Simple DIY crossfeed

[Deleted]

@ anybody.

Don't hesitate to ask questions about this board/xfeed like what values to change if you want to make a Xfeed between the subtle and medium version for instance.

[PinkFloyd]

Aug 19, 2010 11:42:19 GMT @cjarchez said:

You finished yet Mike! ;D

Haven't even started Chris. I am bogged down with work at the moment and ALL of it very tricky stuff (ie: exploding DarkVoice amp, V-CAN with all it's pads lifted etc.) I am also busy doing plumbing, gardening etc. and my wheelbarrow needs a new tyre

The Chinese headamp arrived last Monday and I haven't even unpacked it yet.... I have SO much on at the moment that I don't really have the desire to do "personal" audio stuff after a day working on other's gear.... I just think "oh bollocks, I'll do it at the weekend"

I'm also working on a pair of solar powered garden sculptures and just cannot get them 100% watertight.... everytime it rains "hard" there is water ingress which makes it's way into the circuit..... it's amazing just how water can get in even when you think you have provided an airtight / waterproof seal. I'm not going to be defeated though.... these things WILL go into commision as planned!

I want them to be outside 24/7/365 so they have to be able to withstand the weather up here. Let me give you an example of what they are up against.... I took the wheelbarrow's wheel off and left the "empty" wheelbarrow sitting in the garden.... the sculptures were outside too..... came indoors and had a nap (about an hour) woke up to the sound of rain LASHING on the windows.... went outside and the wheelbarrow was FULL to the brim with water!!! So these sculptures have to be 100% able to withstand this type of battering.

Anyways..... hopefully I'll populate a crossfeed board this weekend

[Deleted]

There are NO more boards available, all gone

... sorry

[FritzS]

Frans,

My board are here too, many thanks.

I want to made the middle version .... have anyone experience about all three?

[FritzS]

Aug 17, 2010 19:29:30 GMT @solderdude said:

a small tutorial how to connect it between a cut RCA cable.



I recommend building it into a small aluminium box (or other metalic box) and you must connect this housing with a short piece of wire to one of the two 'ground' pads on the PCB (the screen of the RCA cable) don't leave the housing unconnected.
make sure the wire makes good contact with the housing otherwise it is likely to pick um hum or stray RF signals.

This I want to made too - to quick switch behind with/without ... or an additional little bypass switch ...

[matt7941]

Thanks Frans, my boards arrived this morning. Very nice they are too, can't wait to get started on them.

Again, many thanks

Matt

[Deleted]

a note when using a bypass switch.
Because the board has a certain attenuation (depending on the filter) when you pypass it the volume will become louder.
I 'fixed' this in my amp by inserting a little pot in the signal line where the bypass is made.
Then adjusted these pots to match the volume of Xfeed if you like to A-B and really hear the differences.
If requested I will make a small tutorial how to do this.

[PinkFloyd]

I put the "high" version of this together today.... took about 10 minutes.... nice little board, I'll connect it up tomorrow for a listen

[elysion]

Frans, the PCB's you have sent my, have arrived savely.

I will need (a lot) more time than the others to make something out of it, since I'm still a soldering rookie.

I have planned to acquire a soldering iron and other needed tools. A couple of friends have also experience with soldering, but they all live not nearby. Beside some financial reasons (I don't need everything at once... one by one...), I have not always enough time to do everything I want. The next few months could be rather hard at work, I don't know how much time I will have during the winter months.

I think this is really a great DIY project. A very good motivation to get soldering skills and a crossfeed is really missing in my collection. I've started the 3D/binaural/surround sound for headphones thread and crossfeed is exactly what I could not test/hear up to know.

IMO binaural recordings are great way to make good audio that sounds natural. But crossfeed is probably a good way to enhance "standard" recordings to make them more natural and less fatiguing.

[Deleted]

I've just popped a medium xfeed together. I'm at work, so a little limited on music and equipment to try, soooooo,

Using a USB pen out of my laptop to,
NG27 USB amp,
via medium xfeed, (all resistors matched BTW)
to Silver Crest KH2347.

First thing, woh! volume loss, all those resistors take a toll.
2nd, Sound tonal balance change, huge.
With the noise cancelling on, really bright on the verge of nasty.
NC off, aha, that's really rather nice, I couldn't use the 'phones for long without the NC before, I sure could now.

Back to what its meant for: especially on these phones, I used experience a "suck out" sensation on extreme L/R recordings when one side fell almost silent. That is definitely cured.

I'll have to the subtle one together and see what happens.

I was really surprised by the other effects, so far a very usable tool.

Cheers Frans!

[Deleted]

It looks like you inserted the board between the HP out of the amp and the HP itself (which the board was designed for originally, hence the output socket).
The values given are for use between a source and the (highOhmic) input of an amp (10kOhm and higher) for the desired effect.
the loss in volume level when used between a source and input of an HP amp will be around 3dB.

With the values calculated for 10kOm and higher the volume loss will be substantial (over 10dB) and effects will be much different from what was originally 'designed'.
If you want to use the board between a HP-out of an amp and the HP itself the values of the resistors and caps will have to be recalculated for optimal effect and matched to the impedance of the HP.

IF you want to have the X-feed calculated for a specific HP just P.M. me which HP it is (or it's impedance) and I will calculate the optimal values for the board on that specific HP.

[Deleted]

What a pillock!

In the excitement of wanting to try it out I connected it the only way I had available, didn't even think of the differences involved.

Slaps head, and kicks own butt

Having said that, I DO like the effect it has with the KH2347 the way I mis-connected it!
I'll try it the correct way at home

I still can't believe I did that...... ;D

[Deleted]

Hi Frans,

My boards arrived today great quality

thanks

[insomniac]

Frans,

The boards arrived today, thanks.
They're very well made... great job

Dave

[Deleted]

Ahem,

I've wired it the way Frans intended now So it is now before the headphone amp.

Cruddy 'phone pic,


It certainly works, I tried more recordings with iffy L/R arrangements, much better. The "suck out" I mentioned IMPP is also apparent on my other closed 'phones and IS cured by the xfeed .

I tried a couple of recordings that have intentional L to R extremes for a desired effect e.g. "All Good Things..." Spanish version (musically slightly different to the English one) by Nelly Furtado, the intro switches with the beat, this effect is almost nulled by the xfeed.

I think this will be really good added to the subtle board and a switch for either-or-bypass, it is not something I would want in-line permanently, neither is it something to try and forget.

In case you haven't guessed, I like it . As I said before, a useful tool

[Deleted]

How to connect a bypass switch.



buy a DPDT (dual pole dual throw) switch and connect it like described above.
This is the easiest but not most elegant solution.

[Deleted]

Thanks very much Frans, that's appreciated.

[PinkFloyd]

Aug 22, 2010 22:23:35 GMT @cjarchez said:

What a pillock!

In the excitement of wanting to try it out I connected it the only way I had available, didn't even think of the differences involved.

Slaps head, and kicks own butt

Having said that, I DO like the effect it has with the KH2347 the way I mis-connected it!
I'll try it the correct way at home

I still can't believe I did that...... ;D

;D

I've had a listen to the "high" X-Feed and it's way too crazy for my ears.... will try "subtle" next

For those of you who enjoy the crossfeed effect you could also have a go at the Meier version.... it's very subtle www.rock-grotto.co.uk/crossproject2.htm

[PinkFloyd]

Aug 29, 2010 18:23:23 GMT @solderdude said:

How to connect a bypass switch.



buy a DPDT (dual pole dual throw) switch and connect it like described above.
This is the easiest but not most elegant solution.

Howzabout this Frans.....

[Deleted]

This qualifies as the more elegant version because the X feed circuit doesn't load the source when bypassed.
you will need a 4PDT switch (4 Pole dual throw)
It is the prefferd version.
the DPDT switches are more common, but if you have to buy a switch anyway Mike's version is the preffered one.

fitting a voltage divider between the upper 2 horizontal connections will make it so the level doesn't jump up and down switching on/off

[Deleted]

Hi, Frans

On the Bravo/Indeed threads crosstalk between channels was discussed at length, and you offered some excellent solutions on how to eliminate it.

Now, on this thread, crossfeed is being reintroduced and discussed at length. As a classical musician, I know from recording experience that in a natural setting i.e. a concert stage both L & R channel mikes pick up some sound from both sides of the stage, so even if we are able to separate the channels on the headphone amps, there still is some mix of sound, although that can be increased or diminished with a choice of directional vs omni-directional mikes. In other types of music, and in studio situations, the sound engineers can effectively separate the channels. This can be fun to listen to for a short time, but I can understand how with headphones it can become very tiresome because it is unnatural, and gimmicky. Some like it, some don't.

Is the difference between 'crosstalk' and 'crossfeed' that in 'crosstalk' there is distortion, and there is less of it in 'crossfeed'?

I intend to experiment with crossfeed, and will let my ears be the the judges as to whether I would like to incorporate it in everyday listening.

Thanks for all your posts! They all comprise an education in audio technology to inexperienced people like me. Your expertise is indeed greatly appreciated!

[Deleted]

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.

[PinkFloyd]

Frans,

I've tried the subtle feed and found the insertion loss to be a fair bit more than the Meier bass enhanced circuit.... it does the job nicely on heavily panned stereo recordings such as some of the beatles stuff.... I prefer the Meier in a crossfeed "on/off" situation though as the insertion loss isn't as "immediate" as the Linkwitz... the Linkwitz would be on a par with the Meier if the loss wasn't so immediately noticeable.... any way of boosting it (without resorting to active) ?

[Deleted]

the loss in level is inherent to it's workings I'm afraid.
I too find the jump in level too much for comparatative reasons.
Also see my comment in reply 44.
Meier had the same 'problem' and solved it by lowering the level of the 'bypass' signal and I did the same in my amp.
See the amp schematics in reply 13 in this thread you'll notice a pot in the bypass circuit that is in series and uses the 10k vol pot as load.

What I propose is replacing the bypass wires with 2 small linear 10k pots (or 1 stereo lin volpot) but configured the way a vol pot usually is (one leg connected to ground).
Basically a volume control of the bypass signal.
Adjust the bypass level by ear with these pots by switching on/off until there is no more level loss when switching.

It cannot be done the way I did in the amp's schematics because the 'load' of the amp behind it is unknown.
An amp's input resistance (load for the Xfeed) may be between 5k and 500k which will affect the effect the level of the bypass signal too much in this case.
With the pot connected as a volume pot this is avoided and it becomes much less load dependant similar to the Xfeed itself.



pictured is a single (Bourns or other manufacture) 10kOhm ceramic Pot.
size doesn't matter (in this case)
other models and/or types can be used too ofcoarse as long as it is 10 kOhm linear.
the switch is a 4 Pole dual throw switch.

[Deleted]

Frans,

nice diagram, even I can handle that.

I guess if anyone still wanted two different xfeed boards in the same box (eg subtle and medium) you'd just need to pop another switch after the one shown and wire it as per the first two diagrams?

Though I suspect peeps are leaning towards the subtle board being enough?