Butler Mosvalve

[darthpoodle]

May not be the place for this but asking anyway. I have a Mosvalve poweramp mv-962. It's missing something, that low end thump you get from a tube amp. anyone have any idea on how to add low end. Maybe  a bass switch like the Marshall 20/20. Thanks!

[PRR]

> thump you get from a tube amp

Get a tube amp.

The MV-962 is a transistor amp. Transistors can do about everything tubes can do, but some things tubes do naturally are wickedly hard to do with transistors.

[petemoore]

  Not at all convinced the Mosvalve can't amplify LF's.
 Not at all convinced the speaker and cabinet tend to produce well defined bass either [for having no idea what kinds I'm talking about].
  LF's and 'thump' seems to be more of a speaker/cabinet thing for guitars [mostly] since it's not too hard to get modern amplification to work well below the 6string frequencies with modern amps.
 When a system is asked to produce low freqencies fails to impress, the first questions should bring the cabinet and speaker into suspicion.
 Otherwise, I have a Mosfet Pyramid amplifier, it has no troubles at all producing deep/defined bass. Also LM3886 amps that 'thump'.
 Knowing something about the amp and speaker [wattage of amp, effeciency of speaker, LF ratings etc.] would allow better than likely guesses.

[PRR]

The amp can make bass fine.

The amp-speaker interaction is tricky, and critical around speaker bass resonance: "thump".

It's possible to design an under-damped transistor amp, but Darth's observations say this one is highly damped. No easy/good way to change this after it is built.

Transformer effects may also play a part.

[Johan]

if you look at Marshall's JCM2000 serises, wich is of course a tubeamp, they have a "deep" switch wich is basicly a resonance filter introduced to the feedback loop.
it gives real massive low end.
perhaps something similar could be aplied to you solid state amp?...

http://www.schematicheaven.com/marshallamps/jcm2000_100w_dsl100.pdf  the middle circuit page 1, is introduced to lower left corner page 2

to even know if it's possible, you would need a copy of the schematic for the mosvalve, but perhaps this cold give you an idea..

be warned thou..solidstate amps are not forgiving at all towards tinkering..
J

[Caferacernoc]

Actually you can easily lessen the damping factor so it has the the interaction with the speaker like a tube amp. Just add some series resistance:

1ohm for a little of the effect. Up to 8ohms, or whatever your speaker is rated at, for a lot.

[PRR]

The series resistance to get "tube damping" is high enough to lose a LOT of power, 1/2 to 1/4.

[Caferacernoc]

The series resistance to get "tube damping" is high enough to lose a LOT of power, 1/2 to 1/4.

Good thing he has 80 watts times 2!       

[dschwartz]

sounds to me like a damping issue. ..easiest way to fix it is ti put an EQ on the fx loop and boost the 100Hz feqs about 6-8dB....

Of course if you are using 8 or 10 inches speakers, there´s not much you can do