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Linn Sondek DIY mods that work
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Old 10th April 2015, 08:39 PM   #21
nigel pearson is offline nigel pearson  United Kingdom
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Have a look at this. Be careful as it is 340 VDC. Very cheap and very good.

http://www.diyaudio.com/forums/loung...ml#post4286281
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Old 11th April 2015, 05:59 AM   #22
el donkey is offline el donkey  United Kingdom
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Quote:
Originally Posted by nigel pearson View Post
Have a look at this. Be careful as it is 340 VDC. Very cheap and very good.

http://www.diyaudio.com/forums/loung...ml#post4286281
Ill, read that in detail again later. As a side point is there a thread on checking hi voltage with a scope safety, believe a transformer is needed?
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Old 11th April 2015, 06:14 AM   #23
el donkey is offline el donkey  United Kingdom
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My mose/hurcules and project arm arrived. when fitting noticed my phono cable was under tension so sorted that. I was too impatient to try each item separately. Together they have improved the sound, just cleaner/smoother is the way id describe it rather than more detailed but I now need to try a different cable to the phono stage.
to be able to play a 12" 45 is a novelty, on went Snake dance Lizard by the March Violets. Long time since I heard that :-)

I also took the arm board off and sanded flat the dimples from the three screw holes and reattached without too much pressure.


While looking at the pressed chassis I did wonder what a machined alloy one does instead. Is it the stiffness or damping. Id imagine alloy will have less 'ring' but is that moving from the 'theory'. I tapped it and it didn't seem to ring, sure it does when not fitted.

Anyone tried adding some extra stiffening to the original as apposed to damping.
if the keel sounds better my question would be why rather than how?
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Old 11th April 2015, 08:15 AM   #24
andyr is offline andyr  Australia
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Quote:
Originally Posted by el donkey View Post

if the keel sounds better my question would be why rather than how?
The Keel does sound better - as to why ... my take on this is simple - but you won't get Linn saying this (hehe ... bcoz then they'd have to admit that for 30 years they'd "done it wrong"! ).

What the Keel does is provide a rigid connection between the arm and the platter (as it's just one monolithic unit) - which enables the low level detail (that is lost with the lossy connection between the armboard and the pressed-steel subchassis - 3 pissy little screws!), to be picked up.

IMO, Linn had to engineer the lossy connection because of the inherent vibrations in the pressed-steel subchassis. With the Keel, they machined the subchassis + armboard out of one piece of aluminium (which has better self-damping behaviour than steel), and took care to minimise vibrations - or maximise vibration sinking! - by:
a) doing the machining slowly, letting the stresses in the metal caused by the machining, settle before doing more machining, and
b) CNCing the 'wells' in the underside of the Keel, presumably to attenuate vibrations.


Regards,

Andy
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Old 11th April 2015, 09:33 AM   #25
nigel pearson is offline nigel pearson  United Kingdom
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I heard the new chassis when it came out. As I was in a hurry I mistook it for solid alloy. The sound was better and most interestingly it the timing sense. Put into simple words the bass is tighter. This would seem to be a motor problem so the chassis helping is interesting. One cheap speculation is have a piece of perhaps aluminium sheet and a plywood lower section. 3 ply would be OK fixed with epoxy. Cut in pockets to take the bits. I would keep the tiny screws. We always used super glue to strengthen the screw holes. Let it set before using.

The Keel as far as I can see is chaotic. My guess is it was done by guessing. It would be OK to do that. It stops resonance building.

I think the how ridged arguement is really about how much uncontrolled movement there is. In fact some of the nasty pick up arms have what looks to be very ridged construction. Some that look awful like the Hadcock are very good. Linn I am sure did not really know why the LP12 sounded so good. It has nothing to do with Ariston who wanted a different and cheaper version. The LP12 out of Ivor's own mouth is a TD150. He said he owned one and didn't like the TD160 as much. Ariston marketed it but thought it cost too much. Linn made 50 then were left with 100 next batch. These were remade as the first LP12's. All the Aristons I have heard are in my opinion the bronze medel version after TD150 in silver. It is small things. Aristons rep told me Ivor unlike anyone he knew would listen to screws. Ray Collins wouldn't say a word against him and had been his friend. Ray would be from the film Get Carter. When he smoked no smoke came out. I think Ivor took the TD150 like the violin to be correct and just tries a small thing at a time.
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Old 11th April 2015, 10:10 AM   #26
nigel pearson is offline nigel pearson  United Kingdom
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Quote:
Originally Posted by el donkey View Post
Ill, read that in detail again later. As a side point is there a thread on checking hi voltage with a scope safety, believe a transformer is needed?
It is always a very very bad idea. My work needs me to do it. Best not to. If you use an isolation transfomer it helps a little bit ( Valhalla isolated ). I then build a 10 to 1 attenuator and hard wire a BNC plug to 50R coax for the scope. 2 x 100 K and 20 K would be OK, that should work with 0.6 watt resistors. Put the 20 K in the middle and feed from either side of it. This gives the scope a chance of surviving. When Valhalla the coax braid taken to 0V or grey of motor , more correctly 0V side of 20 K. My example shows what the voltages should be +/- 10% DC in the previous link. The very big deal of the isolation transformer is ground and live can not be connected together. The safety of you and the safety of the scope is better. Safe is not the word I would really use. A low cost RCD helps. These cost 8 and fit in the plug. 30 mA is usual. If you fit a bleed resitor you can make them more senstive. As you are isolated they won't help much. They help mostly if a wiring error is made.

BTW. An isolation transformer does slightly improve the Valhalla. The reason is simple. The 50 Hz oscillator is powered via a dropper resistor. This make the PSU assymetrical as regards the power amp section. If the oscillator is powered from a 9 V DC supply this improves ( don't even think of doing this ). The isolation transformer allows the ballance to recentre a little with much the same effect. Do not ground the transformer secondary centre tap. This will loose what you set out to do. The sage advice would be to do it, that's the problem with sage advice. The cheapest upgrade is 2 x 220uF > 250 V to replace the 2 x 47 uF. The third 47 uF is optional. The main ones go east west acrosss the PCB and the third is on it's own like the upright of the letter T. Please read my link to Subjective verses Measurements.

Isolation transformers are expensive. The Vigortronics range from Rapid Electronics include 55-0-55 ( any will do ). This is a very cheap and excellent way to do it. From memory the 110 V Valhalla input is OK. It is a voltage doubler so is not identical if memory is right. This shows the hum on the Valhalla. You will not see it with the standard crystal. This is a 45 RPM one. Step one is a PSU to the oscillator ( don't ). Next the 2 x 220 uF. Last is the floating isolation transformer. I also used a Maplin transformer for low powered valve amps made by Danbury. This gives 230 V in and out ( EL 84 , ECL84 etc ). This from memory was the best. These are my notes to myself so forgive.

Click the image to open in full size.

Last edited by nigel pearson; 11th April 2015 at 10:39 AM.
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Old 11th April 2015, 12:29 PM   #27
nigel pearson is offline nigel pearson  United Kingdom
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Vigortronix Toroidal Transformer 120VA 0 55V 0 55V | Rapid Online
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Old 11th April 2015, 08:26 PM   #28
el donkey is offline el donkey  United Kingdom
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Thanks for the detail Nigel. So its not as simple as say using an old 240/24v transformer between the scope and point to test.
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Old 11th April 2015, 08:34 PM   #29
el donkey is offline el donkey  United Kingdom
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Im sure this will have been tried before, but what would cutting some fiberglass cloth to shape and resining to the underside of the pressed steel. Or add some ribs and. Bond? This would add some stiffening/damping. Is it all about the exact amount of damping. Hence adding soft damping is too much.
or is it about energy disapation?
If so, find the frequency of the motor noise then spot weld a tuning fork to the chassis to disapate it.
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Old 11th April 2015, 09:02 PM   #30
richardr is offline richardr  United States
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Default Flip the top and add a power supply

Flip the top plate to get the motor opposite the tonearm. This quiets the tt quite a bit. Second, if you have the nirvana power supply(basically none but a cap) try using a signal generator into an amp and using a transformer to drive the table at about 70V. Getting the freq clean and perfect goes a long way on the LP12. Otherwise, I would suggest that you buy a different table if you want authoritative bass or some other sound. The LP12 is limited like all tables in what it can do.

Richard
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