A few notes on the Denon DN 308 and other Denon DD Turntables. As some of you know I restore many of the magnificent old Denon DD tables mainly the DP3000, 2000, 6000 and 80 - I turn them into these http://pbnaudio.com/audio-components/audio-turntables/groovemaster/groovemaster-vintage-directThere is a few mentions above about the platers on these. Please note that the rubber mat that they were originally supplied with is an integral part of the platter system , with the mat on, the platter is virtually "dead" The design of these mats vary some, the earlier DP3000, 6000 and 7000 have a circular ribbed design, the newer DP2000 have a softer but also circular ribbed design, the 75 and 80 have a almost flat but much harder rubber mat. On the older ones 3000, 6000 and 7000 the platter it self have a raised center portion which makes it hard to use any other mat than the originally supplied mat, the 2000, 75 and 80 have a flat platter making it possible to use almost any aftermarket mat desired. We are in the process of making copper mats with a large center holes that will make the platters on the 3000, 6000 and 7000 flat facilitating the possibility of using any desired aftermarket mat. The weight of these will be apx 4.5 lbs adding substantially to the weight of the platter. lewm above mentions that the weight of the platter should not be increased substantially because the servo control is "tuned" to the weight of the platters they are controlling, I find absolutely no evidence of this - checking the already astonishingly accurate drive systems with a phoenix engineering tachometer which displays RPM with a 5 digit read out i.e. 33,333 the added weight only makes any slight variation in speed better - the 6000 and up, after restoration, typically runs with only a one number variation on the very last digit i.e 33.333 to 33.334. For an example a DP2000 with a Micro Seiki CU500 mat and a SS record clamp increasing the weight of the platter with over 100% makes the drive system even more consistent. The platters on the 75 and 80 are a laminated design with a light sub platter carrying a much heavier platter on three leaf springs, there is rubber dampening material applied into every other one of cavities at the circumference of the sub platter with the alternating ones having foam rubber pads that couple the platter to the sub platter. on restoring them the foam rubber obviously is replaced, On the DN308, the drive system is quite substantial the motor is gigantic the outside rotor is apx 3/4" thick and laminated with what appear to be brass for added weight. I have procured 3 of these and will restore them into new table top machines with plinths made from Slate and Hardwood also they will be fitted with 4" custom made by Steve Blinn Isoped's. I envision them having the possibility of using two arms, I'll probably supply them with either a SME V12 or a 312S. Also since these don't have a strobe light the Phoenix Engineering Tachometers will be built in to the control interface. The platters will be damped, possibly by spraying a polymer on the bottom on them then laminating them with a copper mat. Really looking forward to this project, if any of the above DN308 owners are interested in this please let me know, as I'm already building 3 - 5, 6 or 10 for that matte is not an issue. As far as how many of the DN308 is out there Im guessing at less than 2000 of them. Of the three I have here the oldest one is from May 1978 and it is number 472 the two other are quite newer one is from Jan 1992 # 1558 and from Jan 1993 # 1608. They are very close to identical. On a side note restoring / "GrooveMastering" 3each DP7000 machines to be fitted with the SAT tone arm for a major cartridge manufacture, this project too will be lots of fun. Good Listening Peter |
Any news about KODO turntable ?? |
Ken,
Thanks for the color. I might do the same thing on the platter for my 308. It would be great to get a better one. I would love to build a better platform as well - rather than the MDF box. As to numbers, in Japan at least, there are probably a fair bit more DN-308s than 100 because it seems like every NHK broadcast center and recording location, and a huge number of schools/universities/libraries/museums/etc were convinced to buy them (by government bureaucracy-funded NHK). I expect this was because of pressure to monetize the time spent by the engineers, and commit everyone to the NHK standard. I have heard that NHK effectively designed much of this table for Denon using their own engineers. FWIW, I have probably seen a couple dozen 308s over the years, and fewer 307s, and still fewer 306s (which I think were belt-drive). I have probably seen 20% of that number of console tables like this made by Victor and Matsushita (the original pro-use in the early 70s were Matsushita-labelled, not Technics it appears).
As to usage... it does have that funky headphone jack for headphones of a particular impedance (one can still buy them for about $350), and the mini speaker, but it is clear they were also meant to play for broadcast as well because the thing has a built-in phono stage AND preamp with 600ohm balanced output for direct-to-amp playback. When I talked to Denon today, the two people I know there separately said that Denon would refuse to service a table owned by an individual in Japan and it was explicitly up to the user to figure it out for himself. Not a terribly satisfactory response, but it is what it is. Thankfully, there are a number of people out there in the private sector who can service them.
The same people, speaking about the DP-100, said that the DP-100 was sold to a few radio stations but the vast majority were sold to consumers. Most commercial users took the DN- series because they came with a service/maintenance contract (like most companies do with copiers these days), whereas the DP-100 did not come with the same service package.
As to total numbers made, on the DN-308 (and earlier DN-307 and DN-306) they said they WOULD not answer. As to the DP-100, they said they COULD not answer because the data was lost (but noted that it was only an order-built machine, and production lasted 4 years). That is four times I have asked in the last year to four different people involved with Denon servicing and four times I have been told they have no idea. Not encouraging, but it is what it is. Based on serial numbers, I know it approaches 50.
As to the motors in the DP-100 and the DN-308. They are, I was told today by a guy who serviced the DN-308 in the past and now does old tables in the consumer section, completely different beasts. This makes some sense when I think about it because the DN-308 came out before the AU-169 cutting head motor (which is in the DP-100) which was first presented in a technology show in 1979. I think my Denon DN-308 comes from 1979 (you can check your date by looking on the bottom row of the serial number plaque on the front underneath the console portion; an "S" (or a 昭和 or a 昭) and a two-digit number; "45" is 1970 and "55" is 1980 - If you have an "H" or 平成 then a number, it will likely be a single-digit number and H1 was 1989).
Separately, you've got mail... |
Lewm,
If I'd had my wits about myself I would've called you a week or so ago. I'll be driving to ATR Services on Thursday to attend my THIRD seminar and pick up my last machine. I've attended two seminars so far and feel as though I'm the dunce in the class, which I am. Everyone else is from the studios that record the music we all listen to. The techs and studio owners leave me in the dust but I'll keep on keeping on.
Ken |
Ken, I keep forgetting that we are near neighbors. We should get together for a dd fest one of these days. Lets make email contact. Howard serviced my L07D and it is now in use. SP10 Mk3 will soon follow.
Interesting thing about the L07D is that Kenwood planned for increasing platter mass by providing a switch on the PS that alters the servo when one is using the optional peripheral ring and center weight. In addition, there was an optional ceramic mat that added yet another 1.4 lbs. Someone else calculated that the servo and motor will take up to 21 lbs of platter mass. |
Hi T bone,
I'll attempt to address your points one at a time.
First off, the platter does, did ring like a bell. I threw out the flimsy rubber matt and ordered a new nickel plated copper, plastic platter from TT Weights. It came with their best peripheral clamp ring and heaviest brass center weight. I ordered it when Larry had just sent a prototype to Mikey for evaluation and that new design is what I got. Right now it's sitting on the base platter on the 308.
Not only did the platter ring but the 2 inch particle board plinth transmits every finger tap. Since the 308 was meant for playback of master discs at studios it was listen to on headphones, as loudspeakers had an effect on playback of master discs; from what I understand this was, or is, standard practice in studios. The dp 100, on the other hand was designed for use at radio stations and was fitted with a large spring suspension system; supposedly the biggest difference between the 100 and 308 but I may be wrong. In any cas the plinth, as it stands now, will have to go.
I don't know if it will be necessary to replace the platter with the encoding ring as I don't see how I could do any better than just laminating another layer to the existing platter but that point is up for discussion.
I tried to reach a tech at Denon Pro and got no place as they are separate from Denon America so you may have an in that could help. Since there were less than 100 of the 308s made and not many more of the 100s I would think they use the same motor and just tweaked it electronically, as you suggested to re adjust for a different torque application.
I would appreciate it if you could send a cut away and,or, any other information on the table as I have no manual and could not get one after I bought the table.
Last night I spent a good deal of time on the phone with Steve Dobbins. He was very gracious and is a true gentleman.
I began by asking him about his new tt," The Beat." His knowledge regarding direct drive TTs was obvious as he referred to the many facets involving the design of a direct drive table. He owns around 60 direct drive tables and has done quite a study of the best and worst designs that came down the pike. It sounds like his new table will be a killer with the design innovations he's incorporated.
I finally got around to asking about his custom platters for the Garrard 301 and the few other tables he's tweaked. It was my hope that someday he may apply what he's learned about platter mods and that may lead to an upgrade for my 308. Steve said his plate was full with his present projects but said since he felt the motor on the 308 was as good as any direct drive motor ever made, he may entertain an upgrade platter for my table in the future.
I first saw the 308, I now own, advertised on Audiogon a few years ago. It was impressive looking and I thought expensive for a vintage DD table. It was up for sale for a month and I noticed it didn't sell. A year or so later I saw it up again. This time it sported a cabinet that was redone with rosewood veneer and the price was the same. Peter of PBN Audio owned it and we were friends, so I called him. He told me about the table and what he did to the aged cabinet. After seeing a few pictures of the table in general and the motor and veneering he did it was on it's way from California to Va. The table is impeccable as was the shipping crate he built for it . One could've shipped a newborn baby across the country in it without a scratch.
Dr Howard Stern, the fearless leader of the Richmond Audio Society, hosts the unofficial website of the Kenwood L-07d direct drive TT. He does upgrades for folks that ship him tables from the four corners of the world. Howard has four tables up and running in his system and it didn't take too long for me to convince myself to try a DD table. When the 308 became available again I didn't wait to think about it.
Since there is no law in Audio that limits a guy to just one table I figured it would be a Christmas present to myself for the year 2021, I've done this before!
Ken |
Kftool,
The platter of the DN-308, as is, unfortunately rings like a bell. It is the same
design as was on the DP-6000 which was replaced by the double-platter
construction of the DP-80. It is well worth treating I expect (I have not done
mine) and could be worth completely replacing IF you could replicate the
magnetic encoding on the platter which allows for the magnetic pulse speed
check. If the motor is the same AU-169 unit which goes on the DP-100 (and
I cannot be sure but I will give the Denon service guys a call today), then
there is plenty of overhead for a bigger platter though you might have to tune
torque application part of the speed control circuit to "load" it for
a different platter inertia. The DP-100 platter is 6.5kg. Assuming the motor
is the same, the motor would have a built-in suspension (the main spindle is
supported on an "oil cup" cushion above the stator). As for
vibrations, the DP-80 and DP-100 literature suggests that most of the
vibration which is defeated through the double-platter construction is borne
through the frame/spindle/bearing though the DP-80 makes some claim to
its construction lessening 'howling margin' (which is Japanese for
airborne/speaker-induced vibration) which would suggest the DP-100 does
too. In any case, the platter construction benefits of DP-80 vs DP-6000 are
apparent.
One could conceivably build that onto the DN-308 platter through a retrofit
of a spring-leaf system for the platter (If one made it too tall, one would have
to make it ultra tall and cover the spindle too with a new one). I can send
cutaway pics of the DP-80 method and the DP-100 method (which involves
oil-damping wells within the sub-platter to dampen vibrations borne to the
upper platter) if you want.
In any case, I too am curious about what Steve Dobbins has done with the
separation of motor and bearing. As long as tolerances are tight, I would see
no reason why the motor and bearing have to be physically directly-
connected other than that eventually they sit on the same platform. That said,
I don't think I am about to build one DIY... |
MikeL-I too love the Tommy album-it is a timeless classic. I hope I hear that bass punch you referred to in the Overture. I don't think it exists on the other pressings (Track, Decca, and MCA). Do you have a copy of "Won't get fooled again" on MCA? At the end of Going Mobile, there is a really low bass note which sounds pretty impressive.
If you are a fan of the Who, you need to hear Pete Townsend playing acoustic guitar and singing Pinball Wizard live. To my knowledge, it is only available on the Secret Policeman's Ball LP. This live version of Pinball Wizard with just Pete Townsend playing acoustic guitar and singing is crazy good. I am surprised my copy isn't worn to a frazzle but it still sounds great. |
Mepearson, i have 2 different Classic Records 'Tommy's and the MCA, and another 3 or 4 other various pressings. the 'Simply Vinyl' pressing had a much larger soundstage and the bottom is fuller and more impactful than any of the others.
i try to spread out my listening to this Lp so i don't get tired of it; but i seem to come back to it often. why can't they make music like that any more? |
MikeL-based on your comments about the Simply Vinyl Tommy LP, I ordered one this morning. I have a really nice MCA version, but it doesn't have the bottom end you are talking about. |
Kftool, Since the platter of your tt is probably bolted to the top of the motor to which the magnet is fastened, in a sense you are free to change the platter, as is true of most dd turntables. The Mk3 is the exception rather than the rule. Most dd turntables are like yours. But the restriction is related to platter mass. The drive system was designed for the mass of the platter, and if you change the platter mass dramatically, then the servo mechanism will not work correctly. Problem is that the permissible range of variation in platter mass for any particular dd setup is unknown to most of us. It's safe to say, I think, that with a massive motor, like the one you have in your DP308, you can probably increase mass by at least 20% without any worries. Probably that is a conservative estimate. The only way to find the upper limit is to do the experiment. As to your other point, I do not know to what degree a heavy platter would work to resist airborne vibrations. Only way to do that is to move the tt to a sonically dead part of your listening room or to outside the listening room, IMO.
PS. You're a lucky guy to have a DP308 and the space in which to place it. |
Hi Lewm,
I thank you for your reply and those that, not only spoke to the original thread, but digressed. To strictly stay on the line of the original thread would mean the thread would die out with a dozen or so answers.
My reason for the thread was not only to see how many others resorted to, for any reason, to move the TT to an adjoining space. Topics such as; cable length, walking to another room to drop the stylus, proper stands that abate vibration are all viable reasons to keep the table in the listening room. Last but not least was the design of the TT itself.
I viewed the systems of those of you that responded, no slouches here! The views echoed your replies.
If I may, I'd like to ask a few questions that will pertain to the original thread, but will also expand the answers from the Audiogon "Brain Trust," if I may call it that.
If it's heavy enough it won't vibrate, but different frequencies will excite the mass in different ways as everything has a resonant point or two or?
Some resonances are floor borne and need to be dealt with in a different way than those that are airborne.
Assuming that all floor borne vibrations are nulled out, it leaves only airborne vibrations and the drive motor and bearing to contribute noise.
Lets assume all drive systems contribute some, but very little, noise to the stylus: some are better than others. The platter then needs to address airborne vibrations. If you have a big system and love bass or a smaller system or a room not properly suited to your musical tastes, the platter design may be the deciding factor.
High mass, via Walker with a center clamp , constrained layer damping via VPI with a peripheral ring, TTWeights with a peripheral ring and copper matt and others, vacuum via SOTA and others, and the list goes on-- all attempt to address the problem.
If you choose to repost to this thread I know it will probably be because you have more personal knowledge of the vibrational problems you've dealt with rather than opinions only and that a three thumbs up!!! Yes three.
I for one, after reading Mike's posting, realize that I'm lucky in the fact that the table on my Denon 308 is not a part of the rotor. Is bolted to a tapered shaft and collar. I guess it means that I'd have options to modify the platter. Yippee!!. Nothing is worth having without options for a tweak.
Happy Easter, Ken
|
No doubt the platter and mat have a huge effect on the sound of any tt. This is a universal issue, not just restricted to dd tts. Problem for me is that I don't know what is "the best". In general, high mass seems like a good thing, but after that there is a lot of room for speculation. I believe that high mass is less critical for dd tts than for belt-drive types. I guess if one had the cojones to try it, one could unbolt the magnet from the Mk3 platter and attach it to a platter of one's own design and thereby fit the new platter to the Mk3. A company like TT Weights could make such a platter (and of course Steve Dobbins can make a fab one). |
another related issue when looking at the Mk3 is that the platter is part of the motor assembly. so there is no choice if a better platter is desired. the Mk3 does not have a 'problematic platter'; but just like the bearing issue there is room for improvement.
i can sure hear what Steve's new platter has done for the Garrard, and there is related design in the platter of The Beat. |
From what I read, I believe what Mike is trying to say is that the stator in the motor is decoupled from the bearing which is physically possible. And I was just thinking about such thing couple weeks ago while having the mental experiment of decoupling the DD motor from the platter and bearing but Dobbins beat me to it, pun intended.
After all a DD motor is nothing but a series of coils lay out in a circle that we call a stator and right above is a circular magnet that we call a rotor that's attached to the bearing shaft. In a conventional DD motors, typically, the stator is mounted to the same surface that houses the bearing. It is totally possible that the stator can be mounted separately or decoupled from the bearing. This can address the problem the common complaint about DD table that back torque force vibrating the bearing and plinth and therefore tonearm. So yes, I believe to be quieter than the Mk3 can be achieved. Just happy to see people are putting new ideas into the direct-drive genre. I applaud that!
I agree with Lewm that the Clearaudio Statement is a rather inelegant design.
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|
Yes, some isolation could be achieved by air bearing as in the Rockport or by magnetics, as in the Clearaudio monstrosity. I don't think Steve used either of those methods. So it's a fun thought experiment to figure out how it might be done otherwise. The simplest thing would be to isolate the bearing from the motor coils as well as possible. Then the magnet/stator could still be attached to the platter, as in the Mk3. No part of the motor physically touches the platter/ bearing in this scheme, so unless there is induced vibration in the platter via the magnet/coil interaction, the goal is brought nearer. With a Mk3, you would have to deconstruct the bearing/coil assembly to get there, which is not easy to contemplate in such an expensive and rare piece of gear. But my goodness, the Mk3 is freakin quiet already. |
Lew, Do you know or can you say here just how is the bearing isolated from the motor? very good question. Steve did not explain that to me (or if he did it went over my head). obviously Steve has made plinths for dozens of (Technics SP-10) Mk3's and experimented with various ways to optimize them. in his efforts he ran into a limitation of the Mk3 design, which was the noise which was transferred to the platter thru the bearing which is part of the motor. he determined that isolating the bearing was a key to improving that aspect of the performance. my Rockport solves this problem with an air bearing. i can say The Beat is a little quieter than the already 'quiet' Mk3. |
Mike, Do you know or can you say here just how is the bearing isolated from the motor? It would seem that the very definition of direct drive carries the inherent requirement that there is some degree of association between bearing and motor. I guess the semantics make for confusion. To put it another way, how is it different from the Mk3 as regards the degree of coupling between bearing and motor? Thanks. |
maybe i should post the basics about The Beat. it is a state of the art direct drive tt with a separate power supply. it comes with 2 arm boards. it has a bearing separate from the very high torque direct drive motor.
i had one in my system for 2 days about a month ago. fantastic performance in every way; it sets new reference levels in overall musical energy and particularly bass performance.
i purchased one.
i currently own 2 vintage tt's which have been re-worked and had plinths supplied by Steve Dobbins....who is the manufacturer of The Beat. |
ya mean like here......and maybe here, and then here. yes, i do know about it. then later here. you just need to know where to look. |
