Audio Output Distortion
I am a relative noob to the world of pro audio equipment. I have made many speakers over the years, and they work well, but I have recently come across a strange problem with recent purchase and here I present my research notes and links to the various resources.
The Problem
I have recently acquired an akai rhythm wolf drum machine, and the main signal output is showing some strange behavior.
When I'm using a high quality pair of headphones such as Sennheiser HD280 Pro the sound quality from the rhythmolf is excellent. I am particularly interested in The Sound of the bass drum here.
So the bass drum or kick drum gives out very delicious low rich bass when using the headphones which is what I like the here . . .! . . . however when I plug the output into a speaker which I normally use for listening to music the bass drum sounds very thin and the hardly any bass is produced.
If you turn the volume on the kick drum too far then it starts to distort in a crackly sort of way so I'm trying to figure out what's going on there why am I getting thin bass when I'm using a speaker and what am I getting why am I getting good base when I'm using headphones.
I should say this behaviour repeats on 3 types of speaker:
- Small Sony Bluetooth Speaker - Works fine with synth, and other drum machines.
- Soundboks 2 - Very heavy duty unit, works fine with synth, and other drum machines.
- Home Made Speakers - 2 Large Active Speaker containing 4 x TPA Amplifiers and 4 x 10" subwoofers. Which when playing music from spotify are extremely loud.
The Fix = Mix . . er
I contacted AKAI Support there response was:
"The problem with the weak, distorted kick drum might be expected as it is not recommended to directly connect a speaker to the rhythm wolf Main Out. Instead, use a standard 1/4" (6.35mm) TRS cable to connect this line-level output to the input of an audio interface, mixer, amplifier system, etc. Additionally, stereo headphones can be connected to this output. If the Synth Out is left unconnected, the Main Out will include the drum and bass synth voices. However, if a cable is connected to the Synth Out, the Main Out will include the drum voices only."
I also contacted the chap I bought it from:
Me: "Hey mate did you always run this through a mixer"
Seller: "Hi yes I did run it through a mixer. It has some serious sub on the unit, I'd check the EQ settings on your speaker and set it to "flat" is possible."
Noob Fault Finding
Below are musing on why this is happening.
First Reaction
An initial experiment I tried was to route the output to a headphone amplifier and then the headphone amplifier to the speaker. This didn't work. Very thin "sniky" bass drum.
Research
So something coming out of the Rhythm Wolf is the wrong level for the 3 speakers I have tried out. The output has too much power, or not enough, or the receiving speakers are expect something within a certain range and that isn't happening. So lets figure this out:
Impedance
My HD280 Pros are 64 Ohms.
"Most headphones have an impedance that is typically between 8-600 ohms."
"All these factors, make us arrive at something important known as Impedance Matching."
A guitar amplifier is high impedance. . . I plugged in the drum machine to a Yamaha GA15 and I get the same behaviour as I do with speakers, the kick drum sounds very very weak. I can turn up the snare drum and other outputs and they are very loud and distortion free.
"An impedance mismatch in a circuit or along a transmission line will produce a reflection back to the source of the signal. When a signal reflects, the power transferred downstream towards a load is reduced. Impedance matching provides a dual role of enabling power transfer into a load by suppressing reflections."
So it sounds like it could be impedance. But my guitar amp experiment doesn't work. It need to be low to high.
Voltage
Is it voltage of the output, I have read 2V is typical. Is it more than that or less?
Power Supply
I have read that using a different power supply for the Rhythm Wolf can fix a problem with distorted outputs. However, I have switched the adaptor and it didn't;'t work. THe manual says 12V 2A Supply which is reasonably beefy.
It was supplied with a 12v 600ma, but swapping that to a 12v 2a has not helped.
More amps? Probably won't help.
Distortion Notes
"Possible causes of audio distortion problems may be: Wrong input level to the amplifier. Amplifier gain is set too low or high. Not enough amplifier power."
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