VPI TNT Turntables

The TNT series included versions numbered 1 through 6. I own the TNT6HR. "HR" hot rod, means that the tonearm assembly is directly mounted to the plinth without a typical armboard.

The various TNTs included many evolutionary improvements and not all are agreed upon. The relative merits of various feet and platters especially are often debated here and elsewhere. For me, one of the best improvements was the change in the 12.6 tonearm to the 12.7. That included going to a 3 piece assembly that guarantees proper geometry vs. the older 5 piece assembly that was trickier to align correctly. The 12.7 also returned to include an oil dampening trough which I find to be a benefit. Valhalla wiring also a nice improvement.

The TNT6HR is very similar to the HRX which replaced it, the main difference being the sandwich constructed plinth. Most other aspects are the same between those including the dual motor/flywheel, feet, arm, ring & center clamps. I am not up to speed (pun!) on later improvements/changes to the HRX. 

3D arm seems to be the hot tweak for us VPI owners nowadays.

For sh*ts and giggles, check out the tiny replica in my avatar pic! Cheers,
Spencer 

What you are asking is for someone to write a book because you don’t want to do the research yourself. The information is all out there for you.

There were differences in each generation and differences within generations. Here are the topics, each of which has several variants:

1. Suspensions
2. Bearings
3. Platters
4. Plinths
5. Motors
6. Flywheels
7. Speed controllers
8. Belt tripods
9. Arm size*
10. Arm base*
11. Arm tube*
12. Arm wiring*

To which we can add VPI accessories (stands, clamps, weights, etc.) and third party products and services.

*You say you have chosen an arm, but when you find a TNT for sale it will likely come with an arm.

Did I leave anything out?

So how many combinations are out there? Too many to count and write about without writing a book.

You've chosen a great combo, I have a TNT with two ET 2s on it. The one upgrade I would not do without is the flywheel, whether you have one or two motors. Another important one is the speed controller and then the platter which there is lots of disagreements on.   I would go with the Delrin aluminum cork and lead platter or the latest classic platter with the inverted bearing. As far as the feet go I don't think there's a whole heck of a lot of difference aside from the air bladders di require more maintenance but I don't think it's a big deal. Normally about once every two months I have to add some air and relevel. Takes about five minutes. 

FWIW, I found this posting timely and informative. I just sold my oversize direct-drive Luxman. I'm looking for a VPI (likely a TNT) with a high quality arm. The reason is simple: if it need repair or tweaks, I'm sure I can locate them online. There are undoubtedly better (and more expensive) tables out there but the ability to locate parts and service is indispensable. Also, there are forums for owners that can educate the novice owner. 

Thank you very much for your kind answers.

I wish to replay to melm saying that, of course, I have already read all what I found on TNT turntables, including Audiogon discussions and Mr. Salvatore's review. I also wrote to VPI some days ago but I still have not received their answer. Regarding my choice for ET2 arm, I hear some limits of pivoted arms (my problem), so I need a linear tonearm. 

I am more or less aware of the technical differences of the various TNT versions and of their possible upgrades. What I did not found is the opinion of TNT experts about the sound/performance changes starting from the Jr. I often read that moving from TNT A to TNT B (or including that upgrade) performance "increases", but I don't know what it does indeed mean. Stage is wider? Tonal accuracy of acoustic instruments is better? Does "musicality" really increase moving towards "better" TNTs? 

I hope I have explained my uncertainty and I apologize for my approximate English.

"Analogluvr- The one upgrade I would not do without is the flywheel, whether you have one or two motors. "

What was the biggest improvement you perceived when using a flywheel?

"What was the biggest improvement you perceived when using a flywheel?"

Quite similar to the improvement gained by using a speed controller. More of the same.

luca58,

Just two additional points.  Another source of information, if you have not found it yet, is the VPI forum:  http://vpiindustries.com/forum/index.php

The VPI TNT you will find is probably going to be a used unit since they are no longer being manufactured, though there is a bit of new old stock around.  Therefore it may be useful to seek forum advice about a specific unit offered, its playing potential and its upgrade potential.

Also, since most advertised VPI turntables come with an arm, perhaps you should give that arm a careful listen before replacing it.  VPI arms are generally well thought of and the newer 3D arms are the best yet.

Finally there are many disagreements regarding the best platters, the best bearings, weights, etc.  You will get may different and opposing opinions

analogluvr,

I went from the spring suspension directly to the squash ball one and it was a noticeable and trouble free improvement.  (Though HW says that the squash balls give only 95% of the benefit of the air bladders.)

"Melm-  Quite similar to the improvement gained by using a speed controller. More of the same. "

That's interesting.  A 12 lb 3" flywheel has less than 4% of the inertia of a 20 lb 12" platter; it's difficult to see how that would have much of an effect on speed stability.  Maybe it's the additional isolation of having 2 belts, but then you double down on belt creep.  Any thoughts as to what is causing the change in perceived sound?

Flywheel speed?

I'm not an engineer.  Why don't you buy or borrow a VPI flywheel and try it yourself?  I'm not the only one to observe this; see analogluvr above.  As all TNTs (I think) came with a speed controller of some sort, anyone who has added a flywheel has done it for a reason.  If it didn't add additional audible stability and benefit we would have heard complaints well before now.

I have always thought that the flywheel, like a heavy (and rim-weighted) platter, is the more important component as instantaneous speed accuracy is more important (to me) than average speed stability over one or a small number of revolutions.

I have what I call a 3.5 model. Heavy platter, squash balls from bladders from springs, SME-V, no flywheel and a SDS. I keep the tripod set-up as I believe it evens out bearing wear. The sound is weighty and full but not ponderous as some report. This is the only TNT I’ve heard so I can’t compare it to anything. I do have a Trans-FI air bearing linear tonearm on a different VPI and it competes easily with some of the best at a fraction of the cost. You might look into that is you feel the need to replace whatever comes on the table. It is about $1,000 last time I checked and the designer, Vic, is really great in his customer support.
http://i3.photobucket.com/albums/y57/WntrMute2/photo-11a_zpsjvdghrdy.jpg

I'm not questioning whether it makes a difference, everyone would seem to agree that it does.  I'm interested in finding out WHY it makes a difference.

The reason posited by most is the increased inertia that a flywheel provides improves stability, but the math doesn't support that assertion.  For a solid disk of even density, the formula for rotational inertia is Ir=(m*r^2)/2 where m is mass and r is the radius (note that there is no speed component in the formula).  So for a 20 lb, 12" platter the result is 360 and for a 12lb 3" flywheel it is 13.5 or ~27x smaller.  Now, adding a periphery ring to the platter would definitely help more as the mass is concentrated at the largest diameter (although the mass is smaller compared to the platter).  I just don't see where a smaller, lighter flywheel has that much of an impact at least on inertia, angular momentum or kinetic energy.

FYI, a properly designed speed controller will provide excellent instantaneous speed stability, but long term speed accuracy is improved with feedback.

Like I said, I’m no engineer, but:

Lets assume that the platter speed is affected by the stylus drag, which itself varies according to the music being played. As there is no equivalent drag on the flywheel, small as it may be, it can contribute to a more stable platter speed.

Also, my flywheel has a diameter of 5".  

"a properly designed speed controller will provide excellent instantaneous speed stability" Yes, perhaps, but not excellent enough, since the instantaneous speed stability is clearly improved by adding a flywheel or a periphery ring.

Fellows,

I am no engineer (though I did stay at a Holiday Inn Express) but I have experienced how greater mass/weight has more inertia and would be much harder to change the speed than would one with less mass/weight.  For example, picture changing the speed on a playground merry-go-round that is empty, vs. one that is totally weighted down by a full load of equally distributed passengers.  It will take much more effort to slow down or speed up the heavier one.  The flywheel effect in cars and trucks is another example of the heavier, more massive one continuing to spin at a more stable rate, while the lightweight one will lose rpm more quickly.  I have noticed this too when sharpening tools on a blade sharpening wheel.  It takes much more force to affect the speed of the heavier wheel.  It seems to me that the heavier more massive turntable motor flywheel would be more stable and would be less susceptible to external forces, like fluctuations in power supply, intermittent friction, etc.  I am sure I'm wrong, please explain why. 

Well, from the formula, there are only 2 parameters that effect inertia, mass and diameter.  Diameter will have a greater impact because inertia increases with the square of the radius.  If your flywheel is 5" instead of 3", it changes the additional inertia from <4% to ~20% of the platter.  Maybe that's enough to make a difference?  The periphery ring is probably the better of the two as all of its mass is concentrated at the largest radius.

As far as the flywheel and stylus drag goes, it won't isolate the platter at all;  if anything it will very slightly isolate the motor from the incredibly small amount of additional torque, the platter will still slow because of the stylus drag.  With 2 belts, I would suspect that belt creep is higher than with a single belt, so speed instability caused by stylus drag would potentially be worse.

phoenixengr,

I am going to interpret that as an agreement to what I said.  All of my examples are increasing the mass and the inertia, right?  So the vpi flywheel would be more stable, due to its increased mass?  The more massive flywheel in motion would be more likely to stay in motion, compared to just a simple motor.  We are talking about the speed stability of the motor/drive system here.  You seem to be agreeing, but believe that the two belt implementation is faulty?

I agree that flywheels are a benefit, provided they are constructed properly for the task at hand.  Usually, the flywheel is larger in both diameter and mass than the object it is trying to stabilize.   Increasing mass does help, increasing radius helps much more.   In the case of the VPI flywheel, it is both smaller and lighter than the platter.  I would guess 20% increase of inertia improves stability by 20% as well, all other things being equal. If that explains the improvement in SQ, then mystery solved. If 20% improvement is acceptable for the added cost, then it's a worthwhile investment.

I agree that anything that improves the speed stability of the platter is a good thing. I don't know that adding another pulley (flywheel) and another belt is "faulty", but it bears investigation. All belt drive systems suffer from belt creep which affects speed accuracy and stability. In theory, having two belt drives in series would make belt creep worse (vs 2 belts in parallel around 1 pulley and 1 platter which should make things better), but I haven't measured it.

>FYI, a properly designed speed controller will provide excellent instantaneous
>speed stability, but long term speed accuracy is improved with feedback.

Can you perhaps recommend one? =)

I assume your of the Phoenix speed controller fame due to your feedback comment?

Fwiw I would rather have continuos speed than ever changing speed. But we've gotten into this before. 
The ear will detect changes much more easily than a controller that is slightly off but the same all the time. 

Constant motor speed does not equate to constant platter speed however.

Would you rather have constant motor speed with constantly changing platter speed, or motor speed that changes to keep the platter speed constant?

With respect to the effect of a flywheel, I believe (my physics are quite rusty, about 40 years rusty) the important effect is Angular Momentum and the Moment of Inertia, both of which are directly influenced by angular velocity.  Moment of Inertia also feeds into the torque of a rotating object, once again angular velocity is directly related to torque.  The flywheel acts as a torque multiplier, something the relatively small motor needs.  Also, keep in mind the VPI flywheel is turning at a higher speed than the platter.  I can't speak to the dual motor flywheel, but I have the single motor flywheel and while I haven't measured it's speed (and couldn't find anywhere in a quick search that listed it) it is several times that of the platter.  This further increases it effect beyond what one might expect.

Now if only Brf would chime in we might get a more definitive answer!

If consistent motor speed doesn't equate to consistent platter speed how can inconsistent motor speed equate to consistent platter speed??
Why would the motor speed on your unit be inconsistent????

wait for it

wait for it

oh because the platter speed changed!

oh because the platter speed changed!

By the time you realize it, or your feedback system realizes it to try to adjust for it, it is too late. An adjustment can "adjust" for it after the fact, but it will not really "correct" it. The cat (or error) is already out of the bag.  I guess this lag between finding the error and trying to adjust for it after the fact could be minimized if the sampling was more frequent. Better would be to have an inherently accurate and precise setup. But difficult or impossible to do.

I think we have gotten far afield of helping the OP with his decision or search.

@phoenixengr  Although your comments are appreciated by some including me, they will be far better appreciated if you identify yourself in every post by signing as a party with a commercial interest. 
It comes off pretty lame to read a string of posts that point to the benefits of your product without you telling us that you sell a product. 
FWIW, I've heard great feedback on your speed controller! No ill will intended. Cheers,
Spencer

sbank-

Understood.  My initial comments had nothing to do with speed controllers, I was curious about why a putatively undersized flywheel seems to make such a difference in SQ.  Somehow, the thread got pulled in the direction of arguing over the physics of speed control.  I don't mind sharing my knowledge of that subject, except with people who refuse to learn anything from the exchange (it's difficult to make people understand something when they already know so much).

1 - the other guys are correct - you'll end up buying a used table with some kind of arm on it

2 - the TNT works well with either a linear tracking arm or a pivoted arm  ( use the SME V but have listened to the ET)

Phoenix just to clear the air Im not against you or your product either. I have not heard it yet.  I think it looks like a well-made fairly priced product.  But I am leery given the premise of the whole thing. To me it's theoretically better to hold a constant speed, or attempt to, then to have an ever-changing, corrected speed. I realize neither one is perfect though so they both may work equally well in practice.  I think all the concern over belt creep is way overblownjust to sell us poor saps something else. But that is audio in a nutshell. And as S Bank said you really should identify yourself as has been brought to your attention before. 
Regarding the TNT ET Combo the op is after I think he is on the right track. My table came with the 12 inch arm and I sold it and bought an ET and pocketed some money. The ET far outpreforms the 12 inch arms as well as 95% of the other arms on the planet. The ET is stupid performance for the money. Where are you lady you should be somewhat mechanically inclined and willing to fiddle. That does not mean it goes out of adjustment as some people think I just mean in the learning phase you have to play around with it. 

ET designer Bruce Thigpen is one of Hi-Fi's true geniuses, and all his products serious over-achievers, very underpriced for their performance capabilities. Why isn't ET higher on the radar?! VPI's are THE table for the ET arm.

I think the ETs aren't more popular because people are afraid of them.  Although they shouldn't be, while very different the set up is actually much easier than with a pivoted arm once you figure it out. 

That plus all the tubes, pumps, etc.

I thank you all for your opinions. 

Not that this helps the OP but ...

The discussion never resolved the question raised by phoenixengr: why is there an improvement in sound when using a flywheel? Seems to me a likely cause is motor isolation. The flywheel adds a buffer against vibrations. Those VPI motors are noisy in my experience. I found that moving to a teres verus motor on my Aries 1 - essentially making it an idler wheel tt - improved the sound dramatically. So much so that I can't see ever going back to a belt drive.

The VPI Rim Drive had similar strong reviews but they seem to have mothballed it.

The Hurst AC motors will always be a major limiting factor on the VPI tables.  I own a number of the Hurst motors from the 49mm series up to the 60mm T series and the one consistency is they all vibrate, some much worse than others (within the same series).  It looks like VPI just changed from the 59mm series to the cheaper and smaller 49mm on some of their tables (Classic and Scout, possibly others). 

I ditched my SAMA with the Hurst 5W 59mm series on my Scout table and replaced it with a 3 phase BLDC motor with a custom enclosure and controller.  Best thing I ever did for this table.  Zero burn on the belt, 33/45/78 RPM with the same pulley, reversible rotation for idler drive, lots of torque and the smoothest, quietest motor I've found for a turntable.

http://www.diyaudio.com/forums/analogue-source/288730-3-phase-bldc-motor-turntable-use.html

phoenixengr,

The Hurst motor on my Classic One started making noise within a few months after I started using the table.  I installed a replacement and it wasn't smooth right out of the box, but has since smoothed out.  I doesn't inspire confidence.  The BLDC motor sounds promising.  Do you know where one could be purchased?  You mention that yours in custom; does that mean that your standard psu/tach would not work with a BLDC?

I bought the motor overseas;  it has a 4mm shaft (the Hurst motor is 3/16") so I had to have pulleys made as well.  The PSU is also a prototype and very different design than the Falcon or Eagle, although operation is the same and it works with the tachometer.

Right now, I have no interest in developing it commercially.  I built it to investigate whether it would work better than the Hurst motors, and it turned out better than I could have expected, so mission accomplished, but also, mission complete.

I like the VPI TNT motor and find it has very low vibration.

I bought a spare, in case it can not be repaired.

phoenixengr - You have issues with Harry of VPI, because he did not distribute your products, and your grudges show up here, and on AA.

Actually, I have a problem with Hurst motors, but thanks for your unbiased opinion.

BTW, the motor in your TNT table is not a VPI motor;  it is sold by Hurst and manufactured in China.

The VPI Scout and many VPI turntables that have the motor in the plinth, send vibrations throughout the turntable.

The heavy TNT motor using the "VPI designed" motor case, mounted outside the plinth, does not send vibrations throughout the turntable.

The motor should never be in the plinth IMO, that is a cheap design!

You guys are both right, the hurst motor is the tables weak point and yes it should not be in the plinth. I was amazed years back to see tons of people selling their tnts to get into the then new classic. I don't see how they thought the classic was a better table??  I guess some folks will always chase the latest new thing.....
I do find you have to be careful with vpi, a lot of their changes were made to lower manufacturing costs and marketed as "better"

"I do find you have to be careful with vpi, a lot of their changes were made to lower manufacturing costs and marketed as "better"

Very true, especially the last 15 years!

The problem is not just having the motor in the plinth. Vibrations are transmitted through the belt itself, and they cause all sorts of distortion. I went to great lengths to isolate the motor from the plinth on my VPI table, and I used two different motors, one much "quieter" than the other. I still had a drastic improvement when I went to the (much smoother) Teres motor and ditched the Hurst motor/belt drive configuration altogether.  

Don_c55 - I'd be interested to see you design and market a successful line of high-end audio products. Not so easy. VPI has used cheaper materials because they have to. My Aries 1 turntable is a good example - they used real wood in the construction of the plinth, and made a fantastic turntable. But it was too expensive to produce that way, so in the later iterations they used different (yes, cheaper) materials. Harry Weisfeld said somewhere that the Aries 1 would be an $8000 TT if they sold it today. Nothing wrong with an $8000 turntable but that's a pretty small market niche.  

"I do find you have to be careful with vpi, a lot of their changes were made to lower manufacturing costs and marketed as "better"

Though you may consider this a distinction without a difference, a number of changes may have been made to keep prices form rising,  HW has maintained that it has become far more difficult (translation: expensive) to obtain the quality acrylic that was used to machine what were probably some of VPI's very best platters.  Thus the return to aluminum.  Yes, the original VPI platters were aluminum and lead and the movement from those platters to acrylic and lead so was widely praised that the aluminum was dropped for many, many years.  Then, as now, many who used the aluminum platters sought all sorts of mats for them.

Lead was discontinued as well, though it had very favorable audible advantages: heavy weight and great damping properties.  The shift here was attributed to health effects during manufacture.

And yes, marketing masters that they are, every change was promoted as improving the sound and they had the published reviews to second their promotions.  And along the way they were making improvements in other ways, such as with their bearings, flywheels and speed controllers.

@jollytinker

They made 100 per year of the TNT turntables, and less profit then now.

VPI sells much more, and makes more money now.

Good for them. Harry knows a lot about hype and marketing!

However the TNT series is as good as (or better) than anything they make now IMO.

High sales "does not" equate with high quality.  New is not always better.

@jollytinker

I know a lot about design, having worked in design, in the medical device industry for years.

I would never work in the high end audio industry, because most all customers are irrational!

I admit that VPI marketing isn't always effective. I think they hyped the 3D tonearm for the wrong reasons - the coolness of a new manufacturing technology - rather than its sonic improvements. That contributed to the feeling that the new tonearm was a gimmick, when in fact - or in my opinion - it actually sounds better than the metal ones.  

But that said, I don't think VPI is declining or veering into cheapness. On the contrary, they seem to be weathering their recent transitions quite well.  Musical enjoyment is highly subjective, and therefore "irrational" if you want to put it that way.  That's the beauty and the intrigue of the hobby, not the 'problem'.  

My $.02, anyway.  :) 

Regarding the number of belts used, I have a classic 3 with Eagle/rr and ring clamp, I use 3 belts on a hrx pulley.  When I went from 1 to 3 belts the variability in speed decreased +-2 hundreths.  Now I never see above 33.335 or below 33.331.  I do run faster at 45 sometimes up to 45.005.