Kenwood KD-770D: any suggestion for upgrade?

[sc_ita]

My main TT is a SL1210M5G, and I am very satisfied by it that plays alternatively with two LO MC cartridges: a DL-103R and a DL-301mk2. Naturally, when I change the cart I also change the counterweight... and this is quite annoying. On the other side I have noted that each of the two cartridge sounds very well (IMO) with some type of music, and less well with other (in practice, the DL-103R usually plays my jazz-rock collection, while the DL-301mk2 plays the chamber and symphonic classic).
The conclusion is that I clearly "must" have a second turntable, and thus I decided to buy another DD. After some researches I decided to purchase from E_Bay the Kenwood KD-770D shown below:



At present I have made no interventions on it. The deck is in perfect shape, the tonearm is full working, and it automatically uplifts at the end of the side. This tonearm just seem to need some calibration because it is not perfectly firm. No hum from motor and electronics. No vibration.
When comparing it with the Tech, sonically, I have just the impression of a slight less speed of attach of the notes. But this is a very first impression.

Well, now my question: has any sense to make some interventions on this turntable in order to upgrade it?
If yes, What is the most usefull between the two classical intervention:
1) PSU of the motor;
2) Tonearm.

Is it possible that with a new PSU based on a very simple LM317 regulator, this turntable could gain somewhat in the speed of attach of the notes, or is it only vasting of time and money?

Thank you for any suggestion,
Siro

[Dave Cawley]

Hi Siro

If you used an external power supply and bypass the internal regulator, you should notice an improvement. However a "simple" 317 regulator isn't going to work, you need to get the 317 to work properly and have sufficient transient current availability.

What cartridge do you have fitted?

Regards

Dave

[sc_ita]

In the present first tests I am playing with the DL-301mk2. For the future I have not clear ideas, yet. I imagine that I could tune one TT for classical, and the other for jazz-rock. Do you think that the Kenwood could be more suited with the 103R?

Regarding the PSU, the ideal would be to do the upgrade just inside the cabinet of the TT (which is quite large, and thus I would be very happy to avoid another separate case...) by substitution of the old tranny with a new toroidal and rectification, while for the regulation I have simply read the instructions that accompaign description of the LM317 on the RS comp site. Consider that I am a civil engineer, thus I have only basic notions of electronics...

Bye,
Siro

[Ammonite Audio]

In the present first tests I am playing with the DL-301mk2. For the future I have not clear ideas, yet. I imagine that I could tune one TT for classical, and the other for jazz-rock. Do you think that the Kenwood could be more suited with the 103R?

Regarding the PSU, the ideal would be to do the upgrade just inside the cabinet of the TT (which is quite large, and thus I would be very happy to avoid another separate case...) by substitution of the old tranny with a new toroidal and rectification, while for the regulation I have simply read the instructions that accompaign description of the LM317 on the RS comp site. Consider that I am a civil engineer, thus I have only basic notions of electronics...

Bye,
Siro

Hi Siro

I have a KD-770D, upgraded with an external PSU, which is probably the best single upgrade that you can do for this deck. All it needs is 23.4v DC, suitably regulated, to bypass the crude on-board circuit. It's easy to do, requiring the removal of two components, and soldering the new DC wires in place. Dave is correct about a "simple" LM317 regulator - I tried this and it didn't work; however my Paul Hynes Design external PSU is excellent (an reasonably priced). The Service Manual is available over at Vinyl Engine if you want to look at the schematics.

I would recommend that you don't place any transformer within the plinth - not only will there be some vibration, but the magnetic field can be eliminated altogether if the PSU is off-board.

The standard arm is well-regarded, even though I don't use it myself. Richard at Vantage Audio ( http://www.vantageaudio.com/ ) seems to know quite a bit on that subject, as well as most things Trio-Kenwood.

Other improvements? Try swapping mats, although this is very much a matter of individual taste. I settled on an acrylic mat from SRM Tech ( http://www.srm-tech.co.uk/shop/artic...6aid%3DAPM1%26 ), but it only works really well if stuck to the platter using really thin double sided adhesive tape. God knows why, but that's what works for me. You can also try different feet.

I'm currently looking at ways of improving the KD-770D's main bearing. See my thread over at Vinyl Engine at http://www.vinylengine.com/phpBB2/viewtopic.php?t=22391 . Oil seems to result in a better sound over the standard grease lubrication, but the bearing is not sealed, so oil is not practical unless I can contain it properly within the bearing.

Overall, you have a bit of a gem there with the KD-770D. It's a very different beast from the Technics, being (in my experience) rather more delicate and lyrical. It does not have the same sense of speed and drive, but that's a matter of taste.

I hope this helps!

[sc_ita]

Thank you!
OK, in conclusion, in the next weeks I will follow the route toward the substitution of the PSU. As a first attempt, I will try to avoid the adding of another separate case for it. Considering that a toroidal irradiates quite a limited electro-magnetic field, I hope that I could install it in place of the present tranny (which at present does not produce any sensible hum with my DL-301mk2 cartridge).

Regarding the usage of a LM317 based regulator, from the scheme found from RS comp (e.g. the ON semiconductor model), it seems that the main uncertainty regards the proper value for the output parallel capacitor. Perhaps some try and tests? Or it could be somehow calculated?

The alluminium platter of the Kenwood is very thick and massive, and it sounds like a bell! Happily, the original rubber mat is also quite thick and massive, quite better than the one given with the 1210M5G, and thus is able to damp the bell.

Bye,
Siro

[DSJR]

My first suggestion is a mat transplant, as it's easy to do and reversible. The arm is auto linked it seems, so that may rule out a relatively easy arm removal and a good re-wire by Audio Origami.

I can't answer on the power-supply front as far more experienced people have already suggested this