ReVox B160 fm tuner
 70
EQUIPMENT PROFILE
Manufacturers Specifications
Usable Sensitivity: 10.8 dBf.
50-dB Quieting Sensitivity: Sin-
gle-r.f. mode—13.2 dBf in mono,
34.8 dBf in stereo; double-r.f.
mode—16.7 dBf in mono, 38.3 dBf in
stereo.
Selectivity: Wide, 50 dB; narrow,
100 dB.
Frequency Response: 20 Hz to 15
kHz, +0.5 dB.
S/N: Greater than 80 dB.
THD: Mono, less than 0.07% at 1 kHz.
Muting Threshold: 2.0 pV.
Stereo Threshold: 10 pV.
Auto Tuning Threshold: Distant, 4
wV; local, 100 nV.
Stereo Separation: 43 dB at 1 kHz;
15 dB in Blend 1; 7 dB in Blend 2.
Calibration Tone: 400 Hz at 40 kHz
equivalent deviation.
Power Requirements: 120 V ac,
50/60 Hz; 20 watts, 5 watts standby.
Dimensions: 17.7 in. W x 43 in. H
x 13 in. D (45 cm x 10.9 cm X
33.2 cm).
Weight: 15.4 165. (7 Кд).
Price: Tuner, $2,500; B208 remote
control, $160.
Company Address: 1425 Elm Hill
Pike, Nashville, Tenn. 37210.
For literature, circle No. 90
AUDIO/SEPTEMBER 1988
Photography: ©1 988, Jay Brenner
There aren't too many over-$2,500 FM tuners out there
anymore. I'm told that the old Sequerra tuners, which sold
for that much and more, are still being made, but the
Marantz 10B that started it all is not. So when | came across
one (old FM buff that | am), my first inclination was to try to
determine if the price was justified. After all, FM reception
quality is ultimately limited by FCC broadcast standards set
more than 40 years ago and amended for stereo in 1961. @
You can't, for instance, receive audio frequencies above 15
kHz, and usable sensitivity is limited by the thermal noise
floor of the antenna input impedance. So what makes a
tuner like the Revox B260 worth $2,500? Plenty—but most of
it has to do with convenience features and the tuner’s ability
to tailor reception specifically to the environment and signal
conditions prevailing in your location. NE
Let's begin with some of the more innovative features. You | o
can preset up to 60 stations. That may well be more than the ОМ
number of presets that any other tuner can memorize, but The B260’s control panel could be used
as | see it, the real benefit is the ability to divide those to teach a course in human engineering.
memorized station frequencies into subgroups. Suppose
you like jazz and classical but your spouse or roommate | for a given signal, and some tuners feature a blend position
prefers soft rock and theater musicals. You could find all the | which reduces noise at the expense of some stereo separa-
stations that transmit your kind of music and store them | tion. The B260 offers two blend settings. One maintains
under one subgroup heading, while the preferred stations of | about 15 dB of separation across the entire audio spectrum
other household members could be stored under other | (not just reduced separation at high audio frequencies). The
subgroup headings. As many as nine subgroups can be | other provides only minimal separation (about 7 dB) for
organized and stored on the B260. Of course, all of the | those situations in which most tuners would have to be
more conventional tuning modes are available, such as | switched fully to monophonic mode to make the back-
scanning (with brief auditioning as each usable signal is | ground noise level tolerable.
encountered), direct call-up of memorized stations, scan- To assist the user in setting up proper audio output levels
ning within subgroups, and manual tuning. Another interest- | for recording, there's a built-in calibration tone. As with most
ing feature is called “Auto Tune.” It is a one-touch, initial | tuners having this feature, the tone’s output is at the average
setup programming system in which you need only tune in a | level of most reasonable FM stations, equivalent to 40-kHz
station, touch one button, and the next available preset | signal deviation.
location is automatically assigned to the new station. It goes without saying that, while these convenience fea-
Besides station frequencies, the preset memories hold | tures are all well and good, they alone wouldn't provide
whatever settings you use to tailor the tuner's operation to | sufficient justification for the high price of this FM tuner—
your specific needs and preferences, so you don’t have to | unless its sensitivity, selectivity, and other measured param-
go through all those switches and adjustments every time | eters were among the best available. Happily, they are, as
you call up the stations. Even the tuner’s output level can be | you will see from my lab measurements and listening tests.
set separately for each station, so you can use the same
volume setting whether you're listening to a quiet classical | Control Layout
station or one of those stations which tries to be loudest on If | am ever asked to teach a course on industrial design
the dial by modulating up to (or beyond) the legal limits. | and good human engineering, | think | will borrow a Revox
Information can also be programmed about which of the | B260 to illustrate how a tuner's front panel should be de-
B260's two antenna inputs should be selected for each | signed. To begin with, the B260's low-profile design match-
preset station, as can the degree of stereo blend, i.f. band- | es that of Revox's recently introduced B250 integrated am-
width, and even r.f. sensitivity. There are two r.f. gain set- | plifier. Both units are about 1% inches lower than earlier
tings about 4 dB apart—just enough to make overly power- | Revox audio components, and will soon be available in
ful stations, which might otherwise overload the front-end, | black with gold trim, instead of the company's traditional
usable again. gray and silver.
The B260 display area has provisions for entering the call The B260's programming controls are placed behind a
letters associated with each of the station frequencies you | hinged, smoked-glass cover, completely separated from
memorize. Up to four characters can be memorized for | the main operating controls. There is little chance of a child
each station. | haven't seen that on a tuner since Larry | (or even you) accidentally upsetting previously pro-
Schotz first introduced it on his memorable Micro/CPU 100 | grammed settings.
tuner design more than a decade ago, though some recent When the power switch at the extreme right of the panel is
receivers also offer it. pushed, the tuner is turned on and the last received station
Most home tuners let you switch to mono if stereo back- | is reactivated. Two large rocker pads just to the left are used
ground noise or multipath interference becomes unbearable | for changing stations; their functions and illuminated labels
AUDIO/SEPTEMBER 1988 71
The B260 stores not only
frequencies, but call
letters, station formats,
and tuner settings for
up to 60 stations.
S/N Ratio (dB) vs. Signal Level (dBf)
` OUTEUT
S/H Ratio {dB) vs. Signal Level (dBf)
„x
AUS DUTEUT
10.8
30.9
Fig. 1—Mono and stereo
quieting characteristics,
wide i.f. mode, for “Single
r.f.” (A) and “Double r.f.”
(B) settings.
THR + Noise (%) vs. Signal Level (dBF); € =Mono,-—-——— =$tereo)
THD + Moise (X) vs. Signal Level (dBf); ( =Mona ,--——-=£tereo>
Fig. 2—THD + Nvs.
signal strength at 1 kHz
for wide (A) and narrow
(B) i.f. modes.
change according to the setting of two buttons (“Tuning”
and “Station”) behind the smoked-glass panel.
In “Station” mode, the two rockers scan the preset memo-
ries. The right-hand rocker (now “P-Type Scan”) scans up
or down through the station subgroup, while the left-hand
rocker (“Station Scan’) scans up or down through all 60
programmed station memories, regardless of subgroup.
When the B260 is in “Tuning” mode, the right-hand rock-
er's label becomes “Autotuning,” and it activates the auto-
matic station scan, ascending or descending. The other
rocker becomes “Frequency Step,” and is used for manual
tuning in steps of 10 or 50 kHz, as determined by one of the
secondary controls. That 10-kHz step feature is extremely
useful if you suffer from adjacent-channel interference,
since it enables you to tune slightly away from the interfering
sidebands of the adjacent-channel transmission without de-
tuning enough to introduce serious distortion.
Small pushbuttons labelled “P-Type” and “Enter” set up
the mode for entering a subgroup identification and activate
the input function after retrieval or programming of a station
memory or a program subgroup. Ten numerical keys are
arranged across the upper left of the panel, along with a
larger rocker labelled “Display.” Pushing this pad changes
part of the display area below, which can be cycled through
to read station call letters, tuned-to frequency, or both.
(Station memory number and program subgroup number
are always displayed.) A stereo indicator light is also part of
this display, which occupies nearly the entire lower-left
quarter of the panel.
The secondary controls referred to earlier are under the
smoked-giass cover, which swings smoothly down and out
of the way after a pushbutton labelled “Open” is depressed.
At the same time, a small secondary display, only dimly
visible when the cover is up, becomes clearly visible amidst
an array of secondary pushbuttons. A “Step” button selects
10- or 50-kHz frequency increments when you are in the
manual tuning mode, which is selected by pressing the
nearby “Tuning” button. Pressing the “Station” button, or
closing the hinged lid, cancels the manual tuning mode. The
“Recall” button restores the previously tuned frequency. A
72
AUDIO/SEPTEMBER 1988
ECC Ee
This tuner offers some
unusual choices, such as
two levels of stereo blend
and r.f. gain.
my. Jom TN
—_— _ _ _ _ _ _ _ _-_ _—_—_"_"-"-"-"-"-"-"""-"""""""
Distortion + Moise versus Frequency, FM Tuner Revox Model B260
5
Ap
| À
Distortion + Moise versus Frequency, FM Tuner Revox Podel B268
3
Fig. 3—THD + N vs.
modulating frequency for
wide (A) and narrow (B)
if. modes.
(dB) vs. Frequency CHz); € =Modulated Ch.,~---=linmod.Ch.)
og
Ap
18.0
36.0
-69.0
Frequency (HI), € =Modulated Ch. ,----=lnmad.Ch.)
tion (dB) vs.
narrow (B) i.f. modes.
Note the two blend levels.
Fig. 4—FM frequency
response (solid curves)
and separation vs. Solid curves are output
frequency (dashed with (top to bottom) no
curves) for wide (A) and blend, Blend 1, and Blend 2.
button labelled “Search” determines the signal-strength
threshold that will apply during automatic tuning or scan-
ning. Other small buttons select the antenna input desired,
r.f. gain selection (local or distant), i.f. bandwidth, mono or
stereo reception, stereo blend levels, muting, and such
additional functions as are required for the sophisticated
programming modes featured in this tuner. Two of the re-
maining buttons are used to access alphanumeric charac-
ters for setting up station call letters or whatever label you
choose to program in. The small illuminated display, which
shows up in this area when the hinged cover is lowered, is a
multifunctional display that shows signal strength, center
tuning, muting, antenna, mono mode, high-blend mode,
search mode, audio level, i.f. bandwidth, and r.f. mode.
The rear panel houses the two antenna inputs, stereo
output jacks, and a pair of jacks intended for connection to
an oscilloscope for checking multipath during antenna ori-
entation. There's also a multipin connector for use with
Revox's multiroom infrared control receiver or their pro-
grammable controller when integrating the tuner with other
Revox audio components. An optional wireless remote, the
Revox B208, can control all the tuners main functions,
except “Display,” when the tuner is in “Station” (automatic
tuning) mode.
Measurements
Both of the B260's antenna inputs have impedances of 75
ohms, but neither uses the “F-type” connector we are ac-
customed to. Revox supplied an appropriate adaptor (to
Which a coaxial cable could be wired) as well as a “splitter,”
in case you want to connect your TV antenna or cable feed
to the tuner as well. | used the adaptor to connect my 50-
ohm generator output to the 75-ohm inputs, and | took that
slight impedance mismatch into account in those measure-
ments where it would significantly affect the results. (Nor-
mally, | use my generators 300-ohm output, but the 8260
has no 300-ohm input, and transformers would cause ex-
cessive signal losses.)
Figures 1A and 1B are graphs of S/N ratio versus input
signal level for the single-r.f. (distant) and double-r.f. (local)
AUDIO/SEPTEMBER 1988
79
There’s no subcarrier
leakage, so you can tape
from the B260 without
using your deck’s MPX
filter and cutting the highs.
A
tude (dB) versus Frequency (Hz); FM Tuner, Revox Model B260 modes, respectively. (Since there was virtually no difference
in quieting characteristics between the wide and narrow i.f.
modes, | did not deem it necessary to re-plot these graphs
for the narrow mode.) The chief differences between the
results of Figs. 1A and 1B can be seen at low input-signal
levels. For the distant mode, 50-dB quieting in mono was
achieved with an input signal of 14 dBf, whereas with the
double-r.f. setting, it took nearly 20 dBf of signal strength to
reach the same — 50 dB noise level. The difference was less
profound in stereo, since stereo quieting inherently requires
far more input signal to reach a noise level of — 50 dB. In
this case, it took exactly 38.0 dBf to reach that level of
background noise using the distant setting, and 40 dBf in
the local mode.
Figures 2A and 2B show how THD + N varied with signai
-1.
3.
-5.
Fig. 5—Frequency strength. (For this and all further tests, | used the distant
response. Note vertical mode.) From these graphs, you can see that the 3% point
scale of 1 dB/div. (usable sensitivity) was reached at a signal leve! of between
11.0 and 13.0 dBf, "depending on whether the narrow or
| wide i.f. mode was employed. On my sample, the stereo
Be A TL 2m switching threshold was set higher than specified, so | could
to | not measure performance in stereo at signal levels below 30
dBf (for S/N measurements) or 40 dBf (for THD + N mea-
-20. surements). At strong signal levels, where THD + N is
primarily THD, distortion for a 1-kHz signal measured 0.05%
in mono for the wide if. mode and 0.055% for the narrow
mode. In stereo, THD reached a low point of about 0.09% in
UNMODULATED the wide mode and about 0.4% in the narrow mode.
Figures 3A and 3B show how THD + N varies with
-60. | frequency. (The signal level used for these tests was 65
_7a. e | dBf.) Figure 3A gives results for the wide i.f. mode, while
Fig. 3B illustrates the somewhat higher THD + N levels that
790. result when the tuner is operated in the narrow mode.
-90. | Figures 4A and 4B show frequency response of a modu-
lated stereo channel versus separation, measured at the
A output of the opposite, unmoduláted stereo channel. (The
B dashed curves represent separation, measured in dB.) Fig-
ure 4A shows results obtained in the wide i.f. mode; Fig.
4B, the narrow if. mode. With either of the blend settings,
separation remained virtually the same regardless of wheth-
MODULATED er the tuner was set to the wide or narrow i.f. mode. Note,
foo, that the output from the modulated channel decreased
a bit as | switched from no blend to Blend 1 and then to
Blend 2. In measuring separation, therefore, | had to refer-
ence each separation curve to the appropriate solid-line
-50. CHANNEL curve with which it was associated. Thus, while separation
in the Blend 1 setting appears to be about 19 dB, in reality it
was more like 16 dB when referenced to its corresponding,
modulated-output reference level (the lowest of the three
solid curves). Similarly, separation in Blend 2 was actually
about 11.5 dB, rather than what appears to be 13 dB.
In the no-blend mode, maximum separation at 1 kHz in
the wide i.f. mode (Fig. 4A) measured 43.5 dB at 1 kHz, 41.2
Analysis of stereo crosstalk, for 1887 Modulated 5 kHz Test Signal
0.0
Fig. 6—Separation and dB at 100 Hz, and 36 dB at 10 kHz. Switching to the narrow
crosstalk components for i.f. mode (Fig. 4B), maximum separation decreased to 41.6
a 5-kHz modulating . | dB at 1 kHz and 30 dB at 10 kHz. Although the solid curves
signal, plus subcarrier of Figs. 4A and 4B gave me a good idea of overall frequen-
and sideband components, cy response of the tuner, the vertical scale used in those
tor wide (A) and narrow (B) : graphs is so compressed that almost any tuner’s response
if. modes. would look perfectly flat. | therefore reset my Audio Preci-
82 AUDIO/SEPTEMBER 1988
The switchable r.f. gain
helped make strong
stations more listenable,
and the blend circuits did
the same for weak ones.
E
sion test system to expand the vertical scale from 10to 1 dB | 60 dB. There was absolutely no evidence of spurious sub-
per division, and replotted the same measured frequency | carrier frequency output when the tuner was operating in the
data; the results are shown in Fig. 5. Here you can see that | stereo mode and input signals were in stereo. If such prod-
the response does roll off just a bit at the low end (about | ucts were there, they were below the residual noise levels
—0.2 dB at 30 Hz). It also dips a bit at the high end (about | and, therefore, | could not read them. If you want to record
—0.4 dB between 6 and 8 kHz) and rises again above 10 | FM programs from this tuner onto your cassette deck, you'll
kHz before finally rolling off at around 15 kHz. Response | never have to sacrifice a few kHz of response by switching
was down about 0.7 dB at 15 kHz. in your deck's MPX filter.
Since getting this new test gear, | have gradually aban-
doned my practice of photographing the screen of my | Use and Listening Tests
spectrum analyzer 'scope to show separation and crosstalk | began to fully appreciate the features of this remarkable
for a 5-kHz signal modulating just one channel in the stereo | tuner only when | started listening to some of my favorite
mode. Now | can plot this information on an easy-to-read | stations. The classical music station | most enjoy is noted for
grid, as shown by Figs. 6A and 6B (wide and narrow if. | its practice of keeping modulation levels very low to allow
modes, respectively). | believe that, despite the fact that the | for sudden dynamic peaks, especially when playing CDs,
sweep is made using a somewhat wider bandpass filter | without having to ride gain or use compressors excessively.
than was used on my spectrum analyzer, results are clearer | But that has always meant that, when | switched from that
and easier to interpret. The plot is logarithmic and extends | station to my next most favorite stations (another classical
from 100 Hz to 50 kHz. The upper trace represents the | one and a station specializing in jazz and early pop and
desired 5-kHz output from the modulated channel. lts peak | rock), | usually had to run for the volume control on my
IS set precisely at 0-dB amplitude, making it much easier to | preamplifier. Not with the Revox B260! | simply set the audio
read the separation, which turned out to be just over 40 dB | output level about 4 or 5 dB higher for my favorite low-
in the wide i.f. mode and almost exactly 35 dB in the narrow | modulating station. Now as | switch back and forth between
mode. More important, it is easy to see that, in the narrow i.f. | stations, they all sound about equally loud.
mode (Fig. 6B), not only did the levels of second and third In absolute terms, the Revox B260 was not the most
harmonic components (10 and 15 kHz) increase, but a | sensitive tuner I've ever measured, but that didn't seem to
spurious component can be seen at around 1 kHz. No such | reduce the number of usable signals | was able to pick up.
component is evident in the wide i.f. mode (Fig. 6A). In fact, | was even able to get a couple of local stations that |
Capture ratio was highest in the narrow i.f. mode, measur- | have traditionally not bothered to count in tuner reports
ing just under 1.0 dB. Alternate-channel selectivity mea- | because they usually caused unacceptable levels of rf.
sured 53 dB in the wide mode and greater than 100 dB in | intermodulation distortion. In the case of the Revox B260, |
the narrow mode. Spurious-response and i.f. rejection also | simply switched to the “Double r.f.” setting (| wish they had
exceeded 100 dB, while AM rejection measured more than | called the two settings “Local” and “Distant” since that's
тете ти “-úÁáooc 1 What they really are, functionally) and reduced the r.f. gain
| enough to solve the problem. As for weak-signal stereo
reception, | was really surprised to-find how effective stereo
can be with only a bit more than 10 dB of separation,
providing that separation is uniform at all audio frequencies,
as it is in the-case of the Blend 2 setting. Trading off some
separation in return for background noise that's almost as
low as that heard in mono is worthwhile.
After completing all of my bench and listening tests, |
managed to obtain Revox's separately sold B208 remote
control. This multipurpose remote operates many other Re-
vox components, including the B250 amplifier, B226 and
B225 CD players, and B215 and B710 tape recorders. | was
surprised to find that, although the unit is sold separately,
Revox chose not to include the 9-V battery needed to
operate it. In any event, after reading the operating instruc-
| tions that accompanied the remote, | realized that this unit
| would be great to have if you owned an ali-Revox compo-
| nent system, or at least a few other Revox components. For
the tuner alone, however, it's a bit expensive.
| The reputation that the Swiss have for craftsmanship is
| certainly confirmed by this tuner. Admittedly, you have to be
a pretty serious FM-radio fan to spend the kind of money
needed to purchase this elegantly styled and intelligently
engineered tuner, but | suspect that there are enough such
FM devotees out there to make the B260 the resounding
success it deserves to be. Leonard Feldman
AUDIO/SEPTEMBER 1988
AllegroSound.com
http://www.AllegroSound.com
‘audio in the service of music”
Est. 1973, Los Angeles California USA
Vintage High-End Pro
Buy Sel Frage. Nog Repatr
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