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Mesa M9 Carbine Power Reduced?
- Thread starter Fawkesguy
- Start date
Jim Carr
Dr. Jim
- Jan 21, 2006
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- fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
I have used my fdeck ver.3 a few times with the 15/6/1 and M9. Since I am playing an EADG 4-string at standard A440 tuning, there is no musical program below 41.2034, only noise—the transients and stray stuff that comes along with 1930's electrical music technology.
With the F band set a bit above 30hz, I don't hear any difference, and since I don't need to turn up the bass, anyway, the HPF is probably moot for that situation—can't really hurt, though, LOL!
With the F band set a bit above 30hz, I don't hear any difference, and since I don't need to turn up the bass, anyway, the HPF is probably moot for that situation—can't really hurt, though, LOL!
svtb15
Inactive
- Mar 22, 2004
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- I play it all. Whatever works for the gig. Q+
Its actually a better part.. More current handling ability etc... I guess i did not clarify. I did not mean mesa had a different manufacturer.. Mesas are made in Petaluma CA... What I meant was, it appeared that the MOSFETS on the power board are from a different manufacturer than the older BU901 type...
Just a newer and higher rated updated part.....
Just a newer and higher rated updated part.....
svtb15
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- Mar 22, 2004
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- I play it all. Whatever works for the gig. Q+
!!!Sure they are. But when a manufacturer makes a, for example, BUZ901 MOSFET its made to certain specs, specific to those of BUZ901. These are for instance, Id=8A, Pd=125W, Rds=1.5ohm and Vds=200V.
So either its matching those specs or its a different device alltogether, like BUZ901D, which is rated twice as high on regards of current and power dissipation.
It's the same as with tubes. A 12AX7 has some standard characteristics and specs whether its made by Matsushita, Sovtek, JJ or whatever.
So looks like I need to ask the question again: What MOSFETs do the TransClass amps use? The manufacturer is of no importance. There are thousands of semiconductor factories across the globe.
Jim Carr
Dr. Jim
- Jan 21, 2006
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+1
I do use mine for upright, but find the tech 21 paradriver DI better (for me) because I can do EQ while leaving whatever combo I'm handed set "in neutral."
I know how to dial-out honk, boom, quack, etc. Now if I could only dial-out the parts where I loose my place in the chart!
Jim Carr
Dr. Jim
- Jan 21, 2006
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- fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
Sincere question: Assuming we have the answer to your query, what will that tell us about the power of the 10 or 8 MOSFET-equipped Mesa M9?
svtb15
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- Mar 22, 2004
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- I play it all. Whatever works for the gig. Q+
IIRC the Transclass does not matter what type of Mosfets BU901 or the Newer high ouput type or the quantity... 12 vs 10... vs 8
There are 10 mosfet Transclass M9s and 8 mosfet Transclass M9s.. Transclass is only the term/name that Mesa uses for their (assuming Trade Marked ) topology.
The quantity or manufacturer of the mosfets do not affect the Transclass or Mpulse cicuits .
There are 10 mosfet Transclass M9s and 8 mosfet Transclass M9s.. Transclass is only the term/name that Mesa uses for their (assuming Trade Marked ) topology.
The quantity or manufacturer of the mosfets do not affect the Transclass or Mpulse cicuits .
- Feb 12, 2006
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- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Before jumping on the "counting the transistor" bandwagon, it should be noted (in general) that the number of devices depends on the class of device itself, the type of circuit, the output rating of the amp, how this is achieved and the thermal efficiency of the electro-mechanical package.
As I am not familiar with the specific circuit in these amps, the following examples illustrate the variability that might be possible:
1. The operating class of the amp is an important one, a class H amplifier might require only 1/2 (or less) output devices to achieve rated power compared with an identical amplifier that's class AB. If there's a pair of higher current commutating switch transistors, it's likely class H.
2. With class G, it's also likely that there will be fewer output transististors, because like in class H, the increase in thermal efficiency reduces the stresses on each device.
3. With MOSFETS, there will generally be fewer output devices than in a bi-polar design because MOSFETS do not need to be derated for second breakdown like bi-polars.
4. Differences in power supply voltages can also be responsible for thermal loads, and especially with MOSFETS, it is sometimes much better thermally to operate the drive section of the amp at a higher voltage to overcome higher gate voltage offsets. This will not be obvious to an untrained eye.
5. Mounting of the devices also make a difference. For example, in a grounded bridge design (like Crown and QSC non-class D products), the ability to directly mount the device (collector is always attached to the case) to the heatsink without a voltage insulating, thermally conductive interface eliminates a lot of losses that must be accounted for in other designs.
So here are 5 possibilities, and there are others as well, that could account for differences.
So, the answer to "how many output transistors are necessary?" is enough to get the job done reliably for the particular circuit that is being implimented.
As I am not familiar with the specific circuit in these amps, the following examples illustrate the variability that might be possible:
1. The operating class of the amp is an important one, a class H amplifier might require only 1/2 (or less) output devices to achieve rated power compared with an identical amplifier that's class AB. If there's a pair of higher current commutating switch transistors, it's likely class H.
2. With class G, it's also likely that there will be fewer output transististors, because like in class H, the increase in thermal efficiency reduces the stresses on each device.
3. With MOSFETS, there will generally be fewer output devices than in a bi-polar design because MOSFETS do not need to be derated for second breakdown like bi-polars.
4. Differences in power supply voltages can also be responsible for thermal loads, and especially with MOSFETS, it is sometimes much better thermally to operate the drive section of the amp at a higher voltage to overcome higher gate voltage offsets. This will not be obvious to an untrained eye.
5. Mounting of the devices also make a difference. For example, in a grounded bridge design (like Crown and QSC non-class D products), the ability to directly mount the device (collector is always attached to the case) to the heatsink without a voltage insulating, thermally conductive interface eliminates a lot of losses that must be accounted for in other designs.
So here are 5 possibilities, and there are others as well, that could account for differences.
So, the answer to "how many output transistors are necessary?" is enough to get the job done reliably for the particular circuit that is being implimented.
- Mar 8, 2011
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- Authorized greenboy designs builder/Owner of BNA Audio
My fDeck is permanently strapped to the tailpiece of my Upright. Never even tried it on electric! I got it more for impedance reasons, but the HPF is kinda nice at times. I keep the HPF at around 40hz on upright, sometimes higher on the tricky rooms. Ran it for some gigs with a FEARLESS F115 and my M9. Not a jazz upright sound by any stretch. Big and tanky , and can be super aggressive. Things you don't expect from an upright at all . Very rock and roll. Lately, I'm using a Michael Pope MPP2 and power amp for a more trad thing, but as soon as my F212 gets finished, I'm going back to the M9 for awhile
svtb15
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- Mar 22, 2004
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- I play it all. Whatever works for the gig. Q+
Great post agedhorse. To be more specific though..
This applies only to lateral MOSFETs, and lateral MOSFETs specifically in circuits that operate the devices in linear region (class A, B, AB, C, H, G). However, it is extremely common to see vertical MOSFETs used in circuits that were obviously designed for lateral ones. Why? Because vertical MOSFETs are much cheaper and common than lateral ones. BUZ901/906 are, thank god, lateral MOSFETs as the Mesa design is obviously either class AB or H/G. In fact, I'm pretty sure it's plain class AB like the former SSP.
The very same negative temperature coefficient that protects MOSFETs from thermal runaway in linear circuits may actually result to thermal runaway in switching circuits (e.g. class D and derivates). Switching circuits work better with vertical MOSFETs.
It will tell nothing about power. I'm more interested in other issues. We know that a former design used twelve MOSFETs to reliably produce 600 watts of output power. If they still use the same MOSFET type but just a lesser amount of them we know the design is no longer as reliable due to reasons stated in one of my earlier posts. If they chose more robust MOSFETs for the task then it's of course a different matter. Mainly I'm interested to know whether this was really a reliability mod or a penny pinching mod. It's not like Mesa's been extremely honest with us so far so at this point I'm willing to expect just about anything from them.
This applies only to lateral MOSFETs, and lateral MOSFETs specifically in circuits that operate the devices in linear region (class A, B, AB, C, H, G). However, it is extremely common to see vertical MOSFETs used in circuits that were obviously designed for lateral ones. Why? Because vertical MOSFETs are much cheaper and common than lateral ones. BUZ901/906 are, thank god, lateral MOSFETs as the Mesa design is obviously either class AB or H/G. In fact, I'm pretty sure it's plain class AB like the former SSP.
The very same negative temperature coefficient that protects MOSFETs from thermal runaway in linear circuits may actually result to thermal runaway in switching circuits (e.g. class D and derivates). Switching circuits work better with vertical MOSFETs.
It will tell nothing about power. I'm more interested in other issues. We know that a former design used twelve MOSFETs to reliably produce 600 watts of output power. If they still use the same MOSFET type but just a lesser amount of them we know the design is no longer as reliable due to reasons stated in one of my earlier posts. If they chose more robust MOSFETs for the task then it's of course a different matter. Mainly I'm interested to know whether this was really a reliability mod or a penny pinching mod. It's not like Mesa's been extremely honest with us so far so at this point I'm willing to expect just about anything from them.
There were certainly considerable reliability issues before the change. Based on my interactions with Mesa to date and the overall build quality of their gear, I personally believe there was no "pinching" involved here. One can draw one's own conclusions.
- May 20, 2000
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- Endorsing Artist: Aguilar Amplification, Spector, Dingwall, Tech 21 NYC, Darkglass
Which fdeck is everyone using on electric bass and how can you tell if it would be useful in your set up?
Jim Carr
Dr. Jim
- Jan 21, 2006
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I have a used ver. 3, and am happy with it. I use it when I am slapping a lot, or running the M9 very loud with my conventional cabinets. It seems to make little difference with my 15/6/1.
- Feb 12, 2006
- 61,010
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- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
My example, of course, considered that the amp used lateral devices. An Rds On of 1.5 ohms would make for a terribly inefficient switching device even if nothing else were considered.
IF all else were idenical, 10 devices might be slightly more reliably than 8 devices, but that's a very large assumption IMO. There's also the increased drive requirements of the additional devices that must be factored into the driver capabilities so depending on the drive circuit it could be more or less reliable. I suppose the best answer is "it depends".
I have quite a bit of experience with lateral MOSFETS in audio applications. It's one school of design that has merits but I can also think of merits that bi-polar devices (my own personal preference) have as well so it's really "horses for courses"... so to speak.
IF all else were idenical, 10 devices might be slightly more reliably than 8 devices, but that's a very large assumption IMO. There's also the increased drive requirements of the additional devices that must be factored into the driver capabilities so depending on the drive circuit it could be more or less reliable. I suppose the best answer is "it depends".
I have quite a bit of experience with lateral MOSFETS in audio applications. It's one school of design that has merits but I can also think of merits that bi-polar devices (my own personal preference) have as well so it's really "horses for courses"... so to speak.
Good observation. I found this to be true when trying out some different preamp EQ curves. Testers tend to describe a brighter sound as "faster" and a more rounded tone as "slower", or more "tube like".
I would have to agree with this, as well. Mesa seems to have made the right choice here. No matter how well Mesa handles things it's just not possible to make everyone happy. IMO, as long as the amp is performing well for you and has adequate power, there so be no reason to be upset that they have lowered the specs on the amp. If it's worked for you up to this point, I'm sure it will continue to do so.
- Feb 12, 2006
- 61,010
- 5
- 220,847
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
I think there are some assumptions being made about heat that I'm not sure are warranted. Good thermal design is not rocket science by any means, but does take some understanding with regards to appropriate approach. I have designed several proven high reliability, high powerd 2 ohm power amps and frankly it's just good basic engineering.
Armchair critique of another engineer's work is a whole heck of a lot easier than doing the actual work yourself. Nobody here knows what issues the amp might have had, nor the reasons the engineering team made the original choices they made and any specific revisions that might have deemed necessary or desireable along the way.
Look at the history of any company and their product lines in general and I think it's pretty clear which companies get it and which ones don't. I always appreciate and repsect those that do.
Armchair critique of another engineer's work is a whole heck of a lot easier than doing the actual work yourself. Nobody here knows what issues the amp might have had, nor the reasons the engineering team made the original choices they made and any specific revisions that might have deemed necessary or desireable along the way.
Look at the history of any company and their product lines in general and I think it's pretty clear which companies get it and which ones don't. I always appreciate and repsect those that do.
