Since Denon recommends a 1000 ohm load for flattest response, I tried soldering a 1k ohm resistor in parallel with the 47k input (47,000 x 1000/47000 + 1000 = 980 ohms) of my variable EQ phono preamp. Unfortunately, the sound became even more glacial.
I could have been basking in warmth by now (without losing stereo LP compatibility) if I saved up for an Ortofon SPU mono but the DL102 body fits a Gray Research or clone tonearm slide perfectly. Besides, I would rather add more stereo SPUs to my cache.😉
Since I've been using 1:1 line transformers as digital sound processing devices at the output of my CD players for ages, I decided to try the same trick by wiring the Altec 15356 and UTC A20 with a mild step up - 150:600 and 125:500, respectively. Even if both primaries reflected significantly less than Denon's recommended 1000 ohms, what I heard encouraged me to continue to experiment.
Although I'm not anal retentive about impedance matching, I was curious too see if the sound would improve by using transformers that reflect at least twice the 240 ohm internal impedance of the Denon DL102. I managed to procure the three transformers above: to the left is allegedly a Tamura 600:3k, then I tapped the McMartin MT-4's 10k:60k winding, and at the center is a permalloy 10k:40k, which sells for about $50/shipped from Chinese sellers on AliExpress and eBay.
In the context of my mono hifi set up, the McMartin MT-4 was a bit too warm for my taste. However, even if I upload videos merely for the visual spectacle, the permalloy (above) and Tamura (below) transformers are lush enough for me.😉
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.
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.
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!👍😊
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.😊
Voila!👍
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!😊
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 Touchviscous damped tonearm. It turned out that this Japanese 4-speed idler-driven turntable is actually a rebadged NEAT P58H.
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.
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.
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.
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.
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