garysch

In one of the other threads it was noted that the Privia line has an unbalanced audio output. When feeding professional amplified speakers, mixers, etc., balanced output and balanced cable allows for very long cable runs without hum or change in sonic quality. I own a Radial Pro passive DI box, but that just didn't seem to work right, and I also wanted a dual channel capability because I generally use two amps for the piano or need to feed a monitor and PA sytem. The piano has plenty of output so the matter is strictly that of converting the unbalanced piano outputs to balanced. While there are loads of DI boxes, the lack of info regarding impedance transformation or ratios was disconcerting. My Radial Pro box reduced the levels. Instead, I opted to build my own DI box which proved to be an inexpensive and one evening project. The result is a dual channel box that has eliminated hum, ground loops while converting the outputs as required. The heart of the unit is a pair of Edcor model PC600/600 transformers. http://www.edcorusa.com These are small 600 ohm to 600 ohm transformers that can be wired unbalanced on the input to balanced on the output. They are designed for this use, have a flat frequency response and very low distortion. The transformers are mounted in a 4 x 3 x 1.5" plastic box strapped vertically on opposite sides with a wire tie. Two standard 3 connector 1/4" phone jacks are mounted on each end. The unbalanced inputs are wired: transformer pin 1 to tip, pin 3 to sleeve (pin 2 on the transformer and the ring on the jack are not used). The output or balanced jack is wired: transformer pin 5 to ring, pin 6 to sleeve, pin 7 to tip. In a dual channel box do NOT connect the sleeves of both channels together. If a metal enclosure is used, you must use fully insulated 1/4" jacks. Costs: The transformers are $6.37 each, but with shipping and handling my cost was $28. The four jacks and box will cost you around 15-$18, so for under $50 you have a dual channel matching DI box. One option is to use XLR connectors. That would work in the same size box if you place the transformers on the short sides. The net result is complete hum elimination and the ability to use balanced TRS cables to the powered speakers and the PA. Contact me if you need any other details. Gary

Sorry for the delayed response. I did create a single velocity midi file spanning the affected range. It was then copied/pasted and the velocity increased for each of four successive iterations. The instrument was at factory default settings and the reverb was turned off. The file was recorded first with the main stereo grand, then with the GM grand. Program Changes were inserted in each midi file to select the proper instrument. The issue is still present. I am certainly aware that this could be strictly limited to my instrument. If any are interested in the midi files and /or the resultant mp3 files, please email me for the link. Gary

I owned a 350 (now a PX-3S). That noise is normal and you'll get used to it.

Appreciate your response. I know about the Jensen transformers, which is why I was interested in a much less expensive solution. I'll post back if I find a reasonable alternative.

OK. I'll put it another way. If I play a chromatic scale starting at middle C going up one and one-half octave, the notes Ab through C# (just rechecked and corrected from my first post) have a different timbre. The affected notes are not as bright sounding as the rest of the piano. This same trait is exhibited on all the pianos that are based on the same sample set. I hear the same thing with the speakers or headphones. For the record, I am a graduate piano player and music educator,and currently play in a number of jazz groups. More important is the fact that I have tuned and voiced my own 7' grand for over 40 years and have tuned and voiced pipe organs. And I've done my share of work on sampled instruments as well. I'm going to connect my midi monitor to rule out (or in) a velocity issue.

Thanks for your post. I was tracking down a hum in my PAs (balanced) with my new PX-3 and had come to the conclusion that it, too, was unbalanced. What transformers did you use and from where did you get them? I was just going to ground the unused wire at the Privia end. Gary

Just got a new PX-3. The main stereo grand piano has a group of "funky" notes, i.e., A#5 thru C5 (the octave just above middle C). They are dull at the same velocity compared with the notes on either side. Anyone else notice this? Gary