A Visit with the VPI SDS turntable motor controller

Accurate analog production with a turntable is a tricky business. There is the cartridge, which produces millivolts that have to be amplified up to line level. Then there is the arm, which requires rigidity, vibration dampening, the ability to ride warped and off-center records all while adding nothing to the sound. The turntable body itself is another source of vibration, especially if the AC motor is clamped to the plinth. On top of this, we have speed inaccuracies and vibrations from the motor which can be transmitted to the rest of the turntable system. It's amazing that records can sound as good as they do.

VPI created the Synchronous Drive System (SDS) in order to help correct turntable motor issues. It is essentially a turntable motor controller and line isolator through the use of amplifier with a semi-adjustable quart crystal sinewave generator. This allows the user to dial in the exact frequency for their AC turntable motor, resulting in a locked 33 1/3 rpm. It also has a current sensor to adjust the amount of voltage to the motor, allowing 115VAC as the platter spins up to speed and then it tails down 20-30Vs for normal operation. This has the effect of reducing motor vibration.

I bought mine used via Audiogon and through the use of the KAB Speedtrobe, adjusted the AC frequency down to 59.69Hz to achieve an almost perfect 33 1/3 rpm on my VPI HW19 Mark III turntable.

Sound differences are hardly earth shattering, but more of a baby step towards that impossible goal of achieving audio perfection. Music has more of a "locked in" feel as images are rock steady. Bass sounds slightly deeper as does the soundstage depth. Pitch control is excellent, reminding me of the solidity of the compact disc. I'm very happy with the changes and can't wait to purchase the VPI SAMA outboard motor and a new tonearm.


System:
preamp: Threshold FET-10/HL
phono preamp: Audio Sector Phono Stage
amplifier: Threshold S/500
analog: VPI HW19 MkIII - Rega RB300 with Incognito wiring - Denon DL-103R
speakers: Magnepan 1.6/QR with Sound Anchor Stands
speaker cable: Kimber 4PR/8PR Bi-wire with banana jacks
Interconnects: Cardas Cross and Cardas Quadlink 5C


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Upgrading the Threshold FET-10/HL linestage

My beloved Threshold FET-10/HL linestage is getting a little long in the tooth. The few electrolytics need replacement and the couplers are due for an upgrade as I'm no fan of Mylar capacitors.

I first tackled the Power Supply, replacing the original four diodes with UF4007s. It's hard to find quality axial capacitors and the outboard power supply is too small for fitting in radial capacitors. With that in mind, I ended up replacing the 2200uF/25V electrolytics with 3300uF/35V Nichicon FGs.

Next up is the actual signal unit. 4.7uF power supply bypass capacitors were replaced with Elna Silmics. Inside, it's a tight fit height wise with the input and output coupler capacitors. So I used 1.0uF Rel-Cap PPMFs on the input and 10.0uF Wima Polycarbonates on the output section. This is a much improved upgrade over the original input film and output metallized Mylar capacitors.

How does it sound? Polycarbonate have always been some of my favorite 'sleeper' capacitors and once again they proved their mettle. They are much superior to the original Ero Mylar capacitors with a cleaner, less fuzzy soundstage. There seems to be more minute detail too. The combination of the new parts makes for a much better preamp and a brings this old girl back up to world class level again.


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Upgrading the B&K ST-140 amplifier

This was an easy upgrade - on both boards, replace the 100uF/100V and 47uF power supply electrolytics. The 47uF electrolytic input capacitor was replaced by a 10uF film unit. You can use anything from 10uF to 47uF here. Due to the size of the film capacitors, I bypassed the circuit board capacitors with wire and installed the new units inline on the leads from the RCA jacks.

The end result was an amplifier that sounded much more detailed and immediate. Gone was the treble roll off and plummy bass. The big 47uf electrolytic input definitely added some major coloration to the sound as now it sound much more neutral. Though not in league with my big Threshold S/500, the B&K is now one heck of an amp for the money.


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A Visit with the B&K ST-140 amplifier

My Threshold S/500 amplifier is in need of a rebuild. With that in mind, I decided to buy a interim amplifier to drive my Magnepan speakers. I wanted something cheap as this was also going to be an expendable unit to practice my solid state upgrade skills on. After examining several amplifiers on Audiogon, I selected the budget-priced B&K ST-140 since it is renowned for a smooth tube-like sound. It is also a simple design that would lend itself to potential modifications and allow an easy upgrade path.

As far as I can tell, there are three iterations of the B&K ST-140. The first one, from the early 80s, used a iron core transformer and each channel had a pair of Mosfets to make 70Ws. The second version has a toroidal transformer, bumped up power supply voltage to drive the pair of Mosfets to 105Ws of power. With the increased voltage and power came a decrease in handling lower impedance loads. After all, there is only so much you can ask from a pair of output devices. Both of these versions have gold front panel lettering and rear mounted heatsinks. The final version had blue and red lettering and can handle lower impedance loads with four output Mosfets per channel.



The ST-140 I purchased comes from the second generation. After delivery, I opened up the box and was greeted with a larger than expected amplifier. Though a lightweight compared to the Threshold S/500, it still has a substantial footprint. However, cracking open the case revealed mostly empty space! I suppose some of this is marketing as it is easier to sell an amplifier that looks big and burly compared to some lightweight case size.

First stop was my second system. Out came the Dynaco ST-80 amplifier and in went the B&K. The power difference between the two was immediately apparent as the bass on the KEF Q60s was deeper and more energetic. Spinning a few CDs and records revealed a warm amplifier with plenty of reserve. Treble seemed a touch rolled off, but was plenty smooth. This is obviously someone's idea of how a tube amplifier sounds and perhaps they are right on some level. But tube amps can run the gamut of "soft n' slow" to "rip your ears off" so I'll leave that comparison behind and move on to the main system.

With much back wrenching, I moved the Threshold S/500 off of the rack and installed the B&K ST-140 in its place. The ST-140 is a definite lightweight with a measly two output devices per channel. In comparison, the S/500 has twenty(!!) and can drive just about any insane load imaginable with plenty of reserve.

Spinning up some Blue Nile - "Hats" on vinyl gave the B&K a chance to show its stuff. The sound was very warm and inviting. This is an amplifier made for the music lover. Treble extension was lower than the S/500, but the overall effect was very pleasing. With the ST-140 bass was wooly and underdamped, but fun. Jackson Browne - "Running on Empty" revealed a midrange, that in comparison, was less detailed but was very pleasant. The overall sound was a little darker and more compressed than the Threshold, but it was so easy to sit back and spin records, allowing one's emotions to get carried away with the music. The experience was like listening to a great FM radio station!

The B&K ST-140 highlights the classic conundrum with high end audiophile gear - more resolution has the side-effect of revealing more flaws, lessening the appreciation of the music unless it is well recorded. It also challenges your front end more, shining a spotlight on cartridge, turntable and other flaws. An amplifier like the ST-140 diminishes flaws, having a darker, more "Yin" sound. It is pleasant, but in the end I felt like I was missing something.

Since this is an old amplifier, I still have some capacitor replacements in mind. It will be interesting to see how the character of the sound changes. Stay tuned!


System:
preamp: Threshold FET-10/HL
phono preamp: Audio Sector Phono Stage
amplifier: Threshold S/500
analog: VPI HW19 MkIII - Rega RB300 with Incognito wiring - Denon DL-103R
speakers: Magnepan 1.6/QR with Sound Anchor Stands
speaker cable: Kimber 4PR/8PR Bi-wire with banana jacks
Interconnects: Cardas Cross and Cardas Quadlink 5C


Second System:
Dynaco PAT-4 modified
Dynaco AF-6 tuner
Dynaco ST-80 amplifier
Panasonic linear tracking turntable
Pioneer DVD-V7400 cd player
various budget cables


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A Visit with the Denon DL-103R phono cartridge

With the success of my Audio Sector Phono Stage, I decided it was time to pair it up with a low output moving coil cartridge. Low output MCs can be expensive beasts, ranging from the low hundreds up to the price of a brand new car. The Denon DL-103 is known to be a giant slayer and has a number of users clamoring that it is one of the best sub-$1k carts around. However, looking at the specifications, the low output impedance made it's brother the DL-103R the better candidate. Why is that? The Audio Sector Phono Stage has a zero impedance, so gain is determine by voltage and output impedance. The DL-103R also features better coils and a little more compliance than it's less expensive sibling.

The arrival of the Denon DL-103R revealed a well packaged cartridge with a handwritten test note, a manual and a little cleaning brush. Installation on the Rega RB300 arm was a snap with a my protractor and digital stylus gauge. After everything was lined up, I dialed in the pressure at 2.5G and started spinning some records.

Right out of the box, the 103R is a nice sounding cartridge. Compared to the high output Dynavector 10X5, the sound is a little more laid back. Bass is also a touch reduced but perhaps this is just more control over the lower octaves. The midrange was amazingly clean, quick and utterly involving. The treble is a touch brash, but this could be the effect of a cartridge that needs some break-in or the revealing forward sound of my phono stage. Record noise is also a little more evident.

On Frank Sinatra's "Sinatra At The Sands", the left/right split of the instruments are laid out nicely with ol' Blue Eyes vocals taking center stage. Detail with the Denon was very good with nice hall reverberation and the picking out of individual instruments. When the band got going, the sound never got congested or uncontrolled.

Steely Dan - "Aja" is a complicated album with several time changes and tight drumming. Again the Denon kept everything in control, putting each instrument in the space given by the producer. Stunning, to say the least.

Dire Straits - "Love Over Gold" again showed a cartridge that could handle large dynamic swings and complicated instrument interactions. This was especially evident in the song 'Telegraph Road' where the volume levels crests and recedes with Mark Knopfler's guitar sweeping guitar keeping the musical thread sewn together.

In conclusion, the Denon 103-R is a choice budget low output moving coil cartridge. Any problems are sins of omission as my only complaints so far is the slightly etchy treble and perhaps the last bit of 'inner' detail is missing. But it still is an enjoyable cartridge that punches way above its price. As much as I would like to buy an expensive Dynavector or Shelter cartridge, I would prefer to spend my money on other pursuits - like buying more records!


System:
preamp: Threshold FET-10/HL
phono preamp: Audio Sector Phono Stage
amplifier: Threshold S/500
analog: VPI HW19 MkIII - Rega RB300 with Incognito wiring - Dynavector 10x5
speakers: Magnepan 1.6/QR
speaker cable: Kimber 4PR/8PR Bi-wire with banana jacks
Interconnects: Cardas Cross and Cardas Quadlink 5C


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