Mods for my Musicmaster Bass Amp

[JimmyZ]

I recently bought an old Musicmaster Bass amp from a fellow TDPRI member and I'm going to re-cab it and would like to know what can be done to ehnance the function of the single tone control. Are there easy modifications to these amps that will produce good results for those of us using them for guitar? I have replaced the speaker with a greenback and I know the new cabinet will help (since it will be a nice wood cabinet rather than the particle board they had as OEM). Any advice is welcome.
Music styles run from classic twang to blues (with a Tele of course).

[Tremo]

New speaker, cap job and good tubes is all it needs.

[Brick]

I believe someone said a Harvard tone control would be good...can't remember, and wiring in a fuse could be useful. Some MMBs don't have one.

[Rob DiStefano]

What Tremo and Brick said. Here's one I just made into a head, with fuse and standby switch added ...

[1963neck]

I personally am not happy with my MMB (6v6`s) ...too raunchy or not loud enough . Funny , because I LOVE my champ and wanted something similar but louder .
They`re 2 very different beasts IMO .

So ..I know this has been talked about before ....but here goes .
Since I have a great friend/tech ....I Ask

How involved is it to build a beast in this little package .. ??
2 6L6`s
treble and bass knobs (middle would be even nicer ) .....Kind of a mini bandmaster ..

What would I need ?....2 trannys of course ... how many more pre tubes ?

I know the wiser ones will say don`t do it ....but the size is hard to resist for the flying I do ..thanks

[1963neck]

i found this
http://www.tdpri.com/forum/amp-centr...rb-w-6l6s.html

so ...if we forget it`s a MMB .let me rephrase it ..


Could I build a champ pre section with a bandmaster power section on to a champ chassis ? ( ha! I didn`t say MMB!)

[Rob DiStefano]

IMHO, it's a huge waste of time and dollars to "upgrade" or totally reconfigure a simple MMB. It is what it is, no more or less. Leave it be and just sell it if she ain't yer cup of tea, 'cause there are lotsa folks that will like it for the very good little beastie that it is. Otherwise, yer gonna be on a quest that's sorta like trying to turn a sow's ear into a silk purse. YMMV.

[weelie]

But many have modded their MMB, and been somewhat satisfied too.

And I remember Rob DiS listing some possible mods. Well, I listed some I read on FDP (in posts by a Dutch rockabilly guy), too.

Rob's previous comment about "Champ but with a bigger mouth" is what got me interested in the MMB. But haven't found any here in healthy condition and for a decent price.

[Rob DiStefano]

Originally Posted by weelie

But many have modded their MMB, and been somewhat satisfied too.

And I remember Rob DiS listing some possible mods. Well, I listed some I read on FDP (in posts by a Dutch rockabilly guy), too.

Rob's previous comment about "Champ but with a bigger mouth" is what got me interested in the MMB. But haven't found any here in healthy condition and for a decent price.

Those were very simple mods, mostly to make the amp safer, more reliable and more toneworthy. We're only talking stuff like a grounded power cord, adding the missing external fuse, good tubes, good speaker, maybe new filter and bypass caps, shielding the signal lead from the preamp tube to the vol pot, rewiring the tone pot to be more friendly. The mod question that 1963neck posed is more like reinventing the MMB to a whole different amp, with major tranny and circuit changes. Not a good idea, IMHO.

[weelie]

OK.
Maybe you just said you had a list of mods, but didn't go through them in detail: http://www.tdpri.com/forum/amp-centr...?highlight=fdp

Harmony central reviews mentions some mods (not necessarily to be trusted, of course!): http://reviews.harmony-central.com/r...ass%20Amp/10/1

The "bass squeeze" I refer to was from apost by PeeVee on FDP:
"Note that the Musicmaster Bass was (surprise!) a bassguitar practice amp. It had medium power rated speaker. To avoid the speaker would blow, the bass signal is squeezed right after the input with a (I think) .02 cap. Not any other Fender has this. Just bypass this cap (wire) and find out how much more potential the amp has! It's a simple 5 minute job! "

Just passing on what I've found, don't really enjoy modding myself. Nor have I ever own a MMB!

[Joe K]

Winfield/Zook tweaked mine and it sounds quite good. He also does a major mod to some MMBs turning them into Harvards. Very interesting but doesn't sound like that is what 1963NECK is after.

Hmmm, I wonder what it takes to convert a MMB into a Harvard. I assume that's the (2) 6V6 Harvard as the MMB has two 6V6's. Both of these amps (MMB and Harvard) make 10 watts so perhaps they share other components as well, e.g., tarnsformers.

[1963neck]

Hi again..thanks . I was expecting this reponse ..mostly because I did searches here in the past .
I appreciate your advice and will not do it just to be stubborn .

However .......... Just to be stubborn ....

Could I ask WHY ?
The motivating force here is size ... It doesn`t even have to be perfect .

I have a `66 Bandmaster in a 2x10 cab , a Fargen Blackbird , A princeton Rev ,,,


Believe it or not ....there are gigs where the size of a champ at 30-40 watts..can make the difference of using awful backline or carrying ..

IF I modded a Dr Z Carman Ghia to 6L6`s .....nobody would flame me for messing with a MMB ..

In effect ...All I want is a SMALL amp loud enough to carry the gig.

Given that ... I still don`t understand the WHY behind the "Don`t do it "

Are you saying it`d cost too much ? . Wouldn`t sound good ? Grounding problems ?

thanks to Rob and the boys ......later,Paul

[quackerz]

Originally Posted by Joe K

Winfield/Zook tweaked mine and it sounds quite good. He also does a major mod to some MMBs turning them into Harvards. Very interesting but doesn't sound like that is what 1963NECK is after.

Hmmm, I wonder what it takes to convert a MMB into a Harvard. I assume that's the (2) 6V6 Harvard as the MMB has two 6V6's. Both of these amps (MMB and Harvard) make 10 watts so perhaps they share other components as well, e.g., tarnsformers.

The MMB has a diode recto and a transformer phase inverter. The Harvard uses tubes for these functions. The MMB is cathode biased, the Harvard is fixed bias with a bias tap from the PT and an NFB loop. Seems like a lot of work to me, especially as the MMB is a good sounding amp on it's own.

[Joe K]

Thanks, Q. I appreciate the FAST response!

[zook]

The modest tweeks to a MMB are as follows:

Install fuse (Not al MMB's have a fuse)
Remove death cap
Re cap
I sometimes replace the two diodes with four 1N4007s This reduces a bit of hum if the amp hums. If it doesn't I leave them alone.
Shielded cable from inputs to V1. Configure input like a BF.
Convert Volume/Bass to tweed style (allows more tone variation.)

I replaced the transformers in one and have another here waiting for the same mod. I use transformers large enough to use 6L6s as well as 6V6s/ The PT in the MMB is wimpy. It does change it a bit to give more volume and more headroom.

I've done a few for Rob.

Winnie

[geoffreysnow]

Originally Posted by 1963neck

Given that ... I still don`t understand the WHY behind the "Don`t do it "

Are you saying it`d cost too much ? . Wouldn`t sound good ? Grounding problems ?

I recommend getting a kit because it seems like you have an itch to mod something and the only cure is to do so. Pick a weber kit, build/mod etc and you'll gain knowledge of working on amps.

[Tremo]

I recommend building from Scratch like Crash does. I do NOT recommend becoming yet another Torres-inspired hack butcher.

[Rob DiStefano]

If yer looking for a small footprint 30-40 watt tube amp, the MMB chassis (which is a Champ) is probably never gonna be large enuf to support the large iron yer gonna need to achieve that kinda wattage. But mainly, why kill a good MMB or mess around with attempting to stuff a monster in a paper bag? Like Tremo sez, just build from scratch - get the right sized chassis that'll handle the big iron and have at it. That's exactly what I did and the result is a Super Rosco that Winnie scratch built for me - what an absolute *killer* high headroom 40 watt amp ... WOWeeeeee!

[bluesfordan]

Originally Posted by Rob DiStefano

...result is a Super Rosco that Winnie scratch built for me - what an absolute *killer* high headroom 40 watt amp ... WOWeeeeee!

woah, is that two EL34s or 6L6s?

[Rob DiStefano]

Originally Posted by bluesfordan

woah, is that two EL34s or 6L6s?

6L6's, but this amp can take ANY octal power tube - bias pot on top and I use a Bias Rite for biasing. I've had a set of GT EL34's in but I like the JJ 6L6's better. Eventually will taste test other tubes like KT88's.

[bluesfordan]

Originally Posted by Rob DiStefano

6L6's, but this amp can take ANY octal power tube - bias pot on top and I use a Bias Rite for biasing. I've had a set of GT EL34's in but I like the JJ 6L6's better. Eventually will taste test other tubes like KT88's.

do you use that amp a lot? Its probably pretty loud, NTTAWWT. Are 6V6s octal power tubes? I bet they would sound great with that big iron.

[Rob DiStefano]

Originally Posted by bluesfordan

do you use that amp a lot?

Just got it, about a week or so old - and as you can see from the pic, I haven't even built the cab for it.

Its probably pretty loud, NTTAWWT.

No and yes ... With a Tele or Strat it's Super clean up to about 3/4-7/8 volume that seems more like a 20-30 watt tube amo, and then it gets louder as the overdrive kicks in and then it sounds like 40 watts of kick a$$ tube amp

Are 6V6s octal power tubes?

Yes.

I bet they would sound great with that big iron.

They'll most likely overdrive sooner and that's not what I want from this amp.

....

[bluesfordan]

hm, I'd like to hear that amp sometimes, it has the simplicity I love about my musicmaster bass amp, but with seriously more balls. Seeing as how I'm liking cleaner tones, I'd probably go with the 6L6s.

Post pics of the cab when you make it. Whatcha gonna run it through?

[Rob DiStefano]

Originally Posted by bluesfordan

hm, I'd like to hear that amp sometimes, it has the simplicity I love about my musicmaster bass amp, but with seriously more balls.

Precisely why I dreamed up the concept of the original 25 watt Rosco. It had the right overdrive tones, but lacked the really sparkly clean headroom I now require. The 40 watt Super Rosco delivers the clean goods, in spades. FWIW, there's also a Super Duper Rosco in the making - 100 watts of Mr. Clean into a 2x15.

Seeing as how I'm liking cleaner tones, I'd probably go with the 6L6s.

Yep. But the GT EL34's I tested out had lotsa clean, too. There are SO many octals to test out, so little money and time ...

Post pics of the cab when you make it.

Will do, for sure.

Whatcha gonna run it through?

My fave cab, a 1x15 with a 50w Weber 15F150 - also in the making. For now I'm using a 1x15 cab loaded with a 150w 15" Jensen Neomydium - boy, that sounds pretty darned good and super light weight (the whole cab weighs 18 pounds!)

....

[bluesfordan]

open back 1x15 ? I've been wanting one for a long time, even have a JBL D130F waiting for the right moment.

[edadmartin]

interesting thread,so Ill pop in say hi!!,and put in my .02.
I have a mmb and I made a head for it and use it with my showman tone ring cab with 1 15" jbl speaker in it.I also did a cap job and got rid of the 2 prong cord.I use this in the bedroom studio for practice only,but wanting more I emailed webber and he said a bandmaster with bassman transformers and larger filter caps would give me 35-40 watts of clean bass amp.Ive moved to co springs and it should make a great winter project,so I agree that insted of killing a vintage amp, building from scratch or a good kit will get you there

[Lennon]

Originally Posted by Rob DiStefano

What Tremo and Brick said. Here's one I just made into a head, with fuse and standby switch added ...

Sorry to dig this old thread up, especially on my first post here BUT this is probably one of the most beautiful things I've ever seen. Uber-nostalgic for me. Hey I've got a donor MMB if you want to build another.