Saturday, April 1, 2023

Altec 405A

This ain't no April fool's joke!πŸ˜†

Since the mid-60s (scroll down to pdf page 31), stateside audio experimenters have been trying to squeeze the last ounce of performance from the Coral/Sony "Holey" and Foster/Fostex FE103/Realistic 40-1197 family of 4" drivers. Meanwhile, Japanese aficionados like Old Joe (above), whom I follow on YouTube, kept snapping up Anaheim-manufactured Altec 405As in multiple quantities to stuff into their mini A7 VOTT projects. 

Because of the dearth of units left in the States and my indifference towards engaging in a bidding war versus fellow Asian hobbyists, I patiently hunted them for 20+ years via other channels.

Altec 405A specs

The 405A is a 4"  60-15,000 Hz wide range driver with a sensitivity rating of 92dB/4ft/1W. It's equipped with a massive Indox magnet that's almost the same diameter as its cone.

IMHO and experience, Altec cabinet plans always deliver sonically. Aside from a full understanding of the physics of sound, their engineers used their ears as the final arbiter in a design brief. To me, that trumps any design completely derived from a mathematical formula or computer simulation. So I asked my buddy @ Hommage Audio to fashion a Bonsai pair of Altec 614-style boxes based on the above dimensions.

Interior stuffed with Dacron

For sentimental reasons, I have a pair Realistic Minimus 8s on my test bench. I always thought they were above average, although not extraordinarily special. Same deal with the "Holey Frame" drivers I pulled out of a Sony TC500A RTR machine. To my ears, both FE103 derivatives have an upper midrange resonance, which require an EQ/contour network to make them more listenable.

614 style 405A cabinet

I found the 5.25" Realistic 40-1354A more impressive in spite of its narrow band whizzer honk. Back in the 90s, I played with it in a ported box similar in size to the above Altec 405A cabinet, as well as in a TQWT. Both speaker projects came from the book Designing, Building, and Testing Your Own Speaker System by David B. Weems.

Silbatone box + 755C and 405A in a 0.4 cubic foot ducted port box

Spoiled by years of exposure to Altec 755As and 755Cs in open baffles or 2 cf boxes, and more recently, in Silbatone cabinets, I considered this Altec 405A + Bonsai 614 style enclosure project as a mere novelty experiment.


As soon as I hooked them up to my near-field hifi system, I was pleasantly surprised that they play like their bigger brothers, albeit at a reduced scale. 

It's physically impossible for the 4" cone of the 405A to extend much below 90 Hz, but the roll off is gentle and there's enough harmonics to suggest bass lines. I hear a slight trace of peakiness in the presence region. For my taste though, an EQ filter isn't necessary. 

Although the Altec 405A can't replace the Altec 755C (much less the 755A) in my near-field set up, its midrange depth, micro dynamics, detail resolution and overall tonal balance makes it worthy of the Altec badge!πŸ‘πŸ˜Š

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 😞...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.😊


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!😊

Musicmaster Model 12 + GE VRII

Let's listen to a few monaural hifi tunes!


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

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 did a great job rejuvenating the P58H idler wheel (above left) + another wheel for my ROK L34 Rondine Jr. Unfortunately, Terry's Rubber Rollers website no longer works. Does anyone know if he retired?

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.

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?


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 AussenlΓ€ufer

 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.


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.


Back to Part 1