I have replaced both belts and pinch-rollers on all of my three 951 players (as well as the drive-gear on one of them that had a cracked gear)
I’ve cleaned the heads thoroughly.
But they all suffer from exactly the same issue now.
When inserting a tape they give me the “Clean head” message and they output no sound (even though they play the tape with track-number and time showing in the display)
If I track-search forward to track nr 2 they start to play from track 2.
If I then track-search or rewind back to track 1 they will play and output sound from track 1.
Ocassionally the same thing happens when they turn to the B-side at the end of side A but not always.
If I track search forward a bit and then rewind back to the start of the B-side they will play with sound.
There are also random drop-outs throughout some tapes -not always- (that are not present when I play the same tapes in either of my 300 players)
It seems like they are extremely sensitive.
But how is it possible that three different players behave exactly the same and won’t output sound until I have track-searched forward a bit and then rewinded the tape back?
It sounds like the tape is to blame, to be honest. It’s not unlikely that some tapes are better quality than others, and especially after 30 years we shouldn’t be surprised that some tapes are becoming more difficult to play, I guess.
===Jac
Yes I suspected that as well.
But why do the tapes play perfectly in my 300 players and not in either of the 951’s?
Is it a known fact that the 951 heads are more sensitive than the 300?
And why is it always the same issue when inserting a tape on all three 951 players?
(Clean head message… no sound… track-search forward and rewind back and then it plays with sound)?
That issue just can’t be the tapes alone.
The constant random drop-outs could of course be the tapes in combo with a very sensitive head.
But then all of my three 951’s suffer from extremely sensitive heads.
Could it be the higher bitrate of the 951 that makes it more sensitive?
Isn’t the 951 18-bit and the 300 is only 16-bit
Maybe it needs to read more blocks from the tape that the 300 player does not?
I’m just guessing here as I’m neither an electrician or technician
When all three 951 players suffer from this, it must be the tapes. Do all tapes you use have these issues on de 951?
Your tapes could suffer from dirt on the tape caused by the felt pads inside the cassette (not visible from the outside). Or from the stick-slip effect from the visible felt pad. Clean the visible white felt pad carefully, and see if it changes anything.
Yes I have cleaned all the felt pads on every cassette I own.
But it might of course not have helped 100%
Bit rate shouldn’t make a difference.
I forgot to ask, are you using prerecorded tapes, or tapes recorded on your DCC300?
What happens if you make a recording with the DCC951 and playback on the same DCC951?
Yes i’m only using prerecorded tapes.
I have not tried to record on any of my players as of yet
I have tried several tapes now that suffers from severe drop-outs on all three 951 players.
All of the tapes play without any issues on all my three 300 players.
I guess I’ll just have to face it…
The 951’s are more sensitive to damaged tapes.
I’m just trying to help, for this is new to me. I have no issues whatsoever with my three 951’s.
Did you have a good look at the tapes, are they really physically damaged? And why do they play correctly after track search? I have quite some pre-recorded tapes with the white felt pad that sometimes cause issues at the beginning of side A or B.
It might have to do something with the speed varying too much. What happens when you play an analog tape with a constant tone, or with piano music? Do you hear extensive wow&flutter?
Could be you belts are slipping, or the copper/messing belt pulleys are very dirty. Or it might run too slow or too high on speed. On the other hand, when running dcc tapes the speed is synchronised with the digital stream.
The Clean Head message appears whenever the mechanism has trouble reading a tape. If a tape is bad, you would see the message on any 3rd generation recorder even if the head would be brand new and shiny. The electronics can’t distinguish between a dirty head or unreadable data on a tape.
The data rate on tape is exactly the same regardless of how many bits were used to encode the music. It’s always 384 kbps of music (plus 384 kbps for error correction codes and other data). An 18 bit input source just means that the music can be encoded with greater accuracy and less loss in the compression.
Even the sample rate doesn’t make a difference to the tape data rate. If you record a tape at 48 kHz, there is more data to encode so there is more lossy compression, but the resulting data rate is still 384 kbps. Basically, recording a tape at 48 kHz instead of 44.1 kHz changes what the encoders will remove: at 48 kHz the frequency bands are a bit wider (there are still 32 bands) so the accuracy of the PASC signal is simply reduced slightly.
Reading the tape is basically the same in all DCC recorders. The data rate of every tape is the same. The different sample frequencies and bit depths don’t matter until the data has been error corrected, and the PASC stream is decoded.
Decoding PASC / MP1 basically means synthesizing an audio wave by adding up the information for all 32 frequency bands. Depending on the sample frequency and the number of bits that are used to do the maths, the final bit rate and amount of information changes, The encoding is where the magic happens: The encoder has to decide which information to hide (and where to reduce the accuracy of the recorded signal) to generate the data stream so that it sounds the same as the original.
You could think of PASC like making a painting: When you paint a picture of a landscape, and someone sees the painting, they will recognize what’s on the painting. But unlike the real landscape, you can’t just walk up to the church and see every brick that was used to build it, because the painter decided that painting the general shape of the church was enough to make the church recognizable.
===Jac
Im very thankful for all help I can get.
I’m now more and more convinced that you are right.
The tapes are to blame, but my 300 players are more forgiving with errors.
After playing even more tapes I noticed that on some tapes (where the 951’s get total drop-outs and goes quiet for 1-2 seconds and then get chopping sound and back to quiet again for a couple of seconds and so on) the 300 players have minor fractions of drop-outs. Hardly noticeable if listening from a distance (like in another room)
Wich indeed points to the tapes like you said.
But my reflection also stays true -that the 951’s are far more sensitive to deteriorated/damaged tapes than the 300 players.
At least amongst the six players I have.
Thank you Jac for the extensive explanation.
Great info 
If the tapes were exposed to a damaged pinch rollers (the old pinch rollers on a 951 all get blisters), the pinch roller will permanently damage the tape. If there is a chance that your collection is exposed to that pinch roller, the indeed could suffer all from this very problem.
The blisters are sharp and hard.
Yes this was truly a “dull” moment as I’ve up til now believed that my collection of DCC tapes were in pretty good condition overall, as playing them in my 300 players didn’t gave many errors or drop-outs.
Of course a couple of my tapes were pretty bad even with the 300 players.
But as I’ve now got my three 951 units in playable state it became clear that my tapes are far worse than I first believed.
Of course I can still choose to play them in my 300 players for a more hassle-free listening.
Did you purchase the pinch rollers identical from a certain German seller on eBay?
No.
I purchased them here from the DCC Museum.