Limiting the stereo separation with BassMX
 

I've developed a little audio board that softens the hard stereo separation of the Amiga audio. It does this by mixing the low frequencies from each channel with the audio from the other channel. This leaves the stereo image mostly unaffected but at the same time it makes the audio more balanced when playing on big speakers or headphones.

This is of course not to everyone's taste but I've had some great feedback from musicians, DJs, producers and people from the demo scene. You can listen for yourself (and make your own mind up) as I've put some samples on my blog to listen to, which you can find at www.edsa.uk/bassmx.

external hardware that works on every amiga it take it? if i remember right (a rarity) isnt this why hoffman and a few others use the Amiga600 for a load of DJ'ing as they use 1 audio out port because doing so makes sure all audio goes through 1 cable/source so there is no separation?

Yes, correct. External and should work on any Amiga. Works fine on my 500 and my 1200 for example.

To my knowledge the trick of plugging only L in to get both channels out as mono is available on all Amigas, not just the 600 (could be wrong on that but I do remember my 500 doing it too). This does result in mono audio so all stereo separation is lost, which is why I never really liked doing that at home. For a DJ in a club it may be less important to keep it as much stereo as possible.

I never knew that about the amiga audio output!

The left audio jack for all channels mono only trick definitely worked on my A600 and A1200.

Works with any of the two. It is implemented using a third contact in RCA socket, which is connected to the other channel. If one of plugs is not inserted, the third contact connects to "hot" one, so stereo channels are shorted together.

Unfortunately this doesn't work on the Amiga 500.

Is that so? The reason I thought it also worked on the 500 is that after I had done a repair on my 500 and closed the case I had both channels out of left. That annoyed me since I had just closed her up. I then put a plug in right and it was fine again. When I then (years later) heard of the mono trick on the 600/1200 I just assumed that was what happened on the 500. To be honest it is quite a few years ago that this happened and maybe I don't actually remember that properly!

In the end I never used it since I have a "mono" switch on my amp. But why would I want to listen to mono audio when I have a stereo computer? That's why I designed BassMX - best of both worlds so to speak!

After reading this thread and watching a demo vid, I ordered two for my Amigas. Cool concept!

this sounds like it could bring phasing issues not a great idea to mess with bass that way

also does not fix the situations where the sounds on the frequencies not centered jump from one channel to the other

I can assure you that there are no phasing issues. You can easily hear that from the examples I provided. Phasing issues would be instantly audible when listening on good speakers or headphones.


When that happens it is part of the intended stereo effect of the musician/game designer. In that case it is best to leave it as it is - otherwise you're just mono-ing all the audio, which is not the intention of the system..

The technique here is known as mid/side with EQ. Mid/side is a technique where you encode a left/right signal into two signals, mid, the mono element, side the stereo element. You can then apply other processing to each signal. For example a high pass filter on the side element. This has the effect of making the bass mono when it is then decoded back to left/right.

I did some tests using this method in Ableton and some raw hard separated amiga recordings and the results where really good. My personal preference here was to push the eq quite high and also bring the panning in quite a bit but result was really good.

It's really cool to see such a device available for the amiga, top work here from Edders coming up with this entirely in an analog audio signal. If there was anything I would add would be two pots, one for the cut-off frequency and another to also bring the panning into centre, but I'm sure that complicates this to another level.

Thank you! Yes, I agree with you and looked into giving it a variable cut-off frequency. Unfortunately that would require a 4-way pot for each channel. I think Bourns makes these but they may be special order (my usual suppliers did not seem to stock them). Lowering the order of the filter changes this into a double pot (per channel), but I did not like the effect of the shallow filter. In the end I decided to go with a fixed frequency as this also allowed me to keep the device cheap..

Very interesting device! Ordered one...

Sounds very good indeed! Very nice work.
It also gives 6dB of bass boost right? (by moving the bass to two speakers)

Accordingly to panning low if both sides are playing a bass at the same time then gain would be +6dB while if only one of the two is playing a bass then gain would be +3dB

Hmm, yeah. Maybe more like 3dB (twice the channels, twice the power). To me it sounds like quite a significant boost in the bass department though.
Very groovy :)

I use a small mixer (Xenyx 502 not USB) for headphone work, and speakers that are quite naturally "40% separated" for everything else. I don't like mono because I still want to hear what I'm doing.

But to each their own, and this could have the side effect of making drums sounding like they're panned, with low toms kicks nearer the center. This could also exaggerate levels for bassy sounds, similar to bass boost. I think listeners would think it sounds better, but it would be in the way for me when I mix.

Very cool, was looking for a solution..found it now :)

Hmm... Interesting ! Is an official enclosure planned ? :)
If that's H0ffman approved I might get one !