Music Man Amp Part II

[@cat793c2008]

Great video Keith! I learn every time I watch.

[@zbaby82]

It has a nice clean sound. And the tremolo and reverb sound really good.

[@keithb7]

Glad you like it, yet I’m not done yet. NOS Motorolla LM307H pre-amp op-amps will be installed very soon.

[@johnbravo7542]

Great job,sounds really nice to me.

[@sboy1955]

Thanks for the videos, really enjoyed them 👍🏽

[@ferraridinoman]

Had quite a few Musicman amps originally bought one new in 1978 2x10 65 (as James Burton was playing Musicman at the time) but I exchanged it for a new later Fender twin reverb with the Orange F12 JBL speakers. (Came with a Fender Fork lift, BLOODY HEAVY and sounded very "harsh/clinical" to my old ears). Have since had 2 2x12 130 Musicman amps and currently have a near mint 1977 2x10 65 which is a lovely warm clean sound.(and possible to carry/lift!) Everybody has different ears, and likes different sounds so like all these things its up to the guitarist (and the type of music they play) which amp they think is good! Personally I think Musicman are great, and at the moment relatively cheap compared to many Fenders of the period.

[@peterburi2727]

I had a 112RD 50. It was a good amp, heavy, loud but the only thing that I had a problem with is the clean and distort channels shared the same tone stack. What sounded good on the clean channel didn't sound good on the distort channel. Nice choice on the filter caps, those are F&T aren't they?

[@jimcastillo8950]

Got to hand it to Forrest White and Leo Fender. Those amps kick ass and a lot of musicians used them.....

[@kennyrathbone9719]

can you please show me the model number of the reverb tank, i am repairing one and the tank has been changed and not working,amp responds when rca jack pluged and unplug. do not know were the factory one is, customer doesnt know. any part numbers? i think this is the wrong tank thankyou.

[@qddk9545]

Wikipedia tells us that the Sixty Five was MM´s first amp, and that it was designed by Leo Fender and Tom Walker - a business man and a sales guy 🙂 But maybe they were technical experienced enough to do it. The amp is a cathode driven class B amp, which is a very uncommon circuit, not used by any other guitar companies then or now, as far as I know. But there must be something to it when people like Mark Knopfler and Eric Clapton and a lot of others liked it so much. Cathode driven amps have a very low input impedance, and Class B amps use a high HT, have a very low idle current, and they are very efficient. So you can get more power out of a set of tubes, than on a class AB amp (almost 20% more), and apparently they are not hard on the output tubes, even with the high HT voltages. They are claimed to have a very high distortion, but maybe it is harmonic distortion, so people don´t care about it. A very strange, but interesting concept. It is possible to make a Class B amp with standard grid driven input, but I am not sure if it will sound the same as cathode driven input, and nobody does that either. Though Cesar Diaz has claimed that he rebuild Hendrix´s amps to Class B on his American tours.

[@Bmille1965]

I Have A 212 hd 130 It has a black face with silver logo and i havent seen another one with the black face. Any thoughts?

[@giulioluzzardi7632]

What about the other channel, channel 1 on the left?

[@keithb7]

The left channel now works fine, just as it did when new.

[@bernhardnizynski4403]

Very neat!

[@Michaelsorg7]

Nice tone

[@keithb7]

Thanks. I’m not done making it better yet. All new NOS Motorolla op-amps will be installed soon!

[@qddk9545]

Does it sound the same on the lo power setting?

[@keithb7]

To me it does sound the same on either setting. I cannot seem to hear a differnce. However Most of my playing is at home at low volume levels. I've not had many opportunities to crank it up yet in a live band setting.

[@liammoynihan2187]

You're not clipping the OpAmps there. I took my Music Man 2100-65 head (has the same phase inverter & power amp circuit as this amp) in to an amp tech cause I thought mine needed to be recapped. He told me that these amps can clip the transistors in the phase inverter circuit when the master is low. If you open up the master all the way and push the drive past seven you won't get any clipping/overdrive. It's not a solid-state OD but it isn't tube either, it's a transistor overdrive. EDIT: I thought that transistors were analog, but they are in fact solid-state. However, the OD from this type of component is not as harsh as an op-amp IC.

[@chriscourter4006]

Nice video! Two questions I'm hoping you might answer. Is this the version with the 12AX7 tube - I'm guessing so since you are setting the bias. Also, I was watching you set the bias and on your first check the probe was on the upper resistor on the right hand side. In the second check you were on the lower resistor on the LEFT hand side - does it matter right or left on that lower resistor?

[@keithb7]

I am setting the bias of the power tubes. This amp does not have a 12AX7 phase inverter. It has a solid state pase inverter.