minor internal adjustment to ADS "33" speed

minor internal adjustment to ADS "33" speed

Postby Don C » Tue Nov 17, 2020 11:43 am

Background: I'm a musician, and while not blessed/cursed with "perfect" pitch, I am sensitive to correct (and stable) pitch. I've somewhat preferred some of the better direct-drive turntables in this regard, but have opted to use belt-drives in my main system for various other reasons. I've thus far been pretty happy with my mid-2000s Scout - using the supplied 600RPM motor and ADS, I've never had "problems" with the turntable speed, and the ADS definitely improves PRaT, and a little better speed accuracy and stability, of course.

Itching for an "affordable" upgrade, I decided to try the 300 RPM motor with the bigger pulley - greater surface area for belt contact made sense in my head for less potential for minor belt slippage. (I've read the many threads here for and against the "more torque" argument, and will leave that to those other threads.) And having the ADS meant that I could use the "single speed pulley" and opt for two belts at once - again, even greater surface area and less opportunity for any slippage. This made sense in my head.

So I ordered a new 300RPM motor, single-speed pulley for 11.5" platter, and two new belts. Everything arrived and the motor chang-over was (relatively) uneventful.

Once up and running, I used my KAB SpeedStrobe to set the 33 and 45 speeds on the ADS. 45 was easily set, but with the 33 speed control turned all the way down, the measured speed was still a little too fast. On a hunch, I opened up the ADS and found what I "hoped" to find - small trim-pots on the board behind the two front-panel controls. Making what I thought was a logical assumption that the one behind the 33RPM control knob was a range adjuster, I adjusted, and once at its limit (low, I assume), the front panel control was then able to get the speed down to exactly the correct speed. So, yay for that.

The overall benefit? Even greater improved PRaT (as hoped), and speed stability is CD-locked steady. It will pass muster with even the longest sustained piano and oboe tones. It wasn't unacceptable before, but now it's near-perfect.

Happy!
Harbeth C7ES-3/30 • Pass Labs XA30.5 • McIntosh C220 • Modwright/Sony SCD-XA5400ES • VPI Scout+ADS/JMW-9/Nagaoka MP-500
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Don C
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Re: minor internal adjustment to ADS "33" speed

Postby Don C » Mon Nov 23, 2020 11:32 pm

Let me add that the performance improvement(s) is/are not subtle - it's great! Spinning lots of vinyl again - not that I wasn't before, but it's just that much better now. :mrgreen:

If you're got an ADS/SDS and are of the mind to make a few minor upgrades, I think this is a way to get quite a bit more performance out of a simple Scout without a lot of "money" shelled out - the 300RPM motor and "one-speed pulley" with dual belts are the way to go!

Perhaps a new "Prime" is in the future someday, but this is a nice improvement for now! ;)
Harbeth C7ES-3/30 • Pass Labs XA30.5 • McIntosh C220 • Modwright/Sony SCD-XA5400ES • VPI Scout+ADS/JMW-9/Nagaoka MP-500
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Don C
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Posts: 7
Joined: Sat Dec 01, 2018 7:05 pm
Location: Michigan


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