Happy Holidays!

Happy Holidays and Wishing Everyone a Great New Year! 

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!

Susumu Sakuma

Susumu Sakuma, RIP

(1943-2018)

Photo courtesy of my Flickr friend silver_night 300b 

more Sakuma photos

Sakuma-san and Brian "monofantastico" Clark were my mono hi-fi system heroes!

Denon Aluminum Body Cap

I've been a Denon DL103 user for more than two decades but never considered risking my $250 investment to modifications which involved removing the old and installing another body. 

To circumvent the risk of damaging the stylus/cantilever assembly, Steve Bedard came up with the Denon Aluminum Body Cap.   

The finely machined aluminum cap slips over the Denon DL103 body. I noticed a slightly tighter fit on the DL103R and DL103C1, due to the different housing material used for these higher end models.

Two longer metric bolts are supplied to fit the original Denon nuts to compensate for the added thickness when mounting the cartridge/cap combo to a head shell. 

It has been my experience in this hobby that every time the frequency extremes are improved, something gives and usually, it is the midrange that suffers. 

The classic DL103 is a case in point. It has a wonderful midrange but it has a tendency to congest in the high frequencies during complex musical passages. Brighter recordings can also sound sibilant while the lower frequencies can gain more definition. 

Through the years, Denon has addressed these issues with "upgraded" DL103 versions by revising the coil with finer quality wire and by using more inert materials for the housing. I have two of them - the current DL103R and its predecessor, the DL103C1. Both models refine the frequency extremes but at the expense of a drier and "less colorful" midrange.

Thankfully the "capped DL103" retains and focuses that midrange warmth, almost mimicking an SPU, while the frequency extremes are tidied up. There's just a hint of sibilance and congestion left with the "capped DL103."

Even if there was improvement across the audio band with the aluminum cap installed on either DL103R or DL103C, what was most apparent was better definition in the lower frequencies. 

Could it be that the upgraded DL103 models benefit less from the cap? Perhaps the distinction might be system dependent and/or merely a matter of taste? Just remember, I'm not a mainstream audiophile. 😉 

What I like most about the Denon Aluminum Body Cap is, it doesn't dampen the virtues of the DL103/103R/103C1. It highlights and improves upon what's already there. 

In the big scheme of things, it's hard to find this level of sonic upgrade for under $100. My DL103 is "capped" for good, highly recommended! 👍