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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Sun Oct 20, 2013 8:18 pm
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Roadie
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Actually, I bias my own amps and service them. Over the years I've tought myself how to solder, read schematics and use a multi-meter. My amps sound great to me. I realize voltage changes when current changes. I was curious as to how folks bias their amps-hot, cold or medium. This was just a survey. Thanks for everyone's input. Peace


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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Sun Oct 20, 2013 8:31 pm
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DIY is cool, good job! 8)

You are in the right community for great support when you need it, and it helps that you can also take a little ribbing. :wink:

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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Sun Oct 20, 2013 11:29 pm
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Yeah don't sweat it if Bluesky636 comes off a bit abrubt. I actually like the way he is very factual and to the point. That's very helpful when you are trying to fix something.

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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Mon Oct 21, 2013 7:21 am
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Ha. I've done my share of ribbing. Bluesky brought up a good point without realizing it. Does biasing need to be scientific? As long as you're out of crossover distortion and not red-plating the tubes, go for the tone you like. Everyone's ear is different. Look at Buddy Guy around 1970. His amps, including a Magnavox or two were cranked to the point of farting out, but it sounded so sweet with his beat up strat. I used to bump into him regularly at a club in Columbus, Ohio around OSU in the early, mid-80's. I'd pickup my stuph the next day after a gig and he'd be warming up before the next night's show. He would say, "I just turn the knobs till it sounds right and it did. Thanks guys. It was an interesting discussion.


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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Mon Oct 21, 2013 12:50 pm
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bluesky636 wrote:
shimmilou wrote:
63supro wrote:
...let a qualified amp tech work on your amp...


IIUC, he did have an amp tech do the job, and he listened while the tech "adjusted" between 36 and 35. > "My tech, who has 40 years of experience with professional musicians, lets his customers play the amp before he signs off on it." If it was done by a tech, my guess, the tech did nothing at that point, saw the initial reading go from 36 to 35 (normal with new tubes), and asked; "How does it sound now?", and the OP thought he heard a difference. I have done this myself, set it where it should be set and if they think it isn't quite right, pretend to adjust and ask; "How about that?". It's not surprising how many people notice a difference when nothing at all was done. :wink:


I can tell the difference between 50% and 70% of maximum plate dissipation. I doubt I can tell the difference between 68% and 70%. :lol:


:lol: I agree Bill. A difference of 10% maximum plate dissipation is rough to hear any difference let alone 2%. One or two mA difference in bias is just laughable. :lol:

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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Mon Oct 21, 2013 4:45 pm
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+1000 !!!! Art

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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Thu Oct 31, 2013 12:04 pm
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We're getting off topic at my expense, but have your fun. I can take it. :twisted: Say between 50% and 70% dissipation, Where do you set your bias and why-what tonal differences do you notice based on the type of music you play.


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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Thu Oct 31, 2013 12:20 pm
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Krankster wrote:
Say between 50% and 70% dissipation, Where do you set your bias and why-what tonal differences do you notice based on the type of music you play.


I think that question has already been answered.

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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Sun Nov 03, 2013 3:45 pm
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I did get three people give their opinion. Thank you.


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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Sun Nov 03, 2013 6:24 pm
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Late to the party!! Krank, I don't subscribe to the 70% number. Don't know if a guru came down off the mountain and delivered that number??? But I do know an old tech and electronic engineer, told me to set my RCA's(6L6GC) at about 28ma draw, and forget about it!!! I mean, forget about it for years!! Have always gone with his advice. The amps have been healthy and the sound is plenty thick and dynamic. JMO, Art

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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Sun Nov 03, 2013 6:47 pm
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aclempoppi,

That advice is poor/incomplete, or is for a specific Plate voltage in a specific amp. 28 mA means nothing by itself, you also have to figure Plate voltage. For example, a 6L6 at 28 mA in a push-pull amp with 430 Plate volts is under-biased, idling at only 12 watts, which is about 40%.

The 50% to 70% numbers are based on sound electronic principles, not voodoo, and those numbers will always be accurate because they take Plate voltage, Plate current and tube max wattage rating into consideration as part of the equation, so they work for any type of tube in a push-pull configuration.

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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Sun Nov 03, 2013 10:46 pm
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aclempoppi wrote:
Late to the party!! Krank, I don't subscribe to the 70% number. Don't know if a guru came down off the mountain and delivered that number??? But I do know an old tech and electronic engineer, told me to set my RCA's(6L6GC) at about 28ma draw, and forget about it!!! I mean, forget about it for years!! Have always gone with his advice. The amps have been healthy and the sound is plenty thick and dynamic. JMO, Art


I have to agree with shimmilou. Just saying that your amp is biased at 28 mA (28 mA cathode current? If so, plate current is even less.) without knowing plate voltage is meaningless. I suggest you read this and then show it to that "old tech":

http://www.aikenamps.com/Why70percent.html

By the way, at 50% max plate dissipation for a 6L6GC, 28 mA plate current would correspond to a plate voltage of 536 VDC. :shock: At a more typical plate voltage of, say, 450 VDC, 28 mA plate current would equal only 42% of max plate dissipation. That's getting close to, if not already in, crossover distortion territory.

Maybe that "old tech" thought a 6L6GC has the same maximum plate dissipation as an old metal body 6L6.

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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Mon Nov 04, 2013 2:22 pm
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Geeze!!!! That was a comment on the subject not a set of instructions. Art

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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Mon Nov 04, 2013 3:01 pm
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:lol:

Now, go away or we will taunt you a second time! :lol:

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Post subject: Re: How do you like your tubes biased-Hot or Cold?
Posted: Mon Nov 04, 2013 7:42 pm
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aclempoppi wrote:
Geeze!!!! That was a comment on the subject not a set of instructions. Art


????

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