JMP 2150 pre-amp valves (tubes)

ledfree · 05-13-2008, 03:33 PM

I am thinking about changing the valves in my Marshall JMP 2150 (powercell) 1x12 combo.
For those who maybe not famlier with this amp, it features a post inverter master volume

. In other words. The control panel as two channels with their own volume, 4 inputs ala 1959SLP but with a added master volume and the usual eq controls.
I am thinking of changing the pre-amp valve first, too valves that will not breakup as early as the prescent installed ECC83/12AX7s.
Will this work or make no differance to the gain? I am looking to change it sonicaly to increase the mids and make the highs more sweeter (want for a better word).
Any thoughts?

ledfree · 05-14-2008, 01:18 PM

Anybody...

Adwex · 05-14-2008, 01:21 PM

You could try a lower gain tube, like a 12AT7.

ledfree · 05-15-2008, 12:23 PM

Quote:

Originally Posted by Adwex

You could try a lower gain tube, like a 12AT7.

Funny you should mention a 12AT7, because I have thought about trying one in the phase inverter/V3 position. Someone else as said try one in the gain/V1 position. I am confused.

Adwex · 05-15-2008, 12:38 PM

A 12AT7 is almost the same as a 12AX7, but it has lower gain. They are often used as the phase inverter, and sometimes (rarely, I think) they are used in the V1 position to soften the gain (later breakup).

RiverRatt · 05-20-2008, 10:54 PM

You'd probably be happy with some good NOS tubes. I've got a couple of RCA clear top 12AX7's and a Raytheon 12AT7 in the PI. Good stuff.

05-13-2008, 03:33 PM	#1 (permalink)
ledfree Junior Member Join Date: Feb 2008 Location: Some where in Marshall Land Posts: 9	JMP 2150 pre-amp valves (tubes) I am thinking about changing the valves in my Marshall JMP 2150 (powercell) 1x12 combo. For those who maybe not famlier with this amp, it features a post inverter master volume. In other words. The control panel as two channels with their own volume, 4 inputs ala 1959SLP but with a added master volume and the usual eq controls. I am thinking of changing the pre-amp valve first, too valves that will not breakup as early as the prescent installed ECC83/12AX7s. Will this work or make no differance to the gain? I am looking to change it sonicaly to increase the mids and make the highs more sweeter (want for a better word). Any thoughts?

05-14-2008, 01:18 PM	#2 (permalink)
ledfree Junior Member Join Date: Feb 2008 Location: Some where in Marshall Land Posts: 9	Re: JMP 2150 pre-amp valves (tubes) Anybody...

05-14-2008, 01:21 PM	#3 (permalink)
Adwex Senior Member Join Date: Sep 2006 Location: Long Island, NY Posts: 451	Re: JMP 2150 pre-amp valves (tubes) You could try a lower gain tube, like a 12AT7. __________________ Band Website: http://www.loudrocker.com/

05-15-2008, 12:38 PM	#5 (permalink)
Adwex Senior Member Join Date: Sep 2006 Location: Long Island, NY Posts: 451	Re: JMP 2150 pre-amp valves (tubes) A 12AT7 is almost the same as a 12AX7, but it has lower gain. They are often used as the phase inverter, and sometimes (rarely, I think) they are used in the V1 position to soften the gain (later breakup). __________________ Band Website: http://www.loudrocker.com/

05-20-2008, 10:54 PM	#6 (permalink)
RiverRatt Junior Member Join Date: May 2008 Posts: 26	Re: JMP 2150 pre-amp valves (tubes) You'd probably be happy with some good NOS tubes. I've got a couple of RCA clear top 12AX7's and a Raytheon 12AT7 in the PI. Good stuff.

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