How to Replace an 8 speaker with a TRS 1/4" jack

Thread Starter

zombiepokla

Joined Mar 30, 2009
12
Hi all.

I've started a project where I am using an existing toy cassette recorder circuit with no outputs.. only two 8Ω speakers. I know there is a way to replace these speakers with jacks, I have tried this once before on a toy keyboard that also utilized an 8Ω speaker.. but the jack that i installed [with no extra resistors] was REALLY loud.. If I want to replace an 8Ω speaker with a standard 1/4 inch TRS jack.. do I also need to add an 8Ω resistor in parallel with the speaker terminals or maybe two 8Ω resistors inline/in series with both the positive and negetive speaker terminals? ..or niether.

Thanks!!
 

Audioguru

Joined Dec 20, 2007
11,249
If the 8 ohm output is too loud then attenuate it with a voltage divider made with two series resistors.
Only a very old amplifier made with vacuum tubes needs an 8 ohm resistor as a load.
A modern amplifier made with transistors does not need an 8 ohm load and will be happy driving 10k ohms.
 

CDRIVE

Joined Jul 1, 2008
2,219
You didn't say what you're load is going to be. Are you going to be using earphones or are you feeding the audio to the input of another device? It's easier to give recommendations for the values of a voltage divider when the resistance of the load is known. ;)
 

Thread Starter

zombiepokla

Joined Mar 30, 2009
12
thanks guys. I'm going to be running these outputs into a mixer, and then into a power amplifier. So i'm looking for a line level impedance.. I don't really know anything about impedance or "load" so if someone could give maybe a brief intro.. that'd be much appreciated. thanks for any advice
 

CDRIVE

Joined Jul 1, 2008
2,219
thanks guys. I'm going to be running these outputs into a mixer, and then into a power amplifier. So i'm looking for a line level impedance.. I don't really know anything about impedance or "load" so if someone could give maybe a brief intro.. that'd be much appreciated. thanks for any advice
Chances are a 1K/100Ω resistive divider would work for you. This would give you a 10:1 ratio without much high freq roll off.
 
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