Signal Level, 4CM & POD HD
9th Jul 2012
My rant about the poor design decisions in the Line 6 POD HD500 has sparked a debate in the comments section about whether there really are signal level problems with the POD HD.
Such problems are particularly important for guitarists using the four cable method (often shortened to 4CM) where part of an FX unit is used in front of a physical pre-amp and another part between the pre-amp and power-amp.
So I decided to conduct a scientific - or as scientific as I can - experiment to measure perceived signal loss.
The POD was set up to use a single signal chain, with all empty blocks and empty amp models moved to one side of the signal chain with that side centred via the mixer. The other unused side was muted via the POD’s onboard mixer. This meant I had one long signal chain with no confusion over the POD splitting the signal at any point. I should add that I went back and checked the figures you see below with different signal chain configurations and found the same result. Anyway, on with the test.
I recorded a strummed chord into a Boss RC-3 looper pedal to ensure the signal was the same strength for each test. I then recorded that direct into Reaper. I also recorded the same sequence output from the HD500's FX send and from the unit's 1/4" output.
My findings were as follows. There is a 6db drop in signal level between the POD HD input and FX send and when not using the FX loop something like a 6-8db drop between the guitar input and 1/4" output.
Why is this important? In the 4CM we use the POD FX Send as the input to a physical guitar amp, so to get the most transparent tone we want it to be at the same level as plugging a guitar straight into the amp.
Next I looked into trying to get a similar signal level through the entire device.
To get the same signal in and through the FX send I had to put a Studio EQ block (wasting an FX block when we shouldn't have to if the POD was designed properly) before the FX loop block.
This dealt with the issue of the low FX Send signal. However when bridging the loop with a short patch cable and recording from the POD HD output it was clear that the output was still 2db too low. That 2db was added via the POD mixer.
Why not just add 8db with the Studio EQ? Because I wanted to get the correct signal level through the FX Loop and now clip any devices in it. Care obviously should be taken with FX after the mixer block too once that is boosted 2db.
Anyway, there we have it. There is plenty of signal loss in the POD HD both in the FX loop and through the system itself. So to attempt a more transparent signal using the 4CM with the POD HD500 one has to boost the FX Loop send 6db via an EQ block. Secondly we have to add a further 2db at the end of the signal chain before the POD outputs back to a physical power amp.
These figures concur with those I’ve seen online from others who have conducted similar tests witht he equipment. I think we can pretty confident in stating this is a problem common to the unit and not a one off issue. One hopes Line 6 will address the issue in a firmware update.