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Advice Please : HD 150


Andy Donovan
Posted on Tuesday, September 14, 2004 - 04:37 am:   

Hello all,
I'm after some advice, I've just bought a one fifty HD Head with a 212 one fifty RF Cab,( a real find over here in the UK) I'm using it with my MM Sabre bass (the perfect pair) it sounds great.

I just wondered if its got the right valves in, its has 2 Russian SOVTEC 1885's and 2 usa SYLVANIA 6L6's (are these original?) ....is it OK to mix valves?

I also wanted to get a better idea of what date it was made, I know its between 80-84 heres the
CHASSIS 2100-150, SN A005264
The cab has S14203 stamped on the wooden mount.

Is there any difference between the 212 x130RF and the 212 150RF cabs

Thanks in advance Andy.
Steve Kennedy
Posted on Wednesday, September 15, 2004 - 04:34 pm:   

On the cabinets, I think you mean "RH" style (Reflex Horn). I have never heard of an 'RF" cabinet. These are the MM cabs with the large forward-firing port. The early models had Alnico speakers (the "premium" type of the time).

By the time the 75 and 150 series were made, almost all the speakers MM used were Ceramic magnet units. Ceramic magnets tend to hold their magnetism much longer than the Alnico units.

Th older Alnico units can get noticeably weaker in a shorter period of time. You CAN get them "recharged" if this occurs.

You really ought to have a matched quad of output tubes. This isn't saying it won't run with 2 dissimilar pairs, but the amp will bias and balance out better when all the output tubes match each other, so the amp will be happier and most probably sound better. The output tubes will also tend to age together so imbalances won't be evident as they might with a "mongrel" quad such as what you have.


andy donovan
Posted on Sunday, September 19, 2004 - 10:19 pm:   

Thanks Steve,
Thats a big help, i've ordered 4 Electro Harmonix 6L6's so that should sort things out, I'm getting a man to bias them for me, the USA Valves were a bit pricey.( maybe next time)

As for the date of the amp am I right in thinking there should be a handwritten date somewhere on the cassis?
Steve Kennedy
Posted on Tuesday, September 21, 2004 - 10:21 am:   

Finding dates on Music Man chassis is a hit or miss proposition. Sometimes it is a label, sometimes it is crayon or grease pencil written on the chassis itself in various places, sometimes it's in pencil on a corner of the circuit board.

Since the 150 series was only made from 1980 to 1984 you will fall into this 4-year period somewhere.