Rek O Kut Tips Redux

Rek O Kut L34 Rondine Jr. + S160 tonearm

 Although not quite in the same league as the Garrard 301, 401 and Thorens TD124 + MKII, this classic American turntable marque has a steady stream of enthusiasts and followers. 

I've learned a few more tricks to keep vibration and noise at bay since I uploaded Rek O Kut Tips in the early 2000s.

Old and New Rubber Grommets

Even if they all look alike, Lord rubber grommets have different weight capacities. Unfortunately, there are no tell-tale marks. I only learned about this because I asked one of the sellers.

ROK L34 motor

For the larger and heavier motor used in the L34/L37/B12, I recommend the rubber grommets sold by ebay seller 10stan.

Papst Aussenläufer used in the B12GH

The softer grommets sold by tdsbill provided much better vibration isolation from the smaller and lighter Papst Aussenläufer motor.

Under the chassis of a ROK B12GH

 

With proper rubber grommets installed, make sure the motor floats freely and is not jammed by untidy cable routing.

Talented machinists have been offering brand new idler wheels for Rek O Kut turntables in the $50 range. Since the bearings wear out, it might be more cost-effective to just get a brand new idler wheel from a reputable seller rather than getting your old idler wheel refurbished for $35-$40. 

The performance of the idler wheel in the center is as good as a refurbished original wheel with a good bearing.

Karmadon idler wheel for Rek O Kut L34/L37/B12GH

However, this precision idler wheel by Serge of Karmadon was a significant improvement in noise and vibration reduction over the stock and aftermarket units in the preceding picture. A meticulously grounded rubber wheel of proper Durometer rating is bonded to a hub milled from solid brass fitted with a sintered bearing machined to tighter tolerances. The performance gain was at par with using Audio Silente idler wheels on my TD124!  

1/4" ball bearing
steel vs. ceramic

There's a smoothness in the "feel" of turning the platter over a ceramic bearing even if I can't claim that I heard an improvement in sound. Some say the ceramic bearing can wear out the thrust pad, I haven’t noticed any wear on mine after almost 5 years. Use it at your own risk.

Rek O Kut B12GH + Grace G565G

Using the proper rubber grommets, routing the cables neatly, with a Karmadon idler wheel and a ceramic bearing, the only noise I could detect from the ROK B12GH was air-rush from the built-in cooling fins. However, I wasn't as successful in using it in a lightweight plinth like I was with the Garrard 401 and Thorens TD124. 

Rek O Kut L34 Rondine Jr.
+ 
Denon DA305

Unlike its more sophisticatedly engineered contemporaries from Garrard and Thorens, these Rek O Kut idler-driven turntables really need the help of a massive plinth to absorb noise and vibration.

JE Labs ROK L34 + SME 3012 and Excel ES801
DIY Plinth
ca. early 2000s

Cheap Thrills from Radio Shack + more

It's been three years since I blogged about Radio Shack's demise. I miss browsing at a Rat Shack store even more.😞 Through the years, a number of audio products from the Radio Shack Catalog  have caught the attention of budget-conscious Hi-Fi enthusiasts. 

I've already covered the 40-1354A 5.25" full-range driver and 40-1310 super tweeter in a previous entry. Below are capsule reviews of a few more Radio Shack audio goodies I've played with. Aside from the cool historical factor, IMHO, most can still equal or even outperform many entry-level audio gear today.

Realistic Pro 30 Headphones

The Realistic Pro 30 was introduced in 1981 for $39.95. Its price was reduced to $34.95 in 1983 and then to $29.95 in 1984. It made its final appearance in the 1986 Catalog. Instead of the usual dynamic drivers, these headphones were fitted with planar magnetic drivers, very unusual at this price point then and now.

It was one of the favorites in the orthodynamic round up thread started by wualta in headfi.org 15 years ago.

I got this pair very cheap because it needed new cables. In stock form, it sounds very smooth and refined. It can be tailored to 21st century tastes via judicious damping. The felt dot boosts high frequencies while the additional felt pad focuses the audio band a bit. New ear pads can improve the bass response since the flattened originals are no longer giving a good seal. Yup, speaker tweaks are applicable to headphones too!

Even if this is still a work in progress, I already prefer the sound of my modified Pro 30 to my Grado SR80. If you're patient, these turn up for around $30/shipped on eBay. 

32-1100A Stereo Mixer

 

I never got into DJ'ing/mixing but I couldn't resist this Stereo Mixer at a flea market for a couple of bills. It can be powered by 4 x AA batteries or a wall wart that can produce 6VDC at 35 mA. This mixer sports two magnetic phono preamps, 2 microphone inputs + 1 line level, tape out, a preamp output and a 1/4" headphone jack. No ICs or op-amps in the signal path as far as I can tell.

The headphone amp sounds very clean and has plenty of power for modern low Z headphones but may run out of steam driving higher Z or less efficient planars. I've even used this as a preamp in my near-field system with musically satisfying results!

41-2109 RIAA phono preamp

This outboard phono preamp was available in various permutations from the 70s to the early 90s. The circuit topology is very similar to the the above mixer but the sound is more dynamic and detailed due to the higher voltage rail powering the discrete circuit. 

41-2109 schematic

Some audiophiles claim that it can hold its own against tube phono preamps. It's good, but not THAT good. When pitted against my stock but refreshed Dyna PAS 3, it offered less resolution and was tonally more opaque. It was totally outclassed by my octal and loctal preamps. That said, I don't think you can find an RIAA phono preamp that can beat this bone stock unit for under $100.

 

Optimus LX4

Available only between 1995 and 1996, the LX4 achieved audiophile credibility because of Dick Olsher's review. It used the Linaeum monopole tweeter which provided a lot of air in the high frequencies without the sizzle of run of the mill domes. Unlike the paper coned Minimus 8 below, the LX4's Kevlar coned 4.5" woofer’s medium efficiency isn't as good in tracking micro dynamics. I voiced my original Simple 45/2A3 amp using a pair of Altec 755Cs in open baffles cross referenced to a pair of LX4s in the mid 90s.

Even if this was, and still is, a smooth and coherent sounding speaker at its price point, I wouldn't go as far as choosing this over the BBC LS3/5A. 

JE Labs Test Bench

A test bench isn't complete unless it has the facility to 'sound test' a freshly minted audio project or a newly repaired audio component.

Minimus 8

While I was a high school junior, I owned a pair of Minimus 8s driven by a Realistic SA-10. This speaker evolved from the Solo 103, which used various incarnations of the classic Fostex/Foster 103 4" paper coned full-range driver.

I got this ca. 1982 pair at Goodwill. Considering their diminutive size, these speakers are quite efficient at 89dB/1W/1M. To offset the upper midrange/lower treble tilt, these sound their best mounted flush against the wall. It's an easy load even for a 250mW per channel amp and provides nice background music while soldering.😉

The Realistic Stack

Top Right: Realistic TM-150, center right: Realistic SA-150,
center left: Realistic SA-10 (31-1982A)

Introduced in 1985, the TM-150 and SA-150 tuner/amp combo was riding on the mini-sized components trend of that era. The AM/FM TM-150 tuner has good sensitivity and can pull stations even in my basement shop via a simple omni antenna. 

 The SA-150 amplifier can trace its roots to the Germanium-equipped SA-175 amplifier from the late 60s, followed by the SA-101 from the mid-late 70s, which was succeeded by the SA-102 in 1980. Towards the end of the SA-102's production run, the accounting department tried their hand at circuit design and grafted an LA4440 IC chip amp on the same chassis.😡 This topology was carried over to the SA-150. Surprisingly, it doesn't sound bright or grating. On the contrary, it sounds dark and grainy.😞 It's ok for background music and has a value for the money MM phono stage.

Schematic of the SA-150 RIAA phono preamp
which can be accessed via the tape out
Note the similarity to the 42-2109 phono preamp 

The SA-150 was cosmetically altered in later years and was still available as the RCA SA-155 in the 2002 catalog.

Realistic SA10

Since I owned a Realistic SA-10 amplifier in my youth, I got inspired to search for another sample when I noticed the similarity of its circuit topology to the John Linsley-Hood 1969 Class A amplifier .

JLH 1969 Class A amplifier

Realistic SA-10 (31-1982A) amplifier section

However, the resemblance is only superficial since the JLH 1969 operates in pure Class A and the output stage is quasi single-ended while the Realistic SA-10 is a four transistor push-pull amplifier operating in Class AB1.

!!!WARNING!!! 

The voltages found in these circuits can be lethal! Proceed at your own risk!

Left: later version with IC chip amp
Right: earlier version with discrete solid state circuit

During its long life, the SA-10 was also subjected to cost cutting measures. The later 31-1982B sported IC chip amps in the output section.

Radio Shack could justify their use of IC chip amps on paper since I measured 700mW per channel from both versions. But the similarity ends in the test bench. Even if a different IC chip amp was used, the later 31-1982B also sounds dark and veiled just like the SA-150, whereas the all transistor SA-10 (31-1982A) has a more vivid midrange that reminds me of tubes.😊 

Loudness compensation bypassed + cap upgrades
31-1982A schematic

To be honest, I don't think the cap upgrades made a significant improvement in sound. I changed the output capacitors to protect my speakers and headphones in case of DC output in the speaker terminals due to leaky caps. However, I highly recommend bypassing the loudness compensation circuitry to remove the "Bose Wave Radio" crud.😆

With my DIY headphone adapter attached, the SA-10 (31-1982A) also does a good job as a headphone amp. The separate left and right level controls don't bother me and if I need more inputs I can press my 42-2112 audio source control selector into service.

 

42-2112 audio source selector

This source selector will extend one stereo input to three.

33-1009

If your amplifier doesn't have a headphone jack and puts out 2 watts per channel or more, you need this headphone coupler. This device has attenuating resistors inside to protect your headphone drivers (and your ears 😆) from getting fried.

Realistic SA101

The SA-101 was the unit that got away in '79 because it equalled the cost of my SA-10 + a pair of Minimus 8s. This amplifier hails from the generation of discrete solid state circuits. It has an RIAA phono preamp + two line level inputs, a balance control and 1/4" headphone socket. It's the ideal amp for a retro vinyl LP + headphone set up!😎

The amplifier circuit is virtually identical to the SA-10 (31-1982A) except for the increased voltage and beefed up power supply. Thus, my Fluke 87 measured 4V rms to an 8 ohm load or 2000 mW per channel. This may not sound like much but it drove most of the speakers in my collection to musically satisfying levels. Just like the SA-10 (31-1982A), it has some warmth and depth in the midrange reminiscent of tubes.😊

Why would I listen to the SA-101 and the early version of the SA-10 rather than their later IC chip amp brethren or the Class D chip amp I got from Parts Express a couple of years ago? 

First of all, I'm not a bass head and I don't listen at ear splitting SPLs. I also put more emphasis on sonic refinement which is easier found in flea powered amps (tube and solid state) designed by engineers who honed their skills (and ears) during the vacuum tube era, exemplified by Mr. John Linsley-Hood! 

Postscript

Ms. JE Labs' Office/Sewing Room Set Up

Tish’s office system consists of a Lafayette LA25A stereo integrated amp, fed by a Magnavox CD2000 CD player  + a Kenwood KT880D tuner. The components are flanked by a pair of Akai SW132 Jet Stream speakers.

The LA25A amp was OEM'd in Japan for Lafayette in the early 70s. This unit is very similar to the Lafayette LA25 sans magnetic RIAA phono input.

The Akai Jet Stream is a compact transmission-line (TL) cabinet manufactured in the Philippines in the early 70s. It supposedly contains a Fostex/Foster 103 driver variant. Unfortunately, I can't confirm this without disassembling the woodwork. 

This is a pretty good sounding speaker. The upper midrange forwardness inherent in the Fostex/Foster 103 driver is neutralized by the TL loading even if there's still not much activity below 90 Hz.

The speakers belonged to Tish's dad. He was a Filipino cardiologist and these Akai SW132s were the rear speakers of a quadraphonic system gifted to him by a patient. He also left behind a pair of Jensen Triettes and a Rek O Kut R34 belt drive turntable, which were part of his stereo rig while doing his fellowship in Cook County, Illinois in the early 60s. 

According to Tish, he was also into photography and developed his own negatives. Unfortunately, I never got to meet him. We would've enjoyed talking shop over ice cold beer since we shared a lot of common interests! 

JP's Western Electric WE757A Remake

 

Those were the words of the late Walt Bender in Part II of his Olden Golden Components article in Issue 51 of The Absolute Sound (TAS) in the Winter of 1988. This was my first exposure to Western Electric audio equipment. I eagerly awaited TAS's promised feature of Walt's Western Electric-based audio system but that never materialized. I let my TAS subscription lapse and replaced it with Glass Audio, Sound Practices and Vacuum Tube Valley. 

My only encounter with an original WE757A was a single unit being tested on the tailgate of a Honda Civic hatchback at a ham fest in the early 90s. Keep in mind that this speaker system predates the stereo era by at least 10 years, thus, they were never available in stereo pairs.

In this day and age, the only way a mere mortal can experience a Western Electric WE757A speaker system is to build one using as many of the original parts as one can gather.

This is exactly what John Piro did. He combined a WE/Altec 728B driver with a slightly dented dust cap + the botched up KS12027 he expertly repaired to properly mount an Altec 802D compression driver. 

Then he painstakingly cloned and crafted a WE757A cabinet to house these components. Soon after the speaker system was completed, we met at the Kutztown Fall 2019 Radio Show and he entrusted the evaluation of this speaker system to me.

In keeping with JE Labs methods, I started by evaluating the drivers individually and then compared the JP WE757A to my Altec 753C. I was fortunate to have had lots of time to dissect and enjoy the JP WE757A. Thanks, JP!

WE/Altec 728B

When I visited J-Rob in the summer of 2018, I spent quality time listening to his pair of WE728Bs while talking shop. The very rich harmonic overtones they produce captured my attention just like a fine violin does.

The smaller Altec decal is pasted over the larger Western Electric original. 
JP surmises that this unit started life as a WE728B which got damaged early on 
and was re-coned by Altec using an original WE re-cone kit. 

Technically speaking, the WE/Altec 728B is neither a woofer nor a full-range. It's a wide-range speaker. The RTA trace shows a seven octave range, which pretty much mirrors the original 60-10,000 kHz specification. 

WE/Altec 728B

The 728B tonal balance is very much like its smaller brother, the 755A, with an additional octave of extension in the bass and about an octave less extension in the highs. This and the Altec 414A are the only 12"-15" drivers that I've heard (so far) which don't break up in the 1-2kHz range resulting in shouty female vocals, amongst other nasties.

Dented dustcap

From the upper bass to upper midrange, the 728B has the J-Rob  coined "snap," which it shares with its 755A and 756B siblings. IMHO, these permanent magnet drivers are unparalleled to this day for their life-like midrange and ability to convey a three dimensional realism. OK, perhaps the Western Electric and GIP field coil drivers are even better but as I said earlier, this article is for mere mortals.😉

WE754A vs. WE728B

In the midst of my evaluations, I exchanged private messages with another Western Electric aficionado who's had the rare 

opportunity to compare the WE754A and WE728B drivers. He is currently assembling a pair of WE757As.

 

 With his permission, I'm sharing his valuable listening notes. Thanks, Jonas!

Just wanted to let you know what’s going on with my 757 style speakers. I was blessed to find a WE 728B in an old console in pristine condition. I was able to compare the 754A and the 728B and I liked the 728B much more. The 754A has perhaps a bit more lows but a thicker lower midrange, and less detail and dynamics, and not as smooth as 728B. Compared to other speakers they were very smooth, but when I heard the 728B with a complete absence of grain or distortion, the difference was apparent. They sounded great on things like Gerry Mulligans Baritone Sax on Night Lights. The 754A’s are made for that sort of thing and I think those who love thick midrange would really enjoy them. But they also didn’t have quite as much highs, at least to my ears. I ran them full range so it would have been nice to try out different crossovers to see if the 754A would have been better with a lower cut off. Perhaps so. 

Anyway, I sold both 754A speakers to a young gentleman from NYC who's uncle is a big WE collector from Korea and it was very cool to meet such an WE enthusiast. The uncle came by to listen to them. He apparently has original 757 speakers among many others and said he uses PX-25 tube LS in his amp. With that money I found a second 728B in similar shape to my other, and they are now installed in the John Piro cabinets. 

I do wonder about the differences of the 754A and 728B in the intended applications. The 754A came before the 728B. There is some a lot of talk about it (a bit of ad copy hyperbole but very interesting still) in this issue of Oscillator Magazine, which was put out by Western Electric. Amazing that they put that much time and effort into a trade publication, and to think of what went into the design of these. 

It seems they created the 728B as an updated or “improved” version of their 754A. What I’ve heard is that the 754A has a copper wound voice coil while the 728B had aluminum. Also there’s the obvious difference in magnet structure and power handling.

They sure sound very different. The imaging and spatial depth is far better in the 728B, at least in these cabinets. The 754A seemed to beam more. Of course the published specs aren’t much different nor are the dispersion characteristics listed in the WE specs, but the 754A seemed to beam more in my cabinets. It’s almost like the 728B strip out any unnecessary frequencies and things have a nice space and clarity while the thick midrange of the 754A brought certain instruments out front at the expense of this clarity and separation of instruments. At least to my ears.

So, part of me wonders if they had just made the theater speakers earlier, designed using the 754A, if they were just trying to use up stock, or if there was a specific reason to use them instead? The 754A is slightly more efficient by 1db, and it seems to play a bit lower and have more low range frequency happening even if they go to the same rated frequency range according to their literature. (it was hard to be sure if the 754A went lower, but the lows were more filled out).

Perhaps this increase in lows, even at the expense of clarity and spacial clarity between instruments, was the reason they were used in the theater amps.

Regardless. It seems that WE put considerable thought into the new 728B. I prefer the 728B a lot myself. I wish you could compare them and do a write up! I really look forward to your future blog posts. 

Best,

Jonas Baker

WE/Altec 728B vs. Altec 414A

Altec 414A

The 414A has finally met its superior adversary. In direct comparison with the 728B, the sharp roll off around 4kHz makes the 414A sound less snappy and comparatively muffled.

Altec 414A

The main asset of the 414A over the 728B is a little more than half an octave of extension in the bass range and a couple of dB more in efficiency. In spite of the 728B's obvious superiority, my admiration for the 414A remains, much like my fondness for the 755C.😉

KS12027 vs. Altec 32C

KS12027 horn

KS12027 + Altec 802D + 20275 diaphragm

Since my capsule review last year, I learned more about the nature of the KS12027 horn. The KS12027 surpasses the 32C and Azzolina KS12024 in presenting distinctive harmonic overtones from lower frequency instruments like cellos, basses and, believe it or not, even from the tympani. Vocals and acoustic instruments are uncannily real and three dimensional, just as they are with the 728B, albeit scaled to small format horn proportions. 

When I compared the Altec 32C to the KS12024,  I noted a distinctive "in your room" presence with the latter. This quality is even more prominent in the KS12027, which is another multi-cell type horn.

 

Altec 32C horn

Altec 32C + 802D + 20275 diaphragm

Comparatively, the Altec 32C sounds more laid back than the KS12027. Vocals and lower frequency instruments like cellos and basses had less of the life-like harmonic overtones rendered by the KS12027. High frequency transient speed is also slightly slower. Thus, brushed cymbals and high hat tend to have a splashy quality instead of lightning fast attack and decay coming out of the KS12027.

Although the 32C has the wispy airiness at the extreme top end which the KS12027 wasn't able to match, the addition of the Altec 3000H was not as successful as my previous experiment with the Azzolina KS12024. I think the 3000H can't quite match the transient speed of the KS12027.

I've said it before and would like to emphasize further that the KS12027 is the most natural and real sounding small format horn I've listened to. 

Simple Crossover

Since I don't have access to the original WE702A crossover schematic of the WE757A, I made a simple high-pass 1st order crossover hinged at 5kHz and ran the 728B unobstructed. Definitely not optimized, but good enough for me to enjoy the speaker system.

Altec 753C vs. JP's WE757A

All my listening was conducted using the je2a3 mono integrated amp with Hashimoto H203S output transformer, fed by the following sources: Gates CB77/Gray 108B/GE RPX and Neat P58H/Calrad SV16/DL102, Magnavox CDB650 transport > Arcam Delta Black Box DAC.

Altec 753C

The Altec 753C is very lush and romantic. It gives a middle of the hall presentation compared to JP's WE757A. Its only advantages over JP's WE757A are: almost an octave more bass extension (albeit with less definition), a couple dB more of efficiency and the wispy airiness in the very extreme top end noted earlier in the 32C/802D pairing.

JP/WE757A

Typically, components with similar qualities don't complement each other because their virtues cancel out. However, in this particular case, the WE/Altec 728B + KS12027/802D was an utterly cohesive and coherent blend.

JP's WE757A sounded neutral and more analytic in a very musical way. Transients come across crystal clear and clean. Dynamic nuances at macro and micro levels are also much better conveyed. Even if the music is presented closer to the stage with greater detail and resolution, I didn't experience long term fatigue. 

In spite of the slightly less bass extension vs. the Altec 753C, definition was better. Due to a tad less efficiency, it can benefit from slightly more power. Perhaps an SE300B amp would've improved bass extension and dynamics further.

The sense of realism from its three dimensional midrange is a result of the life-like harmonic overtones produced by the 728B + KS12027/802D pairing.

The Altec 753C set a very high musical standard but JP's WE757A cabinet remake + Altec 728B + KS12027 horn + Altec 802D is more organic, finer and nobler in stature. It brought me closer to the music! 

Now I'm asking myself, how much better would it be with the original WE713C compression driver and the optimized WE702A crossover?

The WE755A, WE756A, WE754A, WE728B, WE753C, WE757A, etc. came from an era when America was at the height of its industrial might. The amount of R&D that went into these transducers will never be equalled. Sadly, these are more appreciated in Asia and Europe.

To add insult to injury, many American audio hobbyists even sneer at these foreigners who pay top dollar for these American-made classics. This gives credence to the saying, "no one is a prophet in their own land."