Friday, April 22, 2022

MC step up transformer redux + Hashimoto HM-7

When I ordered this pair of MC step up transformers from Mr. Isao Asakura of tube-amps.net (highly recommended👏) for my cousin's system, he suggested the use of high-quality 24-gauge stranded copper wire. I also took note of his MC step up page, in which he discussed his chassis mounting experiments.

Taking the cue from my buddy Nate aka Redboy at HifiHaven.com, who’s a prolific audio DIYer and MC step up builder, I ordered a cast aluminum project box + 24-gauge stranded tinned copper wire from Amazon.

Hashimoto HM-7 - specs

Upon inserting the freshly mounted and wired HM-7 into my hifi set up, my Tamura TKS83 and Altec 4722 sounded comparatively hard and mechanical...🤔

I had to retrace my steps.

Tamura TKS83

Those who are familiar with my Homebrewer article in Sound Practices #17 will remember that the TKS83 was mounted on an aluminum plate + wooden base while the Altec 4722 + others were on plastic project boxes. These were also wired using 99.999% 19-gauge solid-core silver wire + Teflon sleeving, Kimber TCSS or a combination of both. 

In hindsight, whether commercial or DIY, all the Japanese MC step up transformers I've seen in the metal or in MJ Radio Experiment and Stereo Sound Tube Kingdom magazines, were always housed in all metal enclosures or chassis.

Altec/Peerless 15095A + 4722

Before doing further listening comparisons, I remounted all my MC step up transformers on cast aluminum chassis and used 24-gauge tinned stranded copper for wiring. Since we're dealing with very delicate signals at tenths of a millivolt, very fine strands of high purity copper wire + maximum shielding make a lot of sense!

Hashimoto HM-7

After the playing field had been leveled, the Hashimoto HM-7 no longer outclassed my beloved MC step up devices. However, I'm pleased to say that the HM-7 sound falls somewhere in between the detailed and dynamic TKS83 and the organically rich and spacious airiness of the classic 4722!


Alas, these cast aluminum boxes weren't available when I started experimenting with microphone transformers as MC step up devices in the late 90s. Otherwise, I would've used them since I love the industrial vibe of unfinished aluminum!



6 comments:

  1. Hi Joseph, those look like classic Hammond 1590 diecast boxes to me. Also my preferred tools for that kind of job.
    All the best from Germany: Holger

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    1. You're right, must be the same OEM in Asia. Nice of you to drop by, Holger! Tschüss!

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  2. Hey, can you please share ,what components you buy for the Hashimoto, what mounts do I buy, glad if you can share your link to the 24-guage wire too. Thanks a lot, Per

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    1. The materials I used were generic: cast aluminum 3.5" x 6" x 2" project case + 24-gauge fine multi-strand copper wire as pictured and above. Nothing fancy and it sounded better than when I used 99.99% silver.

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  3. Hi. Can you recommend a step up transformer for the Shindo spu? Thank you.

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    1. I use the Tamura TKS83 with my SPU#1s, -GM and -G. Unfortunately Tamura has discontinued this model. Assuming your Shindo SPU is electrically similar to my SPUs, you should seriously consider the Hashimoto HM-7.

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