Help modding SS amp. MG15. Enzo?

[THChrist]

Hi everyone. Well, here's the thing. I Have this small amp, a Marshall MG15CDR which i like. It has a unique sound (i used to have a MG15DFX, and couldn't stand its sound) but the "Line Out/CD In" jack is freakin' me out. When i plug a tuner, it works as Line Out. When i plug my Mp3, it's CD In. When I plug a cable to the PC it's Line Out, to the Laptop it's CD In. To another amp it's Line Out, but to a Cab-Simulator it's CD In. I can't stand that anymore. I don't care for the CD In, I never use it anyway, but i want the "Line Out/CD In" to be just "Line Out". Do I need to replace some resistors? anything? It has nothing to do with mono/stereo cables, i've tried both and it's the same thing...

Please, help me..

Enzo?

[Enzo]

I don't understand the problem. What is your beef? You have a pair of jacks that are wired in to the signal path right before the power amp. SO whatever is already in the signal path can be sent out there, and you can also run something into the signal path at that point. You want the output but not the input? FIne only connect cords that go somewhere, and don;t connect signals from somewhere else.

If you are connecting some device hoping to send the guitar signal to it, and it winds up sending sound into your speaker, that isn;t the amp's fault. That sounds like the connetion to the other device is not an input.

[THChrist]

I don't understand the problem. What is your beef? You have a pair of jacks that are wired in to the signal path right before the power amp. SO whatever is already in the signal path can be sent out there, and you can also run something into the signal path at that point. You want the output but not the input? FIne only connect cords that go somewhere, and don;t connect signals from somewhere else.

Not a pair. Just one which doubles as In or Out; and that's what i do. i plug cords that go somewhere: tuner (it works good), another amp (good). the fail is when i plug it on my cam simulator and my laptop (mic input)

If you are connecting some device hoping to send the guitar signal to it, and it winds up sending sound into your speaker, that isn;t the amp's fault. That sounds like the connetion to the other device is not an input.

no no. you see when i plug it on my Laptop, it doesn't make any sound. when i plug another thing on that same jack (of my laptop), it works.
that's because of some kind of "smart" design by the guys at marshall.

since the same jack works as Line Out AND CD In, i'm guessing it's something about impedance or anything like it.

[olddawg]

Are you running into a line level input or a mic level input? Depending on the laptop you might have separate inputs or it might be selectable. If you are overloading the mic input the sound card might just be muting it. You also might have to attenuate the signal or run it through a mixer.

[THChrist]

Are you running into a line level input or a mic level input? Depending on the laptop you might have separate inputs or it might be selectable. If you are overloading the mic input the sound card might just be muting it. You also might have to attenuate the signal or run it through a mixer.

my laptop has just one input (mic/aux). and that's not the only problem, the out doesn't work as it even when i plug it to me cab-simulator. i just wanna make it "line out". i don't care for that "cd in" thing.

[Enzo]

Oh, a single jack? OK, most CD inputs are a pair of RCA jacks for "left" and "right." Either weat it is nothing more than a tap on the signal path through the amp. There is absolutely nothing different about this jack circuit. It has no idea what you connect it to. If you are using it as an output, then if it works into some destinations but not into ohers, then the destination device is not compatible OR the conection cable in not right. WHen you connect it to some other amp and it works, that right there demonstrates that the jack is working, and working correctly. There is no additional circuitry behind it, it has no impedance detecting anything, and it wouldn't matter anyway.

when i plug it on my Laptop, it doesn't make any sound

Meaning the guitar sound doesn't come out of the lap top? Or meaning plugging into the laptop kills sound even out the guitar amp? You can't change the cd in thing because it is all the same. It would be like your bedroom door, it is both an entrance and an exit. You couldn;t very easily turn your beroom door into an exit only and get rid of that entrance thing.

That input is just a point on the signal path where the signal level is about line level. So you can conect it to anything that will accept that level signal. It is also an input in the sense that it is a door onto the signal path, so when things can leave the path there, you can also send other things IN there.

I am betting your connecting cord is the issue. What EXACTLY is on each end of the cable? Is the guitar amp end 1/4"? Same size and shape as a guitar cord plug? It is a mono cord, but it needs to have that extra ring around the end like a headphones plug.

I am also betting the computer end is a small connector, like maybe 3mm, the size of walkman phones plugs. Does that one also have the extra ring around it or not?

Or is it something different?

[THChrist]

Oh, a single jack? OK, most CD inputs are a pair of RCA jacks for "left" and "right." Either weat it is nothing more than a tap on the signal path through the amp. There is absolutely nothing different about this jack circuit. It has no idea what you connect it to. If you are using it as an output, then if it works into some destinations but not into ohers, then the destination device is not compatible OR the conection cable in not right. WHen you connect it to some other amp and it works, that right there demonstrates that the jack is working, and working correctly. There is no additional circuitry behind it, it has no impedance detecting anything, and it wouldn't matter anyway.

ok, i get it. i hate marshall

Meaning the guitar sound doesn't come out of the lap top? Or meaning plugging into the laptop kills sound even out the guitar amp? You can't change the cd in thing because it is all the same. It would be like your bedroom door, it is both an entrance and an exit. You couldn;t very easily turn your beroom door into an exit only and get rid of that entrance thing.

the guitar sound doesn't come out at all. if I unplug the amp and touch the tip, the laptop recognizes the sound (buzz)

That input is just a point on the signal path where the signal level is about line level. So you can conect it to anything that will accept that level signal. It is also an input in the sense that it is a door onto the signal path, so when things can leave the path there, you can also send other things IN there.

got it.

I am betting your connecting cord is the issue. What EXACTLY is on each end of the cable? Is the guitar amp end 1/4"? Same size and shape as a guitar cord plug? It is a mono cord, but it needs to have that extra ring around the end like a headphones plug.
I am also betting the computer end is a small connector, like maybe 3mm, the size of walkman phones plugs. Does that one also have the extra ring around it or not?

Or is it something different?

well, i've tried with stereo cables, mono cables, mono plugs, TRS plugs, 1/8 to 1/4 (since my laptop has small connectors). and it's random. it worked with my old laptop, my pc, korg tuner. Now, i dont care if it doesn't work with my laptop, i just want it to work with my cab-simulator (DIY).


and for something completely different, Enzo, do you know something abot this new MG's?

[olddawg]

(Well, i've tried with stereo cables, mono cables, mono plugs, TRS plugs, 1/8 to 1/4 (since my laptop has small connectors). and it's random. it worked with my old laptop, my pc, korg tuner. Now, i dont care if it doesn't work with my laptop, i just want it to work with my cab-simulator)

As Enzo said you may be running a mono plug into a stereo jack. Have you used a "Y" connector that will split the stereo input of your laptop into two mono inputs? Also, cheap signal plug adapters are notorious for being intermitant, especially if you are connecting more than one to another.

[Enzo]

I know many things, what are you asking?

[THChrist]

I know many things, what are you asking?

the sonic differences, reliability, etc. between the old MG's and the new MG's (MG series 4). i have my doubts about the whole "analog sound + digital controlers", even tho' the front panel looks "cleaner"

[Enzo]

I don't give such things much thought. There are thousands of amps on the market, and I have no time to listen to them all, and frankly to me when I hear one of these I think "Small Marshall SOlid State Amp" and am not really listening for any nuance between them. Nothing against the amps, I just don;t sit there and listen with that critical an ear. I am not in the market to buy one, and once I have it performing as it should I put it aside and move on.

As to reliability, I think most amps are pretty reliable. There are certain things I don;t want to see. That MF350 Mode 4 Marshall is a total sin. SHould never have been put on the market, a total nightmare. And frankly I think the whole Marshall TDA7293 power amp'd line of amps should be rethought. But that is from my point of view. Just because I see a lot of them blown up doesn;t mean much, there are thousands and thousands of them that DON'T blow up. Most problems are mechanical anyway - guys breaking off knobs, breaking jacks, etc.

When I consider buying a product I consider support. Especially if I were in Peru, which brands offer support in terms of parts and service availability. In the USA, I would tour with a Peavey product before most any other for that reason.

[rory]

hi
has anybody replaced the facia channel switch on a marshall mg15dfx with a footswitch.
if so how.rory