JVM205C: Volume loss
So, I recently got a JVM205C (50 watt 2×12 combo version of the JVM2), and I am really enjoying it so far, but I am having some trouble getting the G-System (Red limited edition, 2nd gen) to work optimally. I should add that this is my first attempt at hooking it up to anything.
Laird has written the following on the matter previously:
The FX loop situation on the 410H is a little weird. The amp has 2 loops, and each has SIGNIFICANT flaws. The “FX” loop is a parallel loop with a mix control. With a well-implemented parallel loop, when you set the mix control all-the-way-clockwise it should be “all wet” – with no dry signal in the mix. Hence, a good parallel loop with the mix control all-the-way-up is effectively a serial loop. This is NOT the case with the 410, unfortunately. Even with the mix control turned “all wet” there is still a LOT of dry signal left. As I have explained in detail in my white paper- ANY digital FX unit will sound like $%^& in a parallel loop for simple physics reasons. You need a fully-serial loop. Ok – so the FX loop on the 410 is out. Fortunately, the 410 has an alternative – the “preamp” loop.
The preamp loop on the 410, sure enough, is a fully-serial loop. So what is the problem there? The signal coming from the send is WAAAAAY too hot (voltage/volume is too high) for almost any D/A converter. It blows the DA away and you get clipping galore. You need to drop that voltage before going into the G – and the amp provides no on-board mechanism for doing this without making other significant compromises. Lacking an on-amp way to control the output level of the preamp send, you need SOMETHING to knock the signal down before it goes to the G, and then something ELSE to compensate for knocking the signal down after it passes through the G. Guess what the 2 channels on an LLS-2 can be used for. One for knocking the signal down from well OVER +4dB to something closer to -10dB and then boosting it back up to where the amp wants it after the G has done its thing.
(Source: http://forum.tcelectronic.com/topic/181 … -jvm410h/)
Now, I did try to hook it up to the serial channel, and as far as I could tell, it only started clipping on the orange overdrive channel when I cranked the gain and put the volume at 3 o’clock or higher. Unless I am misreading something, I could definitely live with that.
There is, however, also a significant volume drop. I tried to put just a cable in the loop, and the drop was gone, so that the G-System is definitely the guilty part. Is this problem related to the level being too hot? Would a line level shifter be the way to go, or do I need some kind of buffer, or a different tool, to bring the signal up to the right level? Note that I am using the White Paper, and that the boost specifically is turned off, so that has nothing to do with the matter.