Music Master Bass Amp Mafia

[56telemike]

can anyone tell me if these amps are loud enough to gig with? ...small venue with bass and drums... What other small fender would they compare to? .....just wondering...

[doggy1972]

I would say so, with a fairly high powered, efficient ceramic speaker (not the stock speaker) Not done it myself but I suspect others may have.12 watts is still loud ;)

[Sidney Vicious]

Thought I'd add this 6AQ5A schematic in case anybody is looking for one as the earlier post containing the schematic is now a dead link:

[blindmouse]

Hi,

Well let me in on that Musicmaster Bass amp mafia. Just sneeked one of these amps in. A MMB was always on my mind. I bought a 1971 Musicmaster Bass guitar back in 1971. Still have that baby. One time in the late seventies I sat kneeled down in front of a MMB at Gerritsen Music Shop in The Hague (The Netherlands). I wanted a small practice bedroom amp. I left the shop with a small Roland 30W combo: the bass sound was so much better on that one. But at last, now I got one. It's a 1974 amp - the youngest date I could find was on the OT 606 401. So that's an early one. This one has no fuse and a 125V rounded (not flat) pilot light. First I thought that wasn't original as I am used to the red jewel looks. The early ones with the taillogo seem to have a flat 125V pilot light. I like those details. I'll give it a cap job en try some mods to make it a better guitar amp - I guess I'll change the speaker to. And it's better to place a fuseholder.
I ordered some 6AQ5A tubes and a set of NOS RCA's is on the way. The tubes the amp came with read weak on my B&K tubetester. Now this is a cathode biased amp. Anyone ever tried to set the tube dissipation on a Musicmaster Bass Amp??? 10 to 11 Watts I suppose? I'll keep you informed

[Sidney Vicious]

Originally Posted by blindmouse

Hi,

Well let me in on that Musicmaster Bass amp mafia. Just sneeked one of these amps in. A MMB was always on my mind. I bought a 1971 Musicmaster Bass guitar back in 1971. Still have that baby. One time in the late seventies I sat kneeled down in front of a MMB at Gerritsen Music Shop in The Hague (The Netherlands). I wanted a small practice bedroom amp. I left the shop with a small Roland 30W combo: the bass sound was so much better on that one. But at last, now I got one. It's a 1974 amp - the youngest date I could find was on the OT 606 401. So that's an early one. This one has no fuse and a 125V rounded (not flat) pilot light. First I thought that wasn't original as I am used to the red jewel looks. The early ones with the taillogo seem to have a flat 125V pilot light. I like those details. I'll give it a cap job en try some mods to make it a better guitar amp - I guess I'll change the speaker to. And it's better to place a fuseholder.
I ordered some 6AQ5A tubes and a set of NOS RCA's is on the way. The tubes the amp came with read weak on my B&K tubetester. Now this is a cathode biased amp. Anyone ever tried to set the tube dissipation on a Musicmaster Bass Amp??? 10 to 11 Watts I suppose? I'll keep you informed

Nice amp and setup, blindmouse - the amp is 12 watts -

Here is a flyer that details the specs of the early MMB -



Note that while the flyer claims that the amp came with a fuse and speaker out jack I am unaware of any of these amps that came with either feature.

I believe the earliest 6AQ5A models had the flat light, then the dome/ rounded light, and then the later 6v6 went to the standard Fender jewel -

and welcome to the TDPRI.

[blindmouse]

Hi again,

Now let me tell you some more on this MMB amp. (see my yesterday's posting) I told you I was a bit puzzled about the pilot light of this amp. What puzzeled me more was that this amp came with five chassis bolts instead of just four; four bolts that keep the amp chassis attached to the top. Another chassis bolt kept the OT fixed to the amps chassis. Now I supposed it had been done by someone who didn't have a small screw to get the job done. When I got home and took the chassis out I found out why this fifth bolt was attached just there. I did that by taking the chassis bolt away to fix the OT with a screw: I turned the chassis around and then it was all clear: now the chassis rested on the 6AQ5A output tubes! The long bolt was there to prevent that. Now, that's why I love Fender amps: just a lot of surprises, and a lot of fun. It could have been one of Leo's inventions. It's back right on place now of course. You see this extra chassis bolt on pictures of the early MMB amps. Another surprise came when I inspected wires and solder joints. There is a wire that goes from the 125V pilot lamp to the on/off switch/volume pot. Actualy it is two wires: the one from the pilot lamp (black) meets the wire from the volumepot (dark brown), were they meet the cores are twisted round each other and isolated with a "sock". Now carefully checking this joint I found out this joint wasn't soldered. It was easy to pull these wires apart!?!? This amp ran for 36 years with 117Volts on this wire and it just kept working!! Well, enough for right now, tomorrow my tubes and caps will be in and I'm sure I will get the amp back in great shape.

Bye

[Sidney Vicious]

Originally Posted by blindmouse

Hi again,

Now let me tell you some more on this MMB amp. (see my yesterday's posting) I told you I was a bit puzzled about the pilot light of this amp. What puzzeled me more was that this amp came with five chassis bolts instead of just four; four bolts that keep the amp chassis attached to the top. Another chassis bolt kept the OT fixed to the amps chassis. Now I supposed it had been done by someone who didn't have a small screw to get the job done. When I got home and took the chassis out I found out why this fifth bolt was attached just there. I did that by taking the chassis bolt away to fix the OT with a screw: I turned the chassis around and then it was all clear: now the chassis rested on the 6AQ5A output tubes! The long bolt was there to prevent that. Now, that's why I love Fender amps: just a lot of surprises, and a lot of fun. It could have been one of Leo's inventions. It's back right on place now of course. You see this extra chassis bolt on pictures of the early MMB amps. Another surprise came when I inspected wires and solder joints. There is a wire that goes from the 125V pilot lamp to the on/off switch/volume pot. Actualy it is two wires: the one from the pilot lamp (black) meets the wire from the volumepot (dark brown), were they meet the cores are twisted round each other and isolated with a "sock". Now carefully checking this joint I found out this joint wasn't soldered. It was easy to pull these wires apart!?!? This amp ran for 36 years with 117Volts on this wire and it just kept working!! Well, enough for right now, tomorrow my tubes and caps will be in and I'm sure I will get the amp back in great shape.

Bye

You note two more of the many quirks of the MMB. I used to think the wire issue was a sign of some long ago repair - until I saw it again and again on early MMB's that otherwise gave no sign of having been opened or repaired.

Anybody else run into the wire patch issue that blindmouse noted?

[blindmouse]

Hi, back again on my 1974 Musicmaster Bass amp.

Today my RCA 6AQ5A tubes and my caps came in. This is what I did:

- took out the death cap
- put in a 500mA fuse
- cleaned the pots
- cleaned and retensioned the tube sockets
- soldered the loose ends pilot light vs on/off switch
- changed the stock Mallory 20/20uF/300V to a Ruby 33/33uF/450V
- changed the stock Mallory 20uF/300V to a TAD 22uF/500V
- changed the stock Mallory 2uF/50V to a F&T 25uF/25V
- removed the .0047 cap and made a bypass
- put in a Tung Sol (reissue) 12AX7
- put in 2 RCA 6AQ5A tubes
- fired it up and played my 1976 Stratocaster.

This amp rocks!! I DO love the stock CTS ceramic speaker!
This is a different sounding amp than my Silverface Vibro Champ. It is good as it is.

I even won't perform the tone stack mod on the pots.

Great amp! Regards.

[blindmouse]

Hi,

Now as a follow up I did the Richard Hassebrock tone/volume- and coupling cap mod. Using a 500pF Silver Mica and a .0047 Mallory cap. I had a .022 blue molded cap lying around so I used that though I could have used the blue cap that came from the stock tone circuit. The 1K grid resistor moved up to 2K so I changed that too. The amp is louder now and the highs are coming through nicely. I can even get a kind of acoustical guitar sound from my Stratocaster. I put all removed parts of this amp in a plastic zip bag and put it in the back of the amp. Though who wants to bring it back to stock?
After 36 years this poor sounding, humming amp came to a second life. Many years to come I guess.

Regards

[blindmouse]

Hi again,

Two pictures of my MMB. One of the chassis after the cap job (+fuse job) and one of the chassis bolt that holds the OT up.

Regards

[Rybass]

Hey fellas. It's been awhile. Sorry for the blasphemous pic but it's all I have at the moment. Mine is an '81 or '82 running some no name Chinese 6v6's and a ge 12au7. I tried some EH and JJ 6v6s but they were just too harsh on breakup. The Chinese black labels are super smooth with 12au's or 12ax's.

Loaded with an Eminemce red fang and a bracket I found and mounted to the cab, attached a 1/4 socket to and now I have a speaker out.



I'll post some better pics as soon as I can take some.

[dever]

Hey Rybass, that's a sweet getup. I prefer my MMB with humbuckers.

And how about that faceplate! Am I missing something or is that an aftermarket faceplate?

[dever]

Originally Posted by Sidney Vicious

dever - neat work on that tone control job - thanks posting the pic.
Post when you get that 6AQ5 in.

The 6aq5 is sitting patiently waiting for me to recap it. I put it next to it's 6v6 brother which is notably louder. I jumped the 6aq5 to the 6v6 stock speaker to see if it's the replacement speaker someone put in, but it's not. That 6aq5 is just a quiet amp at the moment. I'll have to take the chassis out and give it the once-over, then look for a better speaker. Pics and progress soon to come...

[Sidney Vicious]

blindmouse:

A closer up picture and/or more info on that fuse installation would be appreciated - looks good.

[dever]

Originally Posted by dever

The 6aq5 is sitting patiently waiting for me to recap it. I put it next to it's 6v6 brother which is notably louder. I jumped the 6aq5 to the 6v6 stock speaker to see if it's the replacement speaker someone put in, but it's not. That 6aq5 is just a quiet amp at the moment. I'll have to take the chassis out and give it the once-over, then look for a better speaker. Pics and progress soon to come...

I took the chassis out of the 6aq5 amp that is significantly quieter than the 6v6 MMB. I'm getting ready to go to the electronics store to see if I can replace the electrolytics, but I noticed a cap I'm not seeing on either schematic. See from the V3 socket, 1st (7th?) pin to ground, there is an orange Sprague of 50mf. Am I missing something or what could that possibly be there for? Everything else checks out very cleanly.

[Sidney Vicious]

That cap does not appear to be stock as you note - I would be tempted to lift one end to see what difference that makes.

[telewacked]

Here's a pic of my SF herd (I sold the VR a few years ago tho').

I love my MMB - it's a fantastic lightweight rehearsal amp. I've tried gigging and found it works great for low volume combo work, but when you've got bass bins, multiple instruments etc. it just wasn't loud enough for me unless fed into the stage monitors, and I prefer to hear the amp behind me.
A question - how the heck did you guys install the speaker jack? I've been wanting to do this but my speaker leads come directly out of the OT on the bottom of the chassis. I thought about an inline 1/4" jack, but thought it would look tacky and might pull too hard on the OT from the weight of it. Also thought about adding two holes in the bottom of the chassis, one for the wires to go into and the second for the jack. If anyone has suggestions or pics, I'd sure appreciate it!

[dever]

Telewacked:

1. A fuse. See my previous post on Jan 24, 2010 on my 6v6 version for a decent pic of how I did it. Others have different setups for the fuse, but it accomplishes the same thing. This mod should be considered mandatory for safety purposes. In essence, drill a ½ inch hole and mount a panel-type fuse holder. Splice into the black power chord wire and solder to the fuse jack tabs. Insert 2 amp slowblo fuse

2. A Speaker jack. I plan to (pending inspiration):
a. drill a ¼ inch hole in the bottom of the chassis and install a switchcraft jack
b. drill another ¼ inch hole near the jack to feed the speaker wires through. For safety, this hole must have a grommet installed to keep the wires from being rubbed through
c. Hook the speaker wires to the switchcraft jack. I don’t know if I’ll have to clip the adapter ends off the existing speaker wires or not, we’ll see
d. Make a 1.5 foot speaker lead out of 16 guage wire and a switchcraft ¼ inch plug to plug into the jack. Solder the other end to the speaker.

[dever]

Originally Posted by Sidney Vicious

That cap does not appear to be stock as you note - I would be tempted to lift one end to see what difference that makes.

I went home at lunch and lifted one side of the cap. Yep, that did it. The cap was knocking out some of the signal. The crap-o aftermarket speaker wasn't helping, but it was the cap. On the upside, I now have a 50mf orange drop in my arsenal.

[Sidney Vicious]

Originally Posted by dever

I went home at lunch and lifted one side of the cap. Yep, that did it. The cap was knocking out some of the signal. The crap-o aftermarket speaker wasn't helping, but it was the cap. On the upside, I now have a 50mf orange drop in my arsenal.

and

Glad it didn't blow up - you do realize I am a lawyer by day?

I only pretend to know something about amps.