PX25A (DA30) Mono SET with Old TANGO Transformers
Among the various backgrounds so far, I was so surprised but grateful to receive Alan-san’s favorable offer to buy one more pair of PX25A (DA30) mono SET amplifiers, but this time with old Tango transformers.
I have a special feeling for the Tango transformers, especially, the output transformer, the Tango FW-50-5S, 5k ohm impedance on the primary side, with huge EI core.
These were once custom ordered by my master, Anzai-san, to bring out the full potential of the GEC PX25A, which was first introduced to Japan by Jean Hiraga-san in early the 70’s, and the transformer became a catalog product of Tango in 1972, a half century ago.
Above all, over the years, these output transformers have easily driven my ONKEN NEW 500MT compression drivers and 5000T Esprit tweeters.
I’ve long enjoyed its beautiful and rich higher contrast tone even at low levels, but haven’t felt any particular sound character. Furthermore, the combination with PX25A and FW-50-5S always took me to the depths of delight in audio and music.
So now, Alan-san, who has a true understanding of my “Real-Sound” concept, could also feel and share my original audio perceptions, was a serious matter for me.
Well, the finish of the exterior and the hammered tone painting with beautiful pale green color on the top panel made me feel the taste of an artwork by the craftsmanship of Yokoyama-san, “Valves’ World” and even I, wanted to keep it close to myself.
Furthermore, I soldered Ultimate Ruby Mica capacitors in two places of the amplifier just before the shipment, to complete the exquisite sound quality I had aimed for many years.
So I was able to ship the amplifiers to Alan-san over the Pacific Ocean in the end of 2019, with wishing for blessing not only on Alan-san and his family, but also on a pair of the direct-heated power tube SET to bring out the true performance over the long days from now on.
Well, thankfully enough, I received the following impressions from Alan-san on 17th February 2020. It seemed my thoughts had come true:
“This has been a wonderful experience with both pairs of the mono SET amplifiers. I am finding very subtle differences between them. First, they both have the ability to give a sense that you are one in the room with the musicians as opposed to them being presented in front of you."
"This “Real-Sound” experience, for me, gives an orientation of a heightened emotional involvement with life and music. The “Tango” transformers, I’m moved to referring to them as the “old souls.”"
"With stringed instruments they have a palatable organic feel that resonates along and within the plucked or strummed strings. It moves me in a different way with jazz and 50’s blues recordings. It is as if there would be the integration of voice or joining with what is happening, a sense of a collective whole that allows a movement of flow within the same plane."
"The “Hashimoto” transformers, the big boys with adolescent and youthful exuberance, what dangerous beasts are these mono SETs. At times, they will grab you and your feet are tapping along, then your legs get a mind of their own, and you find yourself unconsciously sliding across the floor as an old cat that has taken a sip, maybe two, out of waters from the eternal spring."
"A flow of exhausting primordial energy that leaves you both satisfied and paradoxically wanting for more, more, and more. Me, I am very happy, grateful, and thankful, as you once mentioned about the old Western Electric wire, “Very Lucky!!” Thank you again my dear friend. Warmest Regards, Alan.”
My Latest “Resistor Adventure”
To be honest, I hadn’t been confident of some kind of authority about the Model 7's resistance choices until a few years ago.
Certainly, in this series, I introduced Ohmite, 200 series, Brown Devil to strengthen the power supply, and especially in Part 6 (HERE), I highly recommended Ohmite WHE for the cathode resistor.
I still believe that Ohmite WHE is an impeccable resistor with an ideal sounding character at a resistance value of around 1 K ohm for signal circuitry. Of course, I believe these resistors are useful for not only Model 7, but also for many analog devices as well.
The problem was that I couldn't find or come across the best resistors for tube amps with such high resistance value above 5 K or 10 K ohm. As for Alan's Model 7 original, it was a realistic issue of how to handle Allen Bradley's solid carbon resistors.
Allen Bradley solid carbon resistors were mainly used for Model 7 original, as was the case with the audio components at that time, and the custom ordered high-precision carbon film resistors, RN20X series made by CGW, with not only the accuracy but also more preferable sound quality than normal, were adopted in some parts.
This combination provided a well-balanced and attractive sound quality for the Model 7 original, just reported in Part 6. Needless to say, the sound of the Allen Bradley resistor is thick and rich in the midrange and below, and it feels to us very musical.
This resistor might be widely used in recording equipment for making mostly American music sources we have loved, mainly composed of tubes from the latter half of the 1950s to the middle of the 1960s. Above all, the sound quality should be compatible with the tube preamplifier and power amplifier of the reproduction system, in other words, there was no non-conformity between the atmosphere of the music source itself at that time and the sound tendency of the tube amplifier, featuring AB resistors.
With that in mind, and also taking into account the somewhat classic Altec Corona sound by modern standards, I decided to leave the Allen Bradley resistors in for the first modification of Alan-san’s Model 7 on October in 2017.
However, the negative aspects of Allen Bradley resistor, that is, the tendency of the sound quality to lack clearness and openness, the inaccuracy of the resistance value itself, and the long term instability, had always dominated my mind.
I was wondering if there would be any other exit or discovery. At the same time, I also instinctively felt that this was the last barrier to “Real-Sound” that I had been looking for.
Roy-san's Marantz Model 7 Replica that was modified by Yazaki-san.
Well, the following year, in the early summer of 2018, I was asked by Roy-san, also a good friend of mine, to modify his Model 7.
First, I successfully bid off a Model 7 Replica that was produced in the United States for Japanese market in the mid-90s, which still had a beautiful appearance, and was in a mint condition.
However, before actually starting the modification to improve the sound quality, there were a few issues to be solved. This Model 7 Replica was a Japanese version with 100 V specification. Fortunately, I found the 117 V winding on the primary side of the power transformer, and so I was able to set the voltage to 117V, so it would be convenient for Roy-san to enjoy the sound of this Model 7 in the United States.
Furthermore, it was a truly serious matter that the two multi-section block capacitors of the plate power supply had caused quite some capacitance leakage. Because it was difficult to find the compatible parts, it took quite some time, but I managed to find very rare nearly irreplaceable NOS electrolytic capacitors, and was able to install them.
Well, about the concept of the sound character that I aimed for when starting to modify this Model 7 Replica, it may be natural, but first I had to imagine Roy-san's favorite sound quality.
Fortunately enough, I knew what kind of audio equipment Roy-san had been enjoying in a lot of discussions so far, so I was able to get the idea of his favorite sound direction to a certain extent.
Recalling that, friendship with Roy-san began more than four and a half years ago. Certainly it was the beginning of this close fellowship that I offered some advice on improving the sound quality of his fascinating preamp featuring the WE310A, at the request of Roy-san.
In subsequent email exchanges, I also found that his audio history was well over 40 years and I was so surprised to hear that he once installed a huge Western Electric horn into his living room. I felt like this about Roy-san, that he was a true and desirable audiophile who dared to turn away from the modern high-end equipment and brand orientation, which was dominated by some kind of bad commercialism in those years.
Just four years ago, in the Autumn, Roy-san selected a SPEC RSA-F33REX as the amp to drive his long beloved, QUAD ESL-57 loudspeakers. These speakers were developed more than half a century ago in the monaural era and were introduced to the market in 1957, just during the transition to stereo LP.
With the release of the Model 7 the following year, those years were blessed with such great vintage equipment.
Needless to say, the ESL-57 is an electrostatic loudspeaker, a truly unique speaker, and it might be the first electrostatic-type speaker to become commercially successful worldwide, I think.
