MRC01
Major Contributor
Seeing @amirm 's review of the Otari reel to reel tape deck motivated me to do some calibration and measurements of a Denon DRM-540 that I bought on eBay for about $50. I don't have a scope or fancy testing gear, so I used my ESI Juli@ sound card. That should be more than sufficient for an old tape deck.
First I cleaned and demagnetized the heads. Boy did that bring back some nostalgia! Next I used calibration tape having 3 kHz and 8 kHz tones. I used the 3 kHz tone to adjust the speed and playback gain / channel balance, and the 8 kHz tone to adjust the head azimuth / alignment. Channel balance wasn't quite the same for these 2 tones so I spent some time going back & forth with alignment and gain pots to minimize and balance the difference. I don't have a scope, so I adjusted azimuth by tweaking the head alignment screw while playing the 8 kHz tone, to find the position that maximizes the output level.
I twirled the adjusting pot through its full range a few times to clean it, then set it as close as I could. The closest I could get it was within about 0.3 % to correct speed, and my calibration tape probably ain't perfect so that's about as good as it gets.
The spikes are thinner than the measurements I took on the old walkman that I restored, suggesting this deck has more stable speed / lower jitter.
I tested frequency response by playing REW sweeps and recording them on old BASF Reference Master II tapes. Back in the day, these were some of the best cassette tapes available. I measured it without Dolby, with Dolby B, and with Dolby C. The flattest response was with Dolby B, so that's what I show below.
Here's frequency response at different recording levels: -20, -10, -3 and +3 dB:
It's got a wonky dip at 56 Hz, which surprised me. But, this tired old deck still has decently flat response, decent channel balance throughout the spectrum, and meets its specifications.
Here's what distortion looks like at different recording levels:
-20 dB:
-10 dB:
-3 dB:
+3 dB:
Above we can see that at +3 dB the tape is approaching saturation, with distortion around -30 dB or 3%. The range from -10 dB to -3 dB looks like the sweet spot, good tradeoff between frequency response and noise/distortion.
Overall, the deck seems to be restored and working well enough, producing classic 1980s sound quality. We are so spoiled today! Most phones and dongles outperform this tape deck. But it was fun to calibrate and feels good to rescue a piece of equipment from going to the dump.
First I cleaned and demagnetized the heads. Boy did that bring back some nostalgia! Next I used calibration tape having 3 kHz and 8 kHz tones. I used the 3 kHz tone to adjust the speed and playback gain / channel balance, and the 8 kHz tone to adjust the head azimuth / alignment. Channel balance wasn't quite the same for these 2 tones so I spent some time going back & forth with alignment and gain pots to minimize and balance the difference. I don't have a scope, so I adjusted azimuth by tweaking the head alignment screw while playing the 8 kHz tone, to find the position that maximizes the output level.
I twirled the adjusting pot through its full range a few times to clean it, then set it as close as I could. The closest I could get it was within about 0.3 % to correct speed, and my calibration tape probably ain't perfect so that's about as good as it gets.
The spikes are thinner than the measurements I took on the old walkman that I restored, suggesting this deck has more stable speed / lower jitter.
I tested frequency response by playing REW sweeps and recording them on old BASF Reference Master II tapes. Back in the day, these were some of the best cassette tapes available. I measured it without Dolby, with Dolby B, and with Dolby C. The flattest response was with Dolby B, so that's what I show below.
Here's frequency response at different recording levels: -20, -10, -3 and +3 dB:
It's got a wonky dip at 56 Hz, which surprised me. But, this tired old deck still has decently flat response, decent channel balance throughout the spectrum, and meets its specifications.
Here's what distortion looks like at different recording levels:
-20 dB:
-10 dB:
-3 dB:
+3 dB:
Above we can see that at +3 dB the tape is approaching saturation, with distortion around -30 dB or 3%. The range from -10 dB to -3 dB looks like the sweet spot, good tradeoff between frequency response and noise/distortion.
Overall, the deck seems to be restored and working well enough, producing classic 1980s sound quality. We are so spoiled today! Most phones and dongles outperform this tape deck. But it was fun to calibrate and feels good to rescue a piece of equipment from going to the dump.