Need some turntable guidance

xaak,

It's simple, really.

All you really need is a signal generator, and a way to amplify the signal to deliver 120 volts. Actually, between 60v and 130v is better because you can tune the voltage to provide adequate drive at the lowest motor vibration possible.

Keep in mind, this is for 120v synchronous motors only.

The signal generator is the easy part. You need to find one that provides adequate granularity so that small adjustments to the output frequency are possible, and it must output sine wave.  I have an old Leader signal generator that works OK for now.

The trickier part is amplifying the output of the signal generator so that it can output up to 130v @ roughly 10w (vpi motor needs 7.5 I think).  For this, I used a Kicker IX500.4 car stereo amp I had laying around and an old 15v laptop power supply (I never throw anything out :) ).  This easily allowed ouput in the range of I was looking for, to output 12w, a safety margin over the 7.5 needed for the motor.

So now I had to turn 5 to 7 volts into 120v.  Looking at my parts drawers,  I found a 6V center tapped line transformer, which normally turns 120v into 6v.  Reversing it and driving the secondary with 6v (not using the center tap), it turns 6v into around 120v.  Then I hooked the primary to a standard wall receptacle, and plugged the motor into the wall receptacle,

With the gain on the signal generator set to 0 and frequency set to 60hz, and the gain on the amp set to maybe 20%, I slowly increased the gain on the signal generator, while monitoring the voltage on a true RMS multi-meter until the platter started spinning.  It took a minimum of 75 volts to start the platter, and once started, it would maintain speed at anything over 60v.

There you have it.

I'm not into vintage for the sake of vintage, most of my stuff was fairly current when I bought it (been doing this a long time). I wouldn't be looking to ditch the VPI for older DD or idler wheel tables.

chakster:
Thanks for the info.

You're welcome. Let me assure you that any of those vintage turntables I have mentioned are much better than VPI or any modern belt-drive at this price. Technics SP 10 mkII, Luxman PD-444, Denon DP-80... those turntables are all HIGH-END direct drive and you will never find anything equal today in terms of price/performance. Garrard will cost more without being any better. 

When I mention any vintage gear (turntable or cartridges) in my posts i'm referring to the best turntables and best cartridges at certain price category TODAY (imo). Not because they are good looking or vintage, but only because they are better. 

You don't have to buy the latest gear when it comes to analog.
But you have to buy the latest gear when it comes to digital.

  

ctor

Yes, a Y connector works, and I have used them many times successfully over the years, even though purists make faces like they just smelled dog poop. I never have, or would mess with your impedance idea but you are more advanced than me.

You may be right, because playing the Grado 'dual mono' cartridge output thru both channels thru a pair of speakers does sometimes give a subtle illusion of location, not frequent, but it does occur, not disturbing, just huh? when you notice it, then you forget it, and just listen. Mono well recorded can be excellent and thoroughly involving.

My single mono amp hesitation is playing from only one speaker that is presumably near a corner of the room normally for stereo imaging and located precisely for room frequency balance. Mono Jazz LP's is frequent for me, a few of us in listening positions for imaging, i.e. Oscar Peterson, play this Stereo LP, then that Mono LP, back to Miles Davis Stereo, ... which is my frequent habit, and why I am truly enjoying the two arm large plinth solution.

When they knew Stereo LP was coming, before 1958 (tape went stereo in 1956), the big studios sent two separate teams, their accomplished mono recording team, get a session done, then a separate recording team of new Stereo whiz kids, repeat the whole process, costly for sure.

I read that Rudy Van Gelder observed this, couldn't afford double ..., so he decided to record in Stereo, and mix mono from that, and have the Stereo masters for the future. Clever Indeed.

chakster,

I'm listening to Eric Clapton Steppin' Out on Decca FFSS using my Denon DP-1250 with a Magnepan Unitrac 1 tonearm and a Grado Reference Platinum cartridge as I type this. I'm waiting on getting my spindle rewired from ET and some new belts for the VPI. It's a very satisfying combination, I'll grant you. The arm and table are certainly vintage though the cartridge is from the mid 90's.

On it's best day, with as perfect a setup I can muster, it never came close to what the VPI/ET2 could do with the same phono cartridge. IMHO and obviously your mileage does vary.

Thanks. That sounds easy enough that maybe even I can do it.