Cheeze-and-Krackers!
I think I am developing the Stockholm-syndrome with a chatBot:
The 6-second answer...even if incorrect.
It's correct, as far as it goes.
This tuner only had one knob, if I remember correctly: the tuning knob.
This tuner (which was used by the chief engineer friend of mine at a local FM station) showed:
A. How bad the FM stations were broadcasting in 1974 (many, if not most: not meeting anything close to what the broadcast sound quality was supposed to be by FCC regulations.
B. What they were doing to make it that bad.
C. What could be fixed on the reception side to make the signal less bad.
(EJ3 comment: Naturally, most of us no longer listen to FM for music, as it has only gone down hill from here [I still do but I use a modified NAD 4300 that helps and there is the occasional good station within 80 miles {about the limit of what my antenna setup can reliably get}).
Here is a test done in Aug 1974 from Audio magazine of some of those things (and showing that the FM-1 had better actual specifications than any test gear available at that time):
Laboratory Measurements
Our usual FM performance measurements were made on the Sequerra Model 1 tuner. Figure 7 attempts to depict, graphically, some of the results, but each curve must be qualified by an excuse. To begin with, IHF sensitivity measured exactly 1.7 microvolts--about as low as IHF sensitivity can ever be if proper bandwidth is maintained, as it is in this model. So, IHF sensitivity is indeed "less than 2.0 µV" as claimed. The 50 dB quieting point was reached with a signal input of 1.9 µV. We usually quote THD for this condition, since in most tuners it still predominates over noise. In the case of the Model 1, however, the residual output at 50 dB quieting, as observed on an oscilloscope was very predominantly noise. Therefore, using an ordinary distortion analyzer (which can't tell the difference between noise and distortion), you'd come up with a figure of 0.3% "noise plus distortion" at 1.9 µV. Actual harmonic distortion is not separately visible on the 'scope until the noise dips below 63 dB or so, which is equivalent to about 0.07% residual THD.
However, even this figure needs qualifying. We are convinced that the Sound Technology FM Generator was not capable of supplying a test signal with better than 0.07% inherent modulation non-linearity, and therefore our reading of 0.07% THD is strictly the result of the test equipment. In other words, Sequerra knows that the THD of the Model 1 is lower than 0.07%, but can't really prove how much lower. His best guess is about 0.04%. The same applies to ultimate S/N, which measured about 75 dB. We know, however, that the generator is only guaranteed to suppress residual modulation down to ±25 Hz when used in the CW (unmodulated) mode. This would permit readings of over 70 dB, and the generator we used did permit a reading to 75 dB. There is no way of knowing how much further down the noise of the Model 1 really is--but we do know that it's lower than -75 dB. As for stereo, residual modulation of the generator is a bit worse so we come up with a -72 dB reading-in itself the lowest reading we have ever obtained, by far, for any tuner operating in the stereo mode, but probably a good deal higher than the true figures, which are just not obtainable with present day test equipment.
Figure 8 shows stereo separation versus frequency and THD versus frequency. The separation curves, at least, are definitive and meaningful and, as can be seen, show separation in excess of 60 dB at mid-band audio frequencies. At 15 kHz, separation was still in excess of 40 dB and well over 50 dB at the low end of the audio spectrum. The only thing the THD curves show is that there is some noticeable increase in THD at the extreme high frequencies in the stereo mode-noticeable, that is, if you consider a change of THD from 0.15% to 0.25% significant at frequencies above 6 kHz. What is obvious from these curves however, is the fact that there were NO visible or audible "beats" produced at any frequency as a result of any interaction between the 38 kHz products and audio products.
Fig. 7--FM quieting and distortion characteristics.
Fig. 8--Separation and distortion versus frequency.
Fig. 9--Panoramic displays.
Additional separate measurements were made for the specifications not listed by Sequerra, and it became obvious why he didn't bother with them. Here are some, with appropriate (and repetitious) comments. Alternate channel selectivity was in excess of 100 dB (we can't say how much in excess because of test equipment limitations). Image rejection was too high to be measured by our equipment. Spurious response rejection was in excess of 100 dB (we can't say how much in excess ... etc.). Capture ratio, as nearly as we could measure it (and it gets pretty tricky below 1 dB) was about 0.75 dB. As Dick Sequerra pointed out, however, a more meaningful statement could be made by pointing out that at 4 dB difference in signal strengths, the stronger signal "knocks out" the undesired weaker one to the extent of over 50 dB! Frequency response is something we can tell you about. It is accurate to the prescribed de-emphasis curve within ±0.2 dB from 30 Hz to 15 kHz. Rejection of 19 kHz output products and 38 kHz output products was in excess of 70 and 75 dB and therefore these components would be totally insignificant in terms of any recorder, regardless of its bias frequency. Rejection of SCA (67 kHz) was too great to be measured meaningfully.
After several hours of making these sometimes frustrating measurements, we decided to relax and play with the unit.
Listening and Utilization Tests
In case you have ever questioned the need for the kind of performance which the Sequerra Tuner can deliver-if you've doubted whether there is an audible difference-let me put those doubts to rest. You can (and I did) hear the difference. I don't think it's a simple case of lower distortion. I don't believe it's just better stereo separation. It's much more subtle than that, and 1 don't intend to explore the reasons in this lengthy report.
Suffice it to say that even in the face of admittedly poor station and transmitter practice (which has become rampant in FM over the last few years) we were able to find program sources that sounded better than we have ever heard FM reception before. Cleaner, quieter, more stable and more like what we had always believed FM radio was all about. Both in its measurements and in its actual audible performance, the Sequerra Model 1 is at least a whole order of magnitude better than anything else around.
Naturally, we were fascinated with the panoramic and other 'scope displays. But, as we used the panoramic display for a while, we came to realize how much we could learn from it. We were able to accurately measure signal strengths by noting the vertical height of the signal pips. (see Fig. 6.) We could even spot SCA transmissions from those stations that engage in this extra service. In one case, we noted extreme overmodulation of the SCA sub-carriers, something we had suspected regarding this particular station for years. What a great field strength meter this would have made in our previous studies of FM antenna capabilities some years back!
Fig. 10-Tuning displays.
Fig. 11-Tuning displays.
Fig. 12-Tuner vector for stereo display.
In the "Tuning Display" mode, we were able to perfectly center-tune any desired station, gauge station modulation levels (and, in many cases, overmodulation levels as well) and detect even the barest traces of multi-path interference. In this mode, too, signal strength is indicated by the vertical position of the display and calibration of the graticule marks was just about perfect. The display, incidentally, has automatic brightness circuitry built in. When the display collapses to a dot (as it will with no modulation in the "tuning" mode, or in the absence of audio signals in the "vector" mode), brightness is automatically reduced so that only a very dim spot of light appears, so as to protect the 'scope face from premature "burn spots." The kinds of displays we observed are illustrated in Fig. 9 (for the panoramic function), Figs. 10 and 11 (when using the display in the tuning mode), Fig. 12 (when using the display to check stereo separation and musical locations) and Fig. 13 (when using the display to feed separate, external audio signals via the rear input jacks). Our immediate thought after playing with these versatile functions for a while was that the FCC ought to equip every one of its mobile monitoring units with a Sequerra Model 1 unit. Perhaps then they could do some policing of the abuses in broadcasting practices which are prevalent all over the country. It wouldn't be a bad idea if every FM station in the country was equipped with this tuner too. It is sure to find its way into these places, because it can provide more useful information regarding a station's radiated signal than any other single piece of FM equipment (and that includes so-called "monitor" receivers) we have ever seen.
In the last analysis, a good FM tuner is for listening. And, ultimately, it is with the dedicated FM listener who demands perfection that the Sequerra Model 1 is sure to make its mark for years to come. As one who has been involved, professionally, with FM equipment for over two decades, I can remember only two tuners which became the classics of their time. The first was the famous REL tuner which was head and shoulders above everything else in the 1950s. In the 1960s, we were introduced to the Marantz 10-B (designed, by the way, by Dick Sequerra and his present active associate Sid Smith-both of whom are as dedicated to good sound as they were when I first met them years ago). And now, in the mid-70's, we have a new standard of excellence-The Sequerra Model 1. I have purposely avoided mentioning prices up to this point because I felt that it was important to understand that this product is in a class by itself and that price is secondary. When you come right down to it, for the features it has, for the performance it gives, and for the musical pleasure it can provide to anyone demanding the finest there is in an FM tuner, $2500.00 is not really all that much to pay for the Model 1. If you're really strapped for cash, but want the tuner so badly that you're willing to buy it without the panoramic analyzer feature (a mistake, in my opinion), you will be able to walk away with one for an even $2000.00-after Sequerra has filled his initial orders which all call for the panoramic version.
Fig. 13--External vector displaying external 4-channel audio program source.
One final word for any of you who may have seen a prototype of this unit at various exhibitions and shows. The unit is actually in production. I saw dozens of completed and partially completed models with my own eyes. The waiting period is at an end. There really is a Sequerra Model 1 Tuner available for purchase. Final confirmation of this fact was brought home to me at the end of my visit, when Dick Sequerra began discussing his thoughts on the next product (in the audio field) that he and Sid Smith are beginning to work on. (I'm not at liberty to discuss it!) I know these dedicated engineers well enough to state, categorically, that they would not even be thinking about the next design program unless they felt that their first magnificent product was safely on its way!
-Leonard Feldman
(
Audio magazine, Aug. 1974
Nice knobs (notice how I dragged this back on topic?!). 
www.mcintoshlabs.com
