Summer 2019 Amp Projects and 6X6 Folding Rangefinder Cameras

Radiotron SE2A3 with Noguchi PMF-15WS

Shot with an Ansco Super Speedex loaded with
Foma 100 and developed in Kodak HC110 dilution B

Ansco Super Speedex
more pics

JE Labs Simple 46 with Noguchi FM-6WS

Shot with a Super Fujica 6 loaded with
Foma 100 and developed in Kodak HC110 dilution B 

Super Fujica 6
more pics

Good light and happy listening!

Hashimoto H-203S from Kasuga Wireless

In September 2018, I lamented the demise of Noguchi Transformers. Fast forward to November, my brother-in-law visited Tokyo, and was kind enough to pick up a couple of transformers at Kasuga Wireless.

How to get to Kasuga Wireless

Kasuga Wireless

Address: 1F, New Akihabara Center, 1-16-10, Kotobuki, Chiyoda-ku, Tokyo 101-0021

Hashimoto H-203S

The H203S was installed as a 3.5k primary Z output transformer in the je2a3 mono integrated amp. 

Testing

Top trace = audio generator

Bottom trace = amplifier output

100Hz

1kHz

10kHz

5.324Vrms to an 8 ohm load = 3.5W 

In the past, I've used Hashimoto transformers for a pair of SE2A3 and a pair of SE10 mono-blocks I built for friends. I know these transformers are well designed, are of high quality construction and sound excellent. Thus, before Hashimoto ceases production, I had to add it to my collection. 

My mono SE2A3 integrated is ready for prime time!

Now I have to find a nice circuit for a pair of Kasuga KA6625ST OPTs. 😉

Morikawa SE2A3 in Jose's Listening Room

Back in the 90s I used to hang out with Ding and Jose at Hamfests in the suburbs of Philly. Jose isn't your typical audio nerd who subscribes to the latest is best mentality. He goes for value for money and although not a DIYer, has an eye and ear for quality design! Even if he has a Technics SP10 + Sumiko MMT turntable combo, most of his listening nowadays is through a high quality pre-bitstream a Denon DCD 1500 and a stable platter Pioneer PD65.

Having heard that a well designed SE2A3 amp is a synergistic match for his Altec 604-8Gs, he spotted and won this Chuyu Morikawa designed Audio Professor SE2A3 amp on eBay. However, the amp had two issues. The input level controls were no longer functioning, and worse, the amp was unstable manifested by extra-musical popping and whistling sounds. Since we're practically neighbors now, I took it home for a check-up.

Under the hood 

Beautiful workmanship, typical of a handcrafted amplifier from Japan

After installing a dual ganged 100k Alps audio taper input pot, I realized that the cause of instability was the step down transformer the eBay seller sold with the amp. It was hardly stepping AC down to 100V. During the amp's residency here at JE Labs it was plugged to a General Radio Variac set to 100VAC. It was stable and quiet. Fortunately Jose also has a Variac on stand by, which he acquired during our Hamfest hunting days.

6Z-DH3A

The amp uses 4 x (2 for each channel) 6Z-DH3A, UX-6 based, high-mu triodes as input/driver tubes. This tube is electrically equivalent to an octal based 6SQ7. AFAIK, there are no plug-in compatible US or European equivalents. 

The input/driver circuitry is configured in SRPP, very similar to what I did in the JE Labs SRPP 45/2A3, albeit with textbook operating points.

5 Volts rms to an 8 ohm load at onset of clipping = 3.125W per channel

Luxman SS5B-2.5k OPT

100Hz

1kHz

10kHz

These square waves show that the Luxman SS5B 2.5K primary SE OPTs are of very high quality. Not much information is available on the internet regarding this transformer aside from completed auctions, but I've encountered this model in schematics and pictures in Asano's two volume tome on tube amplifiers.

Since Luxman SE OPTs were no longer available during the Sound Practices era in the 90s, I would date this amplifier to the 80s, at the latest. That's before Cary introduced the 6SL7 SRPP driven 300B or 2A3 AES SE-1 kit amp to the mainstream market.

I built SRPP circuits back in the day, but was never a fan of this topology. However, this amp made me reconsider my stance. Now I'm asking myself - could it be the textbook operating points and/or the 6Z-DH3A input/driver tubes which made this experience memorable? 

I truly enjoyed listening to this amp, thanks Jose!

Noguchi Transformer Co. Ltd, Closing

Noguchi Transformer Co. Ltd announced that they are closing on September 29, 2018.😞😞😞

Located at the basement of Tokyo Radio Department Store in Akihabara, I was first exposed to their existence in the early 90s through their ads in MJ Audio Technology and Stereo Sound Tube Kingdom magazines. 

MJ 11-1994 

Back in the 90s they ran 2-page ads for Tamura, Tango and their in-house manufactured transformers.

Hashimoto

I was glad to see their store when I visited Tokyo in November 2015. They still had a good stock of Hashimoto, some Tamura and a comprehensive line of their house brand transformers. 

Noguchi + Tamura 

I am speculating that just like everywhere else in the world, the Japanese market for DIY/vacuum tube/single-ended triode amps is also shrinking. This explains why these manufacturers are closing shop, 😞 not to mention the fierce competition from China.

"mid-price" Finemet OPT ad in MJ 12/2015

  

The Noguchi Finemet models represented their finest quality output transformers.

Even if I stretched my budget a bit, it was a good call that I added a pair of PMF-10WS and PMF-15WS + a single Finemet FM3WS-H and a pair of Finemet FM6WS to my collection. 🙂

Sayonara!

!!UPDATE!!

As posted by "dan" in the comments section below, the entire line of Noguchi is now represented by General Transformer in the same location at Tokyo Radio Department Store in Akihabra. 

JE Labs Simple 46

I've been hoarding type 46 power tubes gathered from radio shows I attended with my buddy Chong in the late 90s. Building an SE 46 amp was in my to do list when I packed up for Manila in '08. But things got in the way. Finally, after a round trip across the Pacific, the amp has come into fruition.

Given its designation, one would think that it is just a 45 with dual grids. However, aside from the UX-5 tube socket requirement, the 46 is not quite a 45. It only puts out 1250 mWatts, 750 mWs less than the 45's 2000 mWs. Maximum plate dissipation with grid 2 tied to the plate is 5.5W compared to 10W for the 45. Although it will perform very well loaded with a 5k primary Z output transformer, the textbook recommended load is closer to 7k, due to its higher plate resistance of 2380 ohms vs. 1700 ohms for the 45.

46 tube base
diagram

chassis is punched out and ready for painting

It's been over 20 years since the Simple 45/2A3 was uploaded to the now defunct DIY section of the old Angela Instruments website. So I wanted to reprise that old-school topology with a twist. I considered retaining the octal base and using a grid capped 6F5 or a UX6 based + grid capped type 75, as a tribute to Asano-san. 🙏

However, since I am in loctal mode, I settled on the 7B4 hi-mu triode which is more in unison with the simple theme. The 7B4 is readily available NOS and can be had for less than $5 each from tube dealers. Tube rollers take note, even if loctal tubes are boxed/labelled RCA, Tung Sol, Raytheon, etc. most of them came from the Sylvannia factory in Emporium PA. 😞 

under the hood

!!!WARNING!!!

The voltages found in this circuit can be lethal! Build at your own risk!!!

JEL Simple 46 schematic

Adjust the dropping resistor* (use at least a 10W) so that the operating point for the 46 tube is as close as possible to the tube manual specified 250V max. plate voltage x 22 ma. current draw = 5.5W.  Ideally, the 46 should see 285 volts at the plate - 35V in the cathode = 250V. As shown in the schematic, I am still running my output tubes about 8% over because I was anxious to listen and got lazy to lower the B+ further. 😎

The big surprise was, subjectively, the triode-wired 46 sounds more powerful and authoritative especially in the lower register than the 45. It sounds like the union of virtues between the dark and mythical 10/VT25  + the refreshing airiness of a 45. I've been listening to this amp for over three months and haven't had the itch to switch on my other amps. 😄

CODA

Left to Right - Globe 46, ST 46, ST 45 and 2A3

Globe tubes look really cool and usually sound more lush than their ST counterparts. I personally prefer a Globe 45 over the later ST glass bottled samples. However in the case of the 46, the difference is not as apparent and close to negligible to my ears, So save your $$s and do something less nerdy, like going out on a date. 😉

Addendum

I received this email recently from a seasoned DIYer/audio enthusiast known in various audio forums as Salectric.

"I just saw your blog post about your Simple 46 amp and I read the question someone posed in the Comment section about a suitable power transformer. I actually had Edcor build a custom PT for my 46 amps and the voltages worked out perfectly so I recommend it to anyone wanting to build a 46. I don't know if the particular unit is listed on their website but it should be available through the part number which is the Edcor XPWR 258-120.

The B+ windings have two secondary voltages. It is 345-235-0-235-345 @ 300ma. The purpose of the two voltage taps is to let the transformer function for either choke input or cap input. The lower voltage windings with a 5U4GB and cap input filter give a roughly 290v B+, and so do the higher voltage windings with a 5R4GY and choke input. With a little loss in the OPT and a 32v bias, the 46 has almost exactly 250v across it. There is also a 5V@3A and 6.3VCT.

I ordered it this way because I wanted to compare choke input and cap input with as close to exactly the same conditions as possible. (I tried a 5U4GB with the choke input as well as cap input just to be as consistent as possible.) The best sounding setup was the choke input with 5R4GY so that's how mine is set up. The Edcor is super-quiet. No mechanical buzzing at all."

Budget SE OPTs - Edcor and Noguchi

All output transformers were tested in the je2a3 amp using the same procedure as I did in the Hammond 125ESE many moons ago. Listening sessions were done through the same amp driving a single Altec 2-way speaker system. 

Edcor GXSE15-16-3.5K
Weight = 2.75 lbs

Primary Z = 3.5K

Secondary = fixed @ 16 ohm

Frequency Response = 40Hz - 18kHz, <1dBu 

Maximum DC current = 190 ma.

Core Material = M6, 29 ga. grain oriented steel

I ordered this Edcor OPT to get a feel on what's available to a cash-strapped US-based DIYer. It took over 3 weeks to be delivered to my doorstep at a total cost of $58.67. The nice square waves indicate quality manufacturing. Bass performance was at par with the Noguchis. But from the midrange to higher frequencies it was not quite as open and transparent. Maybe the Japanese manufacturers use higher quality laminations than the M6 steel used in this Edcor? Since the Hammond 125ESE now sells for about $60 before shipping, the GXSE15-16-3.5K would have been much better value for the money if it were offered with at least two secondary taps.  

Colors in Kanji

Noguchi PMF10WS
Weight = 3.2 lbs

Price = JPY 9,070
Approx. US$80

These two pairs of Noguchi transformers were Akihabara souvenirs from our 2015 Tokyo trip. In spite of the significant difference in price, the PMF10WS and PMF15WS are physically the same in size and weight. Based on specs, the PMF15WS has greater bandwidth and more flexibility for use with various output tubes.

Both OPTs tested well on the bench. Even if the 10khz square wave test does confirm better top end response from the PMF15WS, I could not detect its sonic superiority over the other.  Sonically, the PMF10WS is just as good if you don't need the extensive multi-tap flexibility from its more expensive sibling. In terms of tonal balance, I prefer the warmer presentation of either of the Noguchis over the leaner and more analytical Tango U808.

Noguchi PMF15WS
Weight = 3.2 lbs

Price = JPY12,560
Approx. US$112

I'm not sure if Noguchi accepts international orders. But if you're visiting Tokyo, their basement shop (closed Mondays) at Tokyo Radio Department Store is a must see!