amp gurus - need a little help with wiring please

CaughtLikeFire

CaughtLikeFire

New member
ok, so I'm in the process of replacing the OT on my Laney LC15 with a Mercury Magnetics unit. I got rid of the extra wires for the internal speaker and I'm going to run the internal speaker from the line out jack (using a cable with a 1/4" jack on one side and terminals on the other, like Fender does).

my question is this, why are there resistors soldered on to the line out jack (see pic)? I kept them soldered in for now but I'm tempted to get rid of them. If I'm hooking up the 2 speaker leads from the OT directly to the jack, why would I need any other resistors?


IMG_0133.jpg
 
Re: amp gurus - need a little help with wiring please

If I were to guess, I would say NFB. But I am not familiar with these amps at all. I am sure someone with Laney experience will be of more help.
 
Re: amp gurus - need a little help with wiring please

OK - here's your schematic pdf.....

http://www.freeinfosociety.com/electronics/schematics/audio/laneylc15.pdf

Running a speaker from a line-out is going to be very, very quiet.

But if that's the way you want to go - the line out has:
2.2kohm from the output of the TL072
2.2kohm to earth
Both SHOULD be Red/Red/Red.....

You, however, seem to have:
Yellow/Purple/Red 4.7kohm from the output of the TL072 switched
Purple/Grey/Brown 780ohm to earth

With nothing plugged in it looks like 780ohms to ground.
With a jack in the socket it looks like 780ohms and 4.7k (5.5kohm) to ground across the signal.

Makes no sense to me.

But again - the LINE-OUT is intended as a signal to feed a slave amp or a PA, or a mixer
NOT a speaker.....
 
Re: amp gurus - need a little help with wiring please

Thermionik said:
But again - the LINE-OUT is intended as a signal to feed a slave amp or a PA, or a mixer
NOT a speaker.....
Click to expand...

I realized this as soon as I posted yesterday and I should have edited it right away. my amp doesn't have an actual "speaker out" like the newer versions do.

With everything disconnected, it's just a plain old 1/4" jack, right?. I ran the OT wires to the jack but I'm getting no sound from the amp. no crackles, pops or crazy noises, just nothing.

I didn't think that disconnecting the line-out would interrupt the circuit but maybe I was wrong. either that or the wires from the OT to the tube sockets are switched around (but I wired them up exactly the same as the old OT . . . ).

I guess I should stick to wiring guitars :banghead:

thanks for the input, guys :cool2:
 
Re: amp gurus - need a little help with wiring please

ok, got everything fixed!

there was something up with that 1/4" jack. I thought they were all the same (noobie mistake). Extended the speaker leads on the OT and ran them straight to the speaker and now I'm in business.

holy cow was I missing out. volume is double if not triple what it was before and there are no more volume fades or crackling noises. the original Laney-sourced OT must have been long gone. I always thought it was pretty weak-sounding for a 15W amp and now I know why.

looks kinda funny now since the Merc output transfomer is as big as the power transformer :)
 
Re: amp gurus - need a little help with wiring please

Checked schematic - removing the wire to LINE-OUT should not interfere with the signal to the next stage - so you should be hearing stuff. Weird.....
Not being picky - but are you going to the switched or unswitched side of the JACK SOCKET that was LINE-OUT.

Ignore that - read your post that came out with mine - good work man.

OT and speaker will make a BIG diff to loudness one way or another.....
.....in your case - in a GOOD way. Result.
 
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