Decoder: Electro Voice EVX-44

[Wagonmaster_91]

Someone was asking about this decoder on the forum a few weeks ago. This is an Electro-Voice EVX-44 Universal Four Channel Decoder.


I picked this one up for next to nothing and expected it to be on par (or worse) with the bottom line Radio Shack quad synths. I was pleasantly surprised how well these units work. They will never make you trade your Tate or QSD-1, but they do a pretty good job of decoding both SQ and QS as well as the few records actually recorded to be decoded using an EVX-44. The Beach Boys "Surf's Up" album states in the liner notes that it was recorded to be played back using one of these units.


The construction is nothing fancy - brush aluminum front, plastic & aluminum knobs, plastic 'wood grain' sides and metal back and surrounding case. Cheap, but solid with decent input/output jacks. (The pictures make it appear there is some yellowing on the front face, but that is from my flash. This thing looks brand new.)



It has inputs for a quad tape deck and a stereo deck, so pretty versatile as these things go.



The unit only draws 5 watts, so there isn't a whole lot going on inside the single circuit board that holds the electrical components. The decoder switch has three settings (in addition to a discrete pass through for a quad tape deck). The different decoder settings are explained in the owners manual below.





That's all for tonight. I have a few more oddities I upload soon.

Mark

 

[Doug G.]

Mark, do you know what decoder chip is in that unit?

I have a Heathkit AD-2022 and it is supposed to be the same as the EV unit so I'm just curious if the chips are identical.

Thanks,
Doug

 

[Wagonmaster_91]

I'm not sure, Doug. I'm not familiar with the AD-2022, but if that was Heathkit's version of the EVX-4 then I would say no. (I know several companies licensed the design of the EVX-4 and put out their own versions that look identical.)

The EVX-4:



On the other hand, if the AD-2022 looks like the EVX-44, then yes they very well could have the same chips. Post a pic of the Heathkit model, if you can. (I couldn't find one on the net.)

 

[Doug G.]

Here is the front of the AD-2022. It is the Heathkit that is supposed to be the equivalent of the EVX-44. The Heathkit AD-2002 is the equivalent of the EVX-4.

The only thing lacking on the AD-2022 is the discrete inputs and selection, of course. So it combines the functions on one switch. The decoding chip is a Texas Instruments SN16852. It also draws 5 watts.

Doug

 

[jsrstereo]

Mark:

I'm curious about the "Auto" mode for the Separtion Enhancement function in the EVX-44- Does that engage some kind of a logic circuit - can you hear any pumping or other stuff when it kicks in and out?

 

[Disclord]

Mark:

I'm curious about the "Auto" mode for the Separtion Enhancement function in the EVX-44- Does that engage some kind of a logic circuit - can you hear any pumping or other stuff when it kicks in and out?

The auto mode just blends the back channels towards mono to cancel out any Center Front - the more in-phase info there is in the front channels, the more strongly blended the rear channels.

 

[jsrstereo]

The auto mode just blends the back channels towards mono to cancel out any Center Front - the more in-phase info there is in the front channels, the more strongly blended the rear channels.

So I guess the "On" mode does its blending at a fixed rate?

(Disclord: thanks again for another of your informed replies)

 

[Disclord]

I would assume the "on" mode is a set, fixed blend, probably something like 10% across the fronts to maintain at least 20db L/R separation and much more across the back - with SQ's basic matrix a 40% back blend will give 8db Lb/Rb separation with a total of 6db front to back. The "auto" mode probably keeps the blend at minimum until strong CF appears, then blends to cancel the back crosstalk. That way, max separation is maintained as much as possible. The IC is a custom one made for EV and has a 4-pole phase shifter - so it can decode SQ and the modified EV-4 matrix. This was supposed to be the first of the "universal" decoders that could handle all matrix systems with equal results. Of course, that never came to pass.

 

[Wagonmaster_91]

I don't hear any pumping effects in any of the three decoding modes. It sounds very smooth. Great little unit.

 

[jsrstereo]

I don't hear any pumping effects in any of the three decoding modes. It sounds very smooth. Great little unit.

I notice that the EVX-44's third decoding mode is not labeled. Is it simply the EV decoding mode brought over from the EVX-4 for stereo-to-quad synthesis, or what?

 

[Disclord]

There shouldn't be any pumping because it's only doing a channel blending, not expansion. The main artifact you might hear is the rear channels suddenly losing separation as a CF dominates.

 

[jsrstereo]

I notice that the EVX-44's third decoding mode is not labeled. Is it simply the EV decoding mode brought over from the EVX-4 for stereo-to-quad synthesis, or what?

I'm bumping this ancient thread to ask if anyone has an answer to this question.

Thanks, JR

 

[Sonik Wiz]

The function selector has 4 positions: discrete 4 channel pass through, decode of 2 channel source, separation enhancement in auto position (in which it senses the presence of a front center soloist and increases front-back separation to isolate the soloist to the front speakers without reducing the level of back instruments), and full 'on' in which the separation enhancement circuitry is activated at all times.

Taken from:

https://www.worthpoint.com/worthopedia/electrovoice-evx-44-quadraphonic-191361933

 

[MidiMagic]

It's basically an SQ 10-40 decoder with variable blending of the back.

Enhancer off = 10-40 blend
Enhancer on = 10-80 blend
Enhancer auto = variable back blend with center front content

 

[par4ken]

I always though that the basic idea of this decoder was a great one. One decoder that does everything, and no switching required! Always sort of wanted one to try but I seem to recall a review that says that it does everything poorly. That's always what happens when you try to please everyone, no-one is pleased! I just wonder if in the future someone will devise a decoder that will quickly analyse a recording and then automatically set it's self up for the proper/optimum decode?!

 

[Sonik Wiz]

I am familiar with the 1st EV decoder, the EVX-4 which I have. I am also familiar with the EVX-44 discussed here, which I have in the guise of a Heathkit decoder. Evidently there was model in between those called the E-V 44. It's a new one to me.

The original decoder EVX-4 did the best job I've heard of playing back stereo for simple matrix decoder. And then when you put some Enoch Light on it Shazam!

Edit: oops & sorry. On closer look it's just a stereo integrated amp. Never Mind!

 

[Paul Pettegrove]

Electrovoice using all of it EV & EVX “4 related” model naming... it does get confusing... the EVX-44 (mine is NOS)... it has the Texas Instruments SN16852 IC as does my Heathkit AA-2010 Integrated Amplifier (needing complete refresh). The AA-2010 has an adapter card for “Matrix”, no adjustments, same chip. Heathkit Decoder Circuit Board

85-1223-1 with designation of the SN168000N integrated circuit. Price each $5.00. (1974)

 

[par4ken]

I am familiar with the 1st EV decoder, the EVX-4 which I have. I am also familiar with the EVX-44 discussed here, which I have in the guise of a Heathkit decoder. Evidently there was model in between those called the E-V 44. It's a new one to me.

The original decoder EVX-4 did the best job I've heard of playing back stereo for simple matrix decoder. And then when you put some Enoch Light on it Shazam!

Edit: oops & sorry. On closer look it's just a stereo integrated amp. Never Mind!

It's one of those decoder plus rear channel amplifiers, intended as an addon to those with a good stereo already.

Edit; Sonik, not sure what you were referring to, but I was referring to the EV-1244X posted here EVX-4 Decoder Repair

Second Edit; I see that I'm replying to a post from last year!

 

[senorverde]

I thought the EVX-44 was a second generation decoder from EV that sort of did a hohum job of decoding SQ and EV-4 'automatically'. I think the big selling point for this was being able to mix matrixed records on a changer and having them play without having to get up and switch decoders for each album.

Quoting here:

In 1973, Electro Voice signed an agreement with Columbia, and produced the EVX-44 Universal Decoder. The idea here was to make a decoder that can play the EV, QS, and SQ records mixed on a record changer without having to change decoders. They later suggested the same coefficients as an encoder, but no records were ever produced.

The decoder has a front-oriented automatic variable blend that reduces back separation when center front material is present. It can also be set to be blended all the time (lower room diagram), or never blended (upper room diagram). The lb and rb dots farthest apart on the sphere are not blended, the ones closest together are blended. The Metrotec decoder is the EV universal decoder without the blend in the "synthesized quad" position.

https://midimagic.sgc-hosting.com/quadrafon.htm

 

[par4ken]

I thought the EVX-44 was a second generation decoder from EV that sort of did a hohum job of decoding SQ and EV-4 'automatically'. I think the big selling point for this was being able to mix matrixed records on a changer and having them play without having to get up and switch decoders for each album.

Quoting here:

Yes it was, it did EV-4, SQ and QS automatically. Actually the EV-4 coefficients were modified to make it more like SQ (with blend). As I recall it had switchable vari-blend on the rear channels to improve front to back separation. It sounded like a great idea but In actual use it was a compromise for everything!