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The Aphex/Proton Surround Decoder

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Disclord

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After years and years of looking, I finally found and bought a Proton SD-1000 surround decoder which is a 100% clone of the Aphex ESP-7000 surround decoder that Aphex released in 1987. Unlike any other matrix surround decoder, the Aphex/Proton has a logic-directed Center Back surround output and in addition to decoding Dolby Surround (it's not an officially licensed Dolby decoder - Aphex/Proton got their surround license directly from the inventor of surround matrixing himself, Peter Sheiber) it has a full stereo surround mode that, like the Fosgate Tate II 101A, wraps the soundstage around you into a 270 degree U-shaped soundfield.

When Proton licensed the Aphex design, they basically had Aphex just package the ESP-7000 decoder into a newer, better looking box and used more modern, higher quality parts. The channel separation numbers are the highest of any matrix decoder I've ever come across - Center Front to L/R front, 45-50db - Left/Right Front to either rear channel, 50-70db and CF to CB, 80-90db.

the unit lets you adjust the logic enhancement in 3 steps - full enhancement, moderate enhancement which equals about 25db of separation and the minimum which is 6-15db depending on direction. The lower logic levels are for those recordings - mainly classical - that have very complex phase relationships that the decoder can't accurately track, so by reducing the logic enhancement, you are reducing the tendency for the decoder to misbehave and pump or move static images when they shouldn't be.

the Aphex/Proton decoder is a true Matrix Multiplier Vector Cancellation design and uses no gain riding - it relies on the correct matrix coefficients in the matrix multiplier section to cancel sounds from the channels where they don't belong while, at the same time, keeping the total power output (volume level) from every channel exactly the same - the only other decoders that were true constant power decoders were the Fosgate Tate II, the Shure HTS-5300 (the first 2 Shure models were not as accurate as the 5300), and the Involve Surround Master. Not even the 3-band Sansui QSD-1 could maintain constant power - for some reason, all of Sansui's Vario-Matrix decoders increased the level of the 'wanted' channel by 5-6db; the BBC confirmed this in both their extensive tests of various matrix quad formats and during the development of Matrix-H when adapting a QSD-2. Dolby Pro-Logic is supposed to be a constant power decoder, but under certain conditions the surround channel can pump by up to 8db. And PL–II, in every decoder I've heard, seems to have real problems with constant power too.

the Aphex/Proton's logic circuitry is a RatioMetric design that uses peak detection instead of true RMS based logic - the peak detection combined with Aphex's own VCA's and true analog multiplier's lets the logic properly enhance the directionality over a 90+ db range.

the seller of the Proton had listed it on Craigslist several times before, with no takers - face it, only crazy collectors like me want old, outdated surround decoders - and while he was asking $160 for it, I took a chance and offered him $20 plus shipping and a new, still sealed copy of the original, never released, Queen ANATO DVD-Audio disc - he flipped for that offer and accepted!

when the Special Edition of The Abyss had its short theatrical rerelease, I was lucky and got to hear a 'shoot-out' between Dolby Pro-Logic in the CP-65 cinema processor, the Aphex ESP-7000, the Shure HTS -5300 and the Fosgate DSL-2. The Dolby CP-65 came in dead last and sounded so slow in its attack times that you could often hear sounds moving just slightly behind the visual action - the Fosgate, while being co-designed by Jim Fosgate, Peter Scheiber and the Tate inventor, Martin Willcocks, and supposedly having adaptable time constants that continuously varied from a fast attack time of 3ms to a slow of 25ms was also, surprisingly, slow sounding with a blurred soundstage and had a lot of dialog sibilance spill to the surround channel - it also had a front soundstage that wandered L to R based on CF content. The clear winner was the Shure HTS-5300 which sounded like a fully discrete 4-track magnetic film and not a matrix - and like the Involve Surround Master, the Shure's channel separation specs are not particularly impressive - from 15 -25db depending on direction, but the Shure engineers knew how to apply the attack/decay times, etc. to achieve such stunning results. The Aphex was just barely behind the Shure, due mostly to some minor sibilance splatter. The theater was a Dolby SR equipped theater and so did not have the capability of playing stereo surround, so we couldn't check that type of playback.

So, a consumer Dolby Stereo decoder, the HTS-5300 - a non Pro-Logic one I might add, since Shure used their own patented Acra-Vector logic system, and a completely non-Dolby licensed decoder, the Aphex, beat the 'official' CP-65 decoding system for Dolby MP encoded surround titles - and by such a wide margin that it sounded like we were comparing matrix to true discrete sound.

When end my Proton decoder gets here I will be interested in comparing it to the Surround Master - a broadband analog decoder designed in 1986 or so VS a modern 3band DSP based decoder. My gut feeling is that the Surround Master will wipe the floor with the Proton. But it doesn't really matter because, like the Shure, the Aphex/Proton was a decoder I wanted back then and had no ability to buy. So I'm getting to collect the stuff I used to want and pay virtually nothing for it. I will be interested to see how decoding music into 270 surround with the Proton and then encoding it into either QS or Involve and decoding that with the Surround Master will turn out.

maybe I should make a DTS DVD demo of all the different surround decoders I have decoding the same film clip. Would anyone be interested in hearing that?

Oh, and before I forget - get a Desper Spatializer (the consumer unit). I have one and just bought another for $30 on eBay Monday. I'll tell you about it and why I bought two in another post.
 

jsrstereo

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Disclord:

I've recently acquired an SD-1000, but have not yet found to the time to play with it. I'm looking forward to getting it hooked-up - do you have any information regarding its abilities as a quad synthesizer (from non-encoded stereo sources)?

Thanks from John R
 

Disclord

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Disclord:

I've recently acquired an SD-1000, but have not yet found to the time to play with it. I'm looking forward to getting it hooked-up - do you have any information regarding its abilities as a quad synthesizer (from non-encoded stereo sources)?

Thanks from John R
It's music mode is wonderful and wraps the L/R front around to the back and if you use the CB output too, you'll get great Surround EX type effects. So it's a superb surround synthesizer. I do hope you have the remote because its totally useless without it. I love the Aphex design of plugging in cables to activate that channel - if you don't plug in a Center Front cable, it mixes it as phantom center - same for the back. I turned all the level controls above the outputs to thier max setting and use my receiver, which is calibrated, to manage the levels which works perfectly.

anything you want to know, just PM me.
 

jsrstereo

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(I love to resurrect old threads -------------)

Question for Disclord:

Have you yet conducted your comparison of the Proton vs. the Surround Master? Comments?

regards from John R



"When end my Proton decoder gets here I will be interested in comparing it to the Surround Master - a broadband analog decoder designed in 1986 or so VS a modern 3band DSP based decoder. My gut feeling is that the Surround Master will wipe the floor with the Proton."
 

fizzywiggs41

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It's a great loss I think.

Always enjoyed reading his posts on SQ matrix.A true SQ MAVEN.



he does leave quite a legacy of info in those prior posts, btw
 

fredblue

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It's a great loss I think.

Always enjoyed reading his posts on SQ matrix.A true SQ MAVEN.

he does leave quite a legacy of info in those prior posts, btw
Absolutely, hugely knowledgeable and helpful and just one of the nicest guys I ever chatted to here.

Whenever I see one of Ty's old posts I pause for a moment and think of his loved ones who doubtless miss him more than any of us will ever know.

RIP Disclord. Gone but not forgotten.
 

jsrstereo

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RIP Ty - I did not know of his passing. I greatly admired his knowledge, but more so his gracious, generous spirit in sharing that knowledge with us.
 

par4ken

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Sonik Wiz

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Like Ty the Proton SD-1000 was a rare audio mystery to me. I was always intrigued by it & found a new never used one on Ebay for only $150. The story was that two we're given to a distributors rep & one was used & the other one left in the box. Manual, remote control all in sealed plastic & the cord still tied in factory twisty. I was pretty happy even tho I had to get fresh batteries for the remote.....

it has a full stereo surround mode that, like the Fosgate Tate II 101A, wraps the sound stage around you into a 270 degree U-shaped soundfield.
Well yes but it's not that simple. Working with a test disc I realized there is no phase/amplitude combination ever going to produce a left back or right back only position. For the most part it sounded a lot like my old Fosgate model 5 that was pretty much a DPL decoder with a bit of the fronts mixed into the rears to give a slight stereo effect in the music mode. I wasn't impressed much so I have used it very little the last 6 months. I did like it's looks & pretty lights so I left it in my system.

My Anthem AVM 30 has 7.1 output but I have never set it up that because I thought 5.1 is the sweet spot. I got curious & got out a spare Audiosource amp & two more speakers centered & lined up just slightly behind my surround speakers. The improvement is very noticeable on movies with intended back channel info but pretty much worthless with stereo synth via Neo 6 or DPL II & not much help with 5.1 mixes either.

But heck I thought before I return the room back to original config I'd see what the Proton does with a center back output.

What an amazing transformation! It performed much more as I hoped it would. There's still no rock solid left back or right back but it much closer to that now. Old stuff like Thomas Dolby, OMD & Herbie Hancock: Headhunters is delightfully bounce-a-phonic. Newer music like Daft Punk: RAM sounds so much better than DPL II. Beck's Morning Phase is a smooth & subtle composition that sounds so open on this. I have probably spent 10 hours listening this weekend to material I have in surround in addition stereo and stereo I have put TLC into upmixing on the PC doing comparison & just simply loving what I hear on the Proton. I also had new (to me anyway) Beat Crusaders & Ayumi Hamasaki that I listened to for the first time on the Proton & sounded so good I didn't feel the need to experiment.

If I we're to describe the soundfield in two words it would be accurate & balanced. A drum kit tom with reverb moves smoothly from center front to rear. Panning stereo sounds are impressive & over all as sounds come & go in different positions it sounds so complimentary as moves. The transient detail is better than the my Sansui QSD-1000 & the tonal balance is a bit on the bright side like my Fosgate Tate 101. Playing QS on it the front sound stage is more compressed & the rear seems a bit too prominent than it should. I didn't try SQ.

Downside is that even tho my AVM 30 has 7.1 output it has only 5.1 (or 6 if you prefer) analog input. So the center back from the Proton goes straight to the Audiosource Amp One & levels are balanced the hard way by hand matching the center back to a set level on the AVM 30. If I change anything on the Anthem it will all go out of whack so I'll need to find a better way to do this. Other downside is the 150 Hz subwoof from the Proton just sounds terrible. Probably just a 6 dB xover & it either sounds too low or boomy & awful. Again on my Anthem with pure analog inputs all I can adjust is volume & balance no tone controls.

Ty's post on this hardware has lingered in my mind ever since reading it. He never had the chance to follow up on it. But I was so thrilled at the transformation just by using a center back speaker that I had to share it. I think Ty would get a kick if he knew a years old post of his was still getting replies.

Proton SD-1000 is highly recommended as it holds it's own or exceeds quality of stereo to surround compared to analog or digital methods. A decent review on the decoder is here: http://www.hifi-classic.net/review/proton-sd-1000-80.html
 
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elguapo511

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Just getting my proton up and running. It arrived from Austria stanking of cigarettes.

Very scratchy and thin sound.... so d oxit is my only friend at the moment.

Anyone have a manual they can lead me to. Hi fi engine does not.
 

Sonik Wiz

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Just getting my proton up and running. It arrived from Austria stanking of cigarettes.

Very scratchy and thin sound.... so d oxit is my only friend at the moment.

Anyone have a manual they can lead me to. Hi fi engine does not.
Lucky for me my Proton was new old stock so I have a user booklet in perfect condition. I will be glad to scan as PDF over the next couple of days & send it to you. Any particular ??'s I can answer faster than that?

A peek inside your Proton SD-1000:

39745


After working on a different decoder I put the Proton on the workbench to check a few things. To my ears there was something not exactly right about the decoding. Sure enough my quadscope showed that center front, center back, and all positions on the right were textbook perfect. But any signal positions on the left side were crazy all over the place. Alas with awhopping 28 trimpots inside I have little hope of adjusting with out a service manual. And I think that's pretty much impossible to find.
 

elguapo511

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ok, its waking up a bit. I opened it, and a little nervous spray in there. lots of grime, but no dust.

crackles are less and less the more it warms up.... not sure what this calibrate button does.
 

elguapo511

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Yeah, i just opened it. Plenty of trimpots.... and are the pots on the rear just volume? or separation?

Not much I can do but clean it.

Seems like everything is overloading so Im trying to get some gain balance, but each output seems to be at a different level....

thanks in advance for the manual.

i'll ask around about the service manual too.

Lucky for me my Proton was new old stock so I have a user booklet in perfect condition. I will be glad to scan as PDF over the next couple of days & send it to you. Any particular ??'s I can answer faster than that?

A peek inside your Proton SD-1000:

View attachment 39745

After working on a different decoder I put the Proton on the workbench to check a few things. To my ears there was something not exactly right about the decoding. Sure enough my quadscope showed that center front, center back, and all positions on the right were textbook perfect. But any signal positions on the left side were crazy all over the place. Alas with awhopping 28 trimpots inside I have little hope of adjusting with out a service manual. And I think that's pretty much impossible to find.
 

Sonik Wiz

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Yeah, i just opened it. Plenty of trimpots.... and are the pots on the rear just volume? or separation?

Not much I can do but clean it.

Seems like everything is overloading so Im trying to get some gain balance, but each output seems to be at a different level....

thanks in advance for the manual.

i'll ask around about the service manual too.
The trim pots on the back are strictly for output level control. They are mounted sideways so when the screwdriver slot is horizontal they are at mid-point.

Set to cinema & press the left button with separation enhancement set to max. Adjust the balance control for minimum output in the rear channels. This critically adjusts the input balance. If you are playing a mono source you will hear nothing. If there is quite a bit of rear channel information in the sound source you will still hear some audible music. The point is to have the lowest level out of back speakers.

Do you have some QS material? Play in music mode with seperation enhancement set at max or one notch down.
 

elguapo511

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Set to cinema & press the left button with separation enhancement set to max. Adjust the balance control for minimum output in the rear channels. This critically adjusts the input balance. If you are playing a mono source you will hear nothing. If there is quite a bit of rear channel information in the sound to have the lowest level out of back speakers.
[/QUOTE]
Set to cinema & press the left button with separation enhancement set to max. Adjust the balance control for minimum output in the rear channels. This critically adjusts the input balance. If you are playing a mono source you will hear nothing. If there is quite a bit of rear channel information in the sound source you will still hear some audible music. The point is to have the lowest level out of back speakers.
Okay are these some set up notes?

Why cinema mode?

I’m probably going to play 2 channel source material through the proton then out to the four analog ins of my amp set to discrete multi channel. Then one straight to the powered sub. So 4.1.

Any tips on set up for that?


Also. If I don’t have anything plugged into center outs does it simply not rout anything to those channels?

This thing sounds better and better the more I tweet it. Very sensitive inputs. My source needs to be set to mid.
 

Sonik Wiz

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It is better to use cinema mode when adjusting balance because the whole intent of music mode is to send musical information L/R to the rear channels. Cinema mode only looks at center back. Then of course go back to music mode for actual listening.

I found that the mid point in the seperation enhancement worked the best for me.

You are correct: if you don't have anything plugged into center front or whatever the device senses that & does not rout anything to that output. If possible give center back a try. I thought that gave a big improvement.
 

Sonik Wiz

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What does DSR on the remote mean? Seems like it evens the levels a bit.
Firstly I apologize for the delay on scanning the manual for you. My wife just left for a week in Florida so I have zero family obs. I will scan tomorrow.

DSR= Dialogue Scatter Reduction. "When the DSR circuitry is activated it blends certain high frequency information to the front. This reduces sibilance which tends to scatter parts of the dialogue around the room."

It's a movie thing.
 
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