(1971-04) S R mag - Passive Line Level Hafler/DynaQuad "Decoder"

[kfbkfb]

https://www.worldradiohistory.com/A...eo/70s/HiFi-Stereo-Review-1971-04.pdf#page=64


I may build a passive line level Hafler decoder, my active DIY decoder hasn't been switched on since 2000-09.


Kirk Bayne

 

[par4ken]

https://www.worldradiohistory.com/A...eo/70s/HiFi-Stereo-Review-1971-04.pdf#page=64


I may build a passive line level Hafler decoder, my active DIY decoder hasn't been switched on since 2000-09.


Kirk Bayne

Why not? An active version provides much better control then the passive version. The best idea is to make an active decoder where the front channels can be mixed together in phase and the back out of phase. Such a unit can be dialed in for RM, EV-4 or Dyna. It works great with quad headphones!

 

[kfbkfb]

My DIY decoder is ~41 years old, I used it a lot when I was using 2 stereo receivers for quad, I got an A/V receiver w/(original) DPL (and a few other fake surround sound modes) 2000-09.

A passive decoder (transformer based, as diagrammed in the linked article) wouldn't need any components (capacitors and the like) replaced because they get old.


Kirk Bayne

 

[Doug G.]

I built a line-level Hafler type deal back then and still have it somewhere.

Doug

 

[Sonik Wiz]

My DIY decoder is ~41 years old, I used it a lot when I was using 2 stereo receivers for quad, I got an A/V receiver w/(original) DPL (and a few other fake surround sound modes) 2000-09.

A passive decoder (transformer based, as diagrammed in the linked article) wouldn't need any components (capacitors and the like) replaced because they get old.


Kirk Bayne

Any XFMR based Hafler/Dynaquad decoder will be inferior to one implemented with modern IC's, with variable controls per @par4ken. I don't know how old you are Kirk but at 74, I don't worry about a new DIY project needing capacitors replaced in my lifetime.

Some time back there was a really elegant implementation by a member here of a circuit of this design. @DuncanS ? Anyone recollect? Even a very nice case.

 

[kfbkfb]

Further thought about using the Hafler method for creating a fake surround "channel" - the passive speaker matrix option always works.

One example, my 20 year old Pioneer VSX-D514 doesn't output the digital input signals to the analog (tape) outputs, complicating feeding a line level output to an external line level Hafler "decoder".


Kirk Bayne

 

[DuncanS]

Any XFMR based Hafler/Dynaquad decoder will be inferior to one implemented with modern IC's, with variable controls per @par4ken. I don't know how old you are Kirk but at 74, I don't worry about a new DIY project needing capacitors replaced in my lifetime.

Some time back there was a really elegant implementation by a member here of a circuit of this design. @DuncanS ? Anyone recollect? Even a very nice case.

As a sprightly 66 year old I can't remember seeing anything like that, but to quote Tom Jones "Thats not unusual"

 

[par4ken]

Some time back there was a really elegant implementation by a member here of a circuit of this design. @DuncanS ? Anyone recollect? Even a very nice case.

It was Soundfield and the thread started out about the Akai SS-1 Universal Synthesizer. My circuit is in there as well.
The entire thread is very interesting. https://www.quadraphonicquad.com/forums/threads/akai-ss-1-universal-synthesizer.5331/

​

 

[MidiMagic]

I have a Dynaquad-type passive decoder that can be adjusted for any regular matrix.