Marshall JMP 2150 Valve change time

ledfree · 05-14-2008, 01:59 PM

Help!
I've a Marshall JMP 2150 Powercell 1x12 100w combo and I am thinking of replacing the valves (tubes).
First of all, (for those of you who are not familiar with this amp) this amp as what is called a post inverter master volume.

In a nut shell, this amp as two channels with 4 inputs. So the control panel looks like a 1959SLP's but with the addition of a master volume pot.
Now I'm looking to change the pre-amp valves first. What i am hoping to do is reduce some of the gain this amp produces by changing the ECC83/12AX7s with replacments that will reign in some of the distortion that this amp can produce.
I am considering
V1 & V2 position. Either 5751 or 12AY7
V3 position. 12AT7 (jury is still out on this one)
So what do you tech types think will this work or not?

Big John · 05-14-2008, 03:07 PM

For one thing, you have an extremely rare amp. AKAIK, it's the only Marshall with a factory PPIMV. There's been a few popping up on fleabay this year; here's the latest (1, 2). I've played through two of them in my lifetime. I would recommend only changing out the first gain stage tube for a 12AT7 (the one farthest away from the power tubes) first before trying any more positions. Do this and then plug into the lower gain inputs, and I think you'll be surprised at the amount gain in the preamp that gets cut. A 5751 will have a little more gain than the 12AT7, at least that's been my experience.

ledfree · 05-16-2008, 03:17 PM

Cheers Big John, you don't see many 2150's for sale over here in the UK either.

ledfree · 05-17-2008, 03:42 AM

Just a thought. Can anyone tell me would there be reliabillty issues with swapping a ECC83/12AX7 with a ECC81/12AT7?

05-14-2008, 01:59 PM	#1 (permalink)
ledfree Senior Member Join Date: Sep 2007 Location: Staffordshire, UK Posts: 1,572 Thanks: 28 Thanked 8 Times in 2 Posts	Marshall JMP 2150 Valve change time Help! I've a Marshall JMP 2150 Powercell 1x12 100w combo and I am thinking of replacing the valves (tubes). First of all, (for those of you who are not familiar with this amp) this amp as what is called a post inverter master volume. In a nut shell, this amp as two channels with 4 inputs. So the control panel looks like a 1959SLP's but with the addition of a master volume pot. Now I'm looking to change the pre-amp valves first. What i am hoping to do is reduce some of the gain this amp produces by changing the ECC83/12AX7s with replacments that will reign in some of the distortion that this amp can produce. I am considering V1 & V2 position. Either 5751 or 12AY7 V3 position. 12AT7 (jury is still out on this one) So what do you tech types think will this work or not? __________________ Objects in the mirror may be more stupider than they appear. Small print: I reserve the right to change my mind at any time. In other words I'm always right, so there.

05-14-2008, 03:07 PM	#2 (permalink)
Big John Size Matters Join Date: Mar 2007 Location: up and left Posts: 3,943 Thanks: 9 Thanked 115 Times in 29 Posts	Re: Marshall JMP 2150 Valve change time For one thing, you have an extremely rare amp. AKAIK, it's the only Marshall with a factory PPIMV. There's been a few popping up on fleabay this year; here's the latest (1, 2). I've played through two of them in my lifetime. I would recommend only changing out the first gain stage tube for a 12AT7 (the one farthest away from the power tubes) first before trying any more positions. Do this and then plug into the lower gain inputs, and I think you'll be surprised at the amount gain in the preamp that gets cut. A 5751 will have a little more gain than the 12AT7, at least that's been my experience.

05-16-2008, 03:17 PM	#3 (permalink)
ledfree Senior Member Join Date: Sep 2007 Location: Staffordshire, UK Posts: 1,572 Thanks: 28 Thanked 8 Times in 2 Posts	Re: Marshall JMP 2150 Valve change time Cheers Big John, you don't see many 2150's for sale over here in the UK either. __________________ Objects in the mirror may be more stupider than they appear. Small print: I reserve the right to change my mind at any time. In other words I'm always right, so there.

05-17-2008, 03:42 AM	#4 (permalink)
ledfree Senior Member Join Date: Sep 2007 Location: Staffordshire, UK Posts: 1,572 Thanks: 28 Thanked 8 Times in 2 Posts	Re: Marshall JMP 2150 Valve change time Just a thought. Can anyone tell me would there be reliabillty issues with swapping a ECC83/12AX7 with a ECC81/12AT7? __________________ Objects in the mirror may be more stupider than they appear. Small print: I reserve the right to change my mind at any time. In other words I'm always right, so there.

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