New Turntable!

[Ammonite Audio]

Well, not really a new turntable at all; rather a fairly old Kenwood KD-750 sniped off eBay for a reasonable amount for no other reason than I liked it. From what I've been able to glean online, it has a good reputation and the plinth is a much more solid affair than that of my KD-770D, and the motor is a totally different DC servo type. Richard at Vantage Audio was positive about the KD-750 and said that its arm is a good one too, which gave me the confidence to have a pop at this deck that I hope to pick up tomorrow. The arm will go for a bit of Johnny-care at Audio Origami and hopefully the motor control circuitry will need little more than rejuvenating potentiometers that are known to suffer from age and maybe replacing elderly capacitors if necessary.

If it works well, it will give me something to listen to while I have a new fully suspended chassis made up for the KD-770D.

http://cgi.ebay.co.uk/vintage-KENWOOD-KD-750-TURNTABLE-/220654099873?pt=UK_AudioTVElectronics_HomeAudioHiF i_Turntables

[John]

Looks like you got a great deal

[DSJR]

The tonearm is good in terms of resonances, uses the Rega geometry I believe, but could suffer from high lateral friction levels (I have one of my own in desperate need of fettling). The counterweight system may not take too kindly to heavy headshells and an "extra" counterweight would be good. HOWEVER, this may upset the rear-stub decoupling, which was originally designed with a piano-wire tie running inside the usual rubber gland. I believe Vinyl Engine have a service manual which properly explains it..

Now, the turntable......:( This model seemed to suffer from servo-lock failure, causing all sorts of speed problems, both on the HiFi Choice review sample and the donor for my arm, the donor being ditched eventually. I've read somewhere that the preset pots are the culprits and a darned good cleaning with Servisol or similar may be all that's needed, although a new deck shouldn't have suffered this way as in the 'Choice review.

Good luck ;)

[Ammonite Audio]

Well, after an awful drive back from Cambridgeshire through Friday traffic to pick up the KD-750, I'm pleased to say that it's complete and seems to work perfectly. The speed lock operates correctly and my Clearaudio strobe disc gadget confirms that the rotational speed is spot on. The arm is tidy, being fitted with a Kenwood magnesium headshell and (I presume) its original Trio Kenwood MM cartridge. The arm has a standard DIN plug at the base, so I can use either the Neglex or Audio Origami cables. The mounting collar is a superb piece of design, using a large screw down piece to lock the whole thing up tight. Checking the pivot-spindle distance, its about 230mm.

The overall condition of the deck is very good indeed. There are no major marks and the lid is of awesome quality and undamaged. the plinth is a heavy braced plywood affair, with some sort of heavy material bolted in. It looks rather smart!

I shall leave it running today to check for faults and then maybe mount up a decent cartridge for a listen tomorrow.:)

[flapland]

Shuggie

Looks very nice and appears to a have a zebranno type finish from the dark pictures which is good.

Perhaps some photo's for the gallery when setup tomorrow with a cart so we can all oggle it.
Flapland

[Ammonite Audio]

There is a technical hitch, in that one channel is dead, pointing to an internal arm wiring fault. That does not matter, since I was going to send the arm up to Audio Origami anyway. So, apart from being subjected to a good clean, the KD-750 will have to wait its turn.

[Ammonite Audio]

I took the KD-750 over to a friend's yesterday, since he has the skills to look at the tonearm wiring. Turns out there is nothing wrong with the wiring, and he has it playing with a Goldring 1042 mounted in the Kenwood magnesium headshell. He reports that it's "making pretty nice sounds in my main system; a bit soft but quite engaging, not too bad at all". The earlier fault is probably due to the DIN plug at the arm's base being a poor fit with my Neglex cable's plug - it may still need to go up to Audio Origami to have that corrected.

[Ammonite Audio]

The arm is back from Audio Origami and the KD-750 has now been playing, with the Benz Glider SL up front, for several days. It certainly does have a 'soft' presentation in comparison with the "Technics SL-1210 with a bit of culture" feel of the KD-770D. It's the bass that's a problem - it goes deep but it's too indistinct; too wallowy. Is it the arm, or the deck, I wonder? There are two completely different drive systems in use here - the KD-750 has a brushless DC Sevo drive motor, while the KD-770D has an AC synchronous motor, which does allow the use of a colossal Paul Hynes SR5 power supply (to rather good effect). The KD-750 arm has a fairly compliant rubber decoupled end stub which could well be the culprit.

The KD-750 has a thick, perforated rubber mat, which damps platter ringing, but utterly kills the feel and flow of the music. A Funk Achromat is way better, but still the soggy bass remains.

I'm going to swap 'tables over today and put the Ittok on the KD-770D, which should match well with the Glider SL - revisiting my reference should clarify things. My gut feeling is that the KD-750 is mainly let down by its arm, but we shall see (or rather, hear). It's all interesting and relatively cheap fun!

[DSJR]

The 750 tonearm uses Rega geometry. The soft counterweight decoupling was to minimise the arm-cart resonances by several db. I wonder if this is having non-measurable effects further up in the range. i can't afford to, but I really should get mine to Johnnie for re-building and re-wiring. he could use a traditional bolt and nut for the counterweight suspension and this may tighten things up a bit..

Interesting :scratch:

[Ammonite Audio]

The 750 tonearm uses Rega geometry.

Does it? According to my measurements, the KD-750 tonearm's pivot to spindle distance is 230mm, which is a bit longer than for a Rega. The overhang is the same for both at 15mm.

[DSJR]

OK, the Rega is 237mm and the KD 750 is 230mm? Apologies, I thought they were similar enough for it not to be an issue (with a slotted headshell it may not be tbh, as 15 - 20mm fore/aft is often available). I've never been truly manic with the outside edge of the tracing arc, but it's vital to get the inner one as near as possible, and with the inner null point anywhere between 60mm (Rega), 60.3 approx for Stevenson, 65 - 66mm for Linn and SME and I believe even 79mm for some other arrangement it could be anybody's guess tbh.......

I always did 60mm for Rega and similar arms and 65mm for Linn, SME and everything else with the shorter, non-Rega length.

[Ammonite Audio]

OK, the Rega is 237mm and the KD 750 is 230mm? Apologies, I thought they were similar enough for it not to be an issue (with a slotted headshell it may not be tbh, as 15 - 20mm fore/aft is often available). I've never been truly manic with the outside edge of the tracing arc, but it's vital to get the inner one as near as possible, and with the inner null point anywhere between 60mm (Rega), 60.3 approx for Stevenson, 65 - 66mm for Linn and SME and I believe even 79mm for some other arrangement it could be anybody's guess tbh.......

I always did 60mm for Rega and similar arms and 65mm for Linn, SME and everything else with the shorter, non-Rega length.

I'm confused because the Rega spindle-pivot distance is always quoted as 222mm. That's certainly the case for the Rega armboards cut for the SL-1210. Am I missing something, or being dim here?

[DSJR]

I used the VE specification. 222 sounds like the distance without overhang and 337 with?

[Ammonite Audio]

I used the VE specification. 222 sounds like the distance without overhang and 337 with?

I took the specs from VE too. Surely the spindle-pivot distance is independent of any overhang? The two parameters are entirely separate but equally important. Overhang in my book dictates where the cartridge is optimally positioned in the headshell, after the whole arm is located correctly in relation to the centre of the record.

That aside, I have just set the Ittok/Glider SL on the Kenwood KD-770D and "Transformer" is playing as I type. It sounds much better than on the 750 - more pacey, vibrant and controlled, particularly in the bass. The Glider still needs a few more days of running in, during which time it will hopefully get better. Every time I mount or unmount the Ittok I am struck by how easy it is to set correctly. Although the arm must be 25 years old at least, the tracking force dial is utterly accurate too! I love this arm :)

So to return to the KD-750, I shall probably undertake some careful butchery to allow me to mount different tonearms on it, without spoiling its good looks. I still have hopes that it will repay a bit of care and attention.

[DSJR]

I suspect the RB300 specs I nicked confused effective length with pivot to stylus (it's probably me, dosed up to the eyeballs and still all but deaf in one ear - at least the pains gone now...).

Good luck with whatever you end up with ;)

[Ammonite Audio]

Playing with the KD-750 has provided the catalyst for me to get a new, more solid plinth for the KD-770D, which is clearly let down by its cheap and resonant chipboard plinth. So, I have one ordered from Layers of Beauty, in natural lacquered birch ply ( see http://www.layers-of-beauty.co.uk/page8.php ). It will be a tad deeper than the standard plinth, but with the same overall dimensions so that I can use the existing perspex lid. Mass will be higher, of course, but it's not a high-mass construction per se. I could have made one myself, but it would have looked like something knocked up by a half-wit in a shed, using no woodworking tools.

It should all be up and running in time for the London Bake-Off Show on 31 October, appearing in the mains and cables room.