Fettling the Technics SL-1210: Fixing Sibilance

[MartinT]

Something was not quite right a few weeks ago, and in trying to put it right I caused further problems. The Shelter 5000 is such a big cartridge compared with the AT33PTG that I simply ran out of arm height adjustment and could not attain the slightly nose-down attitude preferred by the Shelter. So I thought I would raise the arm mounting plate with spacers and bolt it all down again. Great - several mm higher and now I could get the VTA just right. I thought it sounded better, but it didn't really, just different. I kept subconsciously wondering where the detail had gone and why the sibilance seemed worse.

So tonight, armed with a sheet of Hobbycraft Fab Foam, I took the Dynavector and mounting plate off the deck. I first dismantled the two sections of the German custom made plate then hard glued and bolted them back together (in the same manner as my Mike New base plate is hard glued to the chassis because I never intend to return things to as-bought).

I then made two gaskets from the black foam sheet to the outline of the mounting plate, doubled them up and cut the three bolt holes through. Reassembly was straightforward except that this foam compresses and so I used a spirit level on the arm mounting column to ensure that the plate was totally level with the deck.

Remounting the arm was easy as height/VTA can be adjusted on the fly, so using my miniature spirit level on the headshell (these tiny bubble levels are so handy), I got everything perfectly level again. I did all this using the AT as I had been running it for a few evenings to eliminate the Shelter from the pointing finger of blame.

Wow - now my dynamics are back, upper midrange detail is restored and the sibilance is back down to normal levels. Everything sounds more solid again and the AT sounds dangerously close to the Shelter in sound quality (I maintain that the 33PTG is a superb cartridge with the right arm and step-up tranny).

One sheet of this is all it needed:



The moral of this tale is always to make one change at a time, leave an 'undo' path to put things back the way they were and be careful not to confuse 'change' with 'improvement'. I'm mighty relieved but also feel a moment!

[MartinT]

I wasn't imagining things, it really does sound superb now. I'm deliberately going to live with the AT for a while before going back to the Shelter. After that, I'll be very careful with making any further changes.

Paul's fine silver DC cable has bedded in nicely and does good things with the timing.

[MartinT]

Ok, the Shelter is back in as of last night and sounding mighty fine. Because I have now used a gasket solution rather than spacers, I am back to having only just enough arm height for the Shelter. It's a big cartridge!

One observation is that the AT33PTG is a very good cartridge indeed and only loses out in the midrange area with a touch of shoutiness, which the Shelter betters. However, there is not as much in it as I had first thought. Interesting.

[Marco]

Out of interest, what's the price difference between the two, Martin?

Glad your Techy is singing again - it's so easy for synergy to be upset when changes are made, and in revealing systems, you'll soon hear it!

Marco.

[MartinT]

The AT33PTG cost me then about £400 but is out of production now. The nearest equivalent would be the AT33EV at £530.

The Shelter 5000 lists for about $2200 but it cost me less than $1500 buying from Hong Kong.

The law of diminishing returns applies, combined with my belief that the Dynavector arm extracts considerable performance from all manner of cartridges. You're right about synergy too, it's easy to go astray and quite hard to reverse it sometimes

[MartinT]

And, for closure, I finally found a very good solution courtesy of Marco and HiFi Sound (Stockton on Tees). The idea was to reverse the inner and outer sections of the arm plate so that the step-down becomes a step-up. This leaves a nice flat surface for the arm spindle chuck to mount against and enabled me to discard the spacers previously used.

I also reduced the double-layer gasket described in the O/P to a single layer and bolted it all up tightly. The overall sound took a decided step up the ladder of transparency and sibilance was further reduced. I'm very pleased with this solution.

[WOStantonCS100]

It's always the simple things that seem to escape oneself.

Thinking about that, the Origin Live/Rega armboard for the 12xx, being a two-piece affair, can probably be reconfigured the way you describe, if necessary. I'll have to take a look at that when I get home.

[MartinT]

Showing detail of the stepped arm plate reconfigured for a 'step up', and the deck as it stands now.

[Reid Malenfant]

Urrrgh, Martin What's with the nuts & screw threads



Can't you use some nice allen bolts but the other way up?

[MartinT]

It's called getting the functionality working properly and not worrying about the aesthetics

Unfortunately, I can't use allen bolts as the threading in the centre piece requires bolting from the underside. I'm not bothered as it's barely noticeable in reality. If I can find some mirror dome nuts in that size (M3) then I'll put them on.