Technics M5 Tape Deck - High Frequency Issue
I'm having an issue with my Technics M5 tape deck which involves the loss of high frequencies in the left channel. Under regular listening conditions, the loss is not noticeable to my ears, but when I analyze recordings that I've transferred to my computer, I see that frequencies above 16 kHz are not as strong as they should be. (Not clipped, just weak/soft). The right channel appears to be fine.
I recently caught the issue while transferring some records over to my computer. (I use the record level knobs on the deck to control the output volume to my computer to prevent clipping/distortion). The frequency response starts to diminish past 16 kHz, though sometimes it will try to capture some high frequencies depending on how loud the volume is. Pops and clicks on the record are some examples. Reviewing some recordings that I made a few years ago do not show any degradation in the left channel, so this is something that recently started. Bypassing the tape deck and recording straight from the amp via the tape out correctly captures frequencies over 16 kHz, so that rules out the amp and record player.
While playing back a tape, I noticed that the high frequencies in the left channel are also hampered, particularly those present in the tape hiss. My guess, based on the age of the tape deck (1981-ish), is that the line output filter capacitor for the left channel is going bad and is taking a toll on the high frequencies. Does this sound logical? I can replace the capacitor if this is the case.
Attached are some spectral views. 1st one is of a record, 2nd one is of a tape played back in the deck.
Newer is not always better.