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Old 30th December 2002, 05:57 PM   #11
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Thorens do provide pulleys for 50/60Hz operation. It's a very simple procedure to replace for any user. Of course the sine oscillator is the better option as it will improve the sound considerably. Yes, i have tried it on my ex- Thorens 160S and the sound got a lot more refined with even, believe it or not, reasonable bass. My oscillator has THD at output in the region of 0.1% mostly due to the step-up transformer, compared to 5-6% from the mains.
Another, probably better solution is to copy Linn's Valhalla. Not much worth copying as far as the oscillator is concerned, just the discrete high voltage amp in place of the step-up. I saw someone selling the circuit on ebay (?!) but i'll probably take it off the board whenever i get the time.
If you do make the oscillator the next worthwile step will be providing a second phase-shifted sine and getting rid of the capacitor. My AVR is happy to generate a second sine, only i've never really bothered building a second DAC/AMP/stepup to test it. Will probably do that once i have a Valhalla clone working

cheers

peter
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Old 31st December 2002, 07:27 AM   #12
Raka is offline Raka  Europe
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Default Wien

Could you send me the scheme you used? You don't change to 45rpm, do you?
As far I see the problem is the step-up stage. isn't it? Is a transformerso such a bad thing ?
The sonic advantages are so big, eh? well, then I'll forget about the pulley change and I'll follow the DIY path, and build an oscillator.
Besides, I'm thinking about the voltage applied to the motor. The torque follows a square law for the voltage (triple the voltage means 9 times torque) but I don't know the advantages of the torque ratio. I read somewhere that low torque is better, once the platter is in motion. The starting is not a problem since there is always a hand to help and not let the belt to suffer tracking loss. I will search in the DIY TT thread.
What are the advantages of getting rid of the cap? Maybe that adjusting the angle between signals can improve the vibration of the motor?
You have to tell me more about your TD160. The main bearing of mine is close to perfection. Is a nice tt, what do you think?
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Old 31st December 2002, 07:40 AM   #13
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Default Re: Change in frequency mains

Quote:
Originally posted by Raka
Hi all,

I have a thorens TD160 and a TD295 MKII turntables, but they were bought in the USA, where the mains is 60Hz, and here I have 50Hz. What can I do? PLEASE HELP ME, BUAAAAHHHHH?
Um, try Thorens web site, www.thorens.ch and see if there's a distributor near you.

Cheers, Keith
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Old 31st December 2002, 08:12 AM   #14
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Raka

The building blocks of the DIY PS are very simple, so i've never drawn a circuit. The Wien bridge is described in most electronics textbooks, like 'The Art of Electronics'. Use a simple RC filter set to around 100-150Hz at output and your choice of power amp. Initially i used a Rotel, then an LM3886 and an STK. My case is more demanding as the Garrard 301 takes full 16W.
Spinning at lower than nominal voltage probably reduces vibration as it certainly improves the sound. There is however an optimum voltage which you can determine by listening.
The TD 160 is not my favourite Thorens and that's why i sold mine. It is a nice turntable but i seem to prefer 124 and 125 by a large margin. I also prefer the Linn and the old Garrards (301/401). Yes, i have them all.

cheers

peter
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Old 31st December 2002, 10:55 AM   #15
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Default Re: Change in frequency mains

Quote:
Originally posted by Raka
Hi all,

I have a thorens TD160 and a TD295 MKII turntables, but they were bought in the USA, where the mains is 60Hz, and here I have 50Hz. What can I do? PLEASE HELP ME, BUAAAAHHHHH?
Raka,
Will this do?
http://www.analogue-domain.org.uk/diy/401ps.jpg/

Cheers
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Old 31st December 2002, 12:49 PM   #16
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Thanks for posting the link Bret. I was trying to remember where i've seen this. It will do with minor mods. Replace the 741 with a 5534 or anything respectable if you really want low distortion. Place a capacitor between the oscillator o/p and the LM3886 i/p in order to eliminate DC. It's now not essential to use the electrolytics at the o/p, just connect the step-up directly to 3886. I also see absolutely no point in the 1ohm/10W resistors in the PS, it will work fine without them (actually better).
As with any Wien bridge osc, care and attention are required to obtain stable and undistorted o/p. Some means of measuring distortion will be invaluable.

cheers


peter
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Old 24th January 2003, 01:29 PM   #17
EC8010 is offline EC8010  United Kingdom
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Default 50/60Hz Wien bridges (and Garrard 301's)

Although you can make a 50/60Hz Wien bridge, it can be difficult to keep the distortion down because of thermal cycling of the thermistor/lamp. In this instance, a lamp is likely to be better than the traditional R53 bead thermistor. Another possibility is the state variable oscillator described in Ian Hickman's "Analog Electronics."

A Garrard 301 doesn't have to consume 16W even though the chassis plate specifies 14VA. I assume that you have disabled the eddy current brake? If you resonate the motor by placing a 1.84uF (50Hz) 1.29uF (60Hz) capacitor in series (240V settings), you obtain a nice resistive load. If you drop the voltage to 108V across the motor terminals (reduces vibration), the measured power dissipation in the motor is only 4W. Under these conditions, I thought that quiet bits were slightly quieter and record noise was reduced.
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Old 26th January 2003, 10:25 AM   #18
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Garard 301's,

Yes, they used to take 25 watts with no correction.

Cheers,
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Old 26th January 2003, 10:34 AM   #19
dhaen is offline dhaen  Europe
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Hi,

Although I know nothing about vinyl:
Several years ago I used to supply a "maker" with a 50 / 60 Hz 25 watt power supply for the 301 & 401.

The circuit had 2 parts:

1) A crystal osc, a 50 /60 Hz switchable divider and a Butterworth filter to produce quite a clean sine wave at the reference frequency.

2) A Bridge Tied Load VFET amp, producing 120V per side, antiphase.

The reference osc uses a standard 15VA 2 secondary transformer, and is properly mains isolated.

The BTL circuit was not mains isolated and depended on being mounted in a well insulated and earthed box, and all tests being carried out in an earth free and isolated environment.

I cannot recommend the BTL amp for home construction, but I have no hesitation in recommending the reference oscillator circuit.

I have just 6 PCB's left, which I'm prepared to pass on gratis in the UK, or at US$1, or 1Euro, to cover postage cost elsewhere.
I'll supply the reference circuit, but not the BTL circuit. I suggest that for home construction, a transformer is more appropriate.
It's up to you to work out the power amp bit, but it's only like audio.

The PCB's are double sided copper PTH, with legend. They measure 100mm x 120mm.

E-mail me if you want one. I'll work on the basis of 1 for each request until the're gone.
Please only ask for one if you're sure you'll use it

Cheers,
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Old 26th January 2003, 10:40 AM   #20
dhaen is offline dhaen  Europe
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Here's the schematic of the reference oscillator:
http://www.dhaen.org.uk/vdocs/PHsch_ref.gif

Cheers,
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