Anyone Bias There Own Boogie?
- Thread starter CudBucket
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siggy14
Well-known member
Well you can only bias a boogie if you have had it modified with a trim pot. Boogies are fixed bias so buying either one of them would be a waste.
CudBucket said:
Although yes, Mesa uses a non adjustable fixed bias, a bias probe is necessary "insurance" when using Non Mesa tubes, and the only way to monitor bias drift from age.
I know that I for one would want to know what current my tubes are drawing before they red-plate on me at a gig and blow my OT.
Just my .02
Dom
jackieTHEjokeman
Well-known member
What are some reasons for wanting to bias your Mesa? What tonal changes? I'm curious as it may give me one more thing to look forward to.
I Bias all of my Mesa amps. I also place an adjustable pot in the circuit of the ones that I plan on keeping.
I hated my Heartbreaker until I made the bias adjustable and put some JJ's in it. Now it runs like it should.
Most Mesa amps that I've owned or seen are biased really cold. I don't really like that type of tone. To my ears, they sound much better biased a little hotter. They tend to break up a little quicker and sound much warmer to me.
On my DC-5, I installed a Bias Pot and a switch to go between fixed Bais and Cathode Bias. The difference is subtle in the Lead channel, but the Cathode Bias really makes the Clean channel break up nicely without using the Pull Boost function.
I hated my Heartbreaker until I made the bias adjustable and put some JJ's in it. Now it runs like it should.
Most Mesa amps that I've owned or seen are biased really cold. I don't really like that type of tone. To my ears, they sound much better biased a little hotter. They tend to break up a little quicker and sound much warmer to me.
On my DC-5, I installed a Bias Pot and a switch to go between fixed Bais and Cathode Bias. The difference is subtle in the Lead channel, but the Cathode Bias really makes the Clean channel break up nicely without using the Pull Boost function.
KDS
Well-known member
Monsta,
what are you using to set the bias on your amps? Do you install the upgrade yourself? I was checking out the bias rite a while back. I like the idea of running my tubes a little hotter too.
Thanks!
what are you using to set the bias on your amps? Do you install the upgrade yourself? I was checking out the bias rite a while back. I like the idea of running my tubes a little hotter too.
Thanks!
Monsta-Tone said:
I couldnt agree more.I did the same cathode/fixed bias switch on my 2C+,but later removed it.But I would suggest trying some NOS tubes instead of the JJ's.Right now I have a NOS set of JAN/Phillips 7027A's and have had RCA Black Plate 6L6GC's and various other NOS tubes and nothing can compare to the tone of a good NOS tube biased just so.But even a well biased set of current production tubes will be better if you get the bias just right.Siggy14,even without the trim pot in the bias supply a Bias-Rite would not be a waste as you say,one could still check the bias so you would know they are safe.Even though Mesa and others test the bias point of their power tubes,mistakes happen.and even within a certain grade the actual current draw from one set of graded tubes to another can vary enough to change the tone,so when you put in a new set of graded tubes and the amp sounds like ice,you can check the bias and see that they are colder than the last set.Its always good to know what is going on in the amp for many reasons.The bias mod is so easy and inexpensive,a $2 part and ten minutes to replace one resistor,I think it is foolish not to do it.There is so much great tone to be had with the wider selection of tubes out there available if you have this mod.
If I decide that I want to keep the amp, I install a Bais pot.
It is really easy, and it does only replace 1 resistor. Although, on my Heartbreaker, I am planning on adding a Bias pot for each pair of tubes so that I can run EL-34's and 6L6's together or Yellow Jackets and either of the two.
This will not be easy and will require changing the layout of a few parts.
The only way that any amp can be used to it's fullest potential is to be able to experiment with the tube compliment and Bias.
I personally think it is foolish to limit any great amp to just one available option.
It is really easy, and it does only replace 1 resistor. Although, on my Heartbreaker, I am planning on adding a Bias pot for each pair of tubes so that I can run EL-34's and 6L6's together or Yellow Jackets and either of the two.
This will not be easy and will require changing the layout of a few parts.
The only way that any amp can be used to it's fullest potential is to be able to experiment with the tube compliment and Bias.
I personally think it is foolish to limit any great amp to just one available option.
I am with you 110% Monsta.Every tube has a "sweet spot" and the only way to find it is via an adjustable bias.I even use an adjustable cathode bias set up in all my cathode bias amps,this may seem like "overkill" to some,but as the bias drifts with age you can keep it sounding its best longer.The dual trim pot in your Heartbreaker will give you so much versatility,like having 2 amps in one.
Barry
Well-known member
CudBucket said:
Mesa' approach to it is . They believe that you match the tubes to the amp instead of adjusting/biasing the amp to the tubes . i was told this by someone pretty high up the chain at mesa .
Here is how I take it IMO.
All Mesa Boogie's have an identifiable tone, That's what makes a Mark a Mark, or a Recto a Recto. Mesa builds consistent amps, with signature tones. They select tubes for amps like they do resistors, pots, etc. for consistent reliable tone.
Changing the bias, as well as trying different pre-amp tubes is a way to personalize YOUR tone.
Just my .02
Dom
Edit: Does anyone have info on an adj. bias mod for the Roadster? Hopefully mine will be here in 3 wks or so, and I'm sure she'll be a keeper
PM me with an email address and I will see what I can do. I might be able to draw something up for you, but it will take a couple of days. I would very much caution you against working on your own amps, if you do not know what you are doing. At the very least, you could blow the thing up. At the worst, you could kill yourself.
I tend to believe that this is their theory to a certain point. I also believe that they are trying to make the tubes last as long as they can by biasing them cold, meaning that they do not have the optimum bias current going through them.
In my opinion, and several other's opinions, this makes the amps sound cold and lifeless. Much the same way that your car or truck will not run very well if it is not receiving the proper mixture of fuel and air.
If they biased their amps a little hotter, there would be more power tube breakup, and less preamp tube breakup. Also, the tubes would not last as long. Small price to pay for me to be able to get the tones that I am looking for.
This is what it's all about for me. I can't play like Vai, and have no need to sound like him. I can fake EVH all day, but can't get his tones. I would die to achieve some of Gilmour's tones, but can't. Thus, I decided to start modding amps years ago in the hopes that there is an amp out there that will fill all of my needs (present and future), with a little coaxing. Unfortunately, what I've discovered is that I found the woman that suits all of my needs, and I now trade amps like I used to trade girlfriends. It is probably some sort of lame attempt for me to subconciously overcome the fact that I am lazy and don't practice. Plus, it was a way for me to stay in contact with my musician buddies after we had kids and I no longer had the time to play in bars all night.Life is funny, great tone is priceless.
As for Mesa's "approach",I think it is purely a marketing scheme.They tell you their amps have to use their tubes and guys who are not so tech oriented believe it,and they sell more tubes.The tubes are biased on the cold side for safety reasons,if they were to bias them close to optimum and tell people to just plug and play,the tube would have to be spec'd perfectly,if the tube happens to be a little too hot in an amp there is a chance it could fry.If you were to check,lets say,3 or 4 different graded pairs in the same grade range you will find there is a fairly wide range of current draws within the same "match".Lets them avoid rejecting more tubes as well.Another reason they can get away with the colder bias is the fact that the amps distortion is generated in the preamp not the power tubes,in fact if you try to bias a Boogie as hot as you would a Fender type,you will find the lead modes get somewhat "over the top",the clean modes break up real nice like this,but that is not what Mesa is going for in the clean or rythm mode.For me the biggest advantage to being able to bias the amp is the ability to use NOS tubes and bias them to what I consider optimum for power tube saturation,and have no need for that "buzzy" preamp tube distortion.Vendors who sell tubes matched to Mesa's system benefit from this scheme as well,if they sell you a pair of tubes that are going to be used in a "cold" power section,they are fairly confident the tube is going to last longer,lets them sell tubes that otherwise might have to be rejected if they were biased hotter.A power tube that might exhibit microphonics or noises at 45-50ma's will likely be quieter at 25-35ma's.Look,I am not saying the Mesa scheme doesnt work,or is "wrong",and if you like it that is fine,but there are a lot of great tubes out there that you cant use without a bias control.
The problem with just inserting the Bias King or it's equivalent is that you have to know what your Plate Voltage is too.
If you get one, make sure that it reads both Plate Voltage and Bias Current (read in negative millivolts across a 1 ohm resistor). This way you can get the proper ratio.
Simply setting the bias at -35mv per 6L6 may or may not get you there. I would say that more often than not, it is off my a few millivolts.
If you get one, make sure that it reads both Plate Voltage and Bias Current (read in negative millivolts across a 1 ohm resistor). This way you can get the proper ratio.
Simply setting the bias at -35mv per 6L6 may or may not get you there. I would say that more often than not, it is off my a few millivolts.
rabies,the last paragraph in your post is exactly the reason to add the adjustable bias trim pot to a boogie.Sure it is easier to just plug and play as with the mesa tubes,but if you check the bias when using Mesa tubes you will see that 2 sets of tubes in the same grade will often have a difference in the actual current draw,which could make a difference in the tone of your amp.Years ago when I first got my MKIIC+ I tried the mesa tubes the first time I changed the tubes and the new set were 08ma's colder than the old ones,and about 18ma's colder than I would have set them and made the amp cold and brittle.If you are happy with the Mesa tubes then by all means use them,but the adj.bias will give you more variety.rabies said:
Barry said:
Yeah but that doesn't make it right. They are just trying to change the way people think. If you do it like they say then you are in crossover distortion ALL THE TIME. They are just trying to keep Mesa's out on the street and not in the shop to save some penny's. If done correctly then adjustable bias is the only way to go. The fact that the Recto actually changes voltages of plate current when you switch from tube/diode and bold/spongy to me defeats the purpose of having the switches. What if you wanted a correctly biased tube with a tube ac/dc switch and spongy....... Well it isn't going to happen with the fixed bias cicruit because the switches take your bias down and into the crossover distortion. The closest you can get is with EL34s set to diode and bold.........
calaverasgrande
Member
Anyone have any info on installing a bias pot on a Bass 400 or 400+?
I know that it can be done, have seen it mentioned before on the Talkbass forums.
I may either attempt this myself, or pay a tech to do it. Depending on money and time.
I am pretty comfortable with electronics. I work on pedals, PA gear mic pres etc all the time.
I know that it can be done, have seen it mentioned before on the Talkbass forums.
I may either attempt this myself, or pay a tech to do it. Depending on money and time.
I am pretty comfortable with electronics. I work on pedals, PA gear mic pres etc all the time.
Just as easy as any other Mesa.Just look at the schem at Schematic Heaven.You will see the bias supply,there is a resistor from the "D" point to ground,marked "factory select".It isnt clear on the schem what the value is,but it looks like 100k or so.This is the resistor to sub a cermet pot for.I like to use a pot of roughly 2X's the value of the resistor I am changing.The "multi turn" cermet pots are the best,with them you get a much smoother adjustment.Connect one outer leg of the pot to ground then the wiper and the other leg get connected together to the "D" point.
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