I was having some problems using my EQ and condensor mic with my Yaesu. The problem was I was sending a line level signal into the radio. The EQ doesn't convert to mic level. Several people told me I had to buy an Ibox from W2IHY to remedy the problem. I did some searching and found this product. It changes from line level to mic level, filters RF, a low pass filter, has up to -40db attenuation, ground lift (to eliminate hum and groundloop noise) and phase shift. I hooked it up and it works great ! 
The Ibox sells for around $79. I spent $22.95 on the Art ZDirect and it worked !
I ran my mic into my preamp, then from my preamp to my EQ. From the EQ into the Art ZDirect then to the Yaesu mic input.
The output uses an XLR connection. I used a Heil XLR to a Yaesu 8pin cable to the radio.
They also make one with an XLR input. They have several different products. They are known for their tube preamps.
The Ibox sells for around $79. I spent $22.95 on the Art ZDirect and it worked !I ran my mic into my preamp, then from my preamp to my EQ. From the EQ into the Art ZDirect then to the Yaesu mic input.
The output uses an XLR connection. I used a Heil XLR to a Yaesu 8pin cable to the radio.
They also make one with an XLR input. They have several different products. They are known for their tube preamps.
I found four STA-1's and two STM-2's hiding in the bottom as well as several Hammond 804, 812, 842 and 850 series matching transformers along with three Altec Lansing 1588B preamps. Balanced, unbalanced, high Z , low Z, high level, low level problems are no longer an issue for me with either the radio or computer interfacing. 