A Visit with the B&K Pro-5 preamplifier

The interest in my hobbies wax and wane depending on what else I am doing with my busy schedule. Lately I have been writing, publishing, weightlifting and enjoying time at the beach. With the end of summer, I suddenly had the urge to mess with some audio gear. Since I needed a ‘backup’ to use in case my vintage Threshold FET-10/HL or Audio Research SP-7 preamplifier went down for repairs, I opted to buy a full-function unit. With a B&K ST-140 already in the stable, why not try a matching preamplifier? So I went and bought a B&K PRO-5 for $195 via Audiogon.


Upon arrival, I opened the box and was greeted by a nice looking unit. The gold lettering, handles, and black faceplate are conservative in an 80s kind of way. The back has a number of RCA jacks that appear to be of questionable quality – they look nickel-plated and are soldered directly to a rear-mounted PCB board. The selector switch has a nice solidity, but the other controls feel on the low-rent side.


Cracking open the case, I found the parts quality to be rather pedestrian. For example, the volume, balance, treble and bass pots are small carbon units that look like something you would find on a 1970s receiver. The power-supply is a joke with a tiny transformer, a pair of 1000uf capacitors, and a pair of 15V regulators. The phono stage uses a few capacitors, FETs or transistors, and some op-amps involved. The same is true of the linestage and tone-controls. There really is nothing here that screams AUDIOPHILE with big bold letters, but let’s see how the B&K PRO-5 sounds.

Removing the ARC SP-7 from my second system was easy enough. I then hooked up the turntable to the new preamp phono input and then connected the line outs to the ARC D-52B amplifier. I switched on the preamplifier and the front rocker light turned on with a pleasant glow. With my first record, I was greeted with sound alright, but the left channel was missing. I wiggled the back RCAs and *pop* I started getting sound out of both channels. Obviously these RCA jacks are going to be troublesome for long-term use.

As far as sound in active mode with the tone-controls bypassed, the B&K PRO-5 has a pleasant, slightly warm sound. Some treble detail is a little glossed over, but the bass is good and punchy. Overall depth and soundstage width is a little squashed, but this is certainly a better overall-sound than many other budget preamplifiers I have heard – which is quite surprising considering the lack-luster parts quality. But if there is anything that I have learned from this zany hobby - it’s that you have to trust your ears and not your eyes.

I mentioned the ‘active mode’. You see, the PRO-5 allows you to bypass the active linestage with a push of the button. In this passive mode, the gain understandably drops and you have to crank up the volume control to get the same output as before. But the sound, though less punchy, becomes more neutral. It’s almost like having two preamplifiers in one box. As far as what sounds better – that’s entirely up to your system and musical tastes. Perhaps it is the psychological effect of having to turn up the volume control so much, but I preferred the active linestage for most of my pop/rock music. With classical music CDs, the passive section was given the nod.

In overall quality - both sound and mechanical - the Audio Research SP-7 still wins. It is a little brighter and brasher in comparison, but the overall sound is more neutral. Of more importance - especially in a system that is heavily used by my family - the ARC has much more solid connectors plus a positive volume and selector-switch action.

Note - during my listening sessions with the B&K Pro-5, I found the RCA connections to be very problematic. Later versions apparently used better parts, but for owners of the older model, you are stuck with some very poor connectors. Replacing the RCA jacks with something sturdier looks like a difficult task, but I’m going to give it a try. So stay tuned for a future update.

Second System:
Preamplifier: Audio Research SP-7
Amplifier: Audio Research D-52B
Analog: Dual CS-5000 turntable - Audio-Technica AT95E cartridge
Digital: Pioneer DVD-V7400
Speakers: KEF iQ30
Speaker Cable: Canare 4S11 Quadlink
Interconnects: Cardas Crosslink

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A Visit with the KEF iQ30 speakers

KEF was founded in 1961 by electrical engineer Raymond Cooke. KEF is known for several products, including the BB110 bass driver and T27 tweeter used in the famed LS3/5A broadcast monitor. Through the 70s and 80s, they pioneered the use of new materials and porting to speaker construction. 1988 saw the introduction of Uni-Q which became their signature driver. It’s a time-aligned coaxial driver using a neodymium tweeter where the dustcap is normally located. This unique construction allows KEF speakers to act like a true point-source and has excellent dispersion for listeners sitting off-axis. In the past, I’ve reviewed the vintage KEF C-75, Q30 and the Q60 speakers that first used the Uni-Q. I’ve always enjoyed these older speakers for their smooth midrange and coherent character. With a rounded treble and warm bass, their faults were always of omission– a perfect speaker for budget components and lower quality recordings.

When I decided to replace my Q60s with something that would better fit our latest decor, KEF immediately came to mind. So after some research, I purchased a pair of new iQ30 speakers from accessories4less.com for $399. The iQ30 is a bookshelf speaker that uses a 6.5” Uni-Q driver inside a curved cabinet to minimize internal reflections. Of interest is the tangerine phase plug which reminds me of something that Altec-Lansing used on their vintage horn drivers.

Since this is a small speaker, I also needed to buy a pair of speaker stands. I decided on a pair of VTI UF Series stands from Racks and Stands. Sitting at 24 inches tall. these stands can also be filled with sand to increase stability. Since I have cats and kids, I went this route.

So how does the iQ30 stack up against its older brethren? Let’s find out.

I received the iQ30s three days after placing my order. Packaging was excellent and the speakers arrived without a scratch. This is one great looking speaker with a modern shape and look that works well with the Ikea Expedit shelves I use to store my records. However I found the stock bi-wire links to be troublesome so I replaced these with 18awg bare wire. I then replaced the Q60s with the VTI stands before placing the iQ30 speakers on top.

Initial listening impressions were very impressive. For such a small speaker, the sound is quite dynamic and punchy. The lowest bass is pretty much non-existent which is to be expected for a 6.5" driver. However the upper bass is very good and with pop music, I certainly don't feel like I'm missing much at all compared to the 8" driver in the KEF Q60. For such a small speaker, the iQ30s sound bigger than I expected. I used to run a pair of vintage KEF Q30 tower speakers which also use a single 6.5" driver, but they sounded nothing like this modern iteration of the Uni-Q. In comparison, the iQ30s have more definition, speed, treble extension and detail. Extended listening smoothed out the slightly aggressive treble and increased the resolution even further.

Though the KEF iQ30s are surprisingly dynamic for their size, listeners of bass heavy music will be happier with a larger speaker or an added subwoofer. But for the price, the iQ30s punch way above their class; offering a taste of high-end audio that is highly addictive. Resolution is excellent as is soundstage depth and width. There is a coherency to the sound that reminds me of speakers costing much, much more. Highly recommended, but with caveats since they are limited in bass and will work better in smaller rooms.

Specifications:

Power rating: 15-120W
Input impedance: 8 ohms
Tweeter: 0.75" aluminum tweeter
Midrange: 6.5" bass driver
Crossover: 2.5kHz
Cabinet design: Bass-reflex, ported cabinet
Sensitivity: 89dB
Maximum output: 110dB
Frequency response: 45Hz - 40kHz
Dimensions: 8.7"W x 14.4"H x 12.9"D ea
Weight: 14.8 lbs ea

Second System:Preamplifier: Audio Research SP-7
Amplifier: Audio Research D-52B
Analog: Dual CS-5000 turntable - Audio-Technica AT95E cartridge
Digital: Pioneer DVD-V7400
Speakers: KEF Q60

Speaker Cable: Canare 4S11 Quadlink
Interconnects: Cardas Crosslink

Update (03/26/13): It's rare for me to keep any audio component for so long, but the KEF iQ30 is a good looking and very competent performer.  I recently swapped them for the Spica TC-50s, using the KEF speakers in my main system.  I was very impressed - they handled bass and dynamics better than the Spicas, all while having a much more coherent sound.  With the improved front end and Eico amplifiers, they really do punch higher than their price suggests.  So now the Spicas reside in the second system while the KEFs stay with my more expensive setup.  In the future I would like to explore some more KEF products - perhaps the LS50 or Q300 monitors.

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A visit with the Audio Research D-52B power amplifier

With the arrival of summer, a young man’s (*cough*) fancy turns to power amplifiers. Okay, maybe not. Lately I’ve been more interested in looking at wooded property to buy, walking on the beach and trying to remember what it actually feels like to be a young man. I’ve also been modernizing my 1948 Bungalow into something a little more tasteful. To my eyes, a good-looking stereo always helps and since my recently acquired Audio Research SP-7 needed a playmate, I decided to purchase a matching amplifier.

Trolling through Audiogon the past few months has been interesting because Audio Research gear certainly holds its value. You see, I wanted an amplifier for a future speaker upgrade - perhaps Magnepans – so I was holding out for something with a bit of power. After passing by several expensive amplifiers, I finally gave in and purchased an Audio Research D-52B for only $350.

The original D-52 was introduced in the heady days of 1978 – famous for disco, punk rock and Jimmy Carter. The D-52B revision came out in 1979 and originally sold for a then expensive $995, later increased to $1295 and then $1395. Rated at 50Ws per channel into 8-ohm and only 80Ws per channel into 4-ohms, the D-52B isn’t exactly a powerhouse. But under the lid, you can see a massive transformer flanked by a large number of power supply capacitors. This is one underrated amplifier that should be able to deliver a nice wallop of short-term peak power.

Early Audio Research solid-state gear was met with derision by the audiophile press at the time. That is hardly unexpected since ARC was one of the few carriers left of the mystic tube flame. The introduction of solid-state gear certainly made them few friends and based on the number of Audiogon ads, they have certainly sold less SS than tubes. When I bought my solid-state Audio Research SP-7, sound quality was actually second-tier in my decision. I just wanted something reliable with quality long-lasting controls. However to my surprise, the SP-7 not only worked well, it sounded great.

So how does the Audio Research D-52B sound? Let’s find out.

When I first received the D-52B from the FedEx, I was surprised by the weight. This amplifier weighs in at a nice 39 pounds but still has a relatively compact size. As usual with ARC gear, build quality is high. Removing the lid revealed the previously mentioned large power transformer and (in this case replaced) power-supply capacitors. There are also four output devices per channel, a quality circuit board, and the much-hated but mysterious Audio Research “Analog Modules.”

The first stop was my second system which is to be the eventual home of this amplifier. I removed the Mitsubishi DA-A10 and installed the Audio Research D-52B. Since neither of these amplifiers has a proper power-supply switch, I used the switchable powered AC jack from the Audio Research SP-7. The two ARC pieces with their silver-faces, black handles and high-quality lettering make for a handsome pair. Turning on the SP-7, I was greeted with a nice green LED glow from the D-52B.

The KEF Q-60s in my second system are remarkably forgiving . They aren't all that detailed and the treble has a nice roll-off which helps out the worst of recordings. But even through these limitations, I can tell that the D-52B has more treble detail and apparent speed than the Mitsubishi DA-A10. Dynamics through the 8" Uniq driver are very good as is the overall sound. Though not as "rich" and "full" as a vintage tube amplifier, the D-52B seems to be quite transparent and resolving. I won't mention soundstaging or depth since this second system setup is woefully inadequate for that type of listening because the speakers are too close to the wall and the source quality is too low. At this price level, I'm listening for frequency aberrations and general fidelity. Paired with Audio Research SP-7, this is a surprisingly good system for the money. I'm looking forward to replacing my KEFs with something even better, bringing the my second system even further along.

The second stop was my main stereo rig. The Magnepan 1.6QRs are notorious for their current-sucking demands, so I was interested in seeing how this little amplifier would fare. The last amplifier I tested here, the B&K ST-140 rated at 105WPC, was capable enough but was a notch below the Threshold in sound quality. As usual, removing the mighty Threshold S/500 from the rack was a chore. In comparison the D-52B looks like a pipsqueak but sometimes good things come in small packages.

This turned out to be an unfair comparison against the Threshold S/500 which has five times the amount of available power. At higher listening levels, I could tell the D-52B was running out of steam. Mind you, it never clipped harshly, but dynamics became squashed and the soundstage flattened. However, at moderate listening levels or with less dynamic material, the ARC amplifier turned out to be quite pleasant. Though detail and depth seemed less than the Threshold amplifier, the overall sound was still quite musical. An example of this is my original pressing of Neil Young - Tonight's the Night. Through the Threshold amplifier, I can really get a great sense of the room and it almost feels like you are there. With the Audio Research D-52B the lower resolution leads to less space and depth, minimizing the illusion. However, along the width of the soundstage, every instrument kept its proper place. Voices were very natural sounding as was the treble extension. From Blue Nile to Neil Young, the ARC was a competent amplifier that only suffered when asked for more power than it could deliver.

The Audio Research D-52B is by no means a perfect amplifier, but it is much better than I expected. Since this is a relatively ancient design, I'm also willing to cut it a little slack. With only 50Ws of power, it's really not up to the task of driving inefficient speakers unless you have a small room or prefer lower listening levels. It's also not a particularly resolving amplifier or one that captures the total possible depth from a recording. However, it certainly doesn't deserve the bad press it has received - at least from a sonic point of view - I will have to wait and see about the reliability. But nonetheless, for a second system or for one just built around musical enjoyment, the Audio Research D-52B is an excellent performer. Recommended but with caveats.

Second System:
Preamplifier: Audio Research SP-7
Amplifier: Mitsubishi DA-A10
Analog: Dual CS-5000 turntable - Audio-Technica AT95E cartridge
Digital: Pioneer DVD-V7400
Speakers: KEF Q60
Speaker cable: Canare 4S11 Quadlink
Interconnects: Cardas Crosslink

Main System:
Preamplifier: Threshold FET-10/HL
Phono Preamplifier: Audio Sector Phono Stage
Amplifier: Threshold S/500
analog: VPI HW19 MkIII with SDS - 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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Fixing a Speed Issue with the Dual CS-5000 turntable

My Dual CS-5000 turntable has been having speed issues of late. The platter speed would start out slow and take time to get up to speed. Sometimes in the middle of an album, the platter speed would also minutely drop, effecting the tone of the music. A quick perusal of Google and I found that the power supply capacitors for the DC motor are known to go bad. Since electrolytic capacitors of this sort are inexpensive, I decided to go ahead and replace the originals.

To replace the power supply capacitors - first remove the lid, mat and turntable platter. Also remove the rubber belt at this time. Make sure the turntable is unplugged before proceeding.

The capacitor circled in GREEN is a 2200uF/25V unit. Polarity is indicated on the board, but as a note, the positive side is closest to the spindle. Removing it is easier with a solder-braid or sucker - if those tools aren't available, you can pull on the cap and slow ease it out by alternating your solder iron on each leads. Don't go too hot with your iron or you will risk damage to the PCB board.

The capacitor circled in RED is a 3300uf/35V unit. It's built different than the other unit - with three ground lugs on the edge, soldered onto the board. The positive lead is in the middle, soldered in the board. To remove, I cut out the top lugs and removed the solder on the bottom lug and positive lead. For replacement, I tied the negative lead to the topmost ground lug position closest to the spindle. The positive lead was obviously soldered to the original positive position.


I hate modifying or fixing gear that I really like, but any fears were laid to rest when I fired it up after reassembly. Now the turntable gets up to speed faster and doesn't have any tonal variance issues. Hurrah!


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A visit with the ATN95HE stylus

The Audio-Technica AT-95E cartridge is a budget best-buy. For only $49, it has a great sound that works well for entry-level turntables. With my Dual CS5000, I've put many hours on my AT-95E and enjoyed every moment. But (and there are always caveats at this price range), overall detail and treble extension is certainly lacking compared to more expensive offerings. The sound was very "midrangey" and a little muffled up on top. It is, however, a great tracker and does well with inner-groove distortion.

Since my cartridge was getting a little worn from use, I decided it was time for an upgrade. At only $59.95, I decided to just replace the stylus with LP Gear's AT95HE. The whole cartridge is also available. This "hyperelliptical diamond stylus mounted on a thin-wall Zualam tubular cantilever" was an easy swap since I just had to pull the old stylus out and replace it with the new one. The new cantilever/diamond is more delicate looking and should (in theory) track better too.

The great midrange character of the original is still evident, but treble extension is now much, much better. Perhaps it is just the effect of the treble extension, but detail and transparency has been bumped up a notch. There is an overall refinement to the sound that starts to knock on the door of true audiophile quality.

Overall, a great upgrade to an already great budget cartridge. Very recommended!


Second System:
Audio Research SP-7 preamplifier
Mitsubishi DA-A10 amplifier
Dual CS-5000 turntable with Audio-Technica AT95E cartridge
Pioneer DVD-V7400 DVD player
KEF Q60 speakers
various budget cables