Saturday, March 18, 2023

Musicmaster Model 12 (Gray clone) Tip + GE VRII Hack

Canon P + Canon 50mm f1.8 
Foma 100 in Rodinal 1+50

After many decades of collecting and using classic audio equipment and film cameras, I've learned to accept that sometimes I win, sometimes I lose, but most of the time I break even. And the only reason there is that possibility of breaking even is because I learned to DIY.

This tonearm came with a KS Musicmaster Model 25B12GST idler-driven turntable, which I thought I could resuscitate. Alas, the turntable was beyond saving because a lot of important parts were missing. The tonearm had no head shell slide and the cartridge pin contact points + wiring harness were gone. For many years this tonearm was boxed up along with other parts units sitting in storage.

One day I had an epiphany - will the Karmadon head shell slide fit? 

 I'm happy to report that the two types of head shell slides that my buddy, Sergiy, manufactures for his Gray Research tonearm clone work on this Japanese clone as well as on my original Gray Research 108C. Above left is a solid shell and on the right is a shell with a hole to accommodate the triple play feature of the General Electric RPX and VRII mono cartridges. 

Despite the carnage brought upon the Ukrainians by a deranged autocrat, my Karmadon head shells arrived in less than two weeks. We really have to admire and support these people!

I rewired the tonearm and blu-tacked 4 pennies to make up for the lost hardware.


A blob of 600,000 cSt silicone fluid was injected into the uni-pivot bearing cup.

Since the Karmadon head shell slide is lighter than the original, I used all three copper weights Sergiy provided, added 2 x 5 centavo coins + the GE VRII cartridge = 25 grams. 


I misplaced my VRII cartridge pins ๐Ÿ˜ž...but after a bit of head scratching, I hacked two tube pins from a dead octal based tube and soldered them to the signal wires.๐Ÿ˜Š

Voila!๐Ÿ‘

For more viscous damped tonearm set up information, please click here!

 Even with my 20+ years of experience using this tonearm, it took me a while to dial-in the proper weight compensation due to the missing hardware + adapted head shell slide. Getting a viscous damped tonearm to function properly isn't for the faint of heart and requires patience. If you don't possess these virtues, I suggest you don't consider using one. But I must say the results are well worth it!๐Ÿ˜Š

Musicmaster Model 12 + GE VRII

Let's listen to a few monaural hifi tunes!

๐ŸŽถ๐ŸŽป๐ŸŽน๐ŸŽท


Saturday, March 4, 2023

Japanese Idler-Driven Turntable Part 2: NEAT P58H/Shield MO-19



In the early 2000s, the swinging tonearm mount of the Shield MO-19 caught my attention because it looked like the perfect partner for my Velvet Touch viscous damped tonearm. It turned out that this Japanese 4-speed idler-driven turntable is actually a rebadged NEAT P58H. 

Its performance exceeded my expectations! So instead of relegating it exclusively for mono hifi playback duties, I also enjoy using it fitted with high quality tonearms like the Audio-Technica AT1501-IIDenon DA305, Grace G540LFidelity Research FR54 and others for stereo LPs.

I got this NEAT P58H + Tokyo Sound ST900 tonearm when Tish and I returned to the States in 2016. It wasn't as well kept as the MO-19 and required a bit more fettling. 

The turntable is built on a heavy duty cast chassis with a 1.5 kg cast aluminum platter. Aside from a few discussions in audio forums, the only literature I've found about this particular model is the 1960 NEAT catalog available for download at vinylengine.com.

Everything I've done to my NEAT P58H and Shield MO-19 is documented below. 

Idler wheel + idler arm

The rubber on this NEAT P58H idler wheel was in good condition except for a pinch, which couldn't be removed by minor grinding. So I sent it to Terry E. Witt for new rubber.

Terry of Terry's Rubber Rollers did a great job rejuvenating the P58H idler wheel (above left) + another wheel for my ROK L34 Rondine Jr

Idler wheel installation sequence

The idler wheel should spin freely and quietly after a drop or two of blue 3-In-One SAE 20 motor oil

Idler arm reassembly sequence

The idler wheel arm action should be snappy. If it isn't, back off the nut a bit and/or add a bit of light oil to the sliding surfaces.

A good balance between speed accuracy, torque, and low noise can be achieved by adjusting the idler wheel contact pressure to the inner rim of the platter.


Unplug the turntable from the AC source and manually spin the platter CW or CCW. The platter should gently stop when the speed control knob is turned to any of the speed settings as the idler wheel engages the inner rim of the platter. If the platter stops abruptly or doesn't stop at all, go back to the preceding procedure and adjust the idler wheel position on the idler arm accordingly.


60 Hz pulley dimensions +
red arrow indicates the pulley's set screw for height adjustment

While the turntable is disconnected from the AC source and the speed selector set at 33 rpm, I set a 1-1.5mm clearance so that the idler wheel doesn't touch the shoulder of the 45 rpm step.

Speed Selector Mechanism

With the speed selector at the 78 rpm setting, make sure there's no clearance between the tip of the set screw and the piston which raises and lowers the idler wheel arm mechanism.

Before we move on, how about a track from Style Council?

Motor


The turntable is powered by a fairly substantial 4-pole hysteresis synchronous motor. 

It's not as hefty as American-made Ashlands and Bodines, but bigger than the TD124's E50 and comparable to those fitted to the Garrard 301401, and the ROK B12GH's Papst Aussenlรคufer

 Through the years I've gotten requests for a schematic because some of these turntables were hastily pulled out of installations by flippers for quick bucks on eBay. 


Spring suspended motor = less vibration

Top view of the motor + sub-chassis

The deteriorated bottom rubber mounts (red arrows) can be replaced with rubber grommets

To remove the motor, unsolder the motor wires from their respective connections. Use my hand drawn schematic above as a guide. Then, remove the four nuts marked with blue arrows.

Before pulling out the motor entirely, I marked its orientation (black arrows) in the sub-chassis for easier reassembly.


To disassemble the motor, remove the four nuts marked by the yellow arrows.

Motor parts ID

The top and bottom shells house the sintered bearing well and are almost identical in construction except for an exit hole on top for the motor spindle. I marked the partially visible sintered bearings (or bushings) with blue arrows. To access the bearings for cleaning, remove the spring clips marked with green arrows. 


As shown in the picture above, the bottom shell has a thrust pad. I clean sintered bearings by soaking them in solvent, either lighter fluid (Naphtha) or isopropyl (91% or greater) alcohol (IPA) overnight. For lubrication, I use blue 3-In-One SAE 20 motor oil

The parts inside the bearing well are numbered in sequence for reassembly.

To access the motor bearing, remove the bottom cover, which is held by three small screws + lock washers. Be careful not to lose the tiny 3mm ball bearing. Clean all the components with either Naphtha or IPA. The numbers indicate the sequence for reassembly.

The motor should now be whisper quiet in operation.

Let's take a break and hear a tune from Sinatra at the Sands LP.


Main Bearing


Just like the Shield MO-19, I also found old grease at the end of the threaded bottom cap of the main bearing of the P58H. The lack of an oil seal in the threaded bottom cap further confirms that this is a grease bearing design.

These are the main bearing components after cleaning (soaked in solvent overnight). They're ready for fresh grease and reassembly. I used Phil Wood grease left over from my Raleigh 20 restomod folding bike project

The Garrard 301 grease bearing makes the NEAT P58H bearing look diminutive.

CODA

Although innovative in its own right, the various pictures show that the mechanical design and manufacturing quality of the NEAT P58H/Shield MO-19 isn't quite as sophisticated as the illustrious Garrard 301, 401, or Thorens TD124. I never envisioned it to equal those revered models in terms of performance. However, IMHO and experience, a reconditioned NEAT P58H is a worthy alternative to a restored Lenco or Rek O Kut.


A nice ballad from Dexter Gordon's album Go brings us to a close.

HAPPY LISTENING!


Back to Part 1






Saturday, February 4, 2023

Two Unknown Magnetic Phono Cartridges


I found this interesting phono cartridge on eBay for under $30 shipped. 

It was advertised as a vintage Sony magnetic cartridge. After clicking Buy It Now, I asked the seller for more details. Sadly, my inquiry fell on deaf ears...


My instinct pointed towards an early Audio Technica OEM. However, the chunky plastic body doesn't exactly match the AT-1, AT-3, AT-3M or AT-5 featured on this Japanese website.


The stylus assembly is very similar to that from the AT-5


But the body shape is somewhere between an AT-1 and AT-3S.

  
After getting a feel of cantilever compliance and seeing the bonded conical stylus under a USB microscope, it felt safe to set VTF at 3 grams. The stylus has yet to skip a track!

Although not quite as dynamic, the tonal balance of this vintage cartridge is reminiscent of my all-time favorite Shure M3D. I’ve listened to it extensively mounted on the Tokyo Sound ST900, Fidelity Research FR54, and Bokrand AS309. I would've recommended this cartridge highly as a nice budget alternative to the M3D or M7D IF the eBay seller didn't go AWOL.

I posted about these cartridges at HifiHaven.org and member Fran604g uploaded pictures of a red version of this phono cartridge. The box is marked CM500 stereo moving magnet cartridge.


 A video of the vintage cartridge tracing an Abbey Lincoln track.


While debating whether it was still worthwhile blogging about a mysterious vintage cartridge that can't be found anywhere, an elongated box arrived at our doorstep.


Inside the ginormous box was a tiny little box. Apparently someone in the packing department couldn’t care less about conservation.


It turned out to be my order for a phono cartridge, which showed up on my feed while I was searching for Blue Note Jazz LPs on Amazon. No literature was provided aside from the stickers on the outer box and plastic protective case. The cartridge isn’t even identified with a trademark or model number. Henceforth, this will be referred to as the Amazon cartridge and the other, the vintage cartridge.

A phono cartridge for under $18 shipped and taxed is like an early 80s dรจjร  vu when I could walk into Leonard Radio on Sixth Ave. NYC, listen and browse to my heart's delight, and walk out with a $15 Grado GTE+1.

The plastic body is quite robust weighing about 6.5 grams. Instead of traditional mounting holes, the body is threaded. Over tightening the two Allen head mounting screws can result in stripped threads.  

 The google translate camera app on my iPhone gave the above info. I suppose 2.2 grams acupressure = Vertical Tracking Force, since it uses a stylus not an acupuncture needle. OTOH, the printed 5 gram weight doesn't match my digital scale's reading.

I haven’t mastered the use of my USB microscope and this is the best stylus image I managed to capture. It looks like a nude mounted rock with traces of facets. Could it be an elliptical or a not too highly polished conical? I'm not an experienced stylus peeper, so please let me know what you think. 

I mounted the cartridge on a generic Technics-style head shell and set the acupressure to 2.2 grams on my Bokrand AS309. After a couple of tracks I heard sibilance. Increasing the VTF to 3 grams fixed the problem. IMHO, 2.2 grams is too optimistic!

The metal shield of the Amazon cartridge looked similar to the entry-level Audio Technica AT3600L. So I took it out and, as expected, it sounded comparatively dark and veiled. Switching to the Pfanstiehl conical stylus opened up the sound a bit. However, the full bodied tonality of the Amazon cartridge wasn't at all apparent leading me to believe that the two cartridges don't share the same motor.

The Amazon cartridge is a very exciting performer! Macro and micro dynamics are more nuanced, I hear more air on the top end while midrange vitality and low frequency extension are at par with the vintage cartridgeIf I'm forced to split hairs, I'd say the vintage cartridge is a tad more refined compared to this Amazon special.

Same Abbey Lincoln track traced by the Amazon cartridge

As I was about to link to the item on Amazon, my original source was showing as currently unavailable. But a bit of searching yielded a blue/gray variant as pictured above that's listing from $19.46 to $23.99. Happy shopping!

As featured in the two videos, most of my listening and testing were done via my near field hifi. But I also cross referenced the cartridges fitted to the Bokrand AB309 + Garrard 401 downstream to the Altec 753Cs in the main system. Neither cartridge unseated the Shure M3D as my favorite magnetic cartridge but both provide a level musical satisfaction unimaginable at this price point! 

Addendum


More stylus pictures

Click on the images to enlarge


I forgot to mention that when I did the AT3600L vs. $18 Amazon cartridge comparison, I was reminded of a Pickering V-15 vs. XV-15 match. Could there be a moving iron motor inside this Amazon cartridge?

@gary7 at Audiokarma identified the origin of this Amazon cartridge.๐Ÿ‘ But is it the entry-level $79 or the more bling $129? ๐Ÿค” 

Suffice it to say, I've been enjoying my $18 version so much such that I'm not in a hurry to re-mount the Shure M3D.๐Ÿ˜Š


Here's another video of the $18 Amazon cartridge, this time mounted on a Fidelity Research FR54 tonearm tracing a track from Naked Eyes in honor of Burt Bacharach (1928-2023).