The Technics ST-G7 claims to have a 90 dB dynamic range. Is that equivalent to S/N?
Dolby FM Broadcasting?
- Thread starter kve777
- Start date
Also, Proton had the Schotz FM tuner sections that performed really well in terms of reduced noise.
I had a standalone dbx unit (dbx 228) and it was no better. Never liked it. It might have worked well on reels in the studios, but I found with the consumer version used on cassette that the S/N was just too high to make it work. I could always hear the pumping and breathing. The dbx LPs sounded good initially, but they also had a very odd, very slight, "stifled" sound to them, as though there were something clamping down on or choking the sound. It worked better with some LPs than others. But it was a total shock at the time to hear LPs with no surface noise. CX ("Compatible eXpansion") noise reduction (used by Columbia) was also used on LPs back then, but it died a quick death--CX went on to greater success on the old analog audio Laserdiscs. It was more like a Dolby B in that music could be listened to without decoding, even if it was a little "off."
My Pioneer in-dash does the same. I like hearing our local AM news station clearly on its HD simulcast, but driving around the 'burbs, it gets too frustrating trying to listen when it keeps dropping out. At least in the Detroit market, the additional channels just added double the amount of terribly programmed music...so for music I have no use for it anyway. I didn't pick the in-dash for its HD capabilities--it just came as one of the features. It also makes me wonder whatever happened to Pioneer's old "Supertuner" technology. This certainly is no "super" tuner!
I own a number of outboard TX-1-11's and they're (comparatively speaking) terrific. Most of all because they're somewhat adjustable. Of all of Bob's audio features that were proprietary (of the Carver brand name era) that one's the one with the most hang time. He improved his power supply/transformer designs as time passed. But this one was nearly ideal out of the gate. (again, jmo)
What was the trade name for that tuner circuitry? I forget--it's been a while.
vwestlife
Super Member
"Sonic Holography". Carver claimed to give FM Stereo the same signal coverage and S/N ratio as mono reception. What they actually did was blend everything except the lowest frequencies to mono and then add some fake stereo reverb to it. The result was quiet reception of distant FM signals but with a half real/half fake stereo image. It sounds OK with classical music, but not much else.
Just looking through old Carver stuff--all they called the FM was "Asymmetrical Charge Coupled FM Detector." But I swore they had a name for it.
The Sonic Holography was that phasey stuff they added to stereo to expand the image beyond the speakers. (The idea was to eliminate inter-channel crosstalk--the left speaker's output reaching the right ear, and vice versa; or another way to put it, a poor man's surround sound effect.) It was available as an add-on processor component (called the Sonic Hologram Generator, model C-9) for use in a tape loop. There was a knockoff "Ominsonic Imager" that did the same, and Polk attempted this as well with their SDA speakers (Stereo Dimensional Array). In the recording studio, the Q Sound technology did the same; Sting's album The Soul Cages was recorded with Q Sound. Never cared for it myself (felt it was a gimmicky effect), but YMMV.
The Sonic Holography was that phasey stuff they added to stereo to expand the image beyond the speakers. (The idea was to eliminate inter-channel crosstalk--the left speaker's output reaching the right ear, and vice versa; or another way to put it, a poor man's surround sound effect.) It was available as an add-on processor component (called the Sonic Hologram Generator, model C-9) for use in a tape loop. There was a knockoff "Ominsonic Imager" that did the same, and Polk attempted this as well with their SDA speakers (Stereo Dimensional Array). In the recording studio, the Q Sound technology did the same; Sting's album The Soul Cages was recorded with Q Sound. Never cared for it myself (felt it was a gimmicky effect), but YMMV.
Bob's a genius of no lesser regard than the nosebleed guys. They did give him something to aim for, and he got some pretty brutal pushback when he accomplished it. Again (so as to not have my statement diluted/moved around) I think many of his proprietary features are/were sound, but the Digital Time Lens was the one I had the least faith in. Sonic Holography was terrific as an "alternative" perspective. I don't think he ever meant for it to be left on "all the time". The auto-correlator (transient noise reduction) was reputed to be good (going all the way back to the Phase Linear 4000 if I remember correctly) but I've never heard one in person. Generally speaking I'll take residual noise (groove, etc.) over an artificial suppression scheme. It probably would depend on the disc and program. The ACCD relatively speaking works some small miracles. J. Gordon Holt recommended it as a disc noise reduction system and I found that rendering a bit surprising. I've not tried it. Yet.....
I have heard an AutoCorrolator in a PL 4000, and honestly it sounds pretty good. Takes out the rumble and most of the surface noise without killing the sound. I have a Garrard "Music Recovery Module" that is supposed to get rid of pops and clicks. it does, but it just murders the audio. When switched out it makes a pretty decent phono preamp but the noise removal part is dreadful.
amptramp
Well-Known Member
The original noise processing circuit made for phonographs with high surface noise, the RCA Magic Monitor:
The circuit at the upper right was a separate chassis on premium RCA radios and record players. The 6AV6 amplified and rectified the incoming audio. The output went through a lag circuit to the 6BA6 reactance tube. If there was little audio, there was little bias on the reactance tube and it amplified the capacitance from the 6BA6 plate to the output of the unit. This acted as a tone control with treble turned to a minimum. If there was enough signal, the reactance tube would be cut off and all frequencies would be allowed to pass through. It was an analog control which meant that there were varying levels of rolloff for various levels of signal. The circuit may be old but the amplifier to its left would not look out of place today (although someone would have replaced the 6F6's with 6V6's and the paraphrase inverter would be converted to split phase / long-tail / van Scoyoc cross-coupled to limit low-end phase shift).
As Solomon once said, there is nothing new under the sun, which means this circuit may date back to the Atlanteans.
The circuit at the upper right was a separate chassis on premium RCA radios and record players. The 6AV6 amplified and rectified the incoming audio. The output went through a lag circuit to the 6BA6 reactance tube. If there was little audio, there was little bias on the reactance tube and it amplified the capacitance from the 6BA6 plate to the output of the unit. This acted as a tone control with treble turned to a minimum. If there was enough signal, the reactance tube would be cut off and all frequencies would be allowed to pass through. It was an analog control which meant that there were varying levels of rolloff for various levels of signal. The circuit may be old but the amplifier to its left would not look out of place today (although someone would have replaced the 6F6's with 6V6's and the paraphrase inverter would be converted to split phase / long-tail / van Scoyoc cross-coupled to limit low-end phase shift).
As Solomon once said, there is nothing new under the sun, which means this circuit may date back to the Atlanteans.
vwestlife
Super Member
So, basically it was a tube-based predecessor to National Semiconductor's Dynamic Noise Reduction (DNR).
amptramp
Well-Known Member
Yes, although in the RCA application, it was only used with the phono input but would certainly not be out of place with either AM or FM radio. Considering the technology available at the time, the idea of a pair of common 7-pin tubes implementing this function was quite ingenious.
The Magic Monitor was also the predecessor of the Dunlop Wah pedal used by guitarists where a reactance transistor (Q2 below) is used to tune a coil to move an amplitude peak to various frequencies:
There is more on the geofex site here:
http://www.geofex.com/article_folders/wahpedl/wahped.htm
[QUOTE="vwestlife, post: 11045332, member: 133769"
Especially now that we have thousands of channels and custom music playlists at the touch of a button on our smartphones, public interest in HD Radio remains negligible, and the corporate bean counters are probably going to soon declare it unwanted and obsolete, just like they're doing with CD players, which are also disappearing from the dashboards of many new vehicles today.[/QUOTE]
This. I'm driving a 2007 VW with low mileage, and even though my wife is on me all the time to buy a new or newer car, part of what holds me back is I really like the stereo. It came with the premium system from "Monsoon," which also made a good desktop speaker at one point. And it has a CD player, which is good for an old fart who has lots and lots of CDs.
s.
Especially now that we have thousands of channels and custom music playlists at the touch of a button on our smartphones, public interest in HD Radio remains negligible, and the corporate bean counters are probably going to soon declare it unwanted and obsolete, just like they're doing with CD players, which are also disappearing from the dashboards of many new vehicles today.[/QUOTE]
This. I'm driving a 2007 VW with low mileage, and even though my wife is on me all the time to buy a new or newer car, part of what holds me back is I really like the stereo. It came with the premium system from "Monsoon," which also made a good desktop speaker at one point. And it has a CD player, which is good for an old fart who has lots and lots of CDs.
s.
Years ago I used a 1BX with phonograph records but was put off by the "breathing." However, the fully-encoded dbx discs are great with the dbx decoder.
I recently acquired a 3BX for FM use and it is much better than the 1BX. A little bit of expansion acts as noise reduction. I believe the multiple bands are key; Dolby NR worked on high frequencies only.
I recently acquired a 3BX for FM use and it is much better than the 1BX. A little bit of expansion acts as noise reduction. I believe the multiple bands are key; Dolby NR worked on high frequencies only.
I’ve recently restored a Heathkit AR-1515 with the optional FM Dolby card. Two things:
Turning on that card for regular FM stations improved the sound dramatically.
The decoder card was fairly simple, so building a decoder from scratch shouldn’t be difficult.
Not sure if that helps your desire for the encoding side, though....
RockinRandy
Active Member
I had a pioneer ke or keh 8500 car stereo cassette w/Dolby for tape and FM in 81 I believe. Guy at the audio store said there's no use in buying that unit because no one broadcasts in Dolby around here.
Well I wanted to be the first and only guy around to have Dolby FM. It got ripped out literally from of my 76 olds fi st year of college. Anyway I was and am convinced it took the hiss from the one big radio station while in stereo mode and I'm sticking to it till I die.
Well I wanted to be the first and only guy around to have Dolby FM. It got ripped out literally from of my 76 olds fi st year of college. Anyway I was and am convinced it took the hiss from the one big radio station while in stereo mode and I'm sticking to it till I die.
Dolby FM had a 25us pre-emphasis, thus the same de-emphasis for the receiver. using 25us de-emph for a 50us pre-emph source from the tx, will not have the correct freq response.
Dolby ckts were usually compression on the tx/record side and expansion on the rx/play back side.
I am not sure how you can make that statement, nor why anyone would want to. I was under the impression that one would use a chip to do that and the details I have no idea about. Do you know something that I do not know?
Dolby ckts were usually compression on the tx/record side and expansion on the rx/play back side.
I am talking about the decoder card. I’m physically looking at it right now, the component count is low, the routing is simple and large, and it is a single layer, through hole board so the decoder is or can be simple... and therefore making one from scratch, with the knowledge of this card, would be simple.
I have zero experience with the encoding side.
This is probably like worrying about how many angels can dance on the head of a pin, but FWIW, constructing a Dolby decoder by any means requires that Dolby Labs be paid a licensing fee. The most common approach was to use a decoder chip from a maker like (I think) Signetics, where the chip maker had effectively paid the fee and passed the cost along to the price of the chip. I expect it would be pretty hard to find one of those chips nowadays. And I'd be a little surprised if Dolby Labs was still granting new licenses for Dolby B, so there might not be any way to achieve this legally with any amount of engineering effort.
Frivolously yours,
chazix
Edit: Oh, hey, looks like I'm wrong again - I remembered the most common chip number, NE545, and there's at least one vendor on the interwebosphere that claims to have some in stock. So, piece of cake, construct away!
Frivolously yours,
chazix
Edit: Oh, hey, looks like I'm wrong again - I remembered the most common chip number, NE545, and there's at least one vendor on the interwebosphere that claims to have some in stock. So, piece of cake, construct away!