Your choice? Plexi vs Bassman

nick · 2011-04-13T18:23:27+00:00

'68 Marshall JMP SuperPA, 100w '69 Bassman, 50w Which would you choose? ? My personal Pros/Cons Bassman: Pros: 1.) Head is small enough to cart to gigs 2.) Definately loud enough with 50w 3.) Gets very dirty with my Les Paul! 4.) AB169 circuit which is apparently the BF Cons: 1.) Not much clean headroom (with my Les Paul) 2.) Head wants a 4ohm cab, I have 2x16ohm Greenbacks Marshall: Pros: 1.) Takes pedals insanely well ??? 2.) Plenty clean headroom, only breaks up at plenty something on the dial 3.) Dont be fooled by the PA part, done some reading and apart from the extra 4 inputs, its a Plexi, some suggest removing those inputs 4.) Switchable 4,6,16 ohm output Cons: 1.) Its huge.. and weighs a ton 2.) Slight buzz which could be an old valve or dodgey cap

JeremyE

nick wrote
JeremyE wrote From the description I'd say the bassman needs attention, it should have more headroom for cleans. I have a 68 with the ab165 circuit and it doesnt break up with humbuckers or single coils all the way to the top. Then again I think it does need some TLC soon to.
It is possible its caused by the slight impedence mismatch of the speakers (8ohms vs 4ohms) and the fact that they are Greenbacks? Not really known for their sparkling cleans ?

The impedance mismatch would mean that your volume is halfed when going into the speakers. Therefore you will have to drive the head and valves harder to attain higher volumes, so the amp will be closer to breakup to get a good live volume, so this may very well be the issue. I'd imagine the greenback would also break up sooner. I love greenbacks and they should be able to get plenty loud without breaking up. If the plexi stays clean though then its not the speakers breaking up.

Reinhard

How many of you guys have played a plexi marshall? This sucker sounds really good :yup:

nick

vic wrote Nick, does the BM also go dirty with single coil guitars ? ...What's the condition of its pre-amp and power valves ?

Gets dirty after about 6 on the dial. It has new(ish) matched JJ 6l6's and older 12ax7s. It is seriously quiet for an old amp, barely a hiss from it

AlanRatcliffe

Reinhard wrote How many of you guys have played a plexi marshall?

The Plexi and the Bluesbreaker are the only Marshalls, IMO. ? Love hearing other guys use them ('specially the LP and 335 players), but they just do not work for me.

FenderBender

Nick I'd try your bassman on a decent 4ohm cab before you make any decisions.
From my tech point of view, the bassman is far more solid and almost overdesigned, from the chassis right through to the transformers.

nick

Right so Ive been swopping between the two and as far as I can see I have two options..

1.) Buy 2x 8ohm 12" Greenbacks for my cab and see how they sound with the Bassman
2.) Sell the Bassman and aquire the Marshall

This is like choosing between children ☹ ?

vic

nick wrote Right so Ive been swopping between the two and as far as I can see I have two options..

1.) Buy 2x 8ohm 12" Greenbacks for my cab and see how they sound with the Bassman
2.) Sell the Bassman and aquire the Marshall

This is like choosing between children ☹ ?

Nick, first speak to Karel before you take a decission...maybe it's just something small that can be sorted out for little $. Those silverfaces should easily handle high volumes before breaking up....also as you say it could be an impedance mismatch, but he'll be able to establish that in no time.

nick

vic wrote
nick wrote Right so Ive been swopping between the two and as far as I can see I have two options..

1.) Buy 2x 8ohm 12" Greenbacks for my cab and see how they sound with the Bassman
2.) Sell the Bassman and aquire the Marshall

This is like choosing between children ☹ ?
Nick, first speak to Karel before you take a decission...maybe it's just something small that can be sorted out for little $. Those silverfaces should easily handle high volumes before breaking up....also as you say it could be an impedance mismatch, but he'll be able to establish that in no time.

Graemes right up the road, should be fetching something from him soon may lug it along and ask his opinion ?

FenderBender

It is possible to mount a 25W 8 ohm resistor in the cab, with a switch to connect it across the two greenbacks wired in parallel.
This will present a 4 ohm load to the bassman and the power will be halved. It may be worth hooking one on just to hear how it sounds.
I have a few resistors in stock ready for my next Tube Tamer build. Pull in sometime and we can try it out as such ?

nick

Graeme Parfett wrote It is possible to mount a 25W 8 ohm resistor in the cab, with a switch to connect it across the two greenbacks wired in parallel.
This will present a 4 ohm load to the bassman and the power will be halved. It may be worth hooking one on just to hear how it sounds.
I have a few resistors in stock ready for my next Tube Tamer build. Pull in sometime and we can try it out as such ?

Awesome, then you can also give it a listen and tell him if its just me being silly with regard the clean tone ?

nick

Graeme got to hear the Bassman and the Plexi back to back with the same cab, he can now add his opinion on the two ?

FenderBender

Nick's Bassman does not react the same as others that I have had in for servicing/repairs. Cleans are almost unattainable and the preamp tubes break up very early. Rolling back the volume on the guitar makes a slight difference, but she is definitely crunching too soon.

There could be a few reasons for this:
1. There may be an issue with one or more preamp tubes.
2. The input stage may have been modified for more gain.
3. There may be a faulty component/s on the board.

I'd say replace the preamp tubes first and see if there is a difference.
Failing that, checking the circuit against the original AB165 schematic, testing the supply voltages and tracing the audio signal with a scope should shed some light on the issue.

Reinhard

Graeme please don't hurt your back when handling the plexi, it is rather hefty ?

FenderBender

Reinhard wrote it is rather hefty ?

Cos it's full of good tone ?

I'll treat her nicely. I suspect she just needs a cap job ?

Reinhard

Thanks Graeme!

MoJo-JoJoe

MoJo JoJoe wrote I already told you my choice. From your description, it sounds like the Bassman needs attention. Rather spend a couple of bucks getting it some TLC from a decent amp tech ... you won't be sorry! eMail me if you need a contact number for someone, but I'm sure the amp techs on the forum would be happy to have your baby on their workbenches.

Graeme Parfett wrote Nick's Bassman does not react the same as others that I have had in for servicing/repairs. Cleans are almost unattainable and the preamp tubes break up very early. Rolling back the volume on the guitar makes a slight difference, but she is definitely crunching too soon.

There could be a few reasons for this:
1. There may be an issue with one or more preamp tubes.
2. The input stage may have been modified for more gain.
3. There may be a faulty component/s on the board.

I'd say replace the preamp tubes first and see if there is a difference.
Failing that, checking the circuit against the original AB165 schematic, testing the supply voltages and tracing the audio signal with a scope should shed some light on the issue.

nick

MoJo JoJoe wrote
MoJo JoJoe wrote I already told you my choice. From your description, it sounds like the Bassman needs attention. Rather spend a couple of bucks getting it some TLC from a decent amp tech ... you won't be sorry! eMail me if you need a contact number for someone, but I'm sure the amp techs on the forum would be happy to have your baby on their workbenches.

Graeme Parfett wrote Nick's Bassman does not react the same as others that I have had in for servicing/repairs. Cleans are almost unattainable and the preamp tubes break up very early. Rolling back the volume on the guitar makes a slight difference, but she is definitely crunching too soon.

There could be a few reasons for this:
1. There may be an issue with one or more preamp tubes.
2. The input stage may have been modified for more gain.
3. There may be a faulty component/s on the board.

I'd say replace the preamp tubes first and see if there is a difference.
Failing that, checking the circuit against the original AB165 schematic, testing the supply voltages and tracing the audio signal with a scope should shed some light on the issue.
?

yeh yeh ? Will replace pre-amp tubes when the budget allows and see how that goes.

ps. when are we doing the gear thing? This w/e?

MoJo-JoJoe

nick wrote
MoJo JoJoe wrote
MoJo JoJoe wrote I already told you my choice. From your description, it sounds like the Bassman needs attention. Rather spend a couple of bucks getting it some TLC from a decent amp tech ... you won't be sorry! eMail me if you need a contact number for someone, but I'm sure the amp techs on the forum would be happy to have your baby on their workbenches.

Graeme Parfett wrote Nick's Bassman does not react the same as others that I have had in for servicing/repairs. Cleans are almost unattainable and the preamp tubes break up very early. Rolling back the volume on the guitar makes a slight difference, but she is definitely crunching too soon.

There could be a few reasons for this:
1. There may be an issue with one or more preamp tubes.
2. The input stage may have been modified for more gain.
3. There may be a faulty component/s on the board.

I'd say replace the preamp tubes first and see if there is a difference.
Failing that, checking the circuit against the original AB165 schematic, testing the supply voltages and tracing the audio signal with a scope should shed some light on the issue.
?
yeh yeh ? Will replace pre-amp tubes when the budget allows and see how that goes.

ps. when are we doing the gear thing? This w/e?

Can't this w/end, but next weekend looks quite promising. Arjun and I already talked about meeting up next w/end again so why not let's make it a more/merrier thing if your gig schedule permits. My small place should accomodate the 4 of us - assuming Reihard is keen. Would be really cool.

nick

Right so I pulled the pre-amp tubes, they are all Sovtek 12ax7WA's. According to the amp schematic, one tube should be as 12at7 (which is lower gain than a 12ax7) and the rest should be 7025's which are just 12ax7s. Ive got 2 old ECC82s lying around (12au7) so I swopped the tube out and the input gain is lower and I have more clean headroom.

Will order new tubes with the next order 8)

MoJo-JoJoe

I would suggest using the correctly rated preamp tubes in all positions except V1 (first in the chain) ... there you could drop down to a 12AT7. Dropping gain in other places may result in dull lifeless tone. I'm home right now if you want to call me and swing by and collect a new 12AT7 for you to test with.

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