Fender Musicmaster Bass amp- new issue

Keith Cordell · From: San Diego

I got one of these in a trade recently and have been cleaning it up to use as a lap steel amp. I thought it was the less desirable circuit, as it has the 6AQ5A power tubes. I A/B'ed it with a friend's amp that has 6V6GT's in it and I really like mine better! It's not as loud and doesn't overdrive as easily with my single coils, I can crank it and it just gets furry. It's not as loud as I expected, either. Since I have never had one of these, what should I be expecting? I am considering doing the Torres mod to it, as they said it will be a major transformation and it only costs $18. Any thoughts, advice, comments, slings or arrows?

Dan Tyack · From: Olympia, WA USA

I've played through one of these and I really liked it.

However I've heard from mant sources to run don't walk away from anything from Torres.

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

I've had both kinds, and I wish I had one now. One of the best little amps I've ever played through for just plain balls with definition. I like both versions, but you're right - the 6AQ5 version definitely has more balls. Those are some primitive-sounding tubes, used on some early amps - I think some of the early, small Gibsons used them.

These are different than anything else made by Fender during the 70s. Two cathode-biased tubes run push-pull with a transformer phase-inverter, it's a strange beast. Properly set up, they should be, more or less, like a cross between a silverface Champ and a tweed Deluxe. It should be louder and ballsier than a Champ, maintain some of that silverface sparkle, but have more midrangey tube distortion from the cathode bias. The bigger box and speaker help also.

Like Dan, I wouldn't put a Torres mod on anything, but I think I'd leave this amp stock anyway. Once I gave them a good going over, replaced electrolytics, and possibly subbed a good-quality, high-efficiency speaker with some balls, mine were really nice. I think I had a Celestion Vintage 30 in one of mine.

There's not a lot of gain in the preamp section of these. I used the highest gain tube I could find. The very raw-sounding and midrangy Chinese 12AX7A tubes that Ruby used to supply 10+ years ago sounded good. Some older 50s NOS 12AX7A tubes worked well also. But these amps also took a simple clean boost just great - either a straight clean preamp or perhaps a compressor with some gain & not much compression. I find a hair of compression often helps keep these little amps from bottoming out when cranking them. Try it with a Junior or some other solidbody with a P-90. Sounded great with a lap steel too - I had an old Oahu Tonemaster then. But honestly - I just loved these with a P-90. I put an extension nut on my Junior for a while. But I first had to go in and clean these amps up to get what I wanted.

Really - I should stop yacking about these until I get another. Neutral

Keith Cordell · From: San Diego

I got a pile of RCA long blackplate tubes with it, and I had a good 12AX7 so as far as that goes it is pretty bulletproof. Supposedly it was recently recapped but it is not as loud as my Epiphone Valve Junior so I am not sure about whether it was done properly. It does take a boost really well, I recently got a Vintage FX Colordrive and on a clean setting it pushes the amp to a very sweet drive sound. I put an Eminence Legend in it and that seems a little over the top; I might switch it for a Cannabis Rex to see if that is a little more in line with the power output.
I will take your advice and not do the Torres mod. I also read that there is a cap that should be changed or removed that will brighten it up; any idea what to do there?

John Groover McDuffie · From: LA California, USA

I just bought one of these (6V6 version) on ebay, mostly for the chassis, the cabinet is pretty trashed, I think. I am hoping to use it on my church gig for guitar, where a Vibro-Champ is not quite loud enough. (But a Blues Junior is more than I need) I may put it in a JD Newell Vibro-Champ 1-12 combo cab.

FYI I use a multi-FX pedal in front of the amp to get overdrive etc., so a Fender clean-ish tone is what I need from the amp. Any info I can pick up on this thread will be appreciated.

Keith Cordell · From: San Diego

OK, the equipment gods are striking me down... I moved the amp into a new room and set up my gear, only to discover that when I play I get a static noise. The hotter the signal I give it, the louder the static. I tried another speaker, new tubes, removing the effects from the equation... still there. Any ideas for troubleshooting or am I ampless for a while?

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

Start with the easy things first. You say you moved it to a new room. When you go back to the old room, does the problem go away? I have one AC outlet in my house that has inverted polarity - I discovered it recently and I need to fix it. That can cause issues sometimes.

You said it was recently serviced. Do you know how to check for that? I don't want to tell you to go inside and monkey around unless you know how to do that properly. I always start out by cleaning pots, tube sockets, and input and speaker jacks with a good tuner cleaner/lubricant like Caig DeOxit. I also check to make sure wires and cables - especially speaker cables - are securely soldered or otherwise connected if they're not soldered. I do that without any other provocation.

Can you describe "static" a little more? Is it a buzzing sound, scratch like a pot static, a knocking sound, or something else?

There are three transformers on this amp - power, phase inverter, output. Problems with one of those would be the worst thing that could happen, I think. Otherwise, there's not a lot in there - it's a pretty simple circuit. There could be funky resistors, capacitors or small things that are pretty easy to fix - I count 11 resistors, 3 filter caps, 6 or 7 other caps, 2 diodes, and 2 pots. Not a lot to it.

Keith Cordell · From: San Diego

dup post

Keith Cordell · From: San Diego

It's like radio static, but worse. I wonder about the cap thing as it was quiet as the grave before I moved it. I changed the outlet and it's not as bad, especially with a power strip. I think the power supply caps might be funky, I just wonder why they didn't act up before. I really don't know a ton about the repair side of these, but with a simple circuit like this I might be able to deal with it. I am going to see about the caps tomorrow. Thanks for the advice.

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

Yeah - hard to say. The fact that it changes again when you change outlets tells me to start with the AC power. Why a power strip would change anything I don't know. Of course, low voltage could cause problems. I have had problems that disappeared when I plugged into my Furman voltage regulator - or brought it to my buddy's shop - naturally, the problem just goes away. Anyway, make sure the AC power is OK before you go tearing things apart. The $5-10 socket testers can tell you about wiring correctness, and a voltmeter can tell you about AC voltage. There are other things that can be problematic, but you'd need a voltage regulator to deal with that.

I have seen cap jobs not done correctly. Sometimes caps with too-low voltage were used, sometimes they didn't wire them correctly, sometimes they used old, shot caps, and so on.

Just hope it's not the transformers. And don't electrocute yourself if you go into the amp. The nominal B+ on these is somewhere around 300 VDC, which is lower than a lot of tube amps, but still enough to kill you.

Keith Cordell · From: San Diego

Well, I guess I need to get the house fixed and not the amp. I moved the whole mess around to different outlets and about half our outlets cause the noise, the rest don't. I am going to just have to shut down all the power and invert the polarity on the outlets.Grrrrrrr. I still haven't cleaned the gutters....

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

Stephen Gambrell · From: Over there

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