First make sure the tape player is on speed. You'd be surprized how many are off by 2-5%. Next volume level may be critical, note that some tape players do not work well if the headphone connection does not load the amplifier adaquately. The tone control if present should be such that there is no high cut (high frequencies are important!). Lastly the head should be cleaned and properly aligned or the high frequency responce will suffer. What I've seen in previous forays into this stuff since 1975. Tape player ills: Weak batteries (slow play speed and distortion). Extremely poor quality machine (just plain bad). Worn heads (no highs at all). Amplifier that was oscillating at ~25+khz due to lack of speaker load and bad design. Tape that was bad, stretched or binding affecting speed. Bad tape, flaking oxide. Bad tape, actually it was blank. Pinch rollers with flatspots. Bad motor, ran slow. Also one that ran fast. Motor noise in audio ouput, bad motor. Motorboating due to bad cap in power supply (on a battery unit!). Unit that had been dropped had bad azmuth alignment on head resulting in no highs and lack of level in general. This can also happen if the tape is not in place and the play button is forced. I've seen heads broken off mounts due to that. Bad earphone jack (no output). One found to have a playback amp so noisy that you could barely hear loud passeages on a music tape at all. Stuck in record! That one runied a few of the owners tapes! One that didn't like a common ground between the mic, motor or speaker(earphone jacks). It would motorboat if that was done. System ills: Input circuit literally blown up. (user plugged in a 12Vac adaptor that had the right connector). Input jack broken free of the board. Input opamp dead (age or random failure). System broke and needed mod (TRS80 LII hangup). Just a few hints there. Likely I forgot a few. Allison