November HiFi Show 2023

 An event not to be missed by music enthusiasts based in or visiting Manila, Philippines 

Mark November 11-12, 2023 on your calendars.🍻

Celebrating music for twenty years!

Kutztown Radio Show Fall 2023

 What I saw...

...and heard 😊

JE Labs Choke-Capacitance Coupled SE2A3 amp

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

Inspired by my plate choke-loaded 76 line stage preamp adventures, I was curious how a similar driver circuit configuration would sound in an SE2A3 amp. So I pulled out my Radiotron Designer's Handbook, 3rd Edition to gain a better understanding of choke-capacitance coupling (aka plate choke loading) vis-à-vis resistance coupling.

Below are highlights of relevant information I gathered.

Shoten R50 Pentax K to Leica M adapter

Inasmuch as I love music and retrotech high fidelity music reproduction, I think it's healthy to take periodic breaks from hifi. Frequent visitors know that I also enjoy photography, especially using black and white film loaded in old school manual focus cameras. 

So today's blog is about the Shoten R50 lens adapter that's designed to take a 50mm (Note: a 35mm, 45mm, 55mm or 58mm, etc. won't focus accurately) Pentax K bayonet mount lens and fully couple to the rangefinder focus cam of a Leica M body from 0.7 meters to infinity. 

Japanese Idler-Driven Turntable Part 5: Lafayette PK300

I bought this Lafayette PK300 idler-driven turntable because it looked like an improved Shield MO-19 (aka NEAT P58H) with the added feature of an eddy current pitch control as found in the Garrard 301/401 and Thorens TD124.

Ortofon STM-72 + Weller WTCPS repair + Hakko FX-888D

One morning, I discovered the right channel of my Ortofon STM-72 was dead. While waiting for the Weller WTCPS soldering station to heat up, I carefully peeled the foilcal to pull apart the 2-piece tubular housing so I can resolder the broken cable connection(s). 

General Electric A1-400 Speaker

It was past lunch, so I took one last sweep at the Kutztown Spring 2021 radio meet before heading home. That's when I noticed this cabinet with a familiar looking metal-grilled driver partially hidden behind a huge pile of equipment. Without haggling, I handed a couple of ATM bills to the seller and we shook hands.

As soon as I got home I went through my Japanese audio magazine shelf and pulled this Stereo Sound Special Issue about Vintage Speaker Units, published in 2002.

Not exactly the General Electric A1-401 featured in the magazine but the slightly earlier A1-400. Pretty good memory for someone pushing 60, huh? 😉

GE A1-400 specs

As stated in the spec sheet, the perforated metal grill functions as a mechanical roll off filter for the 12" driver and the non-polarized wax and paper capacitor filters frequencies below 1800 Hz from reaching the 2 3/4" cone tweeter.

I also recognized this period correct DIY tuned pipe enclosure designed for corner placement. It was built based on an article published in the May 1955 issue of Audio (go to page 18), authored by Norman H. Bates. 

BTW, AFAIK, he's not related to the lead character in Hitchcock's thriller. 🤣

Vocals are nicely rendered! The transition between the low and high frequency drivers is very coherent, as to be expected between two paper coned transducers. If I were forced to split hairs, I hear a tinge of nasal coloration in the lower region of male vocals, which I never notice with any of my Altec speakers. 

Musical instruments and percussion are also well reproduced! Bass extension and definition of the A1-400 in the tuned pipe corner cabinet is at par with the Altec 756B in a 2.5 cf box, if not a couple of Hz more extended. Top end overtones are silky smooth and airy. Even if this cone tweeter lacks the ultimate transient speed and shimmer of a fine horn/compression driver combination, it's probably the finest I've ever heard!

I guesstimate its sensitivity to be in the high 90s/W/M because it'll boogie, driven by the 1250 mW SE triode connected 46 or 1500 mW SE10 amp. Although I can also listen to my Altec mini 757 with those aforementioned amps at respectable SPLs, it needs at least an SE2A3 for full dimensional monaural listening pleasure. 

Kudos to Mr. Bates' corner loaded tuned pipe cabinet for the aforementioned impressive bass performance and my perceived easy-to-drive/high sensitivity nature of this speaker system. Kids, this enclosure was designed during the slide rule era!👍

Now I'm inspired to pursue my 285mW SE112A mono amp project.😊

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I really enjoy this speaker with a GE RPX or VRII phono cartridge tracing Atomic/Space Age/Exotica Lounge/Bachelor Pad mono LPs from the 50s by the likes of Martin Denny, Arthur Lyman, Walter Wanderley, etc. 

After 21 years of hunting, I finally got a satisfying taste of the GE co-ax. I've seen this on eBay between $150-175, which I believe is a fair price for a unit with intact cones and no voice coil rubbing. A couple of my Instagram contacts even expressed fondness and admiration for this speaker when they saw a glimpse of it in my posts!

I now regret leaving my RCA 501-S1 in the attic 😔 because it would have made for a very interesting shootout. If I can trust my sonic memory though, the RCA didn't have the nasal coloration in the lower midrange I noted earlier. OTOH, the top end of the RCA could be deemed more reticent or refined depending on the listener's taste. 

I debated whether to refinish the cabinet
but the patina grew on me.😊

In the context of my monaural hi-fi system, it shall remain second only to the Altec mini 757 because when I played a young Sinatra LP for my buddy Ding, he initially thought it was Bing Crosby.😄 Sinatra only sounds like Sinatra LIVE or on an ALTEC!👍😎

Let's see what the gentlemen at Stereo Sound thought of its younger A1-401 brother two decades ago...

The scan below is from Stereo Sound Vintage Analog 2, 2014

I can drink to all that!🍻

Finemet FM-MCT1 MC Step Up Transformers

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.🤔

JE Labs Plate Choke Loaded 76 Line Stage Preamp

I acquired this pair of James JS 4120N, 200H @ 15 mA nickel plate chokes from Keith Tan of Euphonia Audio in late '04. Due to my busy performing and teaching schedule back then, they remained boxed up close to two decades.

After going home with me to Manila and back stateside, I finally found time to try the JS 4120Ns in my preamp. After adjustment of voltages and operating points, I was impressed by the increased detail and resolution brought forth by replacing the Allen-Bradley plate load resistors while retaining the sonic aura I've come to treasure from my Bruce Berman-derived 76 > 1/2 6SN7 line stage circuit from Sound Practices Issue 13.

Unfortunately the JS 4120Ns have been out of production for quite a number of years. 😞

!!!WARNING!!! 

The voltages in this project are potentially lethal! Proceed at your own risk!

NOTE: According to the 7N7 data sheet, it has a maximum cathode to heater (filament) voltage rating of 90V. To get around the 142V at the cathode, I lifted the filament potential 65V above ground via a voltage divider network in the B+ supply. Hence, 142 - 65 = 77, which brings it back to spec. 

100 Hz, 1 kHz and 10 kHz square wave output 
from 2 x Hammond 156C plate choke loaded 1/2 7AF7
+ 1/2 7N7 cathode follower

I tried the budget-friendly Hammond 156C plate load chokes in the circuit above on my loctal preamp as well as on my main preamp with the 76 line stage below.

Detail improved but I missed the micro dynamics and organic quality in the midrange of the JS 4120Ns. That said, I'm now using this topology in the nosTDA1541tube DAC in my main hifi set up. Meanwhile the loctal preamp line stage has been reverted back to its original state with Allen-Bradleys.

NOTE: This choke saturates instantly past 8 mA!

Since the Hammond 156Cs are easy on the wallet (just like the 125ESEs I wrote about decades ago😉), why not try and judge for yourself? If you hear potential, then proceed to the nickel plate choke-equipped circuit below.😊

Custom wound Intact Audio 250H nickel plate chokes

When my cousin commissioned his hifi system, I had to search for an alternative to the JS 4120N. Fortunately, Dave Slagle of Intact Audio willingly obliged to custom wind Ni-rich plate chokes for that project!👍

I was so impressed with Dave's nickel plate chokes👏 such that I ordered a pair for myself so I could use the JS 4120Ns for other tubes and circuits. I also confirmed that in order to get the most out of the plate load choke topology, one needs a competent winder, and nickel should be part of the equation!

Even if I always used more rugged 6SN7 GTA and GTB types in the cathode follower section, when I built this preamp over two decades ago, the power supply was configured so that the filament potential was about 75V above ground.

I've always admired the sound (or more appropriately, the lack thereof) of nickel permalloy, having owned the Tamura F7002 and Tango NY15S since the 90s. Even if these output transformers are hefty beasts, which helps the low frequencies, it's not their bass response that captivates the listener. Instead, they present a very natural midrange replete with rich and harmonious overtones, which are virtues I also hear with Finemet.

100 Hz, 1 kHz and 10 kHz square wave output 
from an Intact Audio nickel plate choke loaded 76
+ 1/2 6SN7 cathode follower

After praising the merits of exotic core material, I wouldn’t want readers to get the impression that nickel or Finemet are the quintessential elements to great sound. Tube choice, circuit topology and operating points, parts selection, etc. not to mention the synergy of components in the hifi chain, all contribute to the sonic stew. That's why I encourage audio hobbyists to listen and experiment so that they can carve their path towards their own musical satisfaction. 

Although this video is merely a proof of concept, I got inspired and used my Sony A7II + Voigtlander Ultron 28mm f1.9 LTM lens mounted on a tripod rather than my usual iPhone. So plug in your Koss Porta-Pros or Sennheiser HD6XXs and (hopefully) enjoy!🎶🎹🎻

CD transport: Marantz CD52

DAC: JE Labs nosTDA1541tube + PCLoctal output

Preamp: JE Labs PCL76 line stage 

Amp: JE Labs SE300B mono blocks with Tango NY15S

Speakers: Altec 753C

Maybe 🤔 I'll talk about my plate choke adventures with SE amps next time!😉

 

Cork Turntable Mat

 

 Rubber hardens as it ages and this is exactly what happened to the rubber mats originally supplied with my Garrard 301, 401, Thorens TD124 and other turntables. I'm aware that modern reproductions are available, but I wanted something more affordable and practical. So I surfed and found a 3-pack cork mat with an LP label indentation for $12 on Amazon.

Does this mat make the sound better?🤔 Hmm...frequent visitors to this blog know better that after several decades in this hobby, I've grown averse to typical audiophile hair-splitting.😉

However, I'm happy to report that a few LPs from my collection which are slightly dished or warped now lie flat. That's good and I like the sound.

Try it and hear for yourself!😊

Happy Spinning!🎻🎷🎶