Why don't more amps have bias indicators like the Engl SE?

[indespise]

I don't know if these are a bad idea from a technical standpoint, but from what I can tell it seems like more modern tube amps should have this feature. Is this a difficult feature to design into an amp?

 

For thos ewho don't know what I'm talking about, the SE has LED indicators that you can use to test the bias of each power tube, which in theory should make swapping tubes as easy as sticking new ones in and turning the bias pot until the LED comes on (if I've got that straight).

 

External bias test points were a great idea, but if there aren't any problems with it, this design (the SE's bias LED's) trumps them completely.

[MTDP8350]

Don't know, great point though.

[cloudnine]

But what is a "good" bias? It changes from person to person. The LED coming on would simply give you the manufacturer's idea of a good bias, and as we know in cases like the {censored}ty one {censored}ty the manufacturer is not always correct in what they believe to be the best range.

[Megadeth7684]

Originally posted by cloudnine But what is a "good" bias? It changes from person to person. The LED coming on would simply give you the manufacturer's idea of a good bias, and as we know in cases like the {censored}ty one {censored}ty the manufacturer is not always correct in what they believe to be the best range.

More 5150 bashing...when will you learn 'lil Canadian buddy.

[cloudnine]

Originally posted by Megadeth7684 More 5150 bashing...when will you learn 'lil Canadian buddy.

I'm pretty sure most people agree the 5150's bias from the factory sucks.

[Megadeth7684]

Originally posted by cloudnine I'm pretty sure most people agree the 5150's bias from the factory sucks.

 

 

Not me. I think it's more than fine.

[MTDP8350]

Originally posted by Megadeth7684 Not me. I think it's more than fine.

 

 

+1.

 

Well then again, I've never played on biased one.

[Megadeth7684]

Originally posted by MTDP8350 +1. Well then again, I've never played on biased one.

 

 

I have. I like stock ones more.

[MTDP8350]

Originally posted by Megadeth7684 I have. I like stock ones more.

 

 

heh. Its all taste I guess.

 

I still want another 5150. My damn 15 year old self, noone hires. Oh well.

[Megadeth7684]

Originally posted by MTDP8350 heh. Its all taste I guess. I still want another 5150. My damn 15 year old self, noone hires. Oh well.

[Snakebite20]

Originally posted by cloudnine But what is a "good" bias? It changes from person to person. The LED coming on would simply give you the manufacturer's idea of a good bias, and as we know in cases like the {censored}ty one {censored}ty the manufacturer is not always correct in what they believe to be the best range.

+1

What exactly is "good bias" ?
Manufacturers like Mesa and Peavey (with the 5150) don't want to get problems associated with people changing the bias on their amps, so they make it unvariable. Read Randall Smith's article here:

http://www.mesaboogie.com/US/Smith/biasadjust.html

That article is a pure POS IMO.
It leads the "un techsavvy customer" into believing his crap.

Still, my Mesa doesn't sound bad as it is (stock), but I have plans to screw the whole bias thing and mod the {censored} out of the whole amp as soon as the warranty is over (cause modding voids the warranty).

A MUCH more clever idea than the "bias LED" is to include a bias pot in the back of the amp, so you can tweak your bias while playing to change your tone.

Ultimate control = Ultimate tone

Ohh and BTW, the 5150 and Mesa amps sound good even if biased cold, but I believe they can sound "different" with other bias settings. I didn't say "better", only "different". Many people are satisfied with these amps "as they are".

[JamesPeters]

Originally posted by cloudnine The LED coming on would simply give you the manufacturer's idea of a good bias,

 

 

Also, it won't compensate for different tube types/brands.

 

I do think the LED indicators are a very nice idea though, for the specific purpose intended.

[Snakebite20]

Originally posted by JamesPeters Also, it won't compensate for different tube types/brands.

 

I agree with that statement as long as we assume the LED indicates the bias voltage, but if they did a transresistance transform and actually measure the bias current, then it doesn't matter what tubes are in there as you just have to move the pot a little more to get the same plate current flowing.

[JamesPeters]

Originally posted by Snakebite20 I agree with that statement as long as we assume the LED indicates the bias voltage, but if they did a transresistance transform and actually measure the bias current, then it doesn't matter what tubes are in there as you just have to move the pot a little more to get the same plate current flowing.

 

 

True enough, however some tubes won't want the same current to hit an optimal bias point either. That's more of what I was thinking.

[Snakebite20]

Originally posted by JamesPeters True enough, however some tubes won't want the same current to hit an optimal bias point either. That's more of what I was thinking.

Then I fully agree, as the plate current that is optimal for a certain tube (i.e. make it sound best) is absolutely NOT the same "best current" for every other tube.

Tubes characteristics vary all over the map and this is one of the reasons that advocate in favor of a "musical rebiasing" with each retube, which is impossible to do while taking the LED into consideration.

Unvariable bias supporters can try to debate about this, but the whole point is that the utilmate goal is BETTER TONE period.

And better tone is achieved with optimal bias settings according to each tube sets and each amp (components have tolerances, etc). Of couse, the bias setting must fit into the tube operating range and dissipation, which in return depends on the plate voltage that you have to measure anyways...

So far for the bias LED eh?

[willy22]

What Peters and Snakebite said.

It would also cost more money to add those on.

[indespise]

Originally posted by cloudnine But what is a "good" bias? It changes from person to person. The LED coming on would simply give you the manufacturer's idea of a good bias, and as we know in cases like the {censored}ty one {censored}ty the manufacturer is not always correct in what they believe to be the best range.

 

 

It's designed so you can set it slightly hot or cold according to taste, form what I understand.

[Snakebite20]

Originally posted by indespise It's designed so you can set it slightly hot or cold according to taste, form what I understand.

 

Okay, but what are their references for saying if it's "cold" or "hot" ? See, that's the real problem.

[indespise]

Originally posted by Snakebite20 Okay, but what are their references for saying if it's "cold" or "hot" ? See, that's the real problem.

 

 

I don't know much about biasing form firsthand experience. I need to get the gear and learn.

[AtillaTheHungry]

All you really need is a USB connection on the amp, which you run to your computer, allowing you to use software to adjust the amp's bias.

[Mosby]

Originally posted by Snakebite20 +1 What exactly is "good bias" ? Manufacturers like Mesa and Peavey (with the 5150) don't want to get problems associated with people changing the bias on their amps, so they make it unvariable. Read Randall Smith's article here: http://www.mesaboogie.com/US/Smith/biasadjust.html That article is a pure POS IMO. It leads the "un techsavvy customer" into believing his crap. Still, my Mesa doesn't sound bad as it is (stock), but I have plans to screw the whole bias thing and mod the {censored} out of the whole amp as soon as the warranty is over (cause modding voids the warranty). A MUCH more clever idea than the "bias LED" is to include a bias pot in the back of the amp, so you can tweak your bias while playing to change your tone. Ultimate control = Ultimate tone Ohh and BTW, the 5150 and Mesa amps sound good even if biased cold, but I believe they can sound "different" with other bias settings. I didn't say "better", only "different". Many people are satisfied with these amps "as they are".

I don't think Smith's article is total BS, though not totally right either. I think some of it is a little bit of a jab at the the "You've got to get March '65 NOS Telefunken tubes and then bias just a hair over what legendary amp designer "Bob Blow" does (and you know how he biases his amps, right?)" mentalitly. I also think that too many people treat biasing and tubes as some solve-all problem to {censored}ty tone. Perhaps the bigger problem is not mA's difference in biasing but rather that your bass and treble are at 10, while your mids are at 1. I know a guy who just dropped nearly $500 retubing his $800 amp because he got all NOS tubes. Sure it sounds good, but I'm not sure it sounds that much better then it did before. Bias is not the holy grail of amp tone.....

That said biasing may help you get that extra couple HP out of your amp.

[Mosby]

Originally posted by OneArmedScissors All you really need is a USB connection on the amp, which you run to your computer, allowing you to use software to adjust the amp's bias.

 

 

 

How many amps have USB connections?

[Snakebite20]

Originally posted by Mosby I don't think Smith's article is total BS, though not totally right either. I think some of it is a little bit of a jab at the the "You've got to get March '65 NOS Telefunken tubes and then bias just a hair over what legendary amp designer "Bob Blow" does (and you know how he biases his amps, right?)" mentalitly. I also think that too many people treat biasing and tubes as some solve-all problem to {censored}ty tone. Perhaps the bigger problem is not mA's difference in biasing but rather that your bass and treble are at 10, while your mids are at 1. I know a guy who just dropped nearly $500 retubing his $800 amp because he got all NOS tubes. Sure it sounds good, but I'm not sure it sounds that much better then it did before. Bias is not the holy grail of amp tone.....

 

Well, I never said it was BS at all, just that I think it's a POS article nonetheless.

 

What he says is true and makes sense, but it's the philosophy behind it that tinkers my anger. More precisely the "we, mesa boogie amps, know how you want your tubes to be biased" mentality is something I can't tolerate.

 

Of course, bias mods are NOT the holy grail of tone change I agree with that....but for tone connoisseurs, nothing's better than having FULL control over your amp parameters to find your tone and optimize your amp. Without proper dialing, biasing is useless I agree.

[gibson5413]

Originally posted by JamesPeters True enough, however some tubes won't want the same current to hit an optimal bias point either. That's more of what I was thinking.

 

 

The SE allows you to switch between EL34's and 6L6's and bias according to whichever power section you want. A switch allows the user to switch between both types of power tubes. In most cases, you are right though.

[Deuterium]

My EL Diablo 60-C has it.

The bias test points require a digital multimeter, which is cheap (you can get 'em at any Radio Shack). Plus, the use of the multimeter lets you dial in the bias to the exact number you want (either hot or cold), versus having an LED come on to tell you when it is "good".

Also, the amp comes with a bias switch which allows you to select either EL-34s or 6L6s. The switch must change the plate voltage. So, switching power tubes is easy, breezy!

And yes...more manufacturers should design this feature into their amps.