How do you set your Musicman HD130?

[drbassman]

So, what does a phase inverter do?  Don't get too technical, you know how that confuses me!

[amptech]

So, what does a phase inverter do?  Don't get too technical, you know how that confuses me!

Just think of it as a component that splits the signal from the preamp into two, sending one half of it to
one pair of output tubes and one half to the other pair, making the output stage more efficient.
It´s also known as the driver tube; it just a component that drives the output stage.

It´s not a correct way of explaining what actually happens to the signal, but I´m sure
you can find out more about push-pull, phase inverters and so on in other threads here.

It usually gets pretty boring when technicians try to explain things, the short short version
is rarely used!

[Dave W]

I'm well aware of the fender similarities, but Leo himself didn't have anything to do with musicman amps, did he?
If I remember correctly, he only designed the stingray series instruments, and another which I can't remember..

IIRC Leo and Tom Walker designed the amps, while Tom alone designed the preamp for the basses. As always, I could be wrong.

[amptech]

No, you were right! I have to throw away some of my outdated books

[Pilgrim]

Hmmm...interesting question.  I would have assumed that it inverted the phase of the output so that you could potentially have the + and - signals reversed.

But on reflection, that would most likely cause problems with speaker phasing...so I would have been wrong (again).

[drbassman]

Hmmm...interesting question.  I would have assumed that it inverted the phase of the output so that you could potentially have the + and - signals reversed.

But on reflection, that would most likely cause problems with speaker phasing...so I would have been wrong (again).

Since I am clueless, I dom't worry about making assumptions!  I just don't go there!

[drbassman]

Question:  While playing my "newer" 130, I noticed a very high pitched ringing sound that is coming from the amp itself, like maybe the tubes???

[Highlander]

You lot do lead such closeted lives... here's a list of differing types of PHASE INVERTERS... 

[amptech]

Question:  While playing my "newer" 130, I noticed a very high pitched ringing sound that is coming from the amp itself, like maybe the tubes???

Tubes makes the sound you describe when they age, or even new but poorly selected - they can have loose electrodes or
bad frames/electrode structures - they are microphonic. Tapping them softly with something like a pen, might sort this out.
Usually this is easy to spot with tubes in early stages of the preamp, they amplify this noise a lot more than a PI or output tube. Obviously you have no tubes in the preamp, but do check the tubes for microphonic sounds. Just don´t burn your fingers!

Without hearing the sound it makes it can be other things too, loose mechanical components etc, but bad tubes loves to ring.

[Psycho Bass Guy]

Microphonic power tubes "whoosh;" they don't ring. If you're hearing ringing from the amp itself that's not coming through the speakers, it's probably the glass in the tube envelopes vibrating or making thermal expansion/contraction noises.

[amptech]

Microphonic power tubes "whoosh;" they don't ring. If you're hearing ringing from the amp itself that's not coming through the speakers, it's probably the glass in the tube envelopes vibrating or making thermal expansion/contraction noises.

I didn´t see in the text that the sounds did not pass through the speakers, sorry.

Still, the most understandable way to explain any sound the tube makes by itself and passes through the speakers is to call it microphonic.

High pitch oscillations, funny squeaking etc will still fit into the microphonic category. I can eat your whoosh theory ok,
but I still could advise a customer to check tubes as well  as loose tubes in the socket etc. if he tells me his amp makes a ringing sound.

[amptech]

Question:  While playing my "newer" 130, I noticed a very high pitched ringing sound that is coming from the amp itself, like maybe the tubes???

Didn´t read the whole text the first time, sorry! Before I mounted springs on the power tubes on my 130,
I used to put a couple of thick socks under the rubber feet even when using only the 212 cab.
The ´clips´(if that´s what you call them) that holds the tubes in the sockets doesn´t do much to stop the rattling.
If you play with the amp on the floor, the ´ring´goes away, yes?

[Pilgrim]

You lot do lead such closeted lives... here's a list of differing types of PHASE INVERTERS... 

OOOOooooooOOOOO.  It's alla time clear to me now.

Just like a Flux Capacitor, only different!

[Highlander]

 

Back in the late 70's I was having all sorts of issues with the set of valves that were in my Hiwatt, being terribly microphonic - also, weirdly, every time a police car went past it would pick up their broadcasts...
We were in one studio where we had been stitched up a couple of times and I happened to notice he had a hired Marshall head with the same set of valves - I don't know how it happened but they somehow got mixed up and my problem was cured - no more police broadcasts or microphonic issues...

[Pilgrim]

I used to live about 5 miles from a 5 KW radio transmitter at AM 1250.

When playing my blackface '67 Bassman and 2x15 cab with connection via my coily cord, I often picked up the signal of that station.  I could hear it faintly but clearly through the amp.