modify an LMII for post EQ effect return?

[J.Wolf]

I seem to remember some info about this a while back, wondering if anyone can point me in the right direction. I tried a search, in case you were inclined to helpfully reccomend that.

So, as it is, the effect return on an LMII is pre eq, I'm looking to make the effect return post eq/ essentially a "power amp in" type of deal. Anybody have any info about this?? thanks

[pbasswil]

If you're not electronically handy enough to feret out the schematics from some certified repair guy and modify it yourself, the simplist and cheapest solution for you might be to sell the LMII and buy a LMIII, which has the Pre/Post switch.

Who knows, maybe someone with a LMIII who doesn't need that feature, would be willing to trade for a LMII + some $$.

[dmusic148]

I think you are thinking of the jumper inside, which allows changing the DI output from pre/post EQ.
I doubt you could change the effects loop circuit- everything's surface mounted in these amps, and fairly tamper/repair resistant, unfortunately.

[ac3320]

Originally Posted by pbasswil

If you're not electronically handy enough to feret out the schematics from some certified repair guy and modify it yourself, the simplist and cheapest solution for you might be to sell the LMII and buy a LMIII, which has the Pre/Post switch.

That switch on the LMIII (and the jumper in the LMII) are for the DI, neither allows the LM to act as a poweramp.

Originally Posted by dmusic148

I think you are thinking of the jumper inside...

+1

I too would love to be able to do this, though who knows if it's possible. I've heard the LM pre/EQ is really flat anyways, but it would be nice to bypass it with your favorite tube pedal or something..

[J.Wolf]

Originally Posted by dmusic148

I think you are thinking of the jumper inside, which allows changing the DI output from pre/post EQ.
I doubt you could change the effects loop circuit- everything's surface mounted in these amps, and fairly tamper/repair resistant, unfortunately.

Oh crap, yeah that was it.. In my mind I thought it was for the loop, not the DI.. Typically, if I use the DI on the LMII, its because I like the LMII coloration, so bypassing it would be counterproductive for me. I'd prefer use my radial pre-LMII for a clean DI send.

thanks for the instantaneous clear up folks!

[J.Wolf]

offhand, anyone know if the F500/F1 effects return is the same deal, or can it function in the way I'm looking for?

[dave_bass5]

There are two jumpers in the LMII.
One changes the DI to pre or post EQ and the other changes the FX loop from parallel to serial.
I have the PDF showing where these jumpers are and how to change them. If its any use to you PM me with an email address.

[J.Wolf]

update/heads up

I removed the efx loop jumper and my echoplex performs beautifully in the loop of the LMII (thanks for the pdf Dave!). Seemingly its better sonically than what I had to do before, which was plug my bass directly into the echoplex and then into the LMII. I don't know why I didn't do that a long time ago...

Fastforward to this morning. setting up for a nice outdoor gig with just my LMII and two cabs, plugged everything in and powered up.... and got nothing... Luckily after about 10 sweaty panicked minutes I was fortunate enough to realize what might possibly be the problem.. plugged a cable into the efx send and looped it back in to the efx return, and it worked. So I guess this is the funky trade-off for having a series efx loop in the LMII, you gotta make your own "jumper" between the send and return to get any sound.

so...heads up!

[pacojas]

@J.Wolf

good thing you can problem solve on the fly!

i am interested in getting a copy of that schematic, please! i'm going to an external preamp and would like to eclipse the LMII pre section.
TIA!!!

[Bubba Ghanoosh]

You're welcome.

[JimmyM]

The LMII/III scopes out almost dead flat with all controls nooned and all filters off. Seems like a lot of work to accomplish what you can do by nooning it, but far be it from me to be a spoilsport

[JimmyM]

Originally Posted by J.Wolf

Jimmy, you mean regarding the pre/post DI jumper? that one isn't really an interesting mod for my needs, I was just glad to get the efx loop configured differently.

oh wait, you're talking to the person wanting to bypass the pre section..

Ya, not seeing the point of that when the head does near flat anyway.

[J.Wolf]

Thats interesting. Do you hear the head as "flat" when set nooned at de-filtered? Not wanting to open a can of worms, nor do I think the scopes lie, I'm just curious because I've never perceived the LMII as a flat/neutral/whatever sounding head. I really like the sound, but I have always perceived a built in curve/tone of a certain kind.

[dave_bass5]

Originally Posted by pacojas

@J.Wolf

good thing you can problem solve on the fly!

i am interested in getting a copy of that schematic, please! i'm going to an external preamp and would like to eclipse the LMII pre section.
TIA!!!

Hi. I did see your PM but wont have access to my copy until tomorrow (UK time) but im sure that link will get you it quicker.

As far as i can see the effects loop is pre EQ so using the return as a input is still going to route the signal through the EQ and filters.

[JimmyM]

Originally Posted by J.Wolf

Thats interesting. Do you hear the head as "flat" when set nooned at de-filtered? Not wanting to open a can of worms, nor do I think the scopes lie, I'm just curious because I've never perceived the LMII as a flat/neutral/whatever sounding head. I really like the sound, but I have always perceived a built in curve/tone of a certain kind.

Bass Gear Magazine tested it in their first issue, and said it is almost dead flat with the knobs nooned and filters off.

[pacojas]

Originally Posted by dave_bass5

Hi. I did see your PM but wont have access to my copy until tomorrow (UK time) but im sure that link will get you it quicker.

As far as i can see the effects loop is pre EQ so using the return as a input is still going to route the signal through the EQ and filters.

thanks for your reply!

i have located a few schem's that show how to take the pre out of the loop. it appears you can config a series efx loop, then disconnect the lead that feeds back to the LMII's pre.

perhaps i've mis-interpreted, but the block diagram looks straight foward.

[Jeff Scott]

Originally Posted by J.Wolf

offhand, anyone know if the F500/F1 effects return is the same deal, or can it function in the way I'm looking for?

Yes, they are the same way.