Marshall JMP-1 Pre-Amp Into HT-20 combo?

Discussion - HT Venue amplifiers. Inspiration from Studio to Stage.
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Posts: 6
Joined: Mon Nov 12, 2012 10:25 am

Sun Nov 20, 2016 9:37 pm

Hi All,

Wondering if using the effects return on the HT-20 to hook up a Marshall JMP-1 pre-amp is possible to cut out the Blackstar HT-20 pre-amp and use the Marshall instead? Will this damage my HT-20 in anyway?

Really like the midi function of the JMP-1 pre-amp.

Cheers to anyone who replies with help!

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Posts: 1160
Joined: Wed Jan 29, 2014 7:42 pm
Location: Virginia, United States

Sun Nov 20, 2016 10:11 pm

Nope, it won't hurt a thing. You will basically be slaving the Blackstar power amp to the Marshall preamp.

The only caveat is that you'll have to plug something into the send jack on the HT-20....otherwise the return won't work. Something like a 1/4' headphone adapter usually does the trick.

Posts: 6
Joined: Mon Nov 12, 2012 10:25 am

Sun Nov 20, 2016 10:24 pm

Thanks thephantum for your reply!

Awesome, that's just what I was hoping! Thanks for the tip about the 1/4" headphone adapter in the effects send.


Posts: 6
Joined: Mon Nov 12, 2012 10:25 am

Wed Dec 07, 2016 5:16 am

Just got my Marshall JMP-1 and hooked it all up like the following:

Guitar >>> JMP-1

JMP-1 Master L. Output >>> Blackstar HT-20 Effects Loop Return

Blackstar HT-20 Effects Loop Send has a headphone adapter inserted.

Turn up the Master volume on the Blackstar and . . . nothing. :(

Tried the JMP-1 R. Output - same result, no sound.
Tried no adapter in Blackstar Effects loop Send - same result, no sound.

Not sure what I am doing wrong as it seems pretty simple. Daisy chain JMP-1 to Blackstar. I have a G-Major 2 as well but took that out of the equation for trouble shooting. If I added it back in it would be simply JMP-1 L. Output to G-Major 2 L. Input the G Major 2 L. Output to Blackstar Effects Return. I did try this and the G-Major 2 sees sound as the metres are reading input and output. Very weird.

Any help would be very much appreciated.

Last edited by RC21 on Wed Dec 07, 2016 4:58 pm, edited 2 times in total.

Posts: 6
Joined: Mon Nov 12, 2012 10:25 am

Wed Dec 07, 2016 4:57 pm

Okay I figured it out. I needed something (headphone adapter) in the Input jack where I would usually plug my guitar lead in. Once I did that it worked. I don't have anything in the Effects Send jack.

So this is how I have it all connected:

guitar >>> JMP-1 Input >>> JMP-1 Master L. Output >>> G-Major 2 L. Input >>> G-Major 2 L. Output >>> Blackstar HT-20 Effects Return

Headphone adapter inserted into the Input on the front of the HT-20.

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