Simple DIY crossfeed

[Deleted]

The suggested 2 behind each other won't work properly because of the pots in the bypass circuit of the first PCB will screw up the filter's working of the 2nd X-feed board as the filter needs to be fed from a rather low-Ohmic source

If you leave out the 10k pots (connect a wire between the green-green and pink-pink wire on the switch) you can connect them in series but when both PCB's are in bypass position the volume will be substantially higher + when both filters are switched on it will probably not sound at it's best too .

Fitting only pots in the bypass circuit of the second filter won't work well either as the first filter would play softer then the second one because the 10 kpots + loss of the first filter will be added.

The best approach would be by using a 3x4 rotary switch
This should have 3 positions and (at least) 4 mother contacts.
BUT there is a slight difference in output level between the subtle and medium Xfeed so the 'bypass' pot will have to adjusted to an 'inbetween level' or the output levels of one of the 2 versions (preferably the one you use the most).
If requested I can make a tutorial for this too.

With 3 boards you will need a 4 position/4 mother contacts rotary switch.

To my ears the subtle board works best..

I have 2 (homebrew) portable amps where the filter is on permanently and can't even be switched off.

[Deleted]

Sept 1, 2010 15:04:36 GMT @solderdude said:

a legitimate question.
there is a big difference in crosstalk and crossfeed.
Also there is a big difference between normal crosstalk and the 'nasty' crosstalk in the Indeed/Bravo thingies.

In the Bravo/Indeed there is always a bit of 'normal' crosstalk between the 2 channels which only narrows the stereo but only slightly.
Above a certain voltage in one half of a sinewave the crosstalk becomes MUCH larger from that point on and is a-symmetric and non linear.
This can be clearly heard when the bias is set too low as 'unpleasant distortion' and sounds nothing like the typical non feedback triode distortion which most people find pleasing because of the spectral distribution and amplitude of harmonics generated in this kind of 'distortion'.

Crosstalk is a technical term for bad channel (left and right) separation.
Like the sort you get with vinyl and sometimes tape recordings where the recording head and playback head had a different height position on the tape and tuners.
a small part of the left signal enters the right channel in this case and vice versa.
If there is 100% crosstalk the signal is mono.
It's mostly frequency independant so bass mids and treble have an equal amount of crosstalk AND there is no phase shift/delay in the signal.

In crossfeed (Xfeed) only the lower frequencies are a bit 'monofied' (a certain percentage) and the mid to high frequencies increasingly less and get a slight phase shift when transferred to the other channel.
a totally different effect on the sound.

On higher frequencies with a speaker located on the right, the right ear hears the speaker as normal and the left ear has the sound slightly delayed because of the bigger distance of the LS to the ear and the speed of sound and frequency also because our ear is slightly shielded by the head and the ear is listening 'outwards' there is also a smaller HF part compared to the LF part.
From this info our brain can reconstruct where the sounds came from.
this delay phase shift for the higher frequencies is done by the capacitors/resistors.
For the left speaker the same principle.

as X-feed is an approximation of this phenomenon the sound separation is perceived as 'more natural'.
Doesn't work on artificial head/2 mic recordings with a Jecklin disc for instance as this already has real X-feed embedded in the recording.

On mixed music where every instrument got it's place by the pan adjustment on the mixing console there is an effect.

Wheter one likes the effect or not is indeed more of a personal nature.

Thanks for the excellent explanation, Frans!

I just put together a subtle crossfeed, following your schematic and instructions, and listened carefully to many different recordings. Being a classical musician, in the type of music that I listen i.e., classical music: symphonic, opera, chamber music, etc. the crossfeed to my ears does not work as well as in rock, pop, etc. The latter are usually done in the studio and with a lot of gimmicky mike mixing and unnatural separation between left and right, and I can see how the crossfeed would be beneficial in these cases. Classical music, on the other hand, is usually recorded with the intent to reproduce a concert hall experience, be it to achieve clarity in thick symphonic textures, operatic stage performances with intended depth and large sound stage, or a more intimate recital hall ambiance such as chamber music. Even with directional (cardioid) mikes, frequently used in classical recordings some of the sounds from the left naturally are picked up by the right channel mikes, and vice versa as well as the sounds reflected off the walls of the shell and auditorium walls, the crossfeed already occurs naturally in these cases. The effect of the electronic crossfeed (subtle) that I heard was one of muddying up the sound, especially in thick orchestral texture passages, where I would want to hear maximum detail vs. a big mass of blended sound to a point where individual instruments are totally drowned out and lost in it.

I am sure that the crossfeed will work well with recordings that have artificially separated left from right channels, achieved by very close miking, and/or isolation chambers, and can see how it will help relieve listening fatigue in such cases. I will probably use the crossfeed only when listening to some of these (rock, pop, and others) that need it, but most of my listening is classical with some jazz (classical), and in my humble opinion, and to my classically trained ears, not suitable.

[Deleted]

The cossfeeds are indeed intended for artifically created music such as most studio work where most instruments are recorded with 1 mike in close proximity and their 'placement' is done with a pan pot.
With LS a reasonable 'soundstage' is recreated because of the room acoustics and sonic blending of L and R signals which is not the case when a HP is used as L and R are extremely separated (provided there is no crosstalk).

Classical (in most cases) is not recorded in the same way.

[fault151]

Guys, I have only just seen this post. Are all these boards gone now? Would have been fun to try. I may attempt to build one on a bread board if they are all sold.

[PinkFloyd]

Nov 26, 2010 22:23:23 GMT fault151 said:

Guys, I have only just seen this post. Are all these boards gone now? Would have been fun to try. I may attempt to build one on a bread board if they are all sold.

Mark,

I have a couple kicking about somewhere, I'll look them out.

Mike.

[fault151]

Ok cool, cheers mike.

Oh did you build three as you mentioned earlier in this post so you could switch between the different options?

[PinkFloyd]

Nov 26, 2010 22:30:01 GMT fault151 said:

Ok cool, cheers mike.

Oh did you build three as you mentioned earlier in this post so you could switch between the different options?

Didn't have the time Mark I built the "high" X-Feed one and the other two boards are still blank..... I'll look all three out for you

Mike.

PS: How's the Panda coming on?

[fault151]

Ok thanks, send me a message when you find them.


Yeh the pandas coming on ok. I'm going to be fitting I to the box tomorrow. The panels will have to wait as I have to get them made. I don't have any drills big enough or the right kind of set up to drill holes for the rcas and headphone socket.

[fault151]

I found this image of a diagram to build the corda cross1 does it look right in terms a similar design? I haven't compared all the resistors to the actual list on the Meir site, but at a glance it seems similar.

[xerxes]

A crossfeed was one of the first things I ever built, here it is:



The toggle switch allows you to bypass the crossfeed completely and the rotary switch allows you to select one of three levels of crossfeed.

Here's the original thread from way back: rockgrotto.proboards.com/index.cgi?board=b&action=display&thread=863&page=1

[fault151]

Is this a clone of the corda cross that you have built?

[xerxes]

Yes, it was built from a circuit Mike posted up:



Take a look at the thread I linked to, all the info is there.

[Z]

plans for selling any more of these?