Category Archives: Audio

1960 Grundig SO191 Stereo Hi-Fi Console Repair

Posted on February 27, 2015 by retrovoltage

Updated July 2026 with some additional photos from the archive, and schematics at the bottom. This was a pretty early repair from back in the shop days so there’s a few things I’d do more cleanly for a customer today, … Continue reading →

Posted in Audio, Hi-Fi, Projects, Vintage | Tagged , , , , , | 31 Comments

Bose® 901 Series VI Active Equalizer #199732 Repaired

Posted on February 20, 2015 by retrovoltage

A first for my shop, I recently worked on a Bose® 901 Series VI Active Equalizer! These are considerably newer than the Series I-IV that typically come through the shop, although they’re still getting to be 25+ years old at … Continue reading →

Posted in Audio, Bose, Electronics, Projects, Vintage | Tagged , , , , , | 1 Comment

Harman-Kardon Citation 12 Deluxe Professional Power Amplifier Refurbishment

Posted on January 12, 2015 by retrovoltage

Matching the Harman-Kardon Citation 17S professional pre-amplifier shown previously, this Citation 12 Deluxe power amplifier is its 120W per channel companion. It came to the shop for a preventive rebuild after serving for quite a few years. The owner had the … Continue reading →

Posted in Audio, Electronics, Hi-Fi, Projects, Stereo, Vintage | Tagged , , , , , | 1 Comment

Sherwood S2000-III Tube FM Tuner Repair

Posted on January 8, 2015 by retrovoltage

Sherwood made some excellent hi-fi FM tuners back in the day, and this S2000-III is no exception. Unfortunately, there’s not a lot of documentation about this model available, but that didn’t stop it from getting an overhaul and alignment. The … Continue reading →

Posted in Audio, Electronics, Hi-Fi, Radio, Radios and Tubes, Vintage | Tagged , , , , | 1 Comment

Harman-Kardon Citation 17S Pre-Amplifier Refurbishing

Posted on January 2, 2015 by retrovoltage

I recently got to work on a Harman-Kardon Citation 17S pre-amplifier. Vintage HK gear is some of my favorite to work on: it’s robust, reliable, and built to be easy to service. The Citation 17 pre-amplifier is the companion for … Continue reading →

Posted in Audio, Projects, Stereo, Vintage | Tagged , , , , , , , , | 1 Comment

Watch a McIntosh Tube Amp Come to Life

Posted on December 27, 2014 by retrovoltage

Discovery’s How It’s Made shows us how a McIntosh vacuum tube audio amplifier comes to life: http://www.youtube.com/watch?v=2HgS6gvokEI Definitely worth watching!

Posted in Audio, Commentary, Hi-Fi, Radios and Tubes, Stereo | Tagged , , , , , | Leave a comment

Sony TA-5650 VFET Integrated Stereo Amplifier Overhaul

Posted on December 18, 2014 by retrovoltage

I recently got to work on a very interesting piece of vintage stereo gear from the golden age of hi-fi in the ’70s, the Sony TA-5650 VFET Integrated Stereo Amplifier. It’s a little rough, and while the power amp section … Continue reading →

Posted in Audio, Electronics, Hi-Fi, Projects, Vintage | Tagged , , , , , , , , , | 1 Comment

How Speakers Make Sound

Posted on December 3, 2014 by retrovoltage

If you’re looking for a great visual primer on how speakers convert electricity into the music you hear, check out this fantastic animated infographic by Jacob O’Neil at Animagraffs  How Speakers Make Sound

Posted in Audio, Electronics, Ideas, Resources, Speakers | Tagged , | Leave a comment

Boxed Kit Amps’ Gobo Stereo Amplifier Build and Review

Posted on November 26, 2014 by retrovoltage

If you’re a subscriber to Nuts and Volts Magazine, check out my article in the December 2014 issue where I build, test and review the Boxed Kit Amps Gobo Stereo Amplifier, a great little desktop reference amp for any skill … Continue reading →

Posted in Audio, Commentary, DIY, Electronics, Gadgets, Hi-Fi, Projects, Stereo | Tagged , , , | 2 Comments

VD-1221 Replacement Substitute Diodes

Posted on November 25, 2014 by retrovoltage

VD-1221, VD-1212, VD-1220, VD-1222, and many other vintage multi-junction diodes probe to failure, which are used in bias and RF mixer circuits, can be easily replaced by series combinations of 1N4148 diodes for reliability and longevity. Continue reading →

Posted in Audio, DIY, Electronics, Vintage | Tagged , , , , , , , , , , , , , , , , , , | 8 Comments