in the POD HD500 the fx loop block is LOOSING 5dB on the send with the switch in the "stomp" position.
(I don't have a POD HD500X and it would be nice to know how it behaves on that, but I suspect it will be the same or Line6 would have advertized it...)
this means that, if you connect anything gain related (compression, distortion, preamps, envelope followers) into the fx loop you're getting the *wrong* gain result
of course, also the very popular four-cable-method (http://line6.com/support/docs/DOC-2504) is seriously affected by this problem!
this is something couter-intuitive and *guiltily* not stated anywhere in the manuals.
• Before explaining the details and giving some possible solutions to the problem I have to say that many other threads (on the old forum) have talked about this matter, including one of mine; those posts received many replies and integrations, so what I'll write here is my experience largely improved by all of those posts
http://line6.com/support/thread/90441 (point 2)
• Now let's see the details:
what I (repeatedly and professionally) measured is that, with the stomp/line switch on "stomp" and input pad on "normal", the guitar signal is attenuated by 5dB (approximated with no decimals) along his route from the input, thru no fx and then to the send jack, and then it is partially compensated by a boost of 4dB at the return jack;
[this additional 1 dB difference (again approximated with no decimals) from -5 to +4 is even more inexplicable and could be only on my POD HD 500 unit, so you'll need to test your own; but many users confirmed the problem]
furthermore, as you may know, the stomp/line switch set to "line" gives (correctly) 12dB to the send AND compensates that by attenuating the return by the same amount,
but the line position is "suffering" from the same -5/+4 attenuation/compensation, so you actually get +7dB at the send (+12 -5) and -8dB at the return (-12 +4) as a result;
• I can only guess that a reason for this -5/+4 attenuation/compensation could be to put the fx loop block "unity gain" at approximately half-way between a stomp and a line reference level, but this choice is wrong (or at least badly implemented and guiltily not documented in the manuals)
common sense here: when I connect my guitar directly to any guitar input (stomp-box or preamp) I have a "stomp" signal level, so:
- the stomp position of the switch should definitely be at *real* unity (=same level as the guitar itself)
- consequently the "line" position should give +12dB on the send and -12dB on the return
- then we should have the ability to give or take some dB's on the send as well as on the return via some software trims
if you connect a cable to just one of the fx return jacks (this works also with the Right return, not only the L/mono) the fx loop block acts exacltly like a mono fx block, so it attenuates and sums its inputs and then sends the result to the send jack (to both pins of the TRS jack to be precise), and then splits the return to both outputs of the block
IMPORTANT: you need to read this thread to understand what I'm talking about:
this means that if you are using the [input-1: guitar / input-2: variax] setting and you put an fx loop in default mode into the "pre" path with for example your amp's preamp into it, you are loosing 11 (or 12) dB of gain!!
1) "line attenuated" solution
- set the stomp/line switch to "line"
- use the fx loop with these settings: send: -7 , return: +8 (these values could be precise only on my Pod HD 500 machine, but the order of magnitude is this)
and you'll you get the right gain and level (unity gain)
AND you can boost or attenuate the send AND the return level if you need it!
BUT (and it's a BIG BUT) you'll get more hiss than what it should be
(getting more gain always gives more noise of course, but this is added on top of that)
I tried the stomp and line positions of the fx loop switch, compensating in various ways to their boost/attenuation and the stomp has always a little more hum while the line has clearly more hiss
this has no explanation but is confirmed by many other users
2) "minus two fx-blocks" solution
- set the fx loop switch to "stomp"
- set up this routing:
. a tube comp (settings 100% , 17%) giving +5dB before the fx loop
. the fx loop with default settings (send: 0dB and return: 0dB)
. a fixed volume pedal (at 78%) attenuating by -4dB after the fx loop
that gives you the correct gain and level (unity gain) but with a lot less hiss than the "line attenuated" solution
[note: I called this the "minus two fx-blocks" solution, even if it's not totally an idea of mine, because it's easier to recall; actually this is a variation on the solution offered by Jim Reynolds here: http://line6.com/support/docs/DOC-2522 at point 4 of the "Patch Setup - Effects Only" section
but I found that even if the "studio eq" gain pot is labeled in dB's, the numeric values are wrong (to have a real 6dB boost, you need to see "8dB" on that pot);
furthermore, the studio eq and the tube comp are both intentionally clipping the signal to emulate their analog counterparts and I found that, with my setup, the tube comp has a better sound]
• of course it is (at least) ridiculous to loose two fx blocks to compensate for a hardware design fault
(I don't think the -5dB send level loss is a fault in my specific unit because many people have found the same problem)
and of course, depending on your fx-chain into the pod you could:
- use the mixer as a boost OR cut and loose only one fx block
- use other effects (which must include a volume control) that you normally leave always on, as a boost and/or cut
- use some external analog clean boost and attenuation
- compensate with your amp gain and volume controls
but anyway you put it, each of these solutions ends up as a workaround that the pod needs to let you do a simple thing
• in the end I actually chose a variation of the second solution:
I use the switch on the stomp position and a tube comp with threshold 100 and level 17, BUT I decided NOT to compensate for the +4dB given by the return circuit or I would have to loose another block;
so in the end it's a "minus ONE fx-blocks (partial) solution" ;-)