Kef R105/3 Kube equaliser schematic

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I was at KEF from the mid 70s to the late 90s and yes it was. Thanks. During those years, Peter Baxandall was also used as a consultant, to optimise the trickier electronics projects.
I thought the Kube was a device to convert a fourth order alignment to a sixth order and hence would simply have been an underdamped sallen and key high pass filter

No. Absolutely not. KEF did not ever produce one of those Theile/Keele 6th order reflex designs. One Friend stage was normally used to lower the cut-off frequency of the second order response of a closed box or couple cavity design. I did once use a cascade of two friend circuits to equalise and extend the 4th order low frequency cut-off of a studio monitor reflex design but it remained 4th order.

The Friend circuit is the Friend circuit. It is a single op-amp biquad. It is simillar to the Delyanis single op-amp bandpass circuit but with two extra resistors giving a third input port to allow for different f and Q in the numerator and denominator of the transfer function to be implemented. If you have a fixed second order transfer function to implement then it is the most efficient (canonical) topology to adopt :cool: .

If you want to vary f, Q, etc. with a pot then it is not suitable at all :cannotbe: .

What most people call a state variable filter is normally some sort of two integrator loop. This needs at least 3 op-amps to implement a second order function but has the advantage of allowing seperate pots to control f and Q independantly. Other variants with 4 or more op-amps allow more functions.
 
I know this is an old thread, but it keeps popping up in Google searches.
I'm constructing a new power supply for a 104/2 KUBE, and have located an 18VAC transformer (plug-in) with 3 secondary screw terminals for connecting the cord.
Now I need to source some 3 conductor insulated wire and a 5-pin 270 degree male DIN plug. What's my cheapeest or easiest source to find this stuff, since radio shack no longer carries stuff like this? Somewhere on-line perhaps?

Thanks.
 
OK, I got a Honeywell 18VAC xfmr, and found the 270 degree 5 pin male DIN plugs in a lot of 15, on eBay for pretty cheap. The wire I should be able to find at home depot by the foot I believe. If this works, and I can build several of these, would anyone be interested in having me make them a replacement power supply for their Kube? I'll have extra plugs so I could always order some more transformers and wire.
 
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