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Muzak Tube Amplifiers: The Budget Audiophiler

Muzak is best known for its background music that drives you crazy in the elevator, but as I discovered — they made amazing tube amplifiers as well.

Muzak Model 975A Vintage Tube Amplifier

Life is definitely unpredictable; something that all of us have discovered over the past 12 months. Rather than vociferate on things that none of us can control at the moment, I want to share a good story about a vintage audio discovery that changed how my family and I enjoy music in our home. It’s not from some high-end brand like McIntosh, MartinLogan, or Quad; when that happens – all of you will be the first to know. I want to talk about Muzak this week. No – not the horrible “Muzak” background music we suffer through in the elevator, but the stereo equipment manufactured by that very same company. 

How I found these surprising mono block amplifiers manufactured in the 1950s is one of the reasons why I love vintage audio. 

One of the local banks in Buffalo has a corporate reuse warehouse with a small storefront that sells items of value that the bank no longer needs. Items like furniture, office fixtures, and art. You really don’t expect to find vintage audio equipment for sale in a place like this. 

Muzak Model 975A 1950s Era Tube Amplifier
Muzak Amplifier Model 975A – 1950’s era PA Amplifier

But I did. In this very uninteresting store, I came across a rather curious item. The Muzak Model 975A Amplifier. 

I inquired further about it and was told that it came out of a bank and was quite rare. It also no longer worked; according to the store it made a “pop” when turned on last and created some smoke. 

There was a moment of hesitation because I was not going to take on a project of this magnitude to restore this “elevator” music amplifier and convert it for use at home in one of my vintage systems. 

That being said, I would be lying if I stated that I was not intrigued by the industrial design, the logo, and unique metal cage protecting users from the tubes. It looked rather weathered, which was odd considering that it had probably spent its entire life hidden inside of a closet or office.

Later that night I did a little research to learn more about these strange looking amplifiers. 

Muzak sold these amplifiers as part of a package to banks, department stores, medical practices, and other businesses to facilitate playing background music. In order to make them last, Muzak had to build them with a higher level of quality; imagine playing music through your home for 10-12 hours each day. Every single day of the week.

Muzak Model 975A Tube Amplifiers front

The Muzak amplifiers from the 1950s featured both a mono output for “music” and a public address output to announce new sales on girdles in aisle 4 or lost children. What makes these amplifiers rare is that they were not in the hands of the general public; you couldn’t walk into a stereo store and just buy them. 

Searching online, there wasn’t a lot of information about them. I did find one individual who was an Instagram follower of mine who claimed that his father worked for Muzak and had installed one of these systems in their family home so that he could play music throughout the house. 

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“Father of the Year” Award for that guy. 

I didn’t have a lot of luck finding a pair of the Muzak amplifiers on any of the audiophile sites, but then I struck gold on eBay. 

Someone was selling a pair of Muzak amplifiers that had been converted with RCA inputs, recapped, and set-up for home audio loudspeakers (8 and 4 ohms). 

I quickly emailed the seller and received a response that made me quite intrigued; he was an electrician and audio enthusiast with a side gig of restoring and upgrading rare and older amplifiers. 

Finding one of these amplifiers is rare. Finding a matched pair that have been completely restored is another level of luck. 

Muzak Model 975A Tube Amplifier Side View from eBay Ad
Muzak Model 975A – Side view from the eBay posting

The original ad contained the following verbiage:

  • “Push-Pull 6V6GT output tubes, type 7199 low noise driver tubes, type 12AX7 input amplifier tubes, and 5Y3 rectifier tubes.
  • Each amplifier has 13.5 watts power output with clean sine wave into a 4 ohm load, or 9.5 watts power output with clean sine wave into an 8 ohm load. The 4 ohm output is used for 4 or 8 ohms.
  • Both Amplifiers have 3 new 47mfd 450volt 1050C filter capacitors installed under the chassis; the original filter capacitors were left in place, not connected, to maintain original appearance.   
  • All paper type capacitors have been replaced with new polyester type capacitors.
  • All controls have been cleaned with contact cleaner and function properly.”

I put an offer in minutes later and he accepted. I was now the owner of a “bespoke” pair of Muzak high fidelity power amplifiers. 

I’ve mentioned a few times that how a seller packs vintage audio components is very important; sadly, some people still don’t think they need to spend the money to do that once payment has changed hands. 

Beware of these people. Any seller who won’t take the time to properly pack your item in foam, bubble wrap, two boxes, and make sure it’s bomb proof – it may not be worth the purchase. 

Ian White (our Editor-in-Chief) continuously makes the point that he only buys turntables from Vinyl Nirvana because they go above and beyond in that regard. He’s buying his 3rd turntable from them this year because they work harder than larger audiophile brands to make sure the product is perfect out of the box. 

The Muzak seller did everything right. Everything was properly packed, all of tubes were in their own secure packaging, and he made sure that everything was labelled.

When we removed both amplifiers from the boxes, I was in love with what I saw. How could these be hiding in some closet or bank office for decades? 

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Test & Verify

Muzak Model 975A Tube Amplifiers on the test bench
First day of testing Muzak Model 975A Tube Amplifiers with McIntosh C28 Preamplifier

I test everything I receive on the workbench in the basement. I test for general functionality and sound. Which preamp will sound best? Which loudspeakers will pair best? The Muzak amplifiers arrived at the same time that I was performing a deep clean on my McIntosh C28 pre-amplifier (cleaning potentiometers has become a weekend thing for me) so it gave me the opportunity to test them together. 

I installed all of the tubes, wired everything up, and connected the Muzak amplifiers to a pair of Jensen Model 4’s which I use to check almost everything. The Amazon Echo Dot acted as the source device.

The Echo Dot is not a great sounding source, but I was stunned when I started streaming music through the system. The depth and warmth of the sound just ticked off every box on my sonic list. I’ve definitely noticed that I prefer pairing solid-state and tube gear together on the vintage front. 

The Muzak amplifiers were so impressive that I inserted them into my main rack almost immediately; I chose to not use the McIntosh MQ101 Environmental Equalizer as part of this particular set-up because I didn’t feel that it added anything to the sound. 

How did the low wattage produced by the 6V6GT tubes work with the Ohm F’s? 

My Stereo System Today with Muzak Model 975A Tube Amplifiers and Ohm F Speakers
My Stereo System Today with Muzak Model 975A Tube Amplifiers and Ohm F Loudspeakers

Luckily, my Ohm F’s have been totally rebuilt thus not falling victim to the online myth that you need to drive them with hundreds of watts of power. 

The Muzak/Ohm combination has exceeded every possible expectation that I had. I listen to this system 7 days a week and I could not be happier. 

I did decide after a year to replace all of the output tubes; the matched sets in each amplifier gave them a new lease on life and they look so brilliant when illuminated that I’ve put the tube cages away permanently. 

The Muzak amplifiers are certainly fringe vintage audio components. There is not a huge demand for them and I’m not sure that I could find another pair this clean. What I have learned from the experience is that you don’t know what exists until you venture out of your comfort zone and really try something new.

Muzak Model 975A Tube Amplifiers with Tung Sol Tubes
Muzak Model 975A Tube Amp with Tung Sol tubes
Muzak Model 975A Tube Amplifiers Without Covers
5 Comments

5 Comments

  1. Saurabh Gopal

    April 3, 2021 at 12:54 pm

    Thanks for the input guys! Muzak has expanded a lot since I found out about them way back.

  2. Tom

    November 5, 2021 at 1:29 pm

    I am thrilled to see this article as have been thinking about doing the same with my home stereo for awhile since I stumbled into a bunch of these Muzak amps a few years ago. I read they were designed and built by Stromberg-Carlson so figured they were a quality product. I am in process of replacing the caps and other worn out components as well as AC cables with ground, and input jacks to 1/4” or rca depending on final application. I’ve already tried a couple with 1/4” jacks for use as an electric guitar head and they sound great. I also added a couple simple D- shaped handles on a few. They match the overall design of the amp nicely and definitely make it much easier to pick up and move as they are a bit hefty and have sharp corners.

    • Ian White

      November 5, 2021 at 7:50 pm

      Tom,

      That sounds like a cool project. Take some pictures and share when it’s done.

      Ian White

  3. John Mellsop

    June 9, 2022 at 10:26 pm

    Hi watchers and enthusiasts. I was very excited to come across the above story. As an apprenticed Radio/Audio Tech I, and 2 other registered journeymen manufactured many of these valve amps to the Muzak design exactly as you see in the above photos. The performance standards were a critical element of production.

    As a high school student I had built a guitar/PA amp using a similar circuit but KT66 or KT88 output valves.

  4. Bernard Schmitt

    July 19, 2022 at 2:21 am

    While out of my general wheelhouse (though I do tinker with more modern devices) I picked up a Muzak 1008a from a local grade school baseball scoring booth.

    It powers on and appears to have all original tubes, except they put two wires across the Muzak S1 port, jumpering between 5-7 and the other wire connects 6-8, not sure why.

    They made an external in/out box to adapt to 1/4” plugs. The back of the main unit’s 1 and 2 input go to one of the 1/4” jacks, and they have the output section wired as per the back panel’s diagram for 150 Z, with two 1/4” jacks coming off each pair(A-B and C-D respectively).

    When I plug in a guitar to the input jack and a pair of powered speakers to the outputs, I heard faintly some of the lower bass strings with the Muzak volume at about 7.

    So I checked the T and B pots and they were both fully down. Turning them up halfway only resulted in no longer hearing the guitar at all, just hum.

    I next tried a mic with its own 1/4” plug, and this time I turned up the Mic volume knob…with the same result, no discernable sound coming out.

    The tubes appear to glow at the tips so I think that is promising.

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