There are some pinnacle names that simply standout in history, even that of high end stereo music playback. Take the Dyna Corporation, which was founded in Philadelphia back in October 1955 by none other than legendary audio inventor David Hafler and his colleague Ed Laurent. Although they began by designing and creating high quality transformers that also happened to work well for musical instrument gear, their true interest was in making high end audio components available at affordable prices to the masses. These would be available as both kits (called DynaKit) and fully assembled amplifiers, with other high quality audio components to follow. And it was with great pride that the newly renamed Dynaco Co. rolled out the very first ST-70 in 1959. The 35-Watt stereo amplifier was powered by four EL-34 output tubes running in what we know as ultralinear mode; perfect for the then burgeoning audiophiles just taking note of the new wave in high-fidelity.
Thanks to a plethora of stereophonic recordings being produced for LP and reel-to-reel tape sales at the same time, the demand for more speakers (versus monophonic from the previous era) and consequently amplifiers, grew quickly. And Hafler's simple, efficient, and ultralinear design (where the primary winding feeds the screen grid) reduced harmonic distortion and noise while increasing audio transparency and heft. The ST-70 was quickly accepted as the "poor man's McIntosh", leading to an astonishing 350,000 of them being sold before the last one rolled off the assembly line around 1992. That Series 2 model was designed and created by Sound Valves, manufactured and sold by Panor Corporation, and featured circuit updates, improved parts quality, and even offered rebuilds of the original ST-70 chassis to bring them fully up to the newest specification. And of course the legendary sound and value of the ST-70 has continued to this day; inspiring many to copy, and a few to try for improvements over the years, like the Filharmonia SE by Ars Sonum.
Well, skip ahead to 2018 and the new owner of the Hafler brand name of products has finally (after over two years of redesign and refinement) produced the ST-70, now in its Series 3 iteration. It is similar in size to the original, and the Series 2. But its improvement at the circuit level, especially refinements in the power supply and input tube drivers, which has resulted in a quite noticeable increase in sonics across the board. Those and other carefully considered improvements, such as the use of military grade, double-sided epoxy fiberglass PC boards, poly-composition capacitors, miniaturized high-capacity power supply electrolytic capacitors, and precision metal film resistors, make this new $2999 unit from Dynaco (now owned by Radial Engineering Ltd. of Canada), one of a few worth listening to anew, and with deep respect to David Hafler and Ed Laurent for their amplifier's significant audio heritage that is now in its 63rd year.
As to hook up, all the tubes come already in place, which is great. The stereo input jacks on RCA connectors are thoughtfully located near the center of the rear panel, with standard IEC connector nearby, as well as unique "no-touch" five-way binding posts at the extreme left and right back chassis. It is nice to see an 8-Ohm / 4-Ohm switch next to each set of binding posts, offering the end listener an opportunity to tailor the output to suit any particular speakers in use at the flip of a switch. So once everything is plugged in, turning the amplifier on via the rear center toggle switch will result in sound after a brief 30 second warm-up. The sound quality will continue to improve up to a full hour into warming-up but is nevertheless full, robust, and sweet to the ears at all times.
Turning our attention to the beautiful front panel, there are separate left and right attenuators, which are intended to cure any channel imbalances due to unwanted speaker and room interactions. I might suggest using them as volume controls in a direct source-to-amplifier set-up, but Dynaco does not recommend this. However, they work as designed if a speaker or listening position is noticeably far off the center line. Also in the center of the front panel is a high pass switch, suitable for eliminating rumble from a turntable or excessive bass from a heavy mix or soundtrack. Also present are tube bias lights and adjustment ports, wherein the end user can use a "non-metal" 1/16" flat head screwdriver to adjust the bias for the four EL-34 output tubes until all the indicators glow the same brightness. I used my "tweaker" which is a pencil-sized plastic screwdriver with the right blade size. The adjustment is made after the unit has warmed up (about an hour) but while the unit is not playing any music – easy.
Listening Observations (A)
The fact I'm auditioning several different pieces and ensembles helps me to differentiate how the sound is reproduced with a great degree of certainty. So when I go and listen to a different performance of the same piece on a different label, with different venue and ensemble, I can clearly appreciate the differences in size, shape, echo, and even the essential qualities of the microphone(s) as well as those of the producer and engineer's contribution. So on a different "Magnificat" performed by John Eliot Gardiner and The English Baroque Soloists on a Philips CD, the use of period instruments (versus modern) in an English church setting has a vastly cleaner, leaner sound, than the modern instrument recordings, allowing the particular aural qualities of the orchestra and soloists to spread out more in front of me; again thanks to the solid and robust sound quality of the new ST-70 Series 3. It easily keeps up with an ever changing line-up of great recordings that can showcase depth, heft, and perspective in a deliciously convincing manner.
Part of this is due to the beefier dual-primary power transformer, aided by improved line regulation, increased filter capacitance, and the change to a solid-state rectifier; all creating the necessary foundation for the rest of the amp's circuits to shine much more fully than the original Series 1 amp. And here, switching to a modern orchestral work everyone knows like Carl Orff's "Carmina Burana" that features the same large orchestra, chorus, and soloists in a work coming over 200 years after Bach the elder. Telarc's classic CD and Hi-Res Audio Soundstream remastering features Robert Shaw and the Atlanta Symphony Orchestra. Together with Judith Blegen, singing an exquisite soprano solo in Track 23 that leads out through both full Choral and Orchestra tutties sufficient to task most any system when played loudly enough. But here I found the solid, developed and euphonic reproduction of the ST-70 Series 3 to be detailed, big, powerful, and enveloping with a variety of different dynamic speakers (4-Ologe, 2-Symdex, and 1-Cambridge Soundworks) as well as a planar (Magnepan 1.7i) within my medium sized untreated living room. Filling a larger room might require more power when using an electrostatic, planar or another inefficient speaker, but otherwise everything sounded fabulous in my much larger treated audio listening room.
Listening Observations (B)
Another great album is Harry Connick Jr's aptly titled We Are in Love; another big band sensational for him from 1990 with modern orchestra and recording techniques that capture all the great qualities inherent in previous efforts by Frank Sinatra, Dean Martin, Sammy Davis Jr., and Tom Jones – three decades and more earlier. The opening track is as much a demo piece as any, but through the Dynaco ST-70 Series 3 amplifier it appeared to float free of the speakers, defining a much larger space than either of my listening rooms. And this sense of size and the quality of the bass reproduction makes for a more believable presentation where you are compelled into the illusion, to become a part of that recorded event like you had been there. Other tunes on this program are of small, medium, and large scale. And each is correct in its own mix and use of instrumentation. So that your experience is a toe tapping, musically provocative, memorable moment in your daily life that you will find you cherish much, much more than if it were heard through a less capable and less great sounding design. That's why it took over two years for Dynaco to fully test and voice this practical tribute to the original and loved ST-70.
Finally, my love of music of all kinds leads me to listen to many fun pieces, often from great and cherished composers such as Vangelis who long before and after his contributions to Ridley Scott's Blade Runner was producing albums of similarly intriguing acoustical, magnetic tape, and electrical instrumentation in odd and often conceptually fascinating aural rhythms and hues. The canvas of sound he paints in his 1990 album, The City, begins typically enough with Dawn, and then Morning Paper, continuing on to Nerve Centre; and all the while the sound keeps building, adding layers and subtracting layers. These are sometimes bold strokes of sound from electric guitars or drum machines, but are sufficiently tonalized through his genius as to tantalize us with subconscious suggestions. One can picture The City from inside Vangelis' mind as a sequence of sections describing the emotional state of the Metropolis at the end of the 20th Century. Like any album or composition, it lives or dies based on connecting to its audience. Therefore, I must conclude that while not necessarily the greatest single amplifier in history, the Dynaco ST-70 Series 3 presents a perfect blend of spatial cues, timbral refinement, and head swinging/toe tapping that make music come alive; no matter what format you are listening to.
First, you've got EL-34 output tubes like the original, able to deliver 35 solid sounding, frisson (pronounced free-sawn), a French term meaning "aesthetic chills" inducing Watts into each of two channels. And everything coming before that, from the 12AU7 dual triode input driver tubes, to the beefier dual winding power supply, better parts with higher specifications, military grade glass epoxy PC circuit boards, gold plated inputs and five-way "touch less" outputs, exchangeable IEC power cord, and front accessible bias controls for each of the four output tubes – easily adjustable while the amp is running, and a selectable and tuned 4/8-Ohm output switch to properly match most any speaker load you through at it, makes this amp better.
What this adds up to is a modern and great sounding tube amplifier easily worth the $2999 asking price. The simple joy of plugging in and listening to a modern update of a classic design gives me chills because of the potential to excite the remote audiophile listener, as has been the case for quite some time now. Simple and effective tonal and dynamic contributions of the ST-70 Series 3's amplification made for countless hours or repeated listening where I found myself just as at home with classical, as with jazz, rock, pop, hip-hop, metal, country, soundtracks, and even talk radio and pod casts. And with everything having a certain wonderful and slightly euphonic quality about it, it was all too easy to listen hour after hour - all day long, in fact. And with the ability to match impedance and also adjust bias on the fly, one can tune this baby to suit most speakers and room set-ups, easily.
No device is perfect. But aside from replacing the tubes every so often, an easy matter of removing four screws (two on either side) and then popping out and popping in new tubes – you can't miss with a little care to where the pins go into the matching sockets – and four screws to re-secure the tube cover. You are back to running like new in less than five minutes! And you could potentially experiment with different brands of tubes to get a slightly different sound quality to the presentation. But I found the factory chosen matching JJ Electronics EL-34 to perform wonderfully.
It is clear Dynaco took the necessary time to verify the sound quality and reliability of all parts of this updated design. And the results speak for themselves. If you're looking for musical amplification with an up to date tube circuit that has stood the test of countless listeners expectations for practically 60 years, then you are in luck! Please give the new Dynaco ST-70 Series 3 an audition in your own system or that of a trusted friend and tell me it doesn't brighten your musical landscape. David Hafler's promise is fulfilled, again.
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