Heading for Switching and grounding article series intro page

Part I: Switching and Grounding in Vintage Audio Systems

The first article traces how vintage audio demo systems evolve and explores how that leads to switching needs and grounding problems. Covers futile attempts to solve the problems. Find out about the real solutions here:

Sw and gnding article thumbnail and link

Switching and grounding article (0.5MB)

Diagram showing pair of mono amps with parasitic feedback path

Pair of mono amps turns into an oscillator

Diagram of vintage audio system switching

Good switching for a vintage audio system

Part II:
Building a Line Input Selector for Vintage Audio Systems

The second article showcases a project to build the Line Input switch which was called-for in Part-I. You may be surprised at the interesting design issues which are involved in this seemingly trivial project. Perhaps the most useful parts of the article though, are the detailed tutorials on a method for applying excellent panel graphics and a low-cost template/punch method for making clean, accurate holes. Check it out here:

Line input selector article thumbnail and link

Line input selector article (2.3MB)

Art files for line input selector project (0.6MB)

Photo of finished line input selector

Finished line input selector

Preparing the front panel artwork for the line input selector

Preparing the front panel artwork

Bonus: Line Input Selector Photos and Text from a Builder

John Gadeikis has kindly provided coverage of his experiences building the Line Input Selector. He offers some great tips and an interesting story as well! Click here.

Part III, yet to come...
Building an Automatic Phono/Speaker Switch
for Vintage Audio Systems

Waiting in the wings is a completed Phono/Speaker Switch project, which will become the subject of the third article in this series. Stay tuned!


Reader Comments

Posted by Steve L. July 10, 2015 - 08:39 pm
Hi Dimitrios, Thank you for your kind message. You could do the combining either before or after the switch, with equal results. If you do it before, you could simplify the switch to mono. However, then it wouldn't be useful in possible later stereo applications.

One point about the "combining," of which you might already be aware: It would not be good to simply connect the left and right channels to combine them. Rather, a series resistor should be connected to each channel and the other end of the resistors connected together to yield the mono signal. The value of the resistor isn't critical. I would put it at say, 3.3K. The combining function could be built into the switch box.

A minor point: You mention changing a 6-source system to a 12-source system. Don't forget that the output of the switch occupies one of the existing 6-sources, so you would need a 7-input switch. Best Wishes for your project.

Posted by Dimitrios January 27, 2014 - 01:08 am
Excellent Excellent "How To" on Line Input Selector. I will be building something like that for my application. However, my application will be a mono output into the amp, thus making my 6 source/12 channel amp into a 12 source/12 channel amp for a whole house audio.

My question is: Do I combine the left/right Signals at the outputs of the source or keep everything stereo and separate and combine the Left/Right signal wires at the input of the amp?

Posted by Steve L. July 11, 2012 - 08:59 pm
Hi Clutterbug, Har! Wow, haven't heard "elcaset" mentioned in this millennium! I stayed with reel-to-reel (RTR) until switching to a Hitachi D-800 cassette deck maybe in 1976. By that time, the cassette had overtaken the RTR, so elcaset was never on my radar. Alas, it was a good idea to increase the media size but technology made the cassette shine, especially with the advent of Dolby-C (and the purchase of a Nakamichi ZX-7) in 1980. So poor elcaset never had a chance.

But so far, the minidisc and Nakamichi remain in the main stereo system, instead of the vintage system, so I haven't even faced up to their obsolescence, as yet. The momentous occasion of declaring them vintage, will be a tough day, indeed! :)

Posted by clutterbug July 11, 2012 - 06:10 pm
I like how Minidisk is placed next to 8 track...
where's elcaset?

Posted by Steve L. April 21, 2012 - 08:03 pm
Hi Tom,
The part number for the line input selector switch is given in the parts list on page-14 of the Line Input Selector article. (Perhaps you only saw the first article of this series.) Anyway, the switch info is: switch, rotary 11-posn 4-pole Electroswitch D4G0411N. Digikey 451-1102-ND. Thanks for your post.

Posted by Tom April 21, 2012 - 05:29 pm
You wouldn't happen to have the part number for the switch you used?

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