Hi all

Following on from this thread:

web page

I want to have a go at checking and adjusting the azimuth on my Technics RS-AZ6. Until yesterday I'd never even heard the word azimuth; so I really am in the dark on this one and for starts I cannot even figure how to remove the tape door.

Just wondered if any one can give me any pointers please?

Many thanks

Max

THIS ARTICLE explains what the azimuth adjustment is and why it is needed.

I'm afraid I can't help with accessing the control for Your particular cassette machine, other than to suggest that the cover door usually slides on to clips above -- but they will be plastic and easily broken, so don't force anything!

The azimuth adjustment is usually a small screw or allen bolt fixing one side of the rec/rep head. It will only need a very small tweak!

Hugh

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Technical Editor, Sound On Sound

Edited by Hugh Robjohns (13/02/13 05:42 PM)

As ever, thanks for the great and speedy help.

One point of clarification though...:

Quote Hugh Robjohns:

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I can't help with accessing the control for our particular cassette machine

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IT'S MINE - HANDS OFF!

I recently digitised some old tapes & realised early on that the azimuth needed tweaking on my Yamaha deck. However out of the 2 screws for the playback head (left & right) I had no idea from the manual which was the one for azimuth adjustment. After a while googling I found the service manual in a downloadable .pdf - gratis.

Mine was the one on the left, yours *may* be the right, but it's worth finding out if you don't know already - I believe the other screw is for head removal.

Quote TheBev:

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realised early on that the azimuth needed tweaking

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What was the tell-tale sign in your case?

On some decks there is a spring pushing the head bracket up against the screw head on the side that you adjust. Also, with door the cover off, some decks only expose the screw that you should adjust, keeping the other side inaccessible unless you remove the whole casing.

Remember to make sure that the screwdriver that you use is non magnetic and has the correct tip for the screw.

Edit:- looks like there is a service manual at http://www.hifiengine.com/library/technics/rs-az6.shtml

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

Edited by James Perrett (13/02/13 04:45 PM)

Quote Li-rocchi:

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Quote TheBev:

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realised early on that the azimuth needed tweaking

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What was the tell-tale sign in your case?

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When the head alignment is off, the playback is usually dull, muffled. Pop the lid off, I don't think your model has the screw James is talking about. IIRC, it's a recessed screw so look for a small hole near the playback head. Then you need to figure out what screw driver type you need.

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I'm All Ears.

Edited by ken long (13/02/13 04:49 PM)

Quote Li-rocchi:

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What was the tell-tale sign in your case?

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They sounded bl**dy awful.

Only half joking.. they were all recorded & listened to on an Akai deck, but that was 20 odd years ago & the sound on the Yamaha was basically muffled / lacking in top end. The Yammie deck has a Play / Trim control which I believe offers an eq of sorts which helped a lot, but as it was a kind of one shot deal to record them it seemed best to get the source sounding as good as possible.

I'm never going to record tapes on it again so messing with the azimuth for playback / archiving was a no brainer to me. The best advice is to use your ear till it sounds the best on something like cymbals, then you're there or thereabouts. & as Hugh said it will be just tiny tweaks either way - if at all.

Quote James Perrett:

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Edit:- looks like there is a service manual at http://www.hifiengine.com/library/technics/rs-az6.shtml

James.

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Ah that's it, thanks James.. I really should have bookmarked that site at the time.

The handbook doesn't give any specific azimuth alignment details, but looking at the mechanism exploded diapgram, the rec/rep head is fixed in place with two screws. The one on the left is passes through a rigid collar, while the one on the right passes through a spring -- so that's the one to tweak to tilt the head slightly one way or the other.

H

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Technical Editor, Sound On Sound

Oh - one last thing, it seemed easier to judge the azimuth whilst listening in mono. I've no why this might have been, or even if I was just kidding myself tbh but worth mentioning.

Quote TheBev:

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Oh - one last thing, it seemed easier to judge the azimuth whilst listening in mono. I've no why this might have been, or even if I was just kidding myself tbh but worth mentioning.

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You weren't kidding yourself -- it is the best way to do it (unless you have access to a scope or Goniometer).

The replay head has two vertical slits, one for each track of the stereo audio recorded on the tape. If the head is tilted sideways (which is what the azimuth control adjusts), then it will be replaying one track fractionally earlier or later than the other.

If the same material exists on both tracks, and if you mix those two tracks together, then any time-shifting between them will result in comb filtering -- it's the same effect as mixing the original and slightly delayed signals together that we use for phasing, flanging, chorus etc.

However, in this case there's no modulation going on because the time shift is fixed and static, and it won't sound hollow and phasey because the time delay is incredibly short.

Instead, what you hear is a loss in the extreme HF, because the first comb filter notch is just starting to impinge on the top end of the audio bandwidth, rolling off the HF response sooner than it should.

So... the quick and dirty azimuth adjustment technique is to listen in mono and adjust the azimuth very slightly in each direction while listening for the position that provides the most HF (maximum brightness). When you've found that point the replay head will be aligned to the same azimuth as the record head that made the original recording.

Please note -- that's not necessarily the same as having a perfectly correct (vertical) azimuth because the record head could, itself, have been misaligned.

This is actually a significant point when adjusting cassette machines, because the record and replay heads are usually one and the same. Consequently, if you adjust the azimuth to optimise the replay of one cassette you are also potentially buggering up the azimuth of anything you subsequently record!

Ideally, therefore, before making any recordings you should realign the machine's azimuth to a known reference tape but, since they are expensive and rare, the easiest thing to do is record your own reference tape before you start tweaking. I would suggest recording a couple of minutes of 1kHz tone, 5kHz tone, 10kHz tone, and white noise -- in mono on both tracks.

The white noise is the easiest thing to use for quick resets, and the tones for precise alignment with proper test equipment. You need the 1k and 5k tones to make sure that you don't accidently end up 360 degrees out of phase on the 10k -- which is surprisingly easy to do if you're not careful!

Of course, if you're confident taht you'll never want to record a cassette tape ever again, then you don't need to worry about being able to reset to the original (standard reference) alignment.

hugh


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Technical Editor, Sound On Sound

Thanks for that Hugh - v comprehensive as always, & no I'm confident I'll never have need to record another cassette. At least I know that I wasn't imagining it, or worse spreading incorrect information. I've still got some more to do myself but know that the tape is running too fast - for some reason I'm a bit *more* apprehensive about messing with this so have been delaying.
Back to the service manual I go..

The service manual should say where the speed conetol is -- most modern cassette machines use a servo-controlled DC motor and there will be a speed tweak somewhere -- often on or near the motor itself.

Adjusting speed is relatively easy if you have a piano or similar to hand and know the intended key of the music -- just adjust until sustained notes are in tune with the piano!

H

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Technical Editor, Sound On Sound

In the scenario of continually matching tapes from different machines to a single playback device, are there practical or quality advantages to be had in software correction, Rx2, etc. (not having tried this myself)?

Quote Jeraldo:

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In the scenario of continually matching tapes from different machines to a single playback device, are there practical or quality advantages to be had in software correction, Rx2, etc. (not having tried this myself)?

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No, it is better to align the physical heads if possible. Software correction like RX2 can compensate for the relative delay between channels, easily, and correct the falling hf response... But at the minor expense of increased hf noise.

In contrast, correcting the head azimuth physically restores the hf response without increasing the noise.

A misaligned head effectively has a wider head gap than the physical gap and thus a poorer hf response.

H

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Technical Editor, Sound On Sound

Thanks, Hugh.

Quote Hugh Robjohns:

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A misaligned head effectively has a wider head gap than the physical gap and thus a poorer hf response.

H

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Not a lot of people know that! Well they didn't till now. How am I supposed to wow friends with 'fascinating' facts when you just give them all away?

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It wasn't me!
(Well, actually, it probably was)

...and that's also the reason why I'm not a millionaire!

H

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Technical Editor, Sound On Sound

Quote TheBev:

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I've still got some more to do myself but know that the tape is running too fast - for some reason I'm a bit *more* apprehensive about messing with this so have been delaying.
Back to the service manual I go..

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Altering the speed is something that can be done reasonably successfully in the digital domain if we're talking about a small difference (less than a couple of semitones). Yes, the eq may be ever so slightly wrong and there's an extra sample rate conversion required to do it but sample rate conversions are pretty transparent nowadays and the eq error is going to be similar to the error due to component variations so nothing really to worry about.

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

Thanks James - & Hugh again. Yeah I have altered the speed before of older tapes in software, not because of pitch correction but because I felt the track was all the better for a little urgency. & also if I'm honest - just because I could.

Re my apprehension of opening up the recorder, I just needed Hugh to say it was Ok.

Quote TheBev:

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Re my apprehension of opening up the recorder, I just needed Hugh to say it was Ok.

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As one of my mentors used to say, it's perfectly okay so long as, (a) you don't break anything, and (b) you don't kill yourself.... in that order!

hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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Quote TheBev:

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Re my apprehension of opening up the recorder, I just needed Hugh to say it was Ok.

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As one of my mentors used to say, it's perfectly okay so long as, (a) you don't break anything, and (b) you don't kill yourself.... in that order!

hugh

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I'll try to bear that in mind.