Old Chestnut Next in Queue?

gnnett · « **on:** 9 May 2005, 09:11 am »

Impressed with progress on the Hagdac etc. Keeps the digital team happy.Hoping that next off the block can be the TT DC motor controller 1/2 kit. Still no hurry, the LP12 still runs! But, with Brinkmann producing a valve PS for their TT, this has to be the way to go

I know theirs is an AC motor, but we are jealous now

Please don't forget the analog crew.

Regards

Gn

Yoda · « **Reply #1 on:** 9 May 2005, 04:35 pm »

That would be cool--hadn't heard of this project. If it works for a Linn...then it could retrofit a Thorens? Is it both DC motor control and a DC motor?

Matt

gnnett · « **Reply #2 on:** 10 May 2005, 08:54 am »

Quote from: Yoda

That would be cool--hadn't heard of this project. If it works for a Linn...then it could retrofit a Thorens? Is it both DC motor control and a DC motor?

Matt

Try this link

http://www.audiocircle.com/index.php?topic=13328

hagtech · « **Reply #3 on:** 10 Jun 2005, 07:11 am »

So I had a thought, instead of a dc motor retrofit, how about just making the existing motor run better? Maybe all it takes is an improved signal feed?

I was also thinking, perhaps you can teach an old table new tricks, like playing 78s! Perhaps these ac motors can be made to run at higher frequencies. Wouldn't it be great to have an LP12 or P3 that will run up to 78rpm at the push of a button? How about variable speed or pitch control?

Or maybe the table sounds better with the pulley set to 45, but motor spinning slower to get 33.3 out of it? Could even be battery powered.

Any interest?

jh

Tone Deaf · « **Reply #4 on:** 10 Jun 2005, 07:49 am »

I'd be interested in an AC controller for my LP12, don't really fancy going DC.

Glyn

barpc · « **Reply #5 on:** 10 Jun 2005, 06:17 pm »

Now, you are making me re-think selling my LP-12!

AC motor control would be the ticket.

Brad

gnnett · « **Reply #6 on:** 10 Jun 2005, 10:42 pm »

I have a really old LP12 and ongoing motor condition, operates but do not know for how long, is of concern. I have already an "armageddon" esque supply and have a replacement DC motor but no p/s. So while AC supply that provides a bit more flexibility would be an option, DC would be my first choice. Too many greater minds than I have ended up there.

But a valve AC supply for the old LP12 would be pretty chic

Cheers

Gn

hagtech · « **Reply #7 on:** 11 Jun 2005, 03:04 am »

I'm not convinced the DC is better than AC. Could be, but perhaps it's just the attention to the electronics. A super-clean signal might just be enough to get the job done. And then may not have to monkey with a motor and extra cost. It'll take a lot more research on my part to start getting some of these answers.

Doing a tube version would be easy. The question is, do you want to pay $100 or $500?

jh

Rocket · « **Reply #8 on:** 11 Jun 2005, 03:50 am »

Hi Jim,

I would be interested in getting better performance out of my turntable. Please research the cheaper option $100us.

Quote

So I had a thought, instead of a dc motor retrofit, how about just making the existing motor run better? Maybe all it takes is an improved signal feed?

I was also thinking, perhaps you can teach an old table new tricks, like playing 78s! Perhaps these ac motors can be made to run at higher frequencies. Wouldn't it be great to have an LP12 or P3 that will run up to 78rpm at the push of a button? How about variable speed or pitch control?

Or maybe the table sounds better with the pulley set to 45, but motor spinning slower to get 33.3 out of it? Could even be battery powered.

Regards

Rod

rotcoddam · « **Reply #9 on:** 11 Jun 2005, 04:38 am »

I vote for tubeless.

But I'm sure in a year or two I'll want the tube.

hagtech · « **Reply #10 on:** 12 Jun 2005, 06:37 am »

Looks like this has been done before, the VPI SDS and Walker machines. They both appear to be just line frequency regenerators with adjustments. Heck, I can do that. I like the concept, no table mods, just plug it into a new electronics box instead. We can have two controls, one for speed, the other for voltage (I suppose it is good to run as low as you can get away with).

This would be nice, as it should work with just about any TT with an ac motor. I got my motor back from my trashed MMF-5. It's rated for 2VA (watts). Circuit can be low power. Maybe I will design this same time as HUSH. I'm thinking maybe take what I learned from OS DACs and apply it here to low frequency sinewaves. Digitally regenerate super clean and stable (hey, I have a HAGCLK here) output waveform. Hmmm, the gears are turning...

jh

gnnett · « **Reply #11 on:** 12 Jun 2005, 09:19 am »

Gears, cogs, whatever keep them turning. I am keen so take these thoughts as encouragement to address all issues.
1. My current ps for the LP12 is not much more than an isolation tx, but it replaced the Valhalla regeneration (crude) ps. This, I think, was electronically noisy (emf, emi?)but probably more accurate than my current reliance on the mains frequency.
2. Apart from price, I was also scaried off of the Lingo because of the same reasons. Probably misguided, but think I would have gone Armageddon for the money. Concept, rather than performance sits better (kiss).
3. You would probably want to do a little surgery on the turntable to access the motor rather than leave any existing ps between a well cleaned supply and the motor.
4. Voltages that keep the motor quiet won't necessarily start it. Some juice the motor up with a few extra volts to get the platter turning then back off once it is underway. My supply almost begs for some assistance before shuddering up to speed. (Hmm time I checked that too) Motor may be a little tired.

Just some thoughts and I think I did pretty well recovering from the heart ceasure at your ludicrous suggestion of using ddddigitallll.

Keep up the good work.

Cheers

Grantn

hagtech · « **Reply #12 on:** 14 Jun 2005, 03:22 am »

I think this will have to go dddigital, for the sake of cost and elegance. An all-analog oscillator such as a wien-bridge would suffer a little temperature instability, etc. It also forces the output amplifier to go class A and cost way more (heavy iron).

I think for simplicity, dividing down from a reference crystal is the way to go. Then we can get really small and super-repeatable increments for pitch adjustment. What do you think is enough, +/-2%?

This design also screams for a microcontroller. Synchronize everything, use high frequency magnetics with output filters, not much unlike a digital amplifier. This gets cost and weight down.

I don't like pushbuttons, so maybe optically encoded rotary switch for pitch control. Speed control can be normal rotary [off, 16, 33, 45, 78]. Will need internal jumper for 50/60Hz, maybe also for 120/240V. Knob for voltage control (with start-up boost). Thinking it also needs a display that shows both frequency (or speed?) and voltage.

Won't be so cheap afterall. Perhaps $200 in parts. Don't get too excited. This is gonna take some time. Must finish CHIME first.

jh

flocchini · « **Reply #13 on:** 14 Jun 2005, 03:35 pm »

I have patience. Sign me up.
Best
Bob