wrong bias setting on a dual rec... PLEASE HELP

[jehu]

what are the effects on the amp when this happens?!? i had 6L6's & somehow i THINK i failed to have it on the right bias setting. what does that do to your amp?!?

thanks

 

[siggy14]

Well if you had 6L6's in and you had it on the EL34 posistion more then likley the bias was really high and could have burned out your shortened the life of your output tubes by alot. Now as long as they didnt blow then your amp should be fine for the most part.

Also if the 6L6's you had were very low, then it is possible the EL34 mode did absolutly nothing, currently i am running 6L6's with a very low draw in the EL34 mode on my recto. What this does is bring the bias up to where it should be, which should be around 40 to 45Ma's.

what are the effects on the amp when this happens?!? i had 6L6's & somehow i THINK i failed to have it on the right bias setting. what does that do to your amp?!?

thanks

 

[jehu]

nothing blew. and the 6L6's were definitely old, like from the late 60's probably & well used. thanks for putting my mind at ease Siggy.

 

[disassembled]

Mesa amps are biased in a fairly safe range so running in the EL34 was probably a nice "warm" setting for the 6L6's. Like siggy said no harm no foul so you should be good to go. If I were you I would get a bias meter to make sure the tubes you are using are matched and are operating at the proper current levels.


Greg

 

[jehu]

Mesa amps are biased in a fairly safe range so running in the EL34 was probably a nice "warm" setting for the 6L6's. Like siggy said no harm no foul so you should be good to go. If I were you I would get a bias meter to make sure the tubes you are using are matched and are operating at the proper current levels.


Greg

great idea. i appeciate the suggestion. how much does a bias meter run?!? im gonna assume it can be purchased at most decent electronics stores, such as radioshack.

thanks.

 

[FPFL]

siggy says, "up to where the bias should be"

Should be? I had no idea it was wrong from the factory. Bias is just like tone, the only wrong settings are either -

1. The ones you don't like
2. The ones that blow your tubes

Everything else is tube salesman talk. I love the now common thinking that Mesa are "too cold" from the factory. Hysterical. One of the most popular amp companies in the world just can't get it right! Thats why they overcompensate by nailing it to a certain setting - they don't believe in themselves. Ha!

I love that they are set and if you buy tubes from them you'll know they are a good match. Of course you can buy tubes from others too. It isn't like a computer company made it and only lets their own stuff in.

-P

 

[Boogiebabies]

siggy says, "up to where the bias should be"

Should be? I had no idea it was wrong from the factory. Bias is just like tone, the only wrong settings are either -

1. The ones you don't like
2. The ones that blow your tubes

Everything else is tube salesman talk. I love the now common thinking that Mesa are "too cold" from the factory. Hysterical. One of the most popular amp companies in the world just can't get it right! Thats why they overcompensate by nailing it to a certain setting - they don't believe in themselves. Ha!

I love that they are set and if you buy tubes from them you'll know they are a good match. Of course you can buy tubes from others too. It isn't like a computer company made it and only lets their own stuff in.

-P

I agree about the tube salesman pitch, but Mesa's from the factory are shipped with the bias set to -51 volts. Since this value does not change, it is the tube that draws whatever bias it can from -51 volts. Most Mesa tubes will draw between 17-25ma of bias. In laymans terms this is considered cold, but the amps are loud with good headroom. Settings of 11 to 17ma will produce a crossover distortion, but this is not necessarily a bad thing. If you run the power amp open the rise in current will eventually reach a point in plate dissipation thats not so grainy. Mesa's are designed around this principle. A set of Mesa STR-415's only draws -22ma at -51 volts at 483 plate volts. A GT 6L6GE # 6 draws -22ma. You can call them cold, but they sound incredible. Even adding a bias pot to a Rectifier, IMO is a waste of time. Once you get to -40ma the amps turn to mush. You get to the point where you realize that the biasing of a Mesa at 75% MPD it sounds like a blanket was thrown over the cabinet. I have enough amps that I can sit around all day and play with the tones from different bias settings, but it is just an eventual realization that a good Mesa or GT tube will do the trick. If you want a faster interaction with the power amp, use a Mesa Grey, Blue or White. A GT, especially the American made, a 3-5 will warm the amp up a bit. You have to account for the fact that not every tube amp owner has the ability to take a plate voltage reading and adjust a bias pot. There is absolutely a reason that Mesa's ship with colder tubes. If you sell 10,000 DR's in a year, it's cheaper to replace a tube than a $150 output transformer. The moral is, you can spend a week trying bias settings, or you can just pop some tubes in and play. Once you let the bias bug, you spend more time thinling about every other detail except playing. My method is to leave the Mesa's at a factory bias and use tubes that get me between -20 to -35ma for Simul's and Rectifiers. For my adjustable amps, I never go over 50 % MPD. 75% just drops your headroom and compresses way too quick. Mesa's are about preamp gain and the power amps are just an extention to amplify it. Altering the power section to the point where you leave too little room left for your tube to blossom, you're basically making your amp sound like a dark, flubby amp with a side of suck. I can attest that if you run a tube in a DR at -17ma, if you run with the loop master on and raise the master volume while lowering your preamp output, a cold tube will still offer you sustain and a very pleasant feedback.

Just remember if your a Simul owner, the outer tubes draw much hotter, just like the current Road Kings so you may want to find an EL-34 that does not run too hot. A green or blue would get you within the ballpark where you want to be.

 

[siggy14]

Actually if you know anything about electronics then you will know about crossover distortion and when a amp is biased to low you will get it! and yes crossover distortion is not good.

What are peoples main complaints about the rec's, to flubby of a bottem end, well guess what, that has alot to do with the low bias, as well as other factors.

There are reasons randall smith designed the rec's with low bias, alot of it has to do with fact that he wants to keep them "maintance" free and with in the limites of not having to worry about if a certain tube will go out of those exceptible boundries.

Also if you have a low bias amp the tubes will last alot longer. Now think about it, most people that are going to buy a dual rec are kids, who one cant afford to keep buying tubes, so hell yeah give me a amp with plenty of pre amp distortion and that i dont have to replace the tubes to often!

Mesa has also realized now that alot of people are going for the power amp distortion, the new rec's they are rolling off the line now have a higher bias then the dual rec's made over the past 15 years.

siggy says, "up to where the bias should be"

Should be? I had no idea it was wrong from the factory. Bias is just like tone, the only wrong settings are either -

1. The ones you don't like
2. The ones that blow your tubes

Everything else is tube salesman talk. I love the now common thinking that Mesa are "too cold" from the factory. Hysterical. One of the most popular amp companies in the world just can't get it right! Thats why they overcompensate by nailing it to a certain setting - they don't believe in themselves. Ha!

I love that they are set and if you buy tubes from them you'll know they are a good match. Of course you can buy tubes from others too. It isn't like a computer company made it and only lets their own stuff in.

-P

 

[jbird]

nothing blew. and the 6L6's were definitely old, like from the late 60's probably & well used. thanks for putting my mind at ease Siggy.

I'll accept the above post! Most of it anyways? What gets me is the disregard towards putting unknown, old tubes in; "Like from the late 60's probably, & well used"! And now someone's worried about the well being of they're amp? I tell you what, go get a meter, and start poking around in there! With the disrespect you have towards an instrument made to last forever, maybe you'll get a little jolt of reality! How 'bout not treating your amplifier like a toy! :roll:

 

[siggy14]

Some what true on your statements.

But i disagree about the bias at 40 will not sound good. I have a set of tubes in my rackrecto running in EL34 mode that are at about 40 to 45 MA and the amp sounds great! Better then any recto ever did when the bias was to low.

siggy says, "up to where the bias should be"

Should be? I had no idea it was wrong from the factory. Bias is just like tone, the only wrong settings are either -

1. The ones you don't like
2. The ones that blow your tubes

Everything else is tube salesman talk. I love the now common thinking that Mesa are "too cold" from the factory. Hysterical. One of the most popular amp companies in the world just can't get it right! Thats why they overcompensate by nailing it to a certain setting - they don't believe in themselves. Ha!

I love that they are set and if you buy tubes from them you'll know they are a good match. Of course you can buy tubes from others too. It isn't like a computer company made it and only lets their own stuff in.

-P

I agree about the tube salesman pitch, but Mesa's from the factory are shipped with the bias set to -51 volts. Since this value does not change, it is the tube that draws whatever bias it can from -51 volts. Most Mesa tubes will draw between 17-25ma of bias. In laymans terms this is considered cold, but the amps are loud with good headroom. Settings of 11 to 17ma will produce a crossover distortion, but this is not necessarily a bad thing. If you run the power amp open the rise in current will eventually reach a point in plate dissipation thats not so grainy. Mesa's are designed around this principle. A set of Mesa STR-415's only draws -22ma at -51 volts at 483 plate volts. A GT 6L6GE # 6 draws -22ma. You can call them cold, but they sound incredible. Even adding a bias pot to a Rectifier, IMO is a waste of time. Once you get to -40ma the amps turn to mush. You get to the point where you realize that the biasing of a Mesa at 75% MPD it sounds like a blanket was thrown over the cabinet. I have enough amps that I can sit around all day and play with the tones from different bias settings, but it is just an eventual realization that a good Mesa or GT tube will do the trick. If you want a faster interaction with the power amp, use a Mesa Grey, Blue or White. A GT, especially the American made, a 3-5 will warm the amp up a bit. You have to account for the fact that not every tube amp owner has the ability to take a plate voltage reading and adjust a bias pot. There is absolutely a reason that Mesa's ship with colder tubes. If you sell 10,000 DR's in a year, it's cheaper to replace a tube than a $150 output transformer. The moral is, you can spend a week trying bias settings, or you can just pop some tubes in and play. Once you let the bias bug, you spend more time thinling about every other detail except playing. My method is to leave the Mesa's at a factory bias and use tubes that get me between -20 to -35ma for Simul's and Rectifiers. For my adjustable amps, I never go over 50 % MPD. 75% just drops your headroom and compresses way too quick. Mesa's are about preamp gain and the power amps are just an extention to amplify it. Altering the power section to the point where you leave too little room left for your tube to blossom, you're basically making your amp sound like a dark, flubby amp with a side of suck. I can attest that if you run a tube in a DR at -17ma, if you run with the loop master on and raise the master volume while lowering your preamp output, a cold tube will still offer you sustain and a very pleasant feedback.

Just remember if your a Simul owner, the outer tubes draw much hotter, just like the current Road Kings so you may want to find an EL-34 that does not run too hot. A green or blue would get you within the ballpark where you want to be.

 

[Restless Rocks]

I can only be thankful and humbled that Randall Smith came to the realization (or revelation), that in designing guitar amplifiers worthy of the worlds most competant and innovative musicians, would also have to make them childproof. Does John Pettruci worry most about how many milliamps of current his tubes are drawing or if his pick is still sharp, or either?

 

[disassembled]

[/quote]

great idea. i appeciate the suggestion. how much does a bias meter run?!? im gonna assume it can be purchased at most decent electronics stores, such as radioshack.

thanks.[/quote]

No it cannot be purchased at places like radioshack. Weber makes a device called the Bias Rite which makes for a safe way to check the bias and even the plate voltage.

You can do this with a multimeter but it just gets a bit more dangerous.


Greg

 

[disassembled]

I can only be thankful and humbled that Randall Smith came to the realization (or revelation), that in designing guitar amplifiers worthy of the worlds most competant and innovative musicians, would also have to make them childproof. Does John Pettruci worry most about how many milliamps of current his tubes are drawing or if his pick is still sharp, or either?

There are many manufacturers that share the same view as Mr Smith. I used to be an mA junkie (i had to rebias everything because I was told it would sound best that way) but to be honest the only amp that I felt ever benefitted from it was a Peavey Triple XXX head which gained some volume but the tone remained similar to what it was when I first got it.

I still like to tinker and still am curious as to what the % of MPD the tubes are running at but I no longer am stuck on the mindset that it HAS to be at this number or that number. Part of the fun of tube amps for me is the fact that this maintenance affects the longevity and performance of the amp (kind of like tuning a car for max power, gas mileage, and drivability, etc to get the most out of it) but I would not recommend the masses dive into their favorite tube amp since the risk is pretty great for personal injury and IMO isn't worth the small gains you possibly might incur.

These topics usually have firm believers on 1 side or the other and those that are stuck in the middle that listen to the first credible source they encounter (either their favorite tech, Mesa rep, tube distributor, etc) without even researching any of the facts before they get diahrrea of the keyboard and spread misinformation to countless people.

The fact of the matter is: if you want to run your tubes at 75% of MPD then go ahead if it keeps you happy. There's nothing wrong with it as long as you like it. Finding the right tone is a journey that is never ending for some so experimentation is a must in some cases.

Just my .02 cents

Greg

 

[Restless Rocks]

I too am one to experiment. I have come to realize one thing which is: when I'm here in my shop/ music room/ studio, it may be possible to actually hear the very subtle differences in the perceived sound of different tubes and minor bias settings. I truly love my 60's telefunken 12AX7's for example. But when I'm on a stage next to a loud drummer and his cymbals and a bass player and his cranked SVT with the sound man (and their usual preconceived notions of what your guitar should sound like) I am certain that I could not tell the difference in a set of Mullards or something that came from Radio Shack. Therefore my biggest concern is reliability and consistency. So I keep my valuable vintage tubes here at the house for those times when I can truly enjoy them and not worry about one of them taking a dump in the middle of a song in front of an audience. Randall and Mike and the boys must have known that those of us who use these amps in performing situations would feel releived in NOT having to worry about our amps and be able to focus on what kind of noise our fingers were making come out of them.

 

[Russ]

That is a great place to keep those little treasures. :wink:

 

[siggy14]

There is a difference, but i tend to agree it is subtle. I have always preferred my bias on the warm side, I just do not like it cold, then you start running into problems.

Most people in the 80's biased there marshalls hot, why because it gave them more distortion. But now with amps that create alot of pre amp distortion there is really no need to bias a amp hotter then it should be. LIke i said i prefer mind on the warm side slightly under what the ideal bias should be.

I am glad to hear mesa is finaly shipping the amps with a little hotter of a bias, but still not getting close to the maximum which will probaly put the tubes right where i like them.

I can only be thankful and humbled that Randall Smith came to the realization (or revelation), that in designing guitar amplifiers worthy of the worlds most competant and innovative musicians, would also have to make them childproof. Does John Pettruci worry most about how many milliamps of current his tubes are drawing or if his pick is still sharp, or either?

There are many manufacturers that share the same view as Mr Smith. I used to be an mA junkie (i had to rebias everything because I was told it would sound best that way) but to be honest the only amp that I felt ever benefitted from it was a Peavey Triple XXX head which gained some volume but the tone remained similar to what it was when I first got it.

I still like to tinker and still am curious as to what the % of MPD the tubes are running at but I no longer am stuck on the mindset that it HAS to be at this number or that number. Part of the fun of tube amps for me is the fact that this maintenance affects the longevity and performance of the amp (kind of like tuning a car for max power, gas mileage, and drivability, etc to get the most out of it) but I would not recommend the masses dive into their favorite tube amp since the risk is pretty great for personal injury and IMO isn't worth the small gains you possibly might incur.

These topics usually have firm believers on 1 side or the other and those that are stuck in the middle that listen to the first credible source they encounter (either their favorite tech, Mesa rep, tube distributor, etc) without even researching any of the facts before they get diahrrea of the keyboard and spread misinformation to countless people.

The fact of the matter is: if you want to run your tubes at 75% of MPD then go ahead if it keeps you happy. There's nothing wrong with it as long as you like it. Finding the right tone is a journey that is never ending for some so experimentation is a must in some cases.

Just my .02 cents

Greg

 

[Boogiebabies]

Some what true on your statements.

But i disagree about the bias at 40 will not sound good. I have a set of tubes in my rackrecto running in EL34 mode that are at about 40 to 45 MA and the amp sounds great! Better then any recto ever did when the bias was to low.


I don't see what can be "Some What True" about an opinion. If it was a fact, then I would be lying. This is basically another " Chasing the Dragon" thread on biasing. Now I personally like Bob at Eurotubes, but even having a quad of # 26 6L6's draw -40ma in EL34 mode does not equate to the fact that your amp will not have crossover distortion. Just because the bias is where someone thinks it should be does not guarantee anything. The fact is that your can bias out a certain degree of notch, but you may never truly eliminate it in a Class A/B power section, regardless of your % of MPD. In Class A/B amplifier designs the negative feedback loop has been used to cover up, or mask crossover distortion.
Some people would not know crossover distortion if it was sleeping in their bed with them. Even if you bias using a scope, you can eliminate, or almost eliminate crossover distortion, but you may find yourself running 92% MPD.

There are many opinions, misnomers and just plain untruths about biasing. You can ask 10 amp techs and get 12 different answers.
For tube amp owners who do not understand the entire principal, they are at the mercy of opinions and varying ideals. This is where the bias debate gets people in trouble. If you tell someone your intrpretation on bias, it may be right, or it may be wrong and cause damage. In my previous post I gave a safe opinion to everyone who wants to have a good sounding amp without the fear of damage and does not want to chase the " Dragon" of amplifier biasing.

 

[FPFL]

I'm with BoogieBabies on this one 100%

The gift of Mesa amps is that bias is a complete non issue. Move on, nothing to see here... Remember, there are many more logical ways to adjust your tone that are easy, inexpensive, safe and not permanent.

Messing with the bias on a Mesa to me means you are either bored beyond all sanity and are paying for a mod for no good reason or literally bought the wrong amp for you and are throwing everything and the kitchen sink into making it something it wasn't designed to be.

-P

 

[jehu]

nothing blew. and the 6L6's were definitely old, like from the late 60's probably & well used. thanks for putting my mind at ease Siggy.

I'll accept the above post! Most of it anyways? What gets me is the disregard towards putting unknown, old tubes in; "Like from the late 60's probably, & well used"! And now someone's worried about the well being of they're amp? I tell you what, go get a meter, and start poking around in there! With the disrespect you have towards an instrument made to last forever, maybe you'll get a little jolt of reality! How 'bout not treating your amplifier like a toy! :roll:

get off the high horse. i was using ge 6L6's that were matched pairs, & it ended up sounding great. and it's not disrespect toward my gear if it was an honest mistake.

 

[jbird]

The disrespect I spoke of was'nt about the mistake of forgetting the bias select switch! It was towards the disrespect of trying "old tubes like from the late 60's probably & well used"! Seems a bit experimental, no? But hey, it's your amp, not mine! And you never know, some of those old tubes seem to last forever, and may sound sweet! But, without knowing enough about them, I would'nt just try 'em without a little hesitance. That's all! Can I get back on my high horse now? Thanks!