#1
so...my question is this...

i've seen some pictures of the old marshall around with 4 inputs...and even some with a jumper cable going in two of the input with the actual guitar input going into another...

what are all these inputs for? and what are some of them jumpered?
#2
When my grandpa was in a band in the late 50's early 60's, he said that there was only one cab, and the mic, lead, rythem, and bass where all plugged into it, 'cuz it had 4 inputs. (Ironically, he actually told me this today, lol)
#3
The reason the inputs were jumpered was because on the old plexi, you had 2 channels one normal, and one bright. You could plug into one or the other. The reason people jumpered the channels was for increased gain.
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#4
They used to be so you could plug a bunch of instruments into one amp. Nobody does that anymore because it doesn't sound very good. In old Plexis, there were two input channels, and they both used half of the same 12AX7 preamp tube. Each of those channels has two input jacks, labelled 1 and 2. The input jacks are in parallel, so the signal can go in one and out the other if you want.

What happens when you use the jumper is you are plugging your signal into one of the channels, then using a patch cable from the 2nd input on that channel to the input on the other channel.

Essentially, the jumper allows you to use both channels at once, so you use both halves of the 12AX7. The result is more preamp gain.
#5
Quote by sweet_inc
so...my question is this...

i've seen some pictures of the old marshall around with 4 inputs...and even some with a jumper cable going in two of the input with the actual guitar input going into another...

what are all these inputs for? and what are some of them jumpered?


I have a 4 input JTM45 head, there are two channels a normal and bright channel and high gain/low gain inputs for both.
#6
four jack sockets on the right hand side jumpered equals more gain... great classic late '60s early '70s rock overdrive sound.