QuatraVox and my Realistic STA-76

[BillyBatts]

Hey guys and gals.

I just finished working on my STA-76. I have to replace the dial bulbs every 10 years or so, and I also replaced a few Caps and the main power transformer this time. Also did some alignment and general upkeep. It's good to go now for another 10 years or so.

I have owned this Receiver since I was a kid in High School. I bought it new, on Layaway, over a six month period with odd jobs I did. It was my first HiFi stereo purchase. I'm guessing... 75? Close anyway.

It's only 12 watts per channel, but is fairly well built, and you gotta' love the wood cabinet, and the blue dial with red indicator (Yellow/Red to show center channel tune). I use it in my basement for background when I work out.

This era Shack stuff had QuatraVox. If you're not familiar, QuatraVox was RadioShack's foray into simulated QUAD channel back in the 70's.

From what I see, it's basically a Hafler Circuit, that throws the extra set of speakers out of phase for ambient sound in the background, thus, your ears perceive more depth in the sound, similar to adding 2nd channel echo or more specifically, passive surround sound. It's pretty neat if you've never heard it. Most of the stuff out of the Shack in those days had switchable QuatraVox. B-Channel Speakers were either off/on/QuatraVox.

I have not had a 2nd set of speakers on this old Rig in a long time. I mean since the 70's. so I hooked up a few and engaged QuatraVox. You know, it's pretty neat. I can see how it was appealing back in the day.

Anyone here listen via QuatraVox any longer? I think it's pretty neat, even though very simplistic in how it works.

Comments?

Thanks.

Billy

 

[kermit z]

Very cool that you still have that receiver after all the years I have not heard QuatraVox, so cannot comment. But would be neat to have a listen.

 

[BillyBatts]

Yes, it was my very first HiFi stereo Receiver purchase, WAY back when. I can't ever let it go, and it's actually pretty cool.

I've been streaming Jazz to it tonight with QuatraVox engaged. It really works great for what it is, a 2nd channel out-of-phase Hafler. Imagine a slight echo, but more of a depth perception sense. As if your listening room suddenly grew to a symphony hall.

I had forgotten how "neat" this little add-on was for the Shack back then. Quadraphonic was the rage, and this was their idea to sort of "simulate" 4 channel.

In a word, it's "Cool".

If nothing else, it's a great novelty.

 

[hnash53]

I just got a Realistic STA-76 receiver from eBay for $30, though the shipping was $40+... yikes!! It's is excellent condition and sounds wonderful. This was my first receiver back in 1975 when the STA-76 came out.

But I really like the Quatravox. I have four speakers, two of which are completely re-done Epicure 150s, vintage speakers from the same time, circa 1975. The second pair of speakers contain the old (but re-foamed) original woofers and tweeters that came out of the Epi 150s, but are in smaller enclosures.

I find that no matter what I listen to... vinyl, streaming Pandora, or CDs... I like the Quatravox sound. And I don't think it is a "trick" feature. It actually has a circuit which works to pick up ambient sounds, especially in vinyl, and puts those in the rear speakers. It certainly does "bathe" and immerse one in the sound. I think it's still a very valuable listening mode.

I'm not really into home theater though I have a nice network Yamaha RX-V477 (mainly because I have a modern TV with HDMI).

I am considering a re-cap of the STA-76, but don't know if it really needs it. If it works, don't fix it.

This receiver has convinced me that wattage is WAY overrated when it comes to amplifiers/receivers. This unit's actual RMS per channel wattage is 12 watts. And I can't stand to turn it up beyond half way... it will drive you out of the room. And the bass response is great.

I'd love hearing from other Quatravox and Dynaquad and Quadraphonic and Quadapter listeners.

Thanks!!

 

[oldbarneby]

sta 76

Yes, I bought an sta 76 in 1975, along with a pair of Nova 8s for the front and Nova 7s for the rear. A dual 1225 TT and a 999b reel to reel and I was all set!

The 76 finally died on one channel and a trip to Radio Shack did not get it fixed. I hung on to it for a number of years and then just trashed it.
Two years ago I thought I would look on Ebay for another 76 and low and behold I placed a bid and won. Now I'm back listening to Quatrovox again.

To my ears the rear speakers are always kind of soft, but they are adding a new dimension to the music. I always have it engaged.

 

[hnash53]

I know what you are saying about the rear speakers being kind of "soft." I even lean down to check to hear if anything is coming out of them sometimes. Nevertheless,the rear speakers add something to the sound that I like. It seems that I am hearing things a bit differently when Quatravox is engaged versus when it isn't.

Me too, ... I always have Q-vox on.

I'm thinking of getting another STA-76 and learning how to re-cap the most likely and usual suspect caps. Amazing how much sound 12 watts per channel puts out. Now I understand the senseless wattage wars.

 

[Blast]

At one time I ran the Qvox output from my SA2000 through an adaptor and into another much smaller amp so I could control the level of the effect.

The first album I ever heard in Qvox was Aerosmith 'Rocks'. "Sweet Emotion" is the perfect song to demonstrate the effect as the guitars are switched between center channel and outlying channels during the course of the song.

 

[Doug G.]

The way the Hafler circuit, and others based on it, works is the back speakers play the differences between the left and right channels. That is what appears between the two positive outputs of a stereo amplifier.

And, typically, these signals will be ambient in nature since differences between what the two microphones, in a stereo recording situation, pick up will be mainly from different echoes in whatever room or studio is used.

Recordings made "artificially" by manipulating signals in the studio to make a stereo recording may or may not be as effective using the Hafler system.

Doug

 

[BillyBatts]

I had forgotten I posted this last year.

I love my STA-76 and since I originally posted I always have 4 speakers and the Quatrvox turned "ON" when listening. Ambient sound reproduction sounds better to me than straight stereophonic reproduction. I sometimes wish I had a more powerful Quatravox Receiver, but c'est la vie. We have what we have. 12 WPC is not bad, but I'd like to hear a 50 or 60 WPC with Quatravox engaged just for the extra headroom at higher volumes.

I've only had one major issue with the STA-76 since 1975 when the final caps went, but other than that it's been all minor like replacing the dial fuse lamps. Great low power receiver. You can't call it little because it's actually pretty big for a 12 watter, but back then, everything was big.

 

[KentTeffeteller]

Interesting units. The wattage wars began with the need for increased power when acoustic suspension classics came into common use with the advent of Stereo. With high efficiency speakers, one can do nicely on lower power.

 

[hnash53]

The 2 pairs of speakers I have are indeed acoustic suspension speakers... Epicure or EPI 150s. The sensitivity of these speakers is around 88 dB... give or take a few dB. I re-did everything (new replacement woofers and tweeters and very simply cross overs from humanspeakers.com). I don't know what the sensitivity claims are with the new innards are, but perhaps these rebuilds are even better. This Realistic STA-76 seems to have plenty of "head room" in powering these speakers. Turning it up half way... well, that's waaayyy too loud for me. I am really enjoying this STA-76 and its Quadravox. Like you, BillyBatts, I am leaving the Quadravox engaged all the time.

It "seems" to my ears, that there's more of the Quadravox effect when playing LPs/vinyl than when streaming. The explanation for that is probably... "well sure it is, that was the medium of choice back in those days, so this technology was designed with vinyl in mind."

 

[empirelvr]

...It "seems" to my ears, that there's more of the Quadravox effect when playing LPs/vinyl than when streaming. The explanation for that is probably... "well sure it is, that was the medium of choice back in those days, so this technology was designed with vinyl in mind."

No, it's a little more complicated. First, for modern music, a lot of producers/mix engineers don't "spread" the mix across the stereo image like they used to. Lots of modern recordings are almost mono, or have most of their content mixed to the center. Since the Quatravox circuit uses the L-R info for its effect you'll have less output the more the mix "goes mono."

And for streaming, it's more that the MP3 codecs streaming services use get rid of the very information that the Quatravox/Halfler circuit relies on to do it's "thing." Even vintage stereo material isn't as wide sounding on streaming services because of this information removal. If streaming services used lossless codecs, the effect would be more pronounced when playing appropriate material.

 

[BillyBatts]

The 2 pairs of speakers I have are indeed acoustic suspension speakers... Epicure or EPI 150s. The sensitivity of these speakers is around 88 dB... give or take a few dB. I re-did everything (new replacement woofers and tweeters and very simply cross overs from humanspeakers.com). I don't know what the sensitivity claims are with the new innards are, but perhaps these rebuilds are even better. This Realistic STA-76 seems to have plenty of "head room" in powering these speakers. Turning it up half way... well, that's waaayyy too loud for me. I am really enjoying this STA-76 and its Quadravox. Like you, BillyBatts, I am leaving the Quadravox engaged all the time.

It "seems" to my ears, that there's more of the Quadravox effect when playing LPs/vinyl than when streaming. The explanation for that is probably... "well sure it is, that was the medium of choice back in those days, so this technology was designed with vinyl in mind."

As many know whom see me post in "Today's Jazz Playlist", my Father (RIP) left me a huge mono 45 Jazz collection. I play these on my STA-76 with Quatravox and it sounds spectacular, like I'm in the recording studio. The live recordings are even more amazing. I feel like I'm in the echo hall.

I've got 4 Minimus 7's hooked up to the STA-76 and do absolutely enjoy it. I recently bought new 180g Coltrane and Davis LP's and they sound spectacular as well. My Jazz LP's from the 70's and 80's are superb. My CD collection (Jazz, Rock, Pop, New Age and Classical) sound decent, but not as good as my Vinly on Quatravox.

I remember how hard I worked as a young teen to buy that STA-76 in 1975. Bless my mother's heart (RIP) for giving me the final $80 to get it off layaway. I think it was $249 if memory serves. Worked all summer long like a dog but just could not come up with all the money to take it off Layaway and get it home. It's probably why I cherish it so much. It's in MINT condition and I take very good care of it. I also ENJOY it to the max!

 

[hnash53]

Regarding "streamed music" and Quadravox, is there anyway to recover the loss? I've read that some home theater receivers have an "enhancer" which attempts to recover some of the losses in mp3s. But I've read that that's a "gimmick." Perhaps.

The Quadravox/Hafler circuit... is it possible to modify this circuit with replacement components such that the effect is enhanced? I'm interested in obtaining some other Realistic Quadravox or Dynaquad receivers and seeing if such modifications to the circuit can be done. I'm no electronics wizard/expert, but can wield a soldering iron OK. What do you guys think? Thanks... enjoying this discussion.

 

[Blast]

As was stated Quadravox works best when there is more "spread" in the stereo (more 'difference' between channels).

One of the ways I am aware of to do this (short of going in and remixing the original material, which would be best) is to delay one channel slightly. The more delay = the wider the stereo image = the more pronounced the general QV effect. This won't spread individual instruments out- but, it will widen the stereo 'stage' and increase QV level.

 

[hnash53]

So what kind of component would be used to introduce more "delay"?

Thanks.

 

[Blast]

As a guitarist the first ones that come to mind are for guitarists. Not sure what is available for the home audio market.

Personally I have three digital delay devices. All from the 80's. First, a MXR rack mount:

https://images.search.yahoo.com/ima...9tv0&.crumb=7s2ecbQl.LO&fr=mcafee&fr2=piv-web

Second, a rack mount Digi-Tech DSP128. It wasn't cheap (but, might be now) and WAY more complex than our scope here:

https://search.yahoo.com/search?fr=mcafee&type=A211US518&p=digitech+dsp+128

and, third, a Boss DD-3 pedal. This (or something small like it) would likely be your best bet of the three:

http://riffcityguitaroutlet.com/bos...dftrk=gdfV25107_a_7c3194_a_7c12389_a_7cDD_d_3

You don't need "stereo" delay as you will only be delaying one channel. Therefore, the cheapest one that fits that category would be the one I recommend. These three have adjustable time (which is typical of a delay processor) so you can vary the QV effect. If you check the auction site you can likely find something under $100 that will do the trick.

Hope that helps.

 

[BillyBatts]

Regarding "streamed music" and Quadravox, is there anyway to recover the loss? I've read that some home theater receivers have an "enhancer" which attempts to recover some of the losses in mp3s. But I've read that that's a "gimmick." Perhaps.

The Quadravox/Hafler circuit... is it possible to modify this circuit with replacement components such that the effect is enhanced? I'm interested in obtaining some other Realistic Quadravox or Dynaquad receivers and seeing if such modifications to the circuit can be done. I'm no electronics wizard/expert, but can wield a soldering iron OK. What do you guys think? Thanks... enjoying this discussion.

To my ear, Quatravox adds "Depth" to the playback and more "presence", as if the recording artists were actually in my listening room VS being reproduced. I remember my first listen to Quatravox back about '75. My first thought was, "Hey, this sounds "Better"". "Better" is an interesting word in audio and usually varies from listener to listener.

I quite honestly never gave digital streaming much thought. I just stream it and that's it. I try not to get too technical on why a digital stream may sound a little less present via Quatravox than my old 1970's LP's. I chalked that up to Vinyl VS Digital in my brain, so I do enjoy both. I do Steam a lot of my music via an FM Transmitter and playback via FM reception on my STA-76, so that may have something to do with the fact that I don't sweat any differences.

When I listen to Digital streaming, and engage Quatravox, I do sense more "Depth" and "Presence" to the playback. So I'm happy. Is old Vinyl and analog better? probably, but I never really gave it much thought until this mention.

Don't get me wrong, gentlemen, I respect this debate and understand it. I just try not to get too hung up on "Damn, the is new digital streaming doesn't sound quite as good with Quatravox." I just listen and enjoy, and to my ear, it sounds "better" via Quatravox. "Better" meaning more depth and presence to the playback.

I did take off the four Minimus 7's yesterday and hooked up the new Andrew Jones designed Pioneer Speakers I ordered from Amazon when they were on super sale last month. Bought two pair specifically for Quatravox. I have to say, as much as I always admired the Minimus 7's, I think I like the Pioneer a tad better, but either one would suffice. Again "Better" is very hard to define.
:thmbsp:

 

[hnash53]

Thanks, Blast and BillyBatts, for the continued dialog re Quatravox.

Billy... I find that your description of more presence and "in the room" using QV is pretty accurate. My lady friend even commented on the "in the room" sound without me "suggesting" that to her ears.

As for enhancing the QV effect, Blast, I was more thinking about replacing some of the components in the Hafler circuit on a board in the STA-76, rather than another device.

I've been looking around for a schematic and/or service manual for the STA-76. Have either of you got one... or know where one might be available for download/purchase?

Thanks!

 

[BillyBatts]

Hnash;

All of my manuals are in my Seattle pad at present and I am not there, but will be in a few weeks. If you can hold, I "should" have it. I have not looked for over 20 years, but I know I never throw out ANY manuals on audio gear I purchase. But it is possible it has become misplaced since 1975. I'll check in two weeks.