FenderHead
New member
i know the JCM800 is basically a reissue of the 77 JMP Master Volume.
but whats the difference inside?
but whats the difference inside?
what is the difference between the JMP Master Volume and the JCM800?
- Thread starter FenderHead
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Frazer Stockton
New member
Re: what is the difference between the JMP Master Volume and the JCM800?
https://forum.seymourduncan.com/showthread.php?t=176937 theres some talk about the JMP in here.
And welcome to the forum =]
https://forum.seymourduncan.com/showthread.php?t=176937 theres some talk about the JMP in here.
And welcome to the forum =]
Simon_F
Super Moderator
Re: what is the difference between the JMP Master Volume and the JCM800?
This is a topic about which you will find a lot of debate on the net!
From the introduction of the JMP Master Volumes in 1975 throughout the life of the single-channel JCM800s in the 80s Marshall definitely made changes to that circuit.
I think it is true to say that the last of the JMP Master Volumes (80/81) are the same as the first of the JCM800s. But that circuit was on an evolutionary path!
I have owned JMP MVs from '77 and '80 and found them to be significantly different gainwise and tonally, and I believe this difference to be more than variation in components.
There are people who know lots more about these amps. I've just played a few of 'em!
This is a topic about which you will find a lot of debate on the net!
From the introduction of the JMP Master Volumes in 1975 throughout the life of the single-channel JCM800s in the 80s Marshall definitely made changes to that circuit.
I think it is true to say that the last of the JMP Master Volumes (80/81) are the same as the first of the JCM800s. But that circuit was on an evolutionary path!
I have owned JMP MVs from '77 and '80 and found them to be significantly different gainwise and tonally, and I believe this difference to be more than variation in components.
There are people who know lots more about these amps. I've just played a few of 'em!
Rich_S
HomeGrownToneBrewologist
Re: what is the difference between the JMP Master Volume and the JCM800?
Some of the earliest JMP MV models had one less gain stage. Later on, they re-configured the circuit so that the low-gain input's triode was added into the high-gain signal chain. It stayed this way into the JCM800 era.
Some of the earliest JMP MV models had one less gain stage. Later on, they re-configured the circuit so that the low-gain input's triode was added into the high-gain signal chain. It stayed this way into the JCM800 era.
Last edited:
FenderHead
New member
Re: what is the difference between the JMP Master Volume and the JCM800?
thank you.
thank you.
FenderHead
New member
Re: what is the difference between the JMP Master Volume and the JCM800?
yeah thats what i figure. i knew that the faceplate is similar but i was not quite sure whats the difference inside.
Thanks for the reply
yeah thats what i figure. i knew that the faceplate is similar but i was not quite sure whats the difference inside.
Thanks for the reply
F
Funkfingers
Guest
Re: what is the difference between the JMP Master Volume and the JCM800?
Components. Marshall can only build from what is available. If suppliers go out of business, manufacturers have to find an alternative source.
(Somebody somewhere out there in Forumland will have a vast list of exactly which transformers, capacitors and valves went into which production batches of which models.)
Ageing. The parts inside an original JMP will have deteriorated over time.
Design revisions. Health and safety legislation in the UK means that traditional Marshall features such as the metal Power and Standby toggle switches have been superceded by enclosed plastic rocker types. Similarly, the old "pin" type mains voltage and loudspeaker impedance selectors have been changed to safer enclosed rotary ones. Some will argue that these changes impose some miniscule change upon the sounds from the amplifier.
My suggestion is that you plug your guitar into either (or both) of these heads and buy whichever one your ears prefer.
Components. Marshall can only build from what is available. If suppliers go out of business, manufacturers have to find an alternative source.
(Somebody somewhere out there in Forumland will have a vast list of exactly which transformers, capacitors and valves went into which production batches of which models.)
Ageing. The parts inside an original JMP will have deteriorated over time.
Design revisions. Health and safety legislation in the UK means that traditional Marshall features such as the metal Power and Standby toggle switches have been superceded by enclosed plastic rocker types. Similarly, the old "pin" type mains voltage and loudspeaker impedance selectors have been changed to safer enclosed rotary ones. Some will argue that these changes impose some miniscule change upon the sounds from the amplifier.
My suggestion is that you plug your guitar into either (or both) of these heads and buy whichever one your ears prefer.