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 Post subject: turntable
PostPosted: Wed Dec 30, 2015 8:47 pm 
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God

Joined: Thu Dec 30, 2004 10:50 pm
Posts: 998
Location: Minnesota
I'm thinking about going to the dark side; vinyl. I've wanted to do it for years and just haven't.

I don't have a turntable which brings me to here. What do you guys like? I don't mean this brand is better than that and if you disagree you're an idiot. Well, you might be an idiot but not because of this. Have to channel Jocko some. I'm teasing!

I want to know what makes a good turntable. Why do you like this tech over that tech. I've looked at lots of threads elsewhere and am more confused now than when I started. I just want information, I'm not trying to start a mine is better than yours thing.

I used to use a Mitsubishi DP-EC1 decades ago. I liked the table a lot but find one today, not many around anymore.

the floor is open.....


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 Post subject: Re: turntable
PostPosted: Sat Jan 02, 2016 12:03 pm 
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Muriel
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Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1168
Hi,

Mikeg wrote:
I want to know what makes a good turntable.


We need to define "good".

One design that many consider as "good" is a Turntable with comparably lightweight build where the varying stylus drag in the LP depending on signal introduces speed variations that give this turntable, if set-up correctly a "bounce" or "Pace" that I find distracting but which made it famous. Many british turntables emulate this to some degree. Often the Platter also rings like a bell and this can be excited by the Stylus. Again, different tuning mats are offered to "tune" this effect just so, it is no longer distracting but possibly enhancing.

In this case case use a lightweight suspended structure and weak motor.

In my own books the above is not very good. The best suspended sub-chassis Turntable I had was a well sorted Oracle Delphi, it did rather well but still showed some weakness. I think it simply would have needed more mass and a better suspension system to eliminate these.

I personally prefer to have both platter and plinth very heavy, to suppress any resonances. Usually multi-layer compound structures (I like Metal/Glass sandwiches) are better in suppressing material inherent resonances. Some form of isolation of the table from external resonance is needed, air suspension, string suspension etc., even squash balls. Additionally using a strong motor (brush-less DC?) and rigid coupling between motor and platter (String/Tape drive?) can seriously enhance speed stability under varying modulation. Such a turntable offers a very solid platform for a (for want of a better word) natural and neutral reproduction.

Somewhere in-between are the better Japanese direct drives. Often the plinth is heavy, the platter less so, but servo systems are used to counteract speed stability issues. Often some tuning is needed to get the best. For something you can buy and tweak to acceptable performance they are often an excellent choice. I tend to be partial to the whole range of Technics SL120 derivatives, they can be tuned fairly easily and if well sorted can approach the performance of very serious "solid/stable model" Audiophile turntables.

The default model is the SL1200/1210 DJ Turntable, there is a whole industry providing upgrade parts. The same principles are applicable to others though which may be had cheaper and if enough DIY is possible, the results can be excellent.

I'll happily pontificate about my own take on Japanese DD Turntable tuning if anyone cares.

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


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 Post subject: Re: turntable
PostPosted: Mon Jan 04, 2016 2:05 pm 
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God

Joined: Thu Dec 30, 2004 10:50 pm
Posts: 998
Location: Minnesota
Please do.

I worked with a ME that was into vinyl pretty heavy. We were always going to design our own table but, never happened.

He was of the opinion of the lighter platter was better with matching masses to direct vibrations out of the table. I never could get my head around it. I understand the math but it never seemed to me to be the right thing to do for this application. What do I know....

Mike


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 Post subject: Re: turntable
PostPosted: Tue Jan 05, 2016 4:41 am 
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Muriel
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Posts: 1168
Hi,

Mikeg wrote:
He was of the opinion of the lighter platter was better with matching masses to direct vibrations out of the table. I never could get my head around it. I understand the math but it never seemed to me to be the right thing to do for this application. What do I know....


Well, there are two angles here.

A larger mass will vibrate less for the same energy input, using the right "sandwich" can make the platter (and chassis) extremely non-resonant. My strictly empirical approach showed excellent results with Glass/Metal sandwiches having NO additional damping material. Platters that rung like a bell when struck with a biro turned dead silent with a substantial glass mat on the platter.

The other side is how can we "direct vibrations out of the table"? Have a look at the platter in Cutting lathes... The only direction where the vibration could go is via the bearing into the chassis... Now we have to make chassis to counter resonate etc. et al... Beware, there be dragons that way...

And my first two suggest tuning measures for decent Japanese DD Turntables are indeed a substantial glass platter mat topped with the usual felt or preferably suede leather mat, plus a heavy record weight.

These two are easy and external. For correct cartridge setup the HiFi News test LP is highly recommended, as is a balance to measure tracking force. Also recommended is a Alignment Protractor that does not follow the usual alignments, which try to minimise average tracking error, instead use one that minimises tracking error at the end of the LP, where due to grove spacing and relative groove velocity any error leads to the greatest problems (by comparison at the start of the LP quite a bit of error can be tolerated).

Most Japanese DD's have non-rigid "S" Tonearms. Ideal to mount a Denon DL-103 MC Cartridge.

Mount it to the headshell with the supplied washers between cartridge and shell. If the arm's effective mass is not sufficient to get the resonance frequency right (HFN Test LP to check) you can use lead tape (for golf clubs and/or for making faux stained glass) to increase the mass of the counterweight (apply to counterweight) and wrap some around the arm at around 2/3rd from the pivot (strictly speaking use golden ratio). In fact, I recommend a minimal amount of lead tape at the 2/3rd point even if no mass increase is called for.

The remaining things means you need to go inside.

First, if the table has a Strobe using an LED, find a way to disable this, it throws massive noise into the PSU - often the one for the PLL controller.

Second, re-cap the table completely (if older than a few years) and have a look at the PSU.

In the Technics 12XX and derivitaive range the regulator is a simple 2 transistor series type, quite noisy. The easiest way to improve this is by swapping transistor and zenner diode in the Emitter for a TL431 (use On-Semi, less noise than TI/Nat Semi) in TO92 case and making a low(ish) noise regulator with much improved PSRR. I have seen the same discrete type in many tables. If there is a 3-Pin type, using a NPN BJT or N-Channel Mosfet + 431 can make a quick & efficient low noise reg that is easy to drop in.

The next stop is the raw PSU, I found adding capacitance helps, the 1200 (Gold Limited Edition) in our listening room has an extra 200,000uF (yes, 20pcs 10,000uF/35V!) in the PSU.

If you have the time and inclination you can check the PLL compensation and fine tune it for critically damped response. This does however tend to make the table to have less "PACE", it seems some japanese manufacturers tuned their PLL to emulate the dynamic speed instability of a certain British copy of a Thorens Turntable, some with more sucess 9or to me failure to make a stable table) than others. Put a scope on the PLL compensation Pin, break the table by hand and look at the trace for recovery.

While you are mucking about inside, look at the plinth and notice all the hollow areas inside? If they are needed functionally, simply fill them. Everyone has their own special formula, I like car body sealant (it does smell and you need to let the stuff set and stink out for a few weeks in the Garage) and ball bearing balls or small nuts to mass load. Epoxy that remains slightly tacky after setting with ball bearing balls or nuts is probably as effective and more environmentally friendly.

The final stop is re-wiring the Arm. I just go Kondo style and do it external to the arm, a little less odd looking than this:

Image

I like Audio Note UK Silver wire, but others are available.

After this you will have quite a turntable, the total cost (with cartridge) will be well under 1K.

As RIAA for the DL-103, you can use LT1028/1115 as single stage MC capable RIAA. Take the schematic from the LT1028 Datasheet page 18 and scale the main EQ components by a factor 10, Resistors up, capacitors down. Voila, 60dB Gain. An output coupling cap or DC servo will be needed and the PSU must be super quiet. If you have a spare 400 bucks burning a hole into your pocket, iFi makes a decent MM/MC phono stage as well, but this is DIYHiFi and BYOHiFi.

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


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 Post subject: Re: turntable
PostPosted: Tue Jan 05, 2016 8:32 am 
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Muriel
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Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1168
Hi,

Kuei Yang Wang wrote:
And my first two suggest tuning measures...


One more item.

Presuming the table has no or only vestigal suspension (most Japanese DD are of that type), go to Ikea or a good professional kitchen supplier and buy the heaviest rubber-wood butcher-block type cutting board (in a pinch the ever popular Bamboo will also do) that will fit the whole turntable.

Find some form of air suspenders (recent advances in packaging deliver a wide selection for free with your shopping), you may use bicycle inner tires or formal suspension feet, including for example the so-called "string suspension concept" types or magnetic levitation (I have used four suitable ones with good success in such a situation), budget and imagination are your only limits.

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


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 Post subject: Re: turntable
PostPosted: Tue Jan 05, 2016 2:36 pm 
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God

Joined: Thu Dec 30, 2004 10:50 pm
Posts: 998
Location: Minnesota
Fantastic.
You're thinking exactly what I have been.

I work with motors, brushless servos and drives for years. I have a couple (90mm frame) motors with 1028ppr encoders I can use or play with. Torque ripple depends on the drive used.

Your comments about bearings is why I've been scratching my head. The energy has to go somewhere and going through the bearings is not my idea of a good time. The ME I worked with shook his head and said no problem. Not sure how he would conclude that, I didn't.

I don't have access to the accelerameters and data aq anymore, when I finally do this I'll put something together at home.


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