Laney L5T-112 FX loop: please educate the ignorant

Snags

I've got a L5T-112 (UK made) that I've had for, er, some years (honestly can't remember how long).  I use effects in the loop and have never had a discernible issue with it. In fact, until starting to read here more regularly I'd never even realised that there was an 'issue' with the loop being parallel not series.

Can some patient soul explain to an electronics ignoramus why the issue is an issue, and what causes it to manifest?

I've got as far (I think) as it relating to use of digital effects due to them introducing a slight delay in the signal chain (because Reasons), which then gets out of sync with the dry signal which is automatically passed in parallel (which raises another question: why would they pass the dry signal without some means of adjusting the blend? On my LC30-II there's a wet/dry knob for the FX loop which I get). This apparently makes it sound a bit off, and drops volume?

I've genuinely never noticed anything weird on my effects in the loop, so I'm now paranoid that I'm totally cloth-eared, but I'm guessing I've just lucked out with the pedals I use, even though some of them are definitely digital (but presumably send a blended signal themselves which circumvents the issue?).

Pedals in the loop:

- TC Electronic Flashback X4
- Boss DD-6
- Boss CE-5
- Boss PH-3
- TC Electronic Vortex

Dumb luck, or dumb guitarist?

stickyfiddle

It's because you're forced to a 50/50 wet/dry mix, which limits flexibility a lot. It can also give phase issues with certain pedals.

With a series loop all your signal goes through the pedals in the loop, so you can control the mix fully (assuming your pedals have a wet/dry control. 

It depends on how you want to use it, but for anything where you want the wet sound to overtake the dry (pitch-based stuff, or big ambient reverbs, for example) then it's shite.

Parallel with a full-range wet/dry knob would be much better.

english_bob

Based on my experience with my L20T, if you didn't notice it you really need a different hobby.

Like @stickyfiddle says, the loop splits your signal- half goes through the loop, half goes on its merry way. If you have pedals in the loop that have a digitized dry signal path, this will generate a *tiny* amount of latency (delay) that you'd never normally notice, except when it's combined with the dry, unaffected signal.

The end result when I tried it (with a Vox Delaylab and a Zoom G3) was a chorus-y sort of effect, a huge cut in bass and an equally huge cut in volume. Seriously, it's not a subtle thing that you need Eric Johnson bat ears for, you would have noticed. 

The TC pedals definitely have an analogue dry signal path, which would make them "safe" to use with the Lionheart, and I presume that must be the case with the Boss ones too. If you want to be absolutely sure, disconnect the cables from the effects loop. If the amp suddenly gets loud and sounds fucking brilliant, that's what it was meant to sound like before!




Modding the amp to a fully series loop is fairly simple, and as far as I know the only difference between my L20T and your L5T is the power amp, so the procedure should be the same. There's a single resistor inside, marked "R28" that needs to be removed, then you need to add jumper cables between the switching contacts on the loop send and return jacks. An hour's work at best.

Snags

Thanks both.

I don't have perfect pitch or anything, but neither am I certified deaf, so I'm going to have to assume I've just been lucky in my pedal choices. Or the amp's broken in a good way

I'll do the cable-pulling trick, but I have never noticed any difference between going straight in the front or having the board hooked up. Probably won't get chance to do it for a week or so because of work/away stuff, but will report back shame-faced if it turns out there is a huge difference. Maybe book a session at the doctor's too.

I did have one pedal that was a huge volume suck - tried an EH Memory Man with Hazarai once which was enormous fun but every time I engaged it there was a noticeable drop in volume. I think that I tried it in the front and in the loop and had the same issue either way (it's about three years ago, and I only had it long enough to decide the volume drop made it unusable, so it went back and I got the Flashback X4 instead).

I'll have a look at doing the mod, although I might get a grown-up to help, as my soldering is not my strong point and has reduced proper tinkerers to tears. Even if it isn't causing me aggro now, knowing about the potential will niggle!

Snags

Final dumb question in case I decide to have a crack at this myself:

The wire between send/return - should I be looking to use a particular grade of wire, or is it OK to use more or less anything that's lying around (e.g. strip a section of one core out of 3-core mains lead, or an old extension lead etc.)?  I'm guessing it's not going to carry a great deal of oomph, so doesn't need to be hugely thick, but equally there's some consideration required?

normula1

Any wire should be fine it's only going to be an inch or so long. R28 is a surface mount on the underside of the PCB so you'll need a fine tip for your soldering iron.

Snags

Thanks, appreciated.

DJH83004

I wouldn't do anything until you have had a look at the attached schematic and made sure you are familiar which contacts need linking on the jack sockets. I have marked up the relevant connections and resistor removal in red. I haven't personally tried this mod, but can't immediately see any issues with it.  

Snags

Thanks. I had a bit of a google yesterday too. Interestingly you've shown the new wire going from open to open, whereas one of the examples I found had closed to open. I guess it doesn't make much difference, other than your way making a much more definite break on jack insertion?

NeilMcG

That mod looks like it breaks the signal when a plug is inserted into the fx send socket which isn't usually how fx loops work. 

I'd suggest the red jumper should come from the non-switched side of the fx send socket?

DJH83004

Its the way the original schematic is drawn the contacts are actually 'normally closed', e.g. closed when no plug is inserted  (I have modded the drawing for clarity). So with nothing in the loop the signal passes around the new jumper lead. When jack plugs are inserted in the the send / return sockets the signal is interrupted and passes via the device connected in the loop.   

ICBM

It will work either way, but it’s best to go from the non-switched side of the Send jack so the straight-through path only goes via one switch contact (in the Return jack) not two. Better for reliability.

DJH83004

Take your point IC regarding reliability of the jack socket contacts, I just prefer to totally isolate the signal paths.

normula1

Either way, the jacks are on a little daughter board and should be easy to figure out which connections to link.