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Identifying mm head


Christer from norway
Posted on Friday, October 08, 2004 - 02:34 pm:   

I bought myself a Music Man head today, but I haven't got the slightest idea what sort of model it is. All the logos are for some reason schratced of, but it has 4 EL34 output tubes, a HI/LO switch in front, 2 channels and bright switch. Could any of you please help me out here?
Steve Kennedy (admin)
Posted on Friday, October 08, 2004 - 05:11 pm:   

Since you did not mention reverb, it is obviously an older (1974-77 approximately) HD-130. 130 watts RMS, speaker output jacks usually connected in series.

Schematics here:

http://www.ernieball.com/mmonline/techin fo/old_amps/2475-130_&_2275-130.pdf


Christer from norway
Posted on Saturday, October 09, 2004 - 05:59 am:   

Thank you for your reply!
It has reverb, and vib channel + a deep switch on the front, and you can change the Ohm setting. Does this change a lot when it comes to dating it?
michael kaus
Posted on Saturday, October 09, 2004 - 02:18 pm:   

Those don't change the dating but does it have a 12ax7 PI tube besides the el34's? The earlier amps had it, the second generation had a SS inverter.
Christer from norway
Posted on Sunday, October 10, 2004 - 08:42 am:   

I can't find any 12ax7 besides the other tubes, so I guess it has the ss inverter. What's the difference? It also has a little rust on the output transformer? The amp makes more noise on the HI setting than on the LO. Is that normal? BTW, when cranked up this amp would kill any ol' Fender amp... I normally don't like hybrid solid state amps, I dont think they react as well to my playing dynamics. Music Man is the exception!
Steve Kennedy (admin)
Posted on Tuesday, October 19, 2004 - 10:38 pm:   

The phase-splitter (or inverter) is the circuit that takes the output signal from the preamp and creates the complementary push-pull drive signal for the output tubes.

The earlier tube phase-splitter had a warmer sound but was not as reliable as the solid-state circuit that followed it. The latter solid-state models were made from about 1977 to 1980.

I would expect a little more noise in the high power setting, but if there is a large difference between High and Low power then I would suspect that the high voltage filter caps might need replacing or you might have a noisy output tube.

I'm glad its working for you... with that model you'll probably get the longest life from the amp by running it in the low power mode most of the time. It is easier on the ears in low power too!