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Why such variable SQ on R2R?

ex brickie

ex brickie

pfm Member
I've this weekend finally got my newly acquired Pioneer RT 909 up and running.

I have been playing a Beach Boys tape which happens to be two albums - one each side. The speed is 3 and 3/4 IPS

What seems odd is that playing one way the sound quality isn't great - like a cassette tape and a bit dead and muffled . Playing the other way the music livens up, is crisper and has better treble.

Can the tape heads make a difference like this? Or is it likely to be the reel itself and if so what causes it?

Most of the pre recorded tapes I've bought are 3.75 but I will try one of the faster reels to see how much that improves the sound quality
 
Might it be an azimuth issue, either with your recorders heads or the tape itself? I’d only worry about it if it is consistent over multiple tapes.

Edit: thinking about it the RT-909 is auto-reverse isn’t it? Which direction is worse? Does it use the same replay head for both directions? If it is less good forward than reverse and uses different heads I’d check that head very carefully for wear. Chances are it has been used to play forward far more often than reverse. Always worth demagnetising a tape recorder’s heads too, it can make quite a difference. I bought one of these a while back and it certainly helped both my cassette decks and Akai 4000DB.
 
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Hi Tony
Thanks for a comprehensive reply. I've only tried one tape so I will try others to see if it a consistent issue. On the tape I tried, normal forward play (L to R) was more muffled.
Will think about a demagnetiser as you suggest
No idea re the heads (first I'm a complete novice: second, not had much chance to look closely yet). If a specific hard is worn can they still be replaced? Is it a big job for a techie?
 
I don’t know enough about the Pioneer to know if any spares are available, but it is likely not this anyway. Have you checked the transport for dirt. When I got my far more humble Akai 4000DB back from the auction house the heads were caked with crap that really took some work with isopropyl alcohol and a cotton bud to fully remove. Tape shed can be nasty sticky stuff and your issue may be nothing more than that.

Just clarify a couple of points for me:

Have you tried threading the tape in both directions, i.e. winding to the other spool and turning the tape over?

If so does the problem stay with the tape side (i.e. a or b) or does it stay with the recorder’s playback direction?

This will clarify if the problem is with the specific tape or the tape machine’s replay function in one direction.
 
Hi Tony

Thanks again. It may be next weekend before I get a chance to flip the tapes around. I'll try an alternative tape on the normal L to R to see if I have the same muffling. If I'm lucky and I don't, I've at least isolated that it is a problem of that particular reel.
 
If you haven't used it in a while

1) Buy some isopropyl alcohol and use some Q-tips (or lint free wipes) to clean the heads, the tape guides and all of the metal rollers. (Don't use alcohol on a rubber capstan). They may well be filthy. If you have metal oxide in the crevices of the tape guides, then you can try a toothpick and alcohol to make sure these are clean (don't use a toothpick on the heads).

2) Demagnetise the heads (make sure the machine is switched off and unplugged from the mains - have the demag at least an arms length away, when you switch it on - move it SLOWLY up to, but not touching the heads and then any metal tape guides - then move it SLOWLY away from the machine - switch the Demag off when the Demag is well away room the machine)

3) then take some photos of the heads and tape guides and post them here.
 
I’ll post some pics of my freshly cleaned 909 heads tomorrow if you would like something to compare them too
 
What Charlie said, its all about tape contact with the heads so the head cleanliness and demagnetisation can make an enormous difference
A magnetised head can increase noise and roll off the treble it can also damage your pre recorded tape every time you play it, most noticeable would be loss of treble response.
Its also possible that you are trying to play a 4 track tape on a 2 track head or vice versa ?

Alan
 
All good points Alan - I'm a complete novice to all this! I don't even know the difference between a 2 track and 4 track! I'll read up on line and check my reels. I bought quite a few of my pre recorded reels before even buying the Pioneer deck! I hope they are all compatible (I do know that they are all 7" reels or less (even though the Pioneer does take 10" reels) and nothing I have is above 7.5 IPS recording speed.

I have Isopropyl so I can use a swab there for some cleaning and I'll invest in the demagnetiser and use carefully.

I might just have a duff side to the tape too of course so I must try some others

Thanks everyone for your advice. I'm sure I'll be back for more....
 
337alant said:
Its also possible that you are trying to play a 4 track tape on a 2 track head or vice versa ?
Click to expand...

The RT-909 is a bi-directional auto-reverse deck so uses standard quarter-track stereo tape that can be played in both directions without flipping the tape over. The thing I don’t know as I’ve never actually seen one is whether it uses a single four-track replay head or a pair of standard stereo heads. The head-block would be interesting to see as I’ve never used an auto-reverse deck.
 
The RT-707 which is in many ways a smaller spool version of the RT-909 uses separate replay heads for forward and reverse so it is quite possible that one or other has been misaligned azimuth wise. As Tony has said turning the tape over should give you a clue if this is the case.
 
Cleaning of course should be your first course of action,just be careful with the pinch rollers as the rubber may be deteriorating with age. In fact be wary with alcohol as mentioned above. As advised above turning the tape will narrow down where the problem lies. Three heads and auto reverse does mean more variables of course but also let’s you do more specific tests.

As this machine has a direct monitoring function (note the source /tape button on the left next to the headphone socket) it allows you to directly compare the input to the tape deck with the output from the tape in both directions instantaneously via your amplifiers tape monitor button or by using headphones.
With a decent tape feed a source signal into the machine when it’s in record mode and if using headphones on the 909 switch the source / tape button.
If the tape is good and the heads aligned ( rec and playback each direction) there should be no difference between the two. Do this in both directions and see if there is a difference. You can do this with music, test tones via Spotify or noise between fm radio stations!
If the machine does this correctly it’s likely to be your tape.

There are bias and eq settings on the deck but these but These shouldn’t operate on individual channels, they will have the same effect on both L & R.(the wrong eq settings can give a dull playback depending on the tape).

I guess the head layout will be from left to right PLAYBACK REVERSE, RECORD (both directions) and PLAYBACK FORWARD.
The middle record head Will be like 4 Lego blocks on top of each other, on a 4 track machine the L Channel will be the 4th block ( top block ) and it’s matching R channel will be the 2nd block.
When the tape is turned or the machine has auto reverse the L channel will be the bottom block and the right will be the third block.
The playback heads will be used to pick up on tracks 2&4 and 1&3.



https://www.google.com/search?clien...0i8i30j30i10.E1jxUPSoNrM#imgrc=3_cNp7fddMMQTM:

On the later reel to reel machines the heads were pretty robust so I don’t think wear should be an issue. With the early machines there would be a distinct groove on the head if it was badly worn and you could feel it with a finger nail.
A worn pinch roller can cause alignment issues as well. Instead of a flat surface pressing the tape against the capstan,worn rollers tend to expand in the middle which can draw the tape up or down on the capstan which in turn will raise the tape up or down on the heads usually giving a loss of high frequencies.
So a worn roller could also cause the effect you mentioned.

Hope that helps, or have I confused you even more!!
 
The RT-909 has two play heads, one for each direction. Each play head has azimuth adjustment via clearly market access holes in the head cover.

I'd be reluctant to suggest making any adjustments until you've cleaned and demagnetized as suggested above; even then, it would be a good idea to rule out the particular tape, as Tony suggested.
 
I think you will find the machine records only in the forward direction, only playback is bidirectional. This is the case with the RT-707. Bidirectional record would require a second erase head.

I agree with the need for cleaning and would warn against any adjustment of azimuth unless you have the required equipment and knowledge.
 
Barrymagrec said:
I agree with the need for cleaning and would warn against any adjustment of azimuth unless you have the required equipment and knowledge.
Click to expand...

Agreed. Given the quality, value and scarcity of this machine I’d personally do no more than cleaning and demagnetising the heads and transport. If it still ain’t right pay a professional, it is certainly a good enough machine to merit the expense.
 
Barrymagrec said:
I agree with the need for cleaning and would warn against any adjustment of azimuth unless you have the required equipment and knowledge.
Click to expand...
IME, all that is required to adjust azimuth is a flat blade screwdriver and one's own ears, that is, assuming the latter operate out to at least 8kHz.
 
wow&flutter said:
Cleaning of course should be your first course of action,just be careful with the pinch rollers as the rubber may be deteriorating with age. In fact be wary with alcohol as mentioned above. As advised above turning the tape will narrow down where the problem lies. Three heads and auto reverse does mean more variables of course but also let’s you do more specific tests.

As this machine has a direct monitoring function (note the source /tape button on the left next to the headphone socket) it allows you to directly compare the input to the tape deck with the output from the tape in both directions instantaneously via your amplifiers tape monitor button or by using headphones.
With a decent tape feed a source signal into the machine when it’s in record mode and if using headphones on the 909 switch the source / tape button.
If the tape is good and the heads aligned ( rec and playback each direction) there should be no difference between the two. Do this in both directions and see if there is a difference. You can do this with music, test tones via Spotify or noise between fm radio stations!
If the machine does this correctly it’s likely to be your tape.

There are bias and eq settings on the deck but these but These shouldn’t operate on individual channels, they will have the same effect on both L & R.(the wrong eq settings can give a dull playback depending on the tape).

I guess the head layout will be from left to right PLAYBACK REVERSE, RECORD (both directions) and PLAYBACK FORWARD.
The middle record head Will be like 4 Lego blocks on top of each other, on a 4 track machine the L Channel will be the 4th block ( top block ) and it’s matching R channel will be the 2nd block.
When the tape is turned or the machine has auto reverse the L channel will be the bottom block and the right will be the third block.
The playback heads will be used to pick up on tracks 2&4 and 1&3.



https://www.google.com/search?clien...0i8i30j30i10.E1jxUPSoNrM#imgrc=3_cNp7fddMMQTM:

On the later reel to reel machines the heads were pretty robust so I don’t think wear should be an issue. With the early machines there would be a distinct groove on the head if it was badly worn and you could feel it with a finger nail.
A worn pinch roller can cause alignment issues as well. Instead of a flat surface pressing the tape against the capstan,worn rollers tend to expand in the middle which can draw the tape up or down on the capstan which in turn will raise the tape up or down on the heads usually giving a loss of high frequencies.
So a worn roller could also cause the effect you mentioned.

Hope that helps, or have I confused you even more!!
Click to expand...

Just cos it plays it's own recordings OK doesn't mean both heads are lined up to "correct", "standard";) Could yet well be just build up of oxide on heads etc.... I find for critical recordings it's pretty essential to clean heads maybe every reel of tape or two. Playback more so as narrower head gap but you only record it once so get it right...

I found the best of Japanese technology in tape formulations from Maxell and TDK to be better than all other types...(higher output, more consistent, less drop outs, better HF extension, heads don't need cleaning quite as often) followed by BASF with USA brands rather behind,,, especially in oxide
shedding etc! There's some controversy to discuss... mind you the right mains cable can of course cure even oxide shedding:D

Crossing over to another R2R thread and courting further controversy no doubt... but to me whats the point of recording your own CD's and vinyl?
Talk to that pretty good acoustic folk duo you heard down the pub etc who would just love to be recorded with "old school analogue gear" in a sympathetic relaxed environment over a few beers and some food. Make a day of it. Experiment. get some good live recordings! They're usually really keen IME;)
When you get a mic problem.. like Imelda Marcos had with shoes... It wasn't my fault:D:eek:
 
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