It has been awhile since I posted here last - this used to be THE place for the RTR community, so here goes. For many years I had a Technics RS1520, which had the advantage of switchable IEC/NAB equalization. I sent it to Jeff Jacobs for a refit, which was not possible. Not being a fan of the Technics tape path (I am all thumbs) I wanted to replace it with something else, and Jeff was able to set me up with a Tascam BR20, and I totally prefer the tape path on that. That one is switchable as well. But....I would actually love to play 4 track tapes in my better living room system (I have a Tandberg and Akai in my office, but no room for them in my living room), and I am looking at an Otari MX-5050BII 2, which has a 4 track head as well as the two track. I downloaded a copy of the users manual, and the equalization switch is on the back, not the front like the Technics and the Tascam, but the manual says, and I quote "NAB or IEC for 3-3/4, 7-1/2 and 15 ips. Switchable on the rear panel, but calibration is necessary." Does this mean for recording only, or does one need to calibrate for playback as well? I have been switching on the Tascam - I have all of the TPP tapes, of course, and I have also collected a few 7.5 ips 2 track NAB tapes as well, which I have been playing. Thanks for any insight here.