Dyna Stereo One Twenty

[frankmarsi]

8-11-2020 

Although I lusted for AR-5 speakers in the late 1960s a couple of years prior to buying my first set of AR-3a’s in 1971, I thought if they haven’t seen the article already this is a good read.

This is about a Dynaco amplifier so, I also direct it to “potty-mouth”, “%#*@ing contest over who has the fanciest/costliest gear.” *JKent who I believe still uses one of these amplifiers.

I still have my original that I built from kit form in mid- 1971 which I had to rebuild several times until I finally gave up on it and in late 1974 bought my first Phase Linear PL-400 which changed for the better my whole world of hi-fi. And although I've had a not-too-good experience with this ST-120 amplifier years ago, this article has renewed my opinions for the better.

Getting back to the Dyna ST-120 which I was so excited about building back then.  For “Dynaco’ it was their first transistor model along with their ST-80 and had numerous positive reviews in all the current magazines back then, sadly it was a total failure for me on many levels.

First off, up to a certain level it only went so far powering my newly purchased AR-3a’s before it ran out of steam at 67 watts RMS per-channel, and then it blew out every time I pushed it during inspired listening sessions.  After I replaced the power transistors, it repeatedly destroyed the tweeters so many times, I lost count and AR replaced those tweeters many, many times. AR was very kind in this respect back then in the early 1970's. Dynaco had sent me the two main power transistor boards so often in addition to the power-supply board I simply quit messing with it out of frustration and moved on with the Phase Linear PL-400 amplifier which I had intensely been researching. It was reported to have a far superior quality sound quality and offered a day and night comparison, and they were absolutely correct. Finally I was on the road to true high-fidelity and using super high power which was relatively a new phenom in those days. Many new comers to vintage Hi-Fi have no idea what a revelation such high power was to high fidelity at the time.

It wasn’t until I opened my business in late 1977 and used my 3a’s as front channels with my Phase Linear PL-4000 pre-amp and the PL-400 power-amp that I needed another amp for the back channels. The PL-4000 pre-amp had the derived/pseudo/quasi four channel ability. I needed a second amp for the rear channels so I excitedly went hunting for another amp for the rear.

I went to the “Stereo-Exchange”, their first store located on West 8th. Street and Sixth Ave. the same streets the “Stones” mention in one of their songs on ‘Emotional Rescue’ and there I found another ST-120.    Bernie, the owner had a used one that was factory built so, I trusted that it would be all right and at $89.00 with the brown cage which meant it was even older than mine which had the black cage.  I carried it out the door happily.   I hooked everything up, using my AR-2ax’s for the rears and I discovered that the PL-4000 alleged four-channel because it really wasn't four channel was such a huge disappointment because in actuality it only sent thru ‘ambient’ information into the rear channels.  That rear-channel information was so low in volume and wasn’t helped by the ST-120 low wattage compared to the PL-400 in the front that the only record that was enjoyable was the “Hendrix” ‘Electric-Lady-Land’ album which had tons of ambient information on it. Plus the room was so big at 35' X 22' with 12 foot ceilings that the little Dynano amp was struggling at 67 watts per side at max. Over all, it wasn't very convincing and rather disappointing.

Who knows at some point I may set-up a mini system and add it to my AR-4X's though, I still have my late 1967 Dynaco ST-35 I could use for those.

Regarding the Stereoph__e test review linked below, I was pleased to read the positive comments nonetheless.

https://www.stereophile.com/content/dynaco-stereo-120-transistor-power-amplifier   

* https://community.classicspeakerpages.net/topic/9747-i-just-wish-members-here-would-show-us-photos-of-their-set-ups-and-listening-rooms/