Sequerra Model 1 FM Tuner Reviewed

Sequerra-Model1-FM-Tuner.gifWriting this with full awareness of the risk of seriously alienating the more jingoistic among you, I must report that the three best tuners ever made were American. This is a consensus I found through talking with experts, surfing the net and using my own ears. I had a 20-minute conversation about this with EAR’s Tim de Paravicini, who designed a tasty little tuner for Luxman and who knows about such matters. He agreed. And the irony is lost on nobody.

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Quite simply, before the BBC turned to swill, the UK had the very best broadcasting in the world, in both content and signal quality, while there were precious few stations for UK tuners to have to accommodate. The USA, on the other hand, merely had quantity. OK, so its rock stations were peerless, but the commercial nature of American broadcasting made it pale by comparison to the Beeb at its finest. However, sheer distances and a mix of terrain forced American designers to hone their tuners to a level where they could cope with everything from vast areas with scant coverage to urban locations where a mere whisker of a turn on the dial might find five co-joined stations.

As a result, American tuner designers learned to juggle selectivity, noise rejection, bandwidth, variable amounts of compression and every other consideration, especially, as Tim pointed out, RF rejection, a problem area ‘where nobody could touch the Yanks.’ And the triumvirate of tuners that conquered all, with to-die-for sound-quality thrown in, consisted of the Marantz 10B launched in 1964, the McIntosh MR78 which arrived in 1972, and the Sequerra Model 1 of 1973.

It’s no coincidence that the last of the three bore the name Sequerra, as Richard Sequerra was credited with co-designing the previous decade’s champion, the Marantz 10B, with the deservedly-celebrated Sid Smith. (For the story of the equally-coveted McIntosh MR78, see the forthcoming book McIntosh: For The Love of Music, to be published this year.) Indeed, when the Sequerra first appeared, it was billed by many as ‘a solid-state version of a 10B,’ an instantly-comprehensible way of describing it as the 10B’s logical successor.

As with most products, the 10B had a defining feature. It was a genuine oscilloscope on the front panel that made precise tuning more readily attainable, while providing the more scientific user with an RF spectrum analyzer. Its appeal was not lost on Sequerra, who featured it prominently on the first tuners to bear his name. With its elevated price of $1800 at its launch (rising to almost $4000 in loaded form near the end of its initial run), its no-compromise design and advanced facilities, this tuner landed with the same sort of impact as the Wilson WAMM and the Goldmund turntable: pundits mused that products that expensive had to be superb. Or else.

In production, Sequerra’s Model 1 was as much a concept as it was a specific unit because there were numerous options and variants. It is also known that severely-modified, special-application Sequerras were used by professionals, including American radio stations, to test broadcasts. The options approach applies, too, to the later Sequerras produced by David Day from the early 1980s into the mid-1990s, while the all-new range of DaySequerra tuners launched in 2005 are offered in different versions.

In 1984, the Davidson-Roth Corporation acquired the rights to the Sequerra, which they re-introduced as the DaySequerra FM Broadcast Monitor, the new tuner being an extensively updated version of the original. What makes matters difficult for the collector is the profusion of models from both Sequerra and DaySequerra, including the Model II of 1976-77, a fresh design from 1983 called the Model One Broadcast Analyzer, and the DaySequerras including the FM Reference, FM Reference Classic, FM Studio, FM Studio 2, FM Broadcast Monitor and others, with prices ranging from $3,000 to around $13,000 depending on options, the most costly being the all-singing, all-dancing Panalyzer display.

To compound things further were myriad evolutionary changes barely reflected in external clues. When I reviewed an FM Reference in 1991, 18 months after I auditioned the FM Broadcast, the most I could learn that the Reference was, as I wrote, ‘…more than an upgrade, sort of a “third generation” version, but the details of the changes haven’t reached me. What I can glean from a white paper the company produced is that everything has been uprated to even more ludicrous standards… Many of the improvements involve the use of superior parts which, quite simply, weren’t available even when the Broadcast was designed, while other considerations dealt with easier, more consistent manufacture and greater reliability.’

Typical of what you might find out there – although eBay has of late been relatively Sequerra-free, despite fears for the future of analogue transmissions – is the DaySequerra FM Studio Tuner, the ‘budget’ version of the Model 1. It sold here for £3,950 in 1989, to put the frighteners on you. Common to most Sequerras, it featured two vertical arrays of six buttons per side, a rotary tuning dial, large red digits and the 4.5in instrument-grade oscilloscope.

(By sheer coincidence, the lone Sequerra item on eBay at the time of writing was a CRT tube for the display, with a buy-now price of $250. At the time I reviewed my first Sequerra, I was told that ‘ …the scope on its own would cost roughly a third of the price of the tuner.)

For most models, the 12 control buttons operate four oscilloscope functions, absolute polarity inversion, contour defeat, narrow, normal and wide IF bandwidth selection, ‘mono forcing’, muting defeat and power on/off. At the back are an IEC mains input, a US-style, screw-threaded 75ohm aerial input and four pairs of phono sockets. Two pairs are for signal out, either normal or inverted, while the other pairs (also normal and inverted) feed the oscilloscope for assessing other line-level components, accessed by pressing the button on the front panel marked ‘External Vector Display’.
As for design philosophy, the owner’s manual informed the customer that a sophisticated analogue tuning system was employed in preference to digital tuning
because the company found the trade-offs unacceptable, arguing that digital synthesis tuning is, among other things, noisier and less accurate. The company also felt that that digital tuning has resolution of 12.5kHz with an actual ‘set-on accuracy’ of greater than 8kHz while the DaySequerra was tested for set-on accuracy of
better than 100Hz.
Sound quality was never an afterthought, despite the seemingly overriding concerns for issues unique to tuner design. DaySequerra-era tuners employed true dual-mono audio amplification stages designed by Dan D’Agostino of Krell, each channel using entirely discrete devices and offering balanced operation. The Studio also featured six separately regulated power supplies via a custom-made 250VA toroidal transformer. Military spec parts were used throughout, including 1% Dale metal film resistors, and Roederstein and Mial capacitors. The FM Studio Tuner, when connected to live mains, rested in stand-by mode, with half-illumination of the oscilloscope’s matrix to indicate this status. Because the tuner needed at least 30 minutes to deliver optimum performance when switched on from cold, this pre-warming stage meant that full performance was available within a minute. Pressing the ON button illuminated the digital counter, the legends next to each button and the oscilloscope. Although lacking presets, the Sequerra was a
delight to tune, with a nicely-weighted rotary control reminiscent of the Marantz 10B’s, a bright red digital display of the station’s frequency, and the oscilloscope’s
tuning matrix, with its three-prong assault: Pressing the top button on the left hand array produced the grid over the oscilloscope. Between stations, there was a blue blur at the bottom of the scope. As you neared a station, the blur took on the shape of a small arc, circling up the matrix. The higher the arc travelled, the stronger the signal. For dead-centre tuning, the user simply centred the blue arc over the middle vertical line on the grid; the words ‘stereo pilot’ lit up over the station counter when a stereo broadcast was located. The second and third displays assessed signal and stereo quality. ‘Tuner Vector Display’ produces an x-y grid showing the instantaneous peak deviation of right and left audio channels. Music programme produced an egg-shaped burst emanating from the centre point, while an announcer’s voice yielded a near vertical line; in the case of speech with the voices at stage left and stage right, the two lines veered in the direction of each speaker, the further apart the better the separation. Mono broadcasts produced a vertical line. ‘Tuner Balanced Vertical Display’ was selected when the tuner was used in balanced mode.

Once familiar with the owner’s manual, the user could employ the scope to reveal with great accuracy the exact signal strength, separation, peak deviation of L and R channels and more. This was particularly useful in helping to set up an aerial in an area plagued with multipath problems. ‘Stereo Contour Override’ was an interesting feature reminiscent of older tuners’ ‘blend’ facility. When forcing the tuner to mono (also called stereo defeat) when stereo reception was weak seemed simply too much of a sacrifice, Sequerra’s contour control was used to the best compromise between stereo effect and noise. Note that this function occurred with the button in the ‘out’ position, so those who didn’t read the manual would be listening to contoured sound aimed at achieving separation of 50dB at 1kHz and 40dB at 10kHz, while maintaining an S/N ratio of 70dB. With the button pressed in for defeat, the unprocessed signal was received. The £5457 FM Reference I reviewed in 1991 looked exactly like the Broadcast, with the same functions, plus XLR socketry around back instead of inverted and non-inverted phonos for balanced use. I wrote that it remained, ‘an all-analogue, superheterodyne FM-only unit, testing showing that tuning accuracy is better than 100Hz. The RF front-end uses three parallel tuned RF circuits to produce the proper load impedance for the balanced MOSFET tetrode amp and bipolar mixer devices. Three transformer circuits improve image rejection and RF overload performance. The company eschews the use of AFC circuitry or global feedback, instead using this hideously complex and expensive RF front-end. But that’s why the Sequerra exists.

‘The IF subsystem uses electronic RF switching circuits and parallel IF processors, allowing user selection of three IF bandwidths. The IF filter sections use variable Q circuitry for optimal gain and detector response, as a result guaranteeing the least distortion regardless of the bandwidth selected by the user.’

In use today, fresh from an update [see box], the FM Reference still has a sonic advantage over any tuner in my experience. There’s a warmth to voice – both spoken and sung – while the sense of palpable three-dimensionality is inescapable on well-miked live broadcasts. I use it all the time for news programmes, chat shows and the like, and – through the Lexicon MC-1 in Logic 7 mode – it provides all-encompassing sound in a way I’ve yet to hear from the dreaded DAB. Fatigue? Only depending on the DJ.

Worst case scenario? We only have a few years left before the assholes switch off FM. Even if a working Sequerra FM tuner costs you a few grand, there can be no better way to see, or hear it out.

Read more on Page 2


DaySequerra Updates

Those fortunate enough to own a DaySequerra FM Reference tuner might wish to contact the company for the Signature Upgrade package, which will carry on for a while even though the original tuner ceased production in 2005. According to David Day, ‘The Signature Upgrade further improves the selectivity, distortion and channel separation of the FM Reference tuner as well as completely addressing the major reliability issues with this 15-year old design, namely the cathode ray tube (CRT) and incandescent lamps.’

The upgrade includes the following:

* Replace the oscilloscope tube with a new CRT
* Add new switching circuitry that allows the user to easily turn the oscilloscope off from the front panel when it is not in use. This circuit completely removes the plate and deflection voltages from the CRT, and provides a slow start turn-on, significantly lengthening the life of the tube and completely addressing the main reliability shortcoming of the tuner
* Replace all incandescent bulbs with solid state LED devices
* Replace the RF mixer with a higher image rejection design
* Re-bias the IF amplifiers and replace the IF filters with hand-matched, low group delay filters for improved distortion and channel separation
* Hand-match and adjust the bias points of the FETs in the audio circuit improving the low end as well as transient response.
* A complete alignment

DaySequerra provides a limited lifetime warranty on all upgraded units for defects and workmanship covering parts and labour, except the CRT. The new CRT is
warranted for one year for defects and workmanship, according to Day, ‘but with correct use of the new dimming circuit, the CRT should last for well over 5 years. Mine is now 10 years old and going strong.’

Customers should Day Sequerra at 011 856-719-9900 or visit
to organise collection and request a reservation for the upgrade. Day: ‘We’ve really been overwhelmed with the response to this program, but we do only three upgrades per week.’ That’s because Day insists on listening personally to every unit receiving the upgrade. Total cost of the modification is US $1,680, plus shipping.

SIDEBAR: Manufacturer’s Specifications: DaySequerra FM Broadcast Tuner Wavebands FM only Tuning Range 87.5-108 MHz Display Range 87.2-108.3 MHz Tuning Display Dynamic Range 120dB Tuning Accuracy 0.0005% of tuned frequency Bandwith Selection Wide: 280kHz Normal: 180kHz Narrow: 130kHz Usable Sensitivity 10dBf (stereo) 8dBf (mono) S/N Ratio -65dB 50dB Quieting Threshold 35dBf Separation [email protected] [email protected] Quieting, 1kHz 0.35% (typ 0.10%) [email protected], 1kHz 0.10% (typ 0.08%) SCA Rejection -75dB (typ -85dB) AM Rejection -75dB (typ -85dB) Dimensions 440x375x145mm (WDH) Price (1989) 3,950 

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