Adjustable Bias

[kramerxxx]

Has anyone had this done to a Dual or Triple Rec?

What did it cost you?

Was it easy to do?

Did you or did a tech do it?

Were you happy with the difference in the sound?

Was it worth giving up on the warranty for?

thanks,

 

[boogieslide]

My Mesa 3 Ch DR is being worked on right now by JerryP. Bias mod is included, but he also putting in a MMOT and changing a few other things. It will be hard to say what changes are just from the bias.
I am doing it so that I can control the bias no matter what quad of 6L6s I put in. That way I can get the bias hotter, but maybe not as hot as running the amp in the EL34 position with 6L6 tubes.
Hopefully I can be a little more helpful soon

 

[kramerxxx]

My DR has the MMOT in it. I had Voodoo do the work. I regret not having the bias pot put in at the same time.

I really like the sound of the amp like it is but wonder if a little hotter range would help.

I typically like the Bold/Silicon setting, which is the Hottest range I can get, with EL34 power tubes. I haven't measured it yet with these tubes but with 6L6's I was in the high twenties for milliamp range, (*I have a Weber BiasRite).

I also like the sound of the lower settings too but I usually run a pedal in front to get the gain/sound I want for lower volumes.

I recently read a post from a guy that had mods done to his 5150 by Voodoo that pushed the amp into a direction he didn't care for, it was too HiFi and no longer had the grind it had before. I'm wondering if it is having the Bias too hot and if just setting that back into the high twenties would give him that rawness he is looking for.

 

[boogieslide]

Did you find a big difference with the MMOT over the stock OT?

I think Voodoo does some of the more drastic mods on amps. I wonder if the guy with the 5150 you are talking about had the mods done himself or if he bought the amp already modded. They do mods to people preference so I would think if he really didn't like it he could send it back...or maybe he didn't give them the right samples/descriptions of what he wanted?

I have a 5150II. They come stock with a bias pot, but its range doesn't allow you to really getting the tubes cooking in the right bias. So when JerryP worked on that amp he increased the range of the pot to allow higher bias. I wouldn't say the biasing adds or takes away the aggressive rawness of the amp, but rather it helps make it warmer and fuller sounding. Helps a lot on the cleans too.

 

[oyster]

I have a 5150II. They come stock with a bias pot, but its range doesn't allow you to really getting the tubes cooking in the right bias. So when JerryP worked on that amp he increased the range of the pot to allow higher bias. I wouldn't say the biasing adds or takes away the aggressive rawness of the amp, but rather it helps make it warmer and fuller sounding. Helps a lot on the cleans too.

Helps make it warmer and fuller sounding? How exactly?

 

[kramerxxx]

The Mercury Magnetics OT adds a sonic richness to the notes that you cannot get by just changing tubes or some of the components in the audio chain.

Imagine you have a 1969 Camero with a 4 bolt main 350 small block with a 2 barrel and a 4 speed. Now imagine replacing the stock exhaust with headers, a 4 barrel carb, and a ported and flowed intake manifold. You haven't changed the top speed of the car but you HAVE changed how responsive the gas pedal is, how quickly it acelerates and the sound you hear with this increase of 'flow' for the engine.

That's what a MMOT will do, it will sound more open and responsive with a more 3-D sound.

I have 2 amps with them installed and they are a great investment.

 

[boogieslide]

I have a 5150II. They come stock with a bias pot, but its range doesn't allow you to really getting the tubes cooking in the right bias. So when JerryP worked on that amp he increased the range of the pot to allow higher bias. I wouldn't say the biasing adds or takes away the aggressive rawness of the amp, but rather it helps make it warmer and fuller sounding. Helps a lot on the cleans too.

Helps make it warmer and fuller sounding? How exactly?

Proper (higher) biasing from the stock biasing gets you out of cross over distortion. Not sure I can explain it any other way than the result is a warmer and fuller sound. On the clean channel specifically it takes away some of the brittle, non-musical break up. On the lead there is less buzz and more musical distortion.
Hope that helps...sometimes you just need to hear it

 

[boogieslide]

The Mercury Magnetics OT adds a sonic richness to the notes that you cannot get by just changing tubes or some of the components in the audio chain.

Imagine you have a 1969 Camero with a 4 bolt main 350 small block with a 2 barrel and a 4 speed. Now imagine replacing the stock exhaust with headers, a 4 barrel carb, and a ported and flowed intake manifold. You haven't changed the top speed of the car but you HAVE changed how responsive the gas pedal is, how quickly it acelerates and the sound you hear with this increase of 'flow' for the engine.

That's what a MMOT will do, it will sound more open and responsive with a more 3-D sound.

I have 2 amps with them installed and they are a great investment.

Have you ever installed one yourself? I wonder how hard it is? I know how to solder and can follow directions and schematics.

 

[Guitarzan]

The Mercury Magnetics OT adds a sonic richness to the notes that you cannot get by just changing tubes or some of the components in the audio chain.

Imagine you have a 1969 Camero with a 4 bolt main 350 small block with a 2 barrel and a 4 speed. Now imagine replacing the stock exhaust with headers, a 4 barrel carb, and a ported and flowed intake manifold. You haven't changed the top speed of the car but you HAVE changed how responsive the gas pedal is, how quickly it acelerates and the sound you hear with this increase of 'flow' for the engine.

That's what a MMOT will do, it will sound more open and responsive with a more 3-D sound.

I have 2 amps with them installed and they are a great investment.

Have you ever installed one yourself? I wonder how hard it is? I know how to solder and can follow directions and schematics.

They are not hard to put in at all. I just recently put one in my JCM 2K DSL 50W. The only thing that baffled me at first was Marshall lables the output of their Drake transformers with numbered connections 1, 2, 3 etc. andMercury Magnetics labels their outputs with Ohm values such as 4, 8, 16. Just be aware of this and you'll have no problems. There is a break in period for the transformer, so your tone may shift slightly (for the better IMO) for the first 40-50 hours of play.

 

[kramerxxx]

I can atest to the breakin too. When I first got my Recto back it sounded better but only a little. I'm not exactly sure of the number of hours but I do know that it started livening up once I was able to crank the volume more than practice levels.

That is worth noting too about these amps of Mesa's. They don't really sound 'good' at lower volumes. Don't get me wrong I'm very happy with the sound I get at low volume but turning it up makes it sound Oh So Much better.

Before the mods the presence of the highs was painful, too brittle and the lows were flubby. Not any more...

 

[boogieslide]

Before the mods the presence of the highs was painful, too brittle and the lows were flubby. Not any more...[/quote]

That is exactly what I wanted to hear, because those are my gripes with the DR.
JerryP seems to be happy with the results and also said it has improved the low end tightness and punch.