial Plate voltage reading when doing the math.

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Post subject: Re: Economy Biasing
Posted: Thu Mar 15, 2018 10:30 pm
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Economy Biasing?
Sometimes you can buy new tubes and just put them in. If it sounds good, it's ok with me. What did people do years ago.

Amps like a Pro Junior, Blues Junior, and the original Blues Deluxe don't have a Bias-Adjust. If that's the case, why measure anything. Adjusting a fixed bias amp is more work. And then you have to have the right Bias socket for the tube type, EL84 and 6L6. I'd say it's always a good idea to measure Bias.

edited


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Post subject: Re: Economy Biasing
Posted: Fri Mar 16, 2018 1:49 pm
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I’m kind of cheap too when it comes to gear maintenance, but how often do you need to bias an amp? Why not bring it to someone who has the right tools and have them give it the once-over anyway? IMO either commit to buying the right tools and getting the right training, or take it to a professional.

Like Mr. Miyagi said, “Walk on road, hm? Walk left side, safe. Walk right side, safe. Walk middle, sooner or later, get squish just like grape”.


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Post subject: Re: Economy Biasing
Posted: Wed Mar 21, 2018 6:33 am
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Talked to George Alessandro Of (Alessandro High End Products) yesterday about biasing, and he said plate current is all you need.

Why else would he, the guys at Eurotubes, Tube Amp Doctor, Bias Rite, and a whole slew of others say this if it wasn’t true? They also provide instructions to just check the plate current, and that’s it, you’re done, you have just biased your amp.


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Post subject: Re: Economy Biasing
Posted: Wed Mar 21, 2018 7:23 pm
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Why? Well, they do sell tubes .... :wink:

As mother used to say; “if everyone else was jumping off a bridge, does that make it right?” :lol:

Point being, you can assume, or you can be sure. Which is better?

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Post subject: Re: Economy Biasing
Posted: Thu Mar 22, 2018 9:01 am
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Biasing your amp by just checking, and adjusting the plate current is not assuming, it’s just as accurate as anything else you can do.


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Post subject: Re: Economy Biasing
Posted: Thu Mar 22, 2018 1:34 pm
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Blue Notes wrote:
Biasing your amp by just checking, and adjusting the plate current is not assuming, it’s just as accurate as anything else you can do.


No, it's not. If your amp is healthy, it'll put you somewhere between 60~70% plate dissipation. "Good enough."

But you can't tell if it's closer to 60%, or closer to 70%.


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Post subject: Re: Economy Biasing
Posted: Thu Mar 22, 2018 2:30 pm
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The problem with the Plate-Dissipation method is that I think the equation is wrong. According to Justin Holton, (see link) modern 6L6GC tubes are not that good and really don't meet the 30 watts spec, maybe 25 watts. (ok, I take this statement back, no matter what Justion thinks. You have to assume some wattage, so let it be 30 watts for 6L6's).

http://hotroddiy.com/Biasing-Thoughts-Advanced.pdf

He mentions to bias by ear. But whos got a trained ear? Not me. So then its back to plate current (not cathode).
For me, if it sounds good an you knows your dissipation is ok ballpark, within range, why not go with it. I also like Fenders spec, 60 mv at the Bias test point. Unless you find the sweet spot given a set of tubes, which also may vary between matched sets.


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Post subject: Re: Economy Biasing
Posted: Thu Mar 22, 2018 4:33 pm
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strayedstrater wrote:
Blue Notes wrote:
Biasing your amp by just checking, and adjusting the plate current is not assuming, it’s just as accurate as anything else you can do.



strayedstrater wrote:
No, it's not.

It is for me, to each his own.

If your amp is healthy, it'll put you somewhere between 60~70% plate dissipation. "Good enough."

No, it’s all good.

But you can't tell if it's closer to 60%, or closer to 70%.

It doesn’t matter, it’s never gonna be perfect. There’s no since in being a fanatic about it, you’re just wasting your time.


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