JE Labs: July 2023

Friday, July 21, 2023

Finemet FM-MCT1 MC Step Up Transformers

Looking back to my late 90s home brewer article for Sound Practices issue 17, I noticed that a good number of components in my hifi system then are still serving two and a half decades later. The Tamura TKS83 moving coil step up transformer is one of them.

After building a hifi system for my cousin during lockdown, the Hashimoto HM7s made me realize that while the Tamura TKS83s can equal the HM7s in terms of bandwidth, the TKS83s can sound mechanical. It also became apparent that there are areas in which the classic Altec 4722s and 15095As can be improved upon.

When I finally heard a pair of Peerless 4629s, I was very impressed by their uncanny ability to reproduce very lifelike 3-dimensional vocals. However, I was quite disappointed when I played anything greater than a string or jazz quartet because the sound started getting mushy and dynamically compressed.

Overall, my ears still prefer the smaller and more affordable brother, the Altec 4722!

During the most recent Kutztown radio meet, John Piro handed me this finely crafted wooden box to audition. As mentioned in my Kutztown coverage, a good friend from Manila, Tony, aka Mr. November HiFi Show, scheduled his visit so we can hunt for tubes, parts + LPs.

Upon our return from the expedition, a sumptuous dinner prepared by Tish + a bottle of Ripasso awaited us. We capped the evening by hooking this wooden box to my hifi. Our jaws dropped each time we played an LP!

Housed inside the box is a pair of Finemet FM-MCT1s!

In the ensuing days, I did further evaluation and indeed, these Finemet MC transformers are doing something extra special. My only reservation was, in spite of the potted construction, the FM-MCT1s are more susceptible to hum induction compared to the Altecs and Tamuras. Even if John lined the wooden box heavily with copper shielding, I still had to keep them away from power transformers, AC motors, etc.

Inspired by the sonic niceties I heard, I was undeterred so I contacted Mr. Kimura of General Transformer Sales Co. Ltd. After a few emails aided by Google translate, I finalized my order.

Gtrans.co.jp is headquartered in the same location as the former Noguchi store we visited in 2015, which is in the basement of Tokyo Radio Department Store in Akihabara.

Kimura-san specified a 3-4 week window for delivery. So I downloaded the spec sheet, studied the schematic and ordered a cast aluminum project box from Amazon.

Within 18 days, the transformers were at my doorstep.👏

Finemet FM-MCT1

These are very well made and quite hefty! They're heavier than the TKS83s which, if memory serves me right, are about the same weight as the HM7s.

I chose a different layout for the 145mm x 121mm x 40 mm MC step up transformer chassis for neater routing of RCA cables.

Under the hood

The input and output RCA jacks are on the backside mounted on top of the chassis. Only the ground lug was mounted on the side.

I installed the 3-position gain/impedance load selector in front of the chassis.

No matter which cartridge I used - Denon DL103, -R, -C1, Fidelity Research FR1 MkII, Ortofon SPU #1s, -G, -GM, Supex SD900, etc. - male and female vocals + instruments are portrayed with 3-D presence and realism in a deep and wide sound space. The musicians are in my man cave!

Boosted by the Finemets, even the most analytical and dry-sounding MC cartridges in my stash, like the Goldbug Clement II and Sony XL44 came to life with more warmth. If that's a coloration, it's certainly most welcome!

These Finemet MC transformers seem like they were configured to resolve every note in the complex musical score and massive instrumentation of late romantic symphonies along with the wide range dynamics from pianississimo to quadruple fortes inscribed therein by the composer. They also excel in reproducing the ambience, airiness and spaciousness of the concert hall's acoustics embedded in well recorded LPs.

I finally found a pair of MC transformers which combine the organic midrange and harmonious richness of classic vintage iron + the wide bandwidth, detail retrieval, and dynamic range of modern magnetics!

Ever since I became an audio DIYer, I pride myself in not being impulsive about upgrading components in my hifi. This is a rare exception!😉

CODA

As luck would have it, last week we had a family get together because a cousin based in Tokyo was visiting and brought some goodies!

Stereo Sound
Tube Kingdom Volume 104

If I got it right, in this survey of commercially available MC step up transformers, the Finemet FM-MCT1 was the only DIY unit.

Despite the wacky nature of the Google translate app, the gist comes across as quite positive!

Enjoy browsing the magazine to Bobbi Humphrey's tune spinning on a Garrard 401 + AB309 tonearm with a Supex SD900 boosted by the Finemet FM-MCT1s!✌

Click here for the shielded version update!

Friday, July 7, 2023

Japanese Idler-Driven Turntable Part 4: Realistic Mark-7

Here's a tale of two idler-driven turntables of Japanese origin sold by Radio Shack in the late 50s. They share the same model badge and engineering features but they aren't exactly twins.🤔

This turntable/tonearm combination has been in my collection for over twenty years. I wired the tonearm for stereo because I particularly enjoy using it with the Shure M3D and M7D.

I couldn't find this in any of the Radio Shack Catalogs issued from the late 50s to the early 60s unless it escaped my tired, old eyes.

from page 2 of the 1957 Radio Shack Sale Flyer

However, the A-3 tonearm, which is essentially a Calrad SV12/Musicmaster Model 12/Velvet Touch sibling, was featured in the 1957 sale flyer above.

from page 4 of the 1958 Radio Shack Sale Flyer

This is the Mark 7 turntable recorded in the Radio Shack Catalog Vault.

Based on the shape of the chassis, this Mark 7 is perhaps the younger of the two since it looks very similar to the succeeding Mark 8, which I will discuss in a future installment.

DIFFERENCES

Although not quite as heavy and massive as a QRK or Russco, the cast aluminum chassis is very rigid on both units. The earlier MK7 chassis above is configured to accommodate a 9"-10" tonearm, while the later MK7 below was designed as a "motor unit" like the Garrard 301 and 401.

The speed selector linkage to the idler wheel in both are similar, but due to a slight difference in the motor mounting layout, the idler arm and idler wheels are not interchangeable.

SIMILARITIES

Except for the paint color, this hysteresis motor is exactly the same unit fitted to my NEAT P58H, which I covered in Part 2 of this series. Click here for motor servicing information.

The main bearing is an oil lubricated design, which supports a 3-lb. cast aluminum platter.

MODs & TIPs

Before moving on, the younger MK7 depicted above had a serious issue - the motor has a bent rotor spindle!😔 Will I be able to save it by adapting the motor from another Lafayette PK245 (don't ask my wife how many turntables I own 😆) with a warped platter?🤔

While planning the motor transplant, I examined the MK7 idler wheel condition and decided it might be worth rejuvenating.

So I mounted it on a handheld drill, deglazed the rolling surface with 400 grit sandpaper, and soaked it in brake fluid for over a week. This was suggested to me decades ago by a kind soul who visited the Rek-O-Kut Tips page in my old website. It has worked with two other Japanese idler wheels but I've never tried it on a Lenco or Rek O Kut. Back in those days, it was more convenient to just send Lenco and ROK wheels to Ed Crockett, RIP 😞 or Terry Witt 👍, who's still catering to the needs of audio DIYers.