Author Topic: Bought a Marshall (Read 9972 times)

gwEm · « **Reply #15 on:** January 17, 2007, 12:45:32 PM »

Quote from: LazyNinja

[
Yeah your explanation makes sense, because that's what I thought when I tried it. However, it's now sounding really bad with no defintion on the lower notes. Could just be the tubes I guess, but I have talked with Musicground and I might swap it for a Orange Rocker 30 instead. Do you think it's a bad move?

Well, thats up to you mate. The Orange is a very different amp obviously, I like the raw simplicity of the JMP.

You can get JMP Master Volumes on ebay for a good price. Seems like people didn't catch on to the fact that they're almost identical to the JCM800.

hunter · « **Reply #16 on:** January 17, 2007, 03:40:19 PM »

The Rocker 30 is a really cool amp, but the JMP is much more credible.

Maybe it's just the Bias that needs adjustment (Biasing, my latest obsession) 8)

jpfamps · « **Reply #17 on:** January 17, 2007, 04:30:36 PM »

The Marshall JMP amps do indeed use a fairly low plate voltage, typically 380-400 volts, which results in the amp distorting earlier. The build quality is also very good, for example the pots are not PCB mounted for easy servicing. Personally I think that these are the last great amp Marshall made, although there are arguments for the JCM800.

I sounds like your amp is not working correctly and needs a service. Possibly the filter caps need replacing, or possible the output valves need changing. It's very diffcult to say without seeing/hearing the amp.

Regarding the price, £650 is at the upper end of what these amps usually sell for. For that money I would have hoped to get an earlier small logo version (same amp, cooler box). However, people are now getting hip to JMP era Marshalls, so if you hang on to your amp and look after it you will have an appreciating asset.

HTH AMPS · « **Reply #18 on:** January 17, 2007, 08:40:00 PM »

Quote from: jpfamps

The Marshall JMP amps do indeed use a fairly low plate voltage, typically 380-400 volts, which results in the amp distorting earlier.

I've noticed that the 50w JMP Marshalls run low plate voltages but the 100w amps still run 'em quite high (520v on my old 2203 and I've found similar on other amps I've modded/serviced).

:twisted:

Twinfan · « **Reply #19 on:** January 17, 2007, 09:44:36 PM »

Pah - weakling amps. My Klipps have over 600v plate voltages. :twisted:

So ner-ner ner ner-ner

[/childmode]

stuckin93 · « **Reply #20 on:** January 17, 2007, 11:03:39 PM »

Keep the amp - but take it back to where you bought it & tell em to actually service it & then give it you back as a proper sale-able product

jpfamps · « **Reply #21 on:** January 18, 2007, 10:31:32 AM »

Regarding the above post,, I was referring to the 50 W amps. The 100 Ws do have higher voltages. Incidentally Marshall replacement mains transformers seem to be between the two at around 460-480 Volts.Sorry for any confusion.

JamesHealey · « **Reply #22 on:** January 18, 2007, 02:10:49 PM »

the Musicman HD 130's have 700+ platevolts on EL34's.. now thats really getting some serious juice out of your amp.

I'd take it back to music ground, make them service it for free.. they will do that it's just a shame they have to fob you off with a dodgy amp to make money with such a great shop?

LazyNinja · « **Reply #23 on:** January 18, 2007, 03:03:33 PM »

Yeah either that or I'll get a Rocker 30 or a VH100R both of which theyre willing to swap it for. Still a rip off but at least they'll be new with 3 years warranty. I need a reliable amp. I hate the clean on the marshall now coz well it isnt clean it's kind of sweet child o mine clean at best even with volume rolled right back, but I love its distortion and crunch. Maybe it's just coz Im used to lush cleans of fenders; my HRD with NOS mullard and Jenson speaker has the nicest clean sound Ive personally heard around here. Im going to be trying out the Rocker 30 when they bring it over from London. If I like it enough I'll get that and if not I'll order VH100R.

gwEm · « **Reply #24 on:** January 19, 2007, 09:18:40 AM »

regarding the cleans -

did you try the low sensitivity input? or whip out the capacitor across the gain pot (maybe not though as your thinking of taking the amp back :) ), which will allow you to roll the gain right back and keep the bottom end.

Twinfan: 600v eh? show off ;)

Twinfan · « **Reply #25 on:** January 19, 2007, 09:21:15 AM »

:lol:

LazyNinja · « **Reply #26 on:** January 19, 2007, 10:38:26 AM »

Quote from: gwEm

regarding the cleans -

did you try the low sensitivity input? or whip out the capacitor across the gain pot (maybe not though as your thinking of taking the amp back :) ), which will allow you to roll the gain right back and keep the bottom end.

Yeah I tried the low input, but then you lose the nice sizzling gain... Plus you lose a lot of dynamics imo. I suppose it's alright if you use a distortion pedal but that would defeat the whole point of having a Marshall. Maybe one of those 7581(? forgot the name, the clean ECC83 thing) preamp tubes will help? As for the capacitor, I don't know how amps work at all so that means nothing to me :oops: maybe I should start learning these stuff, sounds useful. Thanks for the suggestion but as you said Id rather not mess with it, at least for now.

NPH · « **Reply #27 on:** January 19, 2007, 11:02:09 AM »

I have a mint condition JMP 50watt combo. First time I used it up full (through a mashall powerbreak) I was stunned. Totally great rocking sound. I just used the volumes on the guitar to change the tone.

Incidentally we took it to Marshall in Milton keynes for a service and when we came in the guy behind the desk said "Oh a Thin Lizzy amp" It seems that they talk about them by referencing the sound they make, and this one does the Jailbreak sound perfectly at volume.

I have one of the earlier ones with the small logo as well, but it has been living in Brighton with one of the Guitar institute teachers for a couple of years, Hmmmm, must give Jim a call and get him to bring it back one day.

gwEm · « **Reply #28 on:** January 19, 2007, 12:11:19 PM »

[quote="LazyNinja]Yeah I tried the low input, but then you lose the nice sizzling gain... Plus you lose a lot of dynamics imo. I suppose it's alright if you use a distortion pedal but that would defeat the whole point of having a Marshall. Maybe one of those 7581(? forgot the name, the clean ECC83 thing) preamp tubes will help? As for the capacitor, I don't know how amps work at all so that means nothing to me :oops: maybe I should start learning these stuff, sounds useful. Thanks for the suggestion but as you said Id rather not mess with it, at least for now.[/quote]

:) Your experiences mirrors my own, which is pretty nice for me.

I agree with what you say. With the "low" input your losing an extra valve amplification stage.

I guess if you remove the capacitor I mentioned, its almost like starting to mod your amp... On the other hand, it is an easy mod to do and requires no soldering. I agree, it does feel wrong to mod a beautiful vintage amp like that. I wouldn't have done it either if I didn't think I could put it back.

_tom_ · « **Reply #29 on:** January 19, 2007, 12:50:54 PM »

Not sure on how the high and low jacks are wired but I just thought maybe you could plug your guitar into an A/B footswitch then a cable into each input so you can easily switch between clean and overdriven?