NRDC-Ambisonic Surround Sound Decoder

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tryphon

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I think what it really needed was a better circuit!
You might have improved the ‘sound’ of the thing but it just couldn’t decode quad very well. It was quite expensive even in kit form and I was very disappointed in its performance. It was so poor in positioning and separation (even compared to the el-cheapo decoders I’d heard until then) that I thought it wasn’t working properly and spent ages fault finding on it only to conclude there was no fault. My experience of using it was pretty much the same as Sonik's.....
It needs tight tolerances for the resistors and capacitors in the phase shifters, which mine have and the commercial kits did not. It outperforms all my other non-logic quad decoders. For Ambisonics, then, it is truly excellent. It outperforms my Onkyo Ambi decoder/amp.
 
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Owen Smith

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It needs tight tolerances for the resistors and capacitors in the phase shifters, which mine have and the commercial kits did not. It outperforms all my other non-logic quad decoders. For Ambisonics, then, it is truly excellent. It outperforms my Onkyo Ambi decoder/amp.
I thought those resistors looked high spec, they look like 1% metal film from what I can see in the picture.

Are the better op amps the surface mount ones on little daughter boards that are then fitted into the chip sockets?

It looks very well built from the pictures, nice neat job you did there.
 

Sonik Wiz

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It needed better op-amps and a better power supply. With those mods, it sounds great.
I've actually had experience with two of the Integrex units. The first one I purchased built from a trip to the factory whilst on honeymoon in the UK. The second one a few years later I built for a friend. I even had an IMF Ambisonic decoder for a while. So I certainly gave that format a good listen to. But as @Soundfield said ultimately there just wasn't anything special about the system. Sansui QS Vario-Matrix sounded fantastic with QS or stereo. My Fosgate Tate sounded wonderful with SQ & stereo. But Ambisonics left me with only a "meh".

However that doesn't stop me from recognizing a passionate DIY project done well. And you have certainly succeeded at that! And do I spy an input peak level you've added to the front panel?

I take it this your main/only decoder? What other cool toys do you have?
 

fizzywiggs41

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20220518_220309.jpg



Integrex also had a decoder ,the forerunner I suppose , which had 45j , and Matrix H , so I thought I'd dig up my old photos of this machine for any and all interested.
 

Soundfield

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Isn't that the unit we've been talking about all along?

Edit: oops, no. Different box different push buttons. Interesting!

Essentially the same machine. The Wireless World design articles were published in the middle of 1977 (but were written earlier) and provided B format, 45J, H, RM BMX and SQ decoding. There were two variants. The initial kits had that exact set of formats:

Int 1.JPG



The BBC introduced matrix HJ in mid 1977. This resulted in a second version with a couple of button changes - the “45J” button becoming “UHJ” and the “H” button becoming “HJ” (the circuit changes would have been trivial):

Int 2.JPG
 
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tryphon

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I've actually had experience with two of the Integrex units. The first one I purchased built from a trip to the factory whilst on honeymoon in the UK. The second one a few years later I built for a friend. I even had an IMF Ambisonic decoder for a while. So I certainly gave that format a good listen to. But as @Soundfield said ultimately there just wasn't anything special about the system. Sansui QS Vario-Matrix sounded fantastic with QS or stereo. My Fosgate Tate sounded wonderful with SQ & stereo. But Ambisonics left me with only a "meh".

However that doesn't stop me from recognizing a passionate DIY project done well. And you have certainly succeeded at that! And do I spy an input peak level you've added to the front panel?

I take it this your main/only decoder? What other cool toys do you have?
I thought those resistors looked high spec, they look like 1% metal film from what I can see in the picture.

Are the better op amps the surface mount ones on little daughter boards that are then fitted into the chip sockets?

It looks very well built from the pictures, nice neat job you did there.
Thanks for your kind words. The improved op-amps are the SMDs on the daughter boards. However, even for the other ones, I upgraded to the later versions, which had (marginally) better specs.
 

tryphon

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I've actually had experience with two of the Integrex units. The first one I purchased built from a trip to the factory whilst on honeymoon in the UK. The second one a few years later I built for a friend. I even had an IMF Ambisonic decoder for a while. So I certainly gave that format a good listen to. But as @Soundfield said ultimately there just wasn't anything special about the system. Sansui QS Vario-Matrix sounded fantastic with QS or stereo. My Fosgate Tate sounded wonderful with SQ & stereo. But Ambisonics left me with only a "meh".

However that doesn't stop me from recognizing a passionate DIY project done well. And you have certainly succeeded at that! And do I spy an input peak level you've added to the front panel?

I take it this your main/only decoder? What other cool toys do you have?
The integrex is my most used surround decoder. I had Marantz back in the seventies (my brother has it now), JVC Nivico CD4, Dynaco and I have a JVC digital surround receiver and an Onkyo 909. I also have a Hughes Retriever and a Fosgate Model Three.
 

tryphon

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Essentially the same machine. The Wireless World design articles were published in the middle of 1977 (but were written earlier) and provided B format, 45J, H, RM BMX and SQ decoding. There were two variants. The initial kits had that exact set of formats:

View attachment 78980


The BBC introduced matrix HJ in mid 1977. This resulted in a second version with a couple of button changes - the “45J” button becoming “UHJ” and the “H” button becoming “HJ” (the circuit changes would have been trivial):

View attachment 78981
The changes were mostly achieved with different resistor values.
 

par4ken

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I built one of these and still have it. Is it worth putting up for sale?
IMHO yes! I looked (on and off) for years for an ambisonic decoder, finally getting the Troy unit (designed for automotive use). It lacks most of the decode functions of the Integrex as well as the distance compensation and the speaker layout settings (perhaps the width control is the substitute for the layout switches?) I don't know what the Intergrex would be worth but would consider the purchase of one if not too pricy!
 

fizzywiggs41

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Just doing a bit of listening with my Troy Ambisonic Processor and it sounds very good on UHJ but not so great on stereo enhance. So without an Ambisonic source I guess that results may vary. I didn't notice a lot of difference adjusting the width control either but my listening tests have just started. I just wish that there were some good popular music titles in UHJ!


There's not very many ,Ken....but off the top of my head :

Cowboy Junkies -Trinity Sessions
Cowboy Junkies -Whites Off Earth Now
Steve Hackett - Til We Have Faces
Alan Parsons - Stereotomy
Trevor Wishart- VOX ,Electric Phoenix
Tim Souster - Sonata Equilization
Kymatik -All Noise Construction/Button Man For The City
Holly Cole Trio- Girl Talk
Michael Stearns- Chronos Soundtrack
Natalie Merchant - Paradise Is There

Also in Ambisonic stereo super stereo ,Cowboy Junkies -Caution Horses
 
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