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Tape Restoration Bliss!
Hey all!
Have not been to the site since last winter (I was in a treasure hunting mode through the summer...) so I have a lot of posts to catch up on. (Hope I'm not rehashing old subjects...)
I've been restoring some of my old reel-to-reel collection lately. DC6 is absolutely wonderful for my needs, but I've had a few quirks. I have been using a Pioneer RT-707 for playback of these tapes, which was the same brand/model I used to record them back in the early 80's. (found it on eBay in nearly unused condition - heads don't even have the beginning of a cut in them!)
I used the suggested procedure for recording a White Noise signal on one of the tapes to play back and obtain the response curve of the deck/tape using the DC6 Spectrum Analyzer. The only thing I did different was I set the Spectrum Analyzer to 20db scale (not the suggested 100db), and I streched out the Analyzer view to fill the entire screen. I didn't have a new tape to work with, so I recorded it on an unused portion of a tape not played often. The Spectrum Analyzer is extremely slow with my old PIII-500, but otherwise it still seems to work fine. (It takes it 2 hours to test a 10 minute signal!)
Using the Multi-Filter consisting of 4 seperate Paragraphic EQ's and a Low Pass Filter (yes - a low pass filter!), I was able to come up with a curve for each channel that was nearly 20 to 20,000Hz +/- 0.5db! (Not too shabby for 3.75 IPS!) If not for the slight rise at about 19,000Hz, the response would have been better than +/- 0.3db! Please note that most tape deck manufacturers (including this one) only claim response specs at +/- 3db - The end result exceeded the performance of the deck itself!
The reason for my using a low pass filter (19,999Hz @ 12db/octave) was because when I tried to counter the playback EQ, I ended up with a sharp rise in the response starting at about 17,500Hz that peaked to about +6db at 20 to 22kHz. I am not sure if it was the limitations of DC6 (or my "antique" computer), but I had trouble setting up the Paragraphic EQ above about 12,000Hz. The "view line" on the EQ would pop away if I tried to narrow the bandwidth or increase the frequency. Correction or improvment of this in DC7 would be a greatly appreciated. It would also be nice if the Spectrum Analyzer would go beyond it's 20kHz (21, 22k?) limit for people restoring CD-4 LP's.
After finally comming up with the response curves, I put on a dbx encoded tape on the deck and fed it into the computer. I applied the Multi Filter frequency response corrections to the seperate channels, & then used DC6 to playback the processed signal out of the sound card into my outboard dbx decoder. At the same time, the decoded signal was fed back into the sound card input, where I used a second instance of DC6 to re-record it. After reviewing the fully processed recording, I nearly forgot I was listening to a recording from a tape as it sounded more like the original LP! I was even able to remove most of the clicks & pops from that 27 year old LP tape copy! Wonderful!!!
The dbx decoder tracked quite well with the EQ processed signal, but was a bit excessive and crisp in the treble end. I believe this was because the tape that I used for the test signal was in fact old & used, which may have reduced the treble response of the test. I have found a factory sealed NOS (new old stock) Maxell UD 35-90 on eBay which I will be receiving in a few days, so I will re-do the test and offer the presets in the near future at the forum for anyone with one of these old decks using this tape. Other than the few quirks I encountered, I was impressed with the results.
Have not been to the site since last winter (I was in a treasure hunting mode through the summer...) so I have a lot of posts to catch up on. (Hope I'm not rehashing old subjects...)
I've been restoring some of my old reel-to-reel collection lately. DC6 is absolutely wonderful for my needs, but I've had a few quirks. I have been using a Pioneer RT-707 for playback of these tapes, which was the same brand/model I used to record them back in the early 80's. (found it on eBay in nearly unused condition - heads don't even have the beginning of a cut in them!)
I used the suggested procedure for recording a White Noise signal on one of the tapes to play back and obtain the response curve of the deck/tape using the DC6 Spectrum Analyzer. The only thing I did different was I set the Spectrum Analyzer to 20db scale (not the suggested 100db), and I streched out the Analyzer view to fill the entire screen. I didn't have a new tape to work with, so I recorded it on an unused portion of a tape not played often. The Spectrum Analyzer is extremely slow with my old PIII-500, but otherwise it still seems to work fine. (It takes it 2 hours to test a 10 minute signal!)
Using the Multi-Filter consisting of 4 seperate Paragraphic EQ's and a Low Pass Filter (yes - a low pass filter!), I was able to come up with a curve for each channel that was nearly 20 to 20,000Hz +/- 0.5db! (Not too shabby for 3.75 IPS!) If not for the slight rise at about 19,000Hz, the response would have been better than +/- 0.3db! Please note that most tape deck manufacturers (including this one) only claim response specs at +/- 3db - The end result exceeded the performance of the deck itself!
The reason for my using a low pass filter (19,999Hz @ 12db/octave) was because when I tried to counter the playback EQ, I ended up with a sharp rise in the response starting at about 17,500Hz that peaked to about +6db at 20 to 22kHz. I am not sure if it was the limitations of DC6 (or my "antique" computer), but I had trouble setting up the Paragraphic EQ above about 12,000Hz. The "view line" on the EQ would pop away if I tried to narrow the bandwidth or increase the frequency. Correction or improvment of this in DC7 would be a greatly appreciated. It would also be nice if the Spectrum Analyzer would go beyond it's 20kHz (21, 22k?) limit for people restoring CD-4 LP's.
After finally comming up with the response curves, I put on a dbx encoded tape on the deck and fed it into the computer. I applied the Multi Filter frequency response corrections to the seperate channels, & then used DC6 to playback the processed signal out of the sound card into my outboard dbx decoder. At the same time, the decoded signal was fed back into the sound card input, where I used a second instance of DC6 to re-record it. After reviewing the fully processed recording, I nearly forgot I was listening to a recording from a tape as it sounded more like the original LP! I was even able to remove most of the clicks & pops from that 27 year old LP tape copy! Wonderful!!!
The dbx decoder tracked quite well with the EQ processed signal, but was a bit excessive and crisp in the treble end. I believe this was because the tape that I used for the test signal was in fact old & used, which may have reduced the treble response of the test. I have found a factory sealed NOS (new old stock) Maxell UD 35-90 on eBay which I will be receiving in a few days, so I will re-do the test and offer the presets in the near future at the forum for anyone with one of these old decks using this tape. Other than the few quirks I encountered, I was impressed with the results.
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