Metropoulos Forum

hi everyone ! as i'm a new subscriber to your fabulous website i would introduce myself with a probably "new " subject .....a 66 67 68 69 "100w" head is usually marked whit a little white square thing on the back and there's 160W or more writed on it ....i red before it was because old tubes were stronger ....but what i would ask is this ; if i build a non master volume "100w" head and have yet just a 2 speakers 120w cab, do i take the risk to blow it???? for you if this is it , should i better add another cab or a master volume mod on the head?? next i would mention that i'm fench so if you guys could answer with not too much complicated words it would be quite cool ...

i would add another thing too...if you think i'm too slow too answer your posts and find it boring , then start considering de difference of time between france and usa !!

Frenchie,
Read through the Speakers & Cabs forum and you will wind that Jim Seavall (Southbay Ampworks) has outlined this quite a fiew times.

A Marshall 100W head is rated at 100W prior to breakup, so with the volmes dimed it's quite a bit more than 100W.

(4) 65W speakers
or
(2) cabs with (4) 25W speakers would be safe.

Any other situation you should consider a PPIMV or Attenuator.

by before breakup you mean before the tubes start to distort the sound??

The old Plexis were very conservatively rated. When Marshall sold them, two cabs, with 100 watts of power handling each (4 25 watt G12M's or 4 30 watt G12H's) were required.

That's because old Plexis would put out 120-140 watts clean, and in overdrive (from 4-10 on the volume knob) 170-235.

So before breakup is a relative term. G12M's breakup/distort sooner than G12H30's. 25 & 30 watt speakers breakup/distort sooner than higher power 65 watt speakers.

I've had too many people buy speakers from me who thought two G12H30 Anniversaries were enough to handle their 50 watt Plexi clone. Then they took my advice on going to 65 watt Scumbacks and they were happy.

You typically need 2 x as much speaker power handling as your amp's clean power rating. So a 50 watt Plexi should have 100 watts of speaker power handling, and a 100 watt Plexi should have 200 watts.

A local amp tech here in SoCal measured an old 68 Plexi 100 watt at 235 watts RMS dimed (on 10). Needless to say, he needed two G12H30 loaded cabs, and that's what the tech said he had, IIRC.

Blown speakers ruin the fun of guitar playing...at least ELECTRIC guitar playing.

ok so i need another 2X12' cab to handle a plexi 100W ....loaded with v30 as the first i own ....for a total of 240w with the both cabs ...i previously think the extra 20w my own cab carries was sufficient but judging by what i hear there the extra 120W will be far more helpfull ...

That's correct, sir.

thanks a lot ....and skuz me for the mistakes i must have made..my english is a bit rusty to my mind

Just curious, though, aren't the JTM100s pushing out less than the later plexies?

frenchie wrote:ok so i need another 2X12' cab to handle a plexi 100W ....loaded with v30 as the first i own ....for a total of 240w with the both cabs ...i previously think the extra 20w my own cab carries was sufficient but judging by what i hear there the extra 120W will be far more helpfull ...

2x12 only gives you 60. you'd need 2 cabs with 4 30w speakers in each. If you only want to speaers per cab, you need to get 65w speakers.

wdelaney72 wrote:

frenchie wrote:ok so i need another 2X12' cab to handle a plexi 100W ....loaded with v30 as the first i own ....for a total of 240w with the both cabs ...i previously think the extra 20w my own cab carries was sufficient but judging by what i hear there the extra 120W will be far more helpfull ...

2x12 only gives you 60. you'd need 2 cabs with 4 30w speakers in each. If you only want to speaers per cab, you need to get 65w speakers.

He's using V30s which are 60W each, so each 2x12 cab is 120W.

you're right nitroliq ....i've heard about that before.....there's many reviews of the super amp 100 saying it is for smaller rooms...but judging by the fact that jim marshall decided to sell them first with an 8 cab , jtm 100 's power must exceed 150 w full cranked ...but not as much as the 235 previously mentionned here by scrumback guy for a 68 unit

.. I think i f--cked up atleast one of my vintage greenies
How much are four of Scumbacks 30w 75hz?

The speakers are $149 each plus shipping to Sweden. Sorry to hear you may have fried one of your originals.