I have an old Technics RSM 255X tape deck that works pretty good. I want to copy off some recordings I made with the dbx circuitry. It has some pretty outrageous hiss which may be due to the tape head wearing out, there is a definite groove on the surface. Does anyone know of a replacement or a source of parts. I could buy another on ebay but it probably has the same issue.
The Technics RS-M255X uses Sendust head # QWY4123Z, the same head was used in several other Technics decks, such as RS-M45 for example. Before looking for a new/restored head (I actually might have a suitable head), it would be useful to check other possibilities. A worn head usually is not a source of an increased noise, more likely symptoms are drop in HF and uneven levels between channels. An excessive noise could be a result of a magnetized head for instance, For starters, just try to put the deck into the recording mode, ideally with a (blank/not important!) Metal tape, the bias will demagnetize the head. Did you record your cassettes with DBX on this very deck or on a different one?
Cheers
Alex
Cheers
Alex
Thanks for the record/demagnetize tip. I’ll try that first.
Yes, the tapes were recorded on this deck. I had some pre-recorded dbx tapes but I can’t find them.
Yes, the tapes were recorded on this deck. I had some pre-recorded dbx tapes but I can’t find them.
One more thing to try: check if the noise is from the deck and not from the tapes themselves, old cassettes can be also "collect" some noise over time, especially if exposed to magnetic fields.
Cheers
Alex
Cheers
Alex
Thanks for the help. I was wondering if cassettes can settle magnetically and lose signal and increase noise, it’s entropy I guess.
The deck itself is very quiet for an old piece of equipment, which is one reason why I’m attempting this project.
The deck itself is very quiet for an old piece of equipment, which is one reason why I’m attempting this project.
With cassettes it depends on many factors. I have in my collection pre-recorded Type I ("Normal") cassettes from 1970s which play very well, with low noise and good HF, so if tapes were kept in a good environment and were of a good quality originally they can last a very long time. On the other hand some of early CrO2 cassettes didn't age well at all. Do your DBX recorded cassettes play with an excessive noise even if DBX is ON?
Cheers
Alex
Cheers
Alex
I haven’t done a lot of experimenting yet, but most if not all of the cassettes have a lot of hiss. Some are better than others. I might be expecting too much from this antique technology after listening to clean, sterile digital sources for so long.
CrO tapes and ferrochrome are allegedly the lowest noise (or rather highest signal level), but compact cassettes are not low noise media and really need Dolby B to be usable for sound recording that's bearable.
One issue is fading, the magnetic particles are so small on these tapes that they may have a thermal half-life for retaining magnetization, the smaller of the particles degrading first.
At the height of magnetic disk drive technology there was the introduction of cobalt magnetic particles coated specially to provide the smallest possible magnetic particles, but cobalt is very different magnetically requiring alignment of particles (*) and stronger magnetic fields to record. They also engineered very uniform particle size to reduce the fading effect over time due to smaller particles flipping.
(*) cobalt has strong uniaxial anisotropy in its magnetism, unlike iron.
One issue is fading, the magnetic particles are so small on these tapes that they may have a thermal half-life for retaining magnetization, the smaller of the particles degrading first.
At the height of magnetic disk drive technology there was the introduction of cobalt magnetic particles coated specially to provide the smallest possible magnetic particles, but cobalt is very different magnetically requiring alignment of particles (*) and stronger magnetic fields to record. They also engineered very uniform particle size to reduce the fading effect over time due to smaller particles flipping.
(*) cobalt has strong uniaxial anisotropy in its magnetism, unlike iron.