I stand corrected. I usually don't record at 15 IPS, I only have one deck that will do it, and I've not measured the response at 0dB. Thanks, Alex.
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Cassette problem - frequency response
- Thread starter pvh1987
- Start date
I stand corrected. I usually don't record at 15 IPS, I only have one deck that will do it, and I've not measured the response at 0dB. Thanks, Alex.
2fives
Active Member
Me think better of the silver version with sidepanels
Thats a nice unit. :thmbsp:
jan_stevns
Super Member
pvh1987
New Member
Some days ago, I recorded some different songs on a Sony UXS tape using Dolby B. I might like Dolby B better than Dolby C - sounds less compressed in my opinion. Maybe it is a question of calibrating/adjusting the deck, but I don't have the knowledge to do that myself for the moment.
I do not find the sound very transparent, but a lot better than it used to be. I believe it is because I recorded so that the peaks only rarely goes above 0 dB. I thought that the background noise would be too strong, but not really.
The biggest problem right know is that the sound tend to dull sometimes. Suddenly, the highs are gone - I can stop the tape, maybe take it out and put it in again, press play - then it is just fine for the next few minutes. Sometimes there is no problems at all. I think that is very strange - could it be a transport problem or some noise reduction issues? What about the Dolby HX Pro?
I also wondered if it is possible to build a Dolby B (or maybe C or S) decode and encode circuit with discrete components or maybe opamps? I have no idea with the complexity of those circuits. I have some documents describing Dolby B, C and S with different graphs illustrating the compression/companding stuff. I guess it is a bit more complicated than a phono preamp?
I do not find the sound very transparent, but a lot better than it used to be. I believe it is because I recorded so that the peaks only rarely goes above 0 dB. I thought that the background noise would be too strong, but not really.
The biggest problem right know is that the sound tend to dull sometimes. Suddenly, the highs are gone - I can stop the tape, maybe take it out and put it in again, press play - then it is just fine for the next few minutes. Sometimes there is no problems at all. I think that is very strange - could it be a transport problem or some noise reduction issues? What about the Dolby HX Pro?
I also wondered if it is possible to build a Dolby B (or maybe C or S) decode and encode circuit with discrete components or maybe opamps? I have no idea with the complexity of those circuits. I have some documents describing Dolby B, C and S with different graphs illustrating the compression/companding stuff. I guess it is a bit more complicated than a phono preamp?
goldear
Certifiable Audio Junkie
Discrete Dolby B decoders were the norm when Dolby B was in its infacy. Teac, Sony Advent, and probably some others all made descrete outboad Dolby B units. Nakamichi even made a couple of outboard Dolby C units. It would be far easier to recap one of those than it would be to build your own unit.
If you want to hear the "ultimate" noise reduction system, then get a good open reel machine and connect an outboard Dolby SR processor to it. Dolby SR was not designed for use on cassettes though.
Also, Dolby B is not as high performance of a system as Dolby C. Dolby C has a very nice feature called "spectral skewing" which provides you with more HF headroom (in addition to HX-pro, which is a completely different system), whereas Dolby B actually somewhat negatively impacts your HF headroom, even when calibrated perfectly.
FWIW: It really sounds like your deck is not calibrated very well, and that this is probably your biggest issue at the moment.
If you want to hear the "ultimate" noise reduction system, then get a good open reel machine and connect an outboard Dolby SR processor to it. Dolby SR was not designed for use on cassettes though.
Also, Dolby B is not as high performance of a system as Dolby C. Dolby C has a very nice feature called "spectral skewing" which provides you with more HF headroom (in addition to HX-pro, which is a completely different system), whereas Dolby B actually somewhat negatively impacts your HF headroom, even when calibrated perfectly.
FWIW: It really sounds like your deck is not calibrated very well, and that this is probably your biggest issue at the moment.
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jan_stevns
Super Member
could be a transport problem, or worn heads - pinchrollers can cause tape skewing, belt issues might cause slippage in the dual capstan syncronisation
if any spareparts are needed on this deck - it's a big problem, spareparts seems to be long gone..
what's the condition of the heads ??
regarding building your own external dolby unit with discrete components - it can be done, but frankly ain't worth the effort
pvh1987
New Member
I have tried cleaning the pinch rollers, capstans and tape head using 99% isopropyl alchohol. I don't know how it is supposed to look, but it is possible to tell the width of the tape, looking at the pinch rollers.
The tape head looks fine, but again - I don't know how it is supposed to look.
The thing that worries me the most right now is the electronics. If I play straight through the deck (listening to the source) it is not as transparent as it should be. I tried to put a square wave trough the machine and it's easy to see that something is wrong. Maybe it is the amplifier circuits made strictly 20-20kHz -3dB, but today, if you were going to do design a small signal amplifier - you would maybe ensure 10-100 kHz -3dB for a high end circuit or something like that.
I don't know how bad it really is, but the transport may be better than the electronics in the Denon DRM-44HX.
To push the limits I should use some kind of high end cassette playback and recording electronics with Dolby B, C and maybe S as well, connected directly to the tape head and then use the Denon as a transport only. But that is crazy - such a product does not exists, as far as I know. It is going to contain bias-stuff as well. I wondered if bias is only used when recording?
The outboard Dolby units are only part of that - I guess you are simply connecting those to the input and output of the deck, not bypassing the bad electronics?
What exactly does Dolby HX Pro? It is impossible to turn off HX Pro on my Denon deck - that's what I know. I heard it is some kind of playback optimizing stuff?
Maybe it is not worth the effort to do anything. Then I could use a lot of money and get a really good Nakamichi and everything will be fine. But it will wear out at some time - what can I do then?
Is pinch rollers very different from each other or is it just about the same for any cassette recorder?
The tape head looks fine, but again - I don't know how it is supposed to look.
The thing that worries me the most right now is the electronics. If I play straight through the deck (listening to the source) it is not as transparent as it should be. I tried to put a square wave trough the machine and it's easy to see that something is wrong. Maybe it is the amplifier circuits made strictly 20-20kHz -3dB, but today, if you were going to do design a small signal amplifier - you would maybe ensure 10-100 kHz -3dB for a high end circuit or something like that.
I don't know how bad it really is, but the transport may be better than the electronics in the Denon DRM-44HX.
To push the limits I should use some kind of high end cassette playback and recording electronics with Dolby B, C and maybe S as well, connected directly to the tape head and then use the Denon as a transport only. But that is crazy - such a product does not exists, as far as I know. It is going to contain bias-stuff as well. I wondered if bias is only used when recording?
The outboard Dolby units are only part of that - I guess you are simply connecting those to the input and output of the deck, not bypassing the bad electronics?
What exactly does Dolby HX Pro? It is impossible to turn off HX Pro on my Denon deck - that's what I know. I heard it is some kind of playback optimizing stuff?
Maybe it is not worth the effort to do anything. Then I could use a lot of money and get a really good Nakamichi and everything will be fine. But it will wear out at some time - what can I do then?
Is pinch rollers very different from each other or is it just about the same for any cassette recorder?
You might not get the quality you want out of that Denon deck.
However, I believe you have run into the problem most users of cassette decks dump the technology on: Tape allignment issues.
To get the best of one particular tape, you will have to make a recording after getting eq for left and eq for right channel right at the given speed you are running your tape (which is set for most cassette decks) and you have to get it right for both recording and playback, you have get rec. level (not master input) right for left channel and for right channel (at a given speed) and you you have to get it right for recording and playback, you have to get bias right for each channel as well and when one process is through, the result of one or both former process' might have changed.
This means it's a kind of "pin-pon" process.......at least for the rec lev and bias.
After getting these things right, record head azimuth has to get right.
Now how much of this is possible on that Denon deck with a (non-existing build-in) tone generator?
"dolph"
However, I believe you have run into the problem most users of cassette decks dump the technology on: Tape allignment issues.
To get the best of one particular tape, you will have to make a recording after getting eq for left and eq for right channel right at the given speed you are running your tape (which is set for most cassette decks) and you have to get it right for both recording and playback, you have get rec. level (not master input) right for left channel and for right channel (at a given speed) and you you have to get it right for recording and playback, you have to get bias right for each channel as well and when one process is through, the result of one or both former process' might have changed.
This means it's a kind of "pin-pon" process.......at least for the rec lev and bias.
After getting these things right, record head azimuth has to get right.
Now how much of this is possible on that Denon deck with a (non-existing build-in) tone generator?
"dolph"
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jan_stevns
Super Member
the rollers in my deck looks pretty much the same - i take it as a sign of wear, not that they are unusable
By the look - i can't see anything worrying me - i've attached a pic of my deck further down for comparising
To be honest - the electronics are not from today - it's 25 years old, and maybe a recap could spiff it up a little, i can't say. I would not jugde anything by sending square wave through - just one coil, and it's affected.
This deck is not a "high end" product, and i'm afraid you're (soundwise)comparing it with decks in a whole other league, like the big NAK's or Tandberg - that's not fair
That subject was recently the talk of the thread
this link may explain things http://en.wikipedia.org/wiki/Dolby_noise-reduction_system#Dolby_HX
they come in many sizes - as in your (and mine too) the left roller has to give space for the tapeguide
and the pic from my own DMR44hx (the one shown earlier)
The right roller on my deck - has tapemark, but not much - this deck hasn't run very much (less than 1000hours)
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