Dynaco Stereo 120 Power Amplifier: Vintage Audio Review Episode

In this episode I look at a Dynaco STEREO 120 Power Amplifier- its repairs and performance.
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00:00 Introduction
02:30 “Tour” of STEREO 120
07:47 Problem #1
11:00 Problem #2
14:38 Measurement Data
15:50 Frequency Response
17:00 Output Impedance
18:15 THD vs. Freq & Power
20:35 System Noise
20:55 Max Power
23:27 Listening & Final comments

[@julianrosas4992]

Hi there, liked your review and changes and upgrades done to your ST120, just want to mention I got mine intact with no mods or parts replace and working very nice unit look in great shape overall, I have had it for five year since I buoght it, I enjoy your video

[@vintageaudioreview]

Thanks for taking the time to comment. Am glad your ST120 is doing fine, particularly since it is all original. THe unit featured in the video is a friend's, not mine.

[@midmodaudio6576]

Nice analysis and review.

[@vintageaudioreview]

I appreciate your taking the time to let me know!

[@ManFromLaBamba]

Luxman offered many tube kit amps, Luxkits. The circuits were very straightforward. Kit amps returned in a way with todays class d amps like hypex ncore, purifi, ice power etc, which provide complete modules one can simply plug together and mount in a case. Sure soldering of discrete components has been replaced by plugging wires into headers…but how many sites could reliably.solder that many tiny smd components by hand anyway?

[@vintageaudioreview]

I certainly agree with you about solder smd stuff- luckily I rarely need to do that unless I am playing around with something modern, which is not often. I have not had Luxman kits come my way. I prefer the look and nostalgia factor of the "vintage gear" to a lot of the newer stuff stuff you mentioned and the sound of the older stuff is just fine (except for maybe some lower level hum hiss). Just like I would like to own a '68 Camaro to drive around sometimes instead of a new Corolla. I appreciate your comments!

[@chrisblock6697]

Very nice tour of the amp (looks pretty well designed for reparability?) and enjoyed the repair discussion. Thanks!

[@vintageaudioreview]

I appreciate your comments as always. I would say that for the most part it was/is fairly easy to work on.

[@douglashoff95]

I built this along with the PAT4 and FM5 back when I was in high school. Still works great. Using my original A25 speakers. By the way, what were the smaller capacitors connected across the big can caps. These are not original.

[@vintageaudioreview]

Am glad your PAT4 & FM5 are still going strong. There were a lot of mods on the unit, including the caps you mentioned. I am guessing they were like 0.1uf @ 400v. Sometimes you will see such caps use to help remove turn on spikes. Thanks for your comments.

[@TriAmpHiFi]

👍

[@vintageaudioreview]

Thanks for the thumbs Up!!

[@hunkydorian]

They never should have made this amp. Transistor technology wasn't really ready yet. I mean, single power supply and a gigantic output capacitor. And that's just one thing.

[@vintageaudioreview]

Remember it was mainly a kit amp. I have tested some nice Solid state amps for the 60's and early 70's, and they seemed decent- thanks for the comments!!

[@spacemissing]

I like the one I have. Kit built by who knows who, totally stock, sounds great. Single-ended power supply and capacitor coupling to speakers is perfectly OK. In fact I think I prefer the way such amplifiers sound at low volume.

[@vintageaudioreview]

@@spacemissing As long as you like the sound and it is working, that is the main thing- thanks for taking the time to comment!