I need some Guitar GuRu help tonight!
 

I traded in my AVT150HX Marshall halfstack for a vintage Marshall head and I need help hooking this thing up. The cabinet is mis-matched for the head and is not a simple one wire plug in like the AVT150.

Show the connectors. ? Vintage marshalls have a two 6mm RCA outputs (guitar lead plugs). Whats into the cab? Cannons? Or the newer twist lock plastic things. Either way, it will still be only a two pole +/- connector- easy to make up a lead.

Remember to match the amp impedence selector to the cab.

Vintage Marshall eh? Youre going to be popular....

Well, it is not vintage like late 60's early 70's vintage, more like mid eighties like when I was in high school. I will snap some pics and upload. The two outputs on the rear of the head are not labeled and while the inputs on the cab are labeled, it is sort of confusing because there is no selector for mono/stereo. I need to keep the ohms on this head at 4 ohms or higher, but would like to keep it right at 4 ohms so that I do not loose my 100w output. If I go under 4ohms, I will damage the head.

Its a JCM800?

The two RCA speaker outs on the amp are to run two mono cabs, usually 8ohm each. Set 8 ohm for one, 16ohm for two. There will be an impedence selector on the back of the amp? Possibly one of those types you turn with a coin, or the older ones had pin plug arrangement that always needed to taped in.

Its not a stereo amp- your cab can run 8ohm in mono? 8ohm on the amp, and a cable (speaker cable not shielded guitar cable- lot of people use a piece of electrical cable) with a 6mm RCA for the amp and whatever connector you need at the cab.

You'll have the cops around in no time.

Close, it is the Mosfet version. The lead 100 Mosfet and man is this thing loud!!! This is supposed to be 100watts, the one I traded in was a tube hybrid that was supposed to be 150w, but this thing totally knocks it out of the water!!! I am running it through a Hughes and Kettner 4x12 that runs their version of Vintage 30's sounds really great, but want to make sure that I don't kill my head. I have wanted one of these since high school.

Ive never owned a trannie Marshall- so consider everything above as a guess only. But- Id reckon all the connectors and selectors came out of the same parts bin.

The cab has only two inputs and it DOES NOT have a stereo/mono selector. This is actually the first cab that I have seen like this. It looks as if the right stereo input doubles as the mono input? What do you think? And, if I run both head outputs to the cab, will I be running 4ohms where I want to be or will I be running 2ohms which is bad?

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OK- this easy. Using the speaker cable you have (stereo 6mm plug- it doesn't matter) Just set the amp to 8ohm, and connect ONE speaker output to the cab input labelled mono 8ohm.

The cab is wired for left/right stereo at 4 ohm each with stereo am, or mono at 8ohm using only that right hand input.

Can you show a straight on pic of the rear panel of the amp? Is there a impedence selector- what are the labels on the speaker outs?

This particular amp is very similar to the JCM 800 since you can blend the clean and gain channels together.

Thanks for the help stuart! If I run both cables to the left and right channel of the cab, will that put me at 4ohms or will it drop to 2ohms output? The reason I ask, is to get the full 100watts out of the head, I need to be running 4ohms. At 8 ohms, I think it drops to 80w output and at 16ohms I think it drops down to 50w output. If it drops down to 2ohms by connecting both leads, I will probably just leave it at 8ohms or investigate what I need to do to rewire the cabinet to get 4ohms...

Let me get those pics for you stuart, there is no impedance selector, the outputs are just labeled 4-16ohms.

Geez- I used to know this stuff. But Ive never run a stereo set up. It all depends on the cab wiring series/parallel. Standard marshall output is usually 8ohm AFAIK- all marshall quads are wired for 8. Id be surprised if you weren't getting 100w at 8ohm. Id be inclined to NOT run two outputs- its not a stereo amp. Id run one @8ohm output to the 8ohm mono side of the cab.

The handbook will online somewhere.

Here is the back of the amp.

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Don't bother, that answers the question. It can handle all those loads. Go with above^. That's "standard". I don't think youre achieving anything by taking two parallel connections from a mono amp to the stereo cab- and I not sure what that would mean WRT impedance.

MInd you- its a trannie head. Theyre pretty bullet proof. If you really want to try, I doubt you'll do any harm.

That's what I'll go ahead and do then, just run one lead to the 8ohm input. I will also look and see if I can find a online PDF manual for it. Not sure if they had them during the 80's or not. Any idea on what that DI output is for?

The DI out is for live or recording use. You can take a line feed directly from the amp to a mixing desk. The knob controls the line level of that output signal.

Its not something guitar players generally do, because we are fussy about The Tonz and usually mic the cabs. With at least 6 mics of different types, at different distances, some even in other rooms. But its good for bass, as no one cares.

Lol, thanks for the help Stuart! This head truly is incredible! Great Marshall tone and enough balls to share with the neighborhood! Here is a demo of the amp:


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Rock.

Totally!

Dude sort of reminds me of Jake from Two and a Half men, I always get a chuckle when I watch his videos.

This thing can get the AC/DC tone easy....


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Ok, if you put the head on 4 ohms, you run it into the "stereo R" side on the cab. I don't understand that 16 ohms jack on the head. If you run a cable out of each of those jacks, does the 16 ohm one then drop to 4 ohms? There are jacks like that. All the heads I've had had dials on the back for 4, 8 and 16 ohms with one or two output jacks.

At home I run a Soldano SLO 100 into a Soldano 4x12 that only has one jack and is rated for 16 ohms. So I put the dial on the head at 16 ohms and run one cable out of one of the output jacks (on the head) into the only cab input.

At one band practice space I have a Mesa Stiletto 4x12 (also with V-30s) and it has three jacks - one for 8 ohm mono and two for 4 ohm stereo. So I run cables out of each of my head's output jacks into the 4 ohm jacks in the cab and put the dial on the head at 4 ohms.

At my other band's practice space I have a Seismic 2x12 with Celestion G12T-75s rated at 16 ohms, but wired in parallel. So that's 8 ohms and I turn the dial on my head to 8 ohms.

Anyway, I asked Michael Soldano about this and he said his amps are tough enough to withstand mismatched impedances. I don't know for how long, but I did forget to change the dial once when I got home and played for a week on the wrong setting and it was fine.

Post this on the Marshall Amp Forum and you'll get a good explanation.

Rick- it just means the amp can handle any load 4-16ohm, and has no manual selector. In a standard Marshall config (mono) one cab at 8, plug in another 8ohm cab from the head, in parallel, the amp is happy at 16ohm. Likewise it can drive the two sides of the stereo cab at 4ohm. But its not a stereo amp, so there seems little point in doing that.