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Sony WM-D6C

Discussion in 'classic' started by Tony L, May 18, 2020.

  1. awl

    awl pfm Member

    I've turned out my WM-D6C and the AC-D4M power supply supplied by Sony in 1990 (I still have the invoices):



    It's rated at 400mA

    Here's the relevant page of the user manual:


    So, this doesn't tally, but as I say, the AC-D4M was supplied by Sony themselves to go with the WM-D6C and has worked fine for the last 30 years!
  2. Tony L

    Tony L Administrator

    That looks exactly right, I think they changed the model number a couple of times, but its still 6V DC, centre negative and about the same mA. That’s clearly the spec I need.
    hairyderriere likes this.
  3. Werner

    Werner pfm Member

    And that's were CC is wrong. Dead wrong.

    True, there were compatibility issues between chrome and ferro-cobalt in the 70s, but these gradually disappeared through the 80s, and by 1987 the BASF-made IEC2 reference tape itself was ferro-cobalt, modelled on the SA's parameters.

    What people are experiencing now is age-related degradation of chrome, even NOS. This pertains to the recording parameters. Existing recordings are not affected, only new ones.

    Overall sensitivity drops, and treble sensitivity drops even more.

    The only way to compensate for this treble drop is to reduce bias. This makes the frequency response flat again, but comes at the cost of a severely reduced Maximum Output Level (MOL) and increased distortion. You can still record on chrome tape, but it won't take peaks beyond 0dB (Dolby level or DIN, not much difference). As a result the total dynamic range you can today realise with chrome is about 59-60dB, up to 62dB for a not-too-affected sample. That is 2-4dB down from these tapes' performance back in the days, and on a par with late-1970s ferro-cobalt. Usable, but far from state of the art.

    I have made a study of this phenomenon: https://audiochrome.blogspot.com/2019/02/cassette-tape-comparative-measurements.html
    Rico likes this.
  4. waxkinglyrical

    waxkinglyrical pfm Member

    The TDK D is fine for duplication from a master cassette tape, as you rightly say the AD is a lot better for a primary recording, also had good results from an AR.
    There are many tapes which are classified as super ferrics and can perform, with the right deck, better than some type II tapes: BASF Ferro Super I, That’s FX, Maxell XLI-S, Fuji FR IS, Denon DX variants, check out the Sony HF range too and the TDK AR-X.
    Most mentioned are no longer cheap, lot less than metals though - but you will be pleasantly surprised as to how good they are.
  5. Tony L

    Tony L Administrator

    I suspect it is me that is wrong, just my interpretation of his videos. The tests I’ve seen him carry out are obviously on NOS tapes so if anything back up your findings, basically that BASF etc proper chrome tapes needs a lot of negative bias to perform.

    Are you basically saying that ferric/cobalt-doped ferric don’t suffer the same ageing processes and are a safer NOS buy? I’ve not tried recording on a cassette for decades, but the old SA, D and metal tapes I have all seem fine. I don’t think I ever had a proper chrome tape as I tended to buy TDK, plus a few That’s, maybe the odd Sony.
  6. waxkinglyrical

    waxkinglyrical pfm Member

    This is what I use on the Walkman WM-D6C...well I’m buggered if I can load the image off the IPad!

    It is a dedicated 6v/700 mA AC power adaptor made by Sony: AC-D4HG

    PM me with your email address and I’ll forward the image if you like.
  7. Tony L

    Tony L Administrator

    Its ok, I know the spec now. I was just wondering if anyone had any recommendations for nice quality modern equivalents. To be honest I’m not even sure I’ll bother, I may just get a really good set of rechargeable batteries, or just use standard AAs, but a charger would save any stress on the plastic battery compartment and remove any risk of forgetting to take batteries out long-term. I’m not planning to use it much, most of the fun will be in the restoration and initial reacquaintance, after that it will likely just sit in the system as an ‘available option’, just as the 4000DB does. I don’t need a cassette deck. No one does!
  8. Werner

    Werner pfm Member

    'negative bias' does not exist. What he means is 'less bias than the one the deck was set for', and without reference this is meaningless. But oh well ... Yes, today chrome will operate at a strongly reduced bias. However, in the 80s-90s chrome ran at about the same bias as ferro-cobalt, and in the 70s chrome ran at a higher bias (which caused problems with cheap recorders, see Angus MacKenzie's writings, link below).

    Absolutely. If the tape is mechanically fine (a big IF, late 80s and 90s tape were polished so hard - for reduced noise - that they tend to self-destruct in any transport that is not 101%) then SA, XLII, UX, ... will give exactly the same electro-magnetic performance as they did 35 years ago. Whereas any true chrome will show reduced sensitivity, treble roll-off, and (luckily) reduced noise.

    Two examples of my own measurements (referenced to Maxell XLII 1994, made on a restored and tweaked-out BX-300):

    BASF Chrome Super II 1989

    Relative bias: -3
    Relative sensitivity: -2.2dB
    THD @ Dolby level: 3.1%
    MOL400(1%): -7.3dB
    MOL400(3%): -0.1dB
    MOL1k(3%): -2.0dB
    SOL10k: -7.6dB
    Bias noise: -56.5dB, -61.9dB(A)
    Dynamic range: 61.8dB

    TDK SA 1990

    Relative bias: -2
    Relative sensitivity: +1.1dB
    THD at Dolby Level: 0.42%
    MOL400(1%): +3.1dB
    MOL400(3%): +6.5dB
    MOL1k(3%): +5.9dB
    SOL10k: -2.6dB
    Bias noise: -54.6dB, -58.7dB(A)
    Dynamic range: 65.2dB

    As you see there is a 3dB performance gap in dynamic range, which is huuuge in cassette terms. But if you read the reviews of that period, then this gap did not exist. Of course it did not: it would have been suicide on the part of BASF.

  9. Tony L

    Tony L Administrator

    Excellent, that is the sort of stuff I’m interested in. The cassettes I think of from a nostalgic perspective are the TDKs, Maxells and Sonys from about 1975 to 1984. Those are the ones I bought as a kid/teen and the ones I’m interested in now. They just have the most iconic artwork, branding, nicest shells etc IMO. I have a few NOS 1979 TDK Ds, ‘82 SAs (both pictured upthread) plus a couple of ‘79 ADs. I may land a couple of similar vintage Maxells and Sonys to complete the retro experience!

    PS Your blog is good/interesting!
  10. Tony L

    Tony L Administrator

    Got my belt and idler kit today so have spent the last few hours fitting them/fixing issues...


    Here’s the starting point. Pretty cramped in here. My goal is to replace the drive belt, capstan idler tyre and two other idlers. The tape counter I can not be bothered with as it is working fine.


    Capstan is easy enough to get out...


    ...and then re-tyre. The new one is on, old one pictured.
  11. Tony L

    Tony L Administrator


    The next stages required removing tiny little circlips, so I worked inside a clear plastic bag to stop them flying away.


    There are two idlers, one is really tiny. I ended up cutting the original tyre off this one as it was tight and I didn’t want to risk breaking the plastic hub. All went ok. The other idler can be seen in the pic.

    Replaced the belt, reassembled it and it still didn’t rewind/fast forward. Damn. After disembowelling it a lot further I found the support arm for the upper idler was frozen solid due to dried-out grease so wasn’t allowing the idler to press on the track on the capstan counterweight.


    It is the little sprung cam thing next to the gear that looks wet in the pic. This was really stuck solid, solid enough I could seem my little screw driver bending when I was nudging it, so for a while I thought it was game over and this was a ‘parts machine’, but I kept at it, flooded it with isopropyl and some light oil and eventually it freed up to the extent it was free moving and working as it should.

    Anyway, its now back together and appears to be working as it should. It plays, rewinds and fast winds, though I’ve not checked recording at all yet. The << and >> buttons not releasing once the tape ends confused me a bit, but checking the manual suggests this is normal behaviour for this device.

    PS I gave all the surface-mount caps a close visual inspection and didn’t spot any signs of leakage, bulging, corrosion or anything, so hopefully they aren’t the ‘capacitor plague’ generation. I never like seeing these things in kit as I just don’t have the tools to deal with them, but hopefully Sony will have used pretty decent ones that will last given the low-voltages in play here.
    Last edited: May 22, 2020
    deebster, Rosewind, cooky1257 and 2 others like this.
  12. hairyderriere

    hairyderriere pfm Member

    Nice documentation of your journey.
  13. Tony L

    Tony L Administrator

    As always with these things taking lots of pictures helps with getting it all back together again later!
    hairyderriere likes this.
  14. Tony L

    Tony L Administrator

    Just checked recording via the line-in and that seems fine too. I used a mid-90s TDK SA and Dolby B and the first track of Steely Dan’s Two Against Nature as it was sitting on the floor in front of the CD player. I set it to peak at +3db. Playback sounds fine, a little ‘cassette-like’ in that there is that characteristic slight loss of top-end and a little dynamic compression, but the pitch is solid and it sounds good. I think its working pretty much as it should now. I’ve no idea what tapes these were set up for at the factory, but I would have thought an SA of what is likely its era was a fairly safe option. I’ll try again without any noise reduction at some point.
  15. Aural

    Aural Chris the Full Range fan

    Dug my TC-D3 out. At the time -95 - I wanted a 'pro' as I was off to deepest Spain for 6 months, but there were none to be had. The TC-D3 was supposedly next best, just no speed adjustment. It was OK last time I tried it.hah! found the (3 volt!??) trannie-nothing moves.
    Intended for it to be a 'when needed' thing, as my Yamaha TC 800 'Cheese wedge' has stopped-belts? Should sell it I guess?
    Aside; my '98 Lexus LS400 had cassette deck built in, so I kept at it!
  16. Tony L

    Tony L Administrator

    I don’t know the D3, though good quality Sony Walkmans of all types seem quite sought after these days by collectors.

    The Yam is certainly worth fixing up if its in good cosmetic condition as its a bit of a design classic. It would look good in any system!
  17. Werner

    Werner pfm Member

    I used to have a WM-D3, purchased in 1993 on my university trip to the US. Very disappointing. The head mount was floppy and did not hold azimuth for more than a minute. I wanted to sell it in 2012, found that it had totally frozen-up, and threw it away. Stupid: with the knowledge I have today I could have revived it, and perhaps even improved.

    At that time I also threw away a Nakamichi CR-2 I bought used and that was DOA. But at least I kept its transport and I fully restored that last year.
  18. JemHayward

    JemHayward pfm Member

    I had a WM-D6C and Nakamichi 700ZXL at the same time. The 'almost as good as a Nakamichi' possibly didn't emphasise the almost bit, but ignoring the frequency extremes, the Sony was amazingly good. It also could play the tapes recorded on the Nak which I used to record quite 'hot' and without even Dolby B (I had the external Dolby C unit for the Nakamichi, but really didn't get on with it). I did quite a few field recordings with the Sony, and recently a friend with a recording studio digitised some old tapes - some were from the 700 and some from the Sony, using a reasonably high end Yamaha that we sourced for the job, cleaned up and azimuth matched to the Nak tapes and I was quite surprised how good they sound. Sadly my Sony died (well became unreliable) after one to many field 'accidents' and the problem was a cracked PCB, so essentially uneconomic to repair. I donated it for spares to a blind journalist who relied on his rather battered WM-D6C for his work, and over the years it donated various bits to keep him going.
    The Sony always sounded it's best on battery. My Sony 'official' PSU actually injected enough noise to come out on the tapes, so I built a LM317 based PSU with lots of smoothing - well worth doing, sounded superb. As the rest of my system was Naim I wrote to Salisbury and explained that I would like my homemade PSU for my Sony to match my HiCap so they send me a CB sleeve (possibly foc, certainly not expensive) to put it in. Those were the days!
    hairyderriere and Dowser like this.
  19. Tony L

    Tony L Administrator

    That’s interesting to know. I don’t think I’ll bother hunting down a proper PSU as I can’t imagine using it enough that battery costs would be an issue. I’ll maybe buy a really good rechargeable set of AAs for it and call it done. I’ll just have to remember not to store it with batteries in!
  20. Werner

    Werner pfm Member

    Service manual: https://www.hifiengine.com/manual_library/sony/wm-d6c.shtml

    Once it is up and running again you may want alignment tapes for speed and the electrical levels.

    Such tapes are still available from China (ebay sellers coollpe and patshuai can be trusted), but they are very expensive. The most economical solution is a combi-tape made by Alex Nikitin; it can be used for speed, azimuth, Dolby level (playback level), and (with limitations) playback frequency response:


    The Sony service manual assumes a different level tape, so you will need some math to translate the levels. At any rate, the very best way for setting playback level is to use a true Dolby level tape and set the resulting AC voltage as per the Dolby IC's datasheet and measured on the IC's relevant pins. This trumps any service manual, which often is confusing or even wrong.

    Alignment tapes must only be used on a deck that is 1) properly demagnetised, 2) perfectly clean, and 3) with a perfectly healthy tape path.

    Stay away from the homemade alignment tapes offered on ebay that are not full track. These are a waste of money, except perhaps for speed adjustment.
    Tony L and s1h1 like this.

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