I completed the build of a 2245H subwoofer built according to the 1983 article here on the forum. It has a finished internal volume of 21.1 ft3, and is port tuned to 24.79 HZ (using two 6" ID vents at ~13.67 in long).
I have a subwoofer pre-out signal to the sub. I have a Yamaha YDP-2006 digital EQ (to act as a parametric EQ and low/high pass filter). The inputs are balanced audio inputs. This signal is then sent to a mono bridged Crown PS 400 (660W bridged).
issue 1: ground loop hum> predictably I have a ground loop hum issue:
-Do I need to use a isolation transformer to power the Denon amp and the subwoofer crown amp from the same ground, or just use a isolation transformer to power the sub's Crown power amp?
Do I need to use an audio isolation transformer on the signal as well??
Issue 2: Once I hooked up the map I had like zero output. I got my mp3 player and ripped a few low Hz tones and used it as a head device to power the sub from the Crown amp>>success>> loud and LOW LOW output.
I looked up the pin outs on unbalanced to balanced audio signals (Denon is an RCA unbalanced sub pre-out presumably). Even though I thought I had the pin out connectors made right (soldered up connectors from audio cable pin outs from a sound engineers website) I still got lack luster sound out??
I then got an old Yamaha integrated amp out, and used it to condition the rca pre-out signal. (ie rca pre-out to aux input, pre-out outputs were then wired to the Crown amp inputs ) Success>> got sound (however got ground loop issues again since the two amps Denon and Crown are not isolated or grounded to the same ground)).
Here's my question:
Do I need to isolate both the power and signal using isolation transformers?
Do I need to use some sort of intermediate pre-amp or line level pre-amp to boost the rca pre-out signal strength before it goes to the crown amp?
(Presumably if I need a line level pre-amp to condition the signal it will also need to be isolated to prevent any ground loop from it as well too)
Hopefully some one can set me straight, as when I tested the sub with the mp3 signal>Yamaha pre-amp>crown as a stand alone there was no ground loop issues (as I expected), and the response was pretty good.
Thanks for the help in advance
Larry