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Richter Mystique Integrated Valve Amplifier ON TEST

groove scribed in it to indicate where it’s pointing, so in day-to-day use it’s hard to see which input is selected, but the minute you touch the control, you can feel where it’s pointing. The power switch is located under a type of meter we haven’t seen on a consumer product for years—an old-fashioned analogue needle-style VU (Volume Unit) meter. And when we say ‘old-fashioned’ we don’t only mean the look and style of the meter… the motion of the needle across the dial face appears to be controlled by a standard d’Arsonval meter movement, which was invented ‘way back in 1882! (By famous French physicist Jacques-Arsène d’Arsonval). The reason for using a VU meter rather than any other type of meter is that a VU meter reflects the perceived ‘loudness’ of an audio signal better than a peak-reading meter because the d’Arsonval movement is quite slow and so mechanically ‘averages’ the audio signal in much the same way as the human ear averages the sounds it hears. The meter on our sample had been calibrated so that when it was showing ‘0dB’ the amplifier was delivering exactly 10-watts into 8Ω via the 8Ω speaker tap. A gold-plated 6.5mm headphone socket is located at the left of the front panel. Above it is a kitschy illustration of a pair of headphones. (Memo to Richter: Just printing ‘Phones’ above the socket would have been just fine by us.)

Around the back of the Richter Mystique we found something quite unusual. Although the Line 1, Line 2 and Line 3 inputs use standard gold-plated RCA sockets, the Auxiliary input is a nickel-plated 3.5mm phone-jack socket. Evidently it’s designed this way so you can easily plug in the analogue output from your iDevice or mobile phone, but if this is indeed the case, why wasn’t the input put on the front panel, where it would be easy to access? There are no ‘Record Out’ outputs on the Mystique, nor Pre-Out sockets.

RichteR Mystique Integrated amplIfIer

Brand: richterModel: mystiquecategory: Integrated amplifierRRP: $1,799Warranty: two YearsDistributor: richter acoustics pty ltdAddress: Unit 45, 176 South Creek road dee Why nSW 2099

(02) 9981 1844 info@richter.com.au www.richter.com.au

readers interested in a full technical appraisal of the performance of the richter mystique Integrated amplifier should continue on and read the laBOratOrY repOrt published on page 40. readers should note that the results mentioned in the report, tabulated in performance charts and/

or displayed using graphs and/or photographs should be construed as applying only to the specific sample tested.

Lab Report on page 40

ment includes all protrusions… volume knob, RCA sockets and so on). But, as you’d expect of a valve design, because of the all-essential heavy transformers, the Mystique still tips the scales at 13kg, despite its small size.

Four small-signal valves are arrayed across the front of the amplifier, being a pair of 12AX7s and a pair of 12AU7s on our sample. The 12AU7 valves carried no branding at all other than the word ‘China’. The 12AX7s

Richter is, of course, best-known for building loudspeakers, having started off in an award-winning way back in the ‘80s with what many

say was Australia’s biggest-selling loudspeaker model ever, the original Richter Wizard, a model that continues on, and is now in its fourth generation. Richter has now decided that it should have its own amplifier… pre-sumably as a ‘best match’ for its loudspeak-ers. Rather than re-invent the wheel, Richter decided to go into partnership with a Chinese hi-fi manufacturer that runs its sales and marketing out of Hong Kong. Richter says it selected one of this company’s most popular models then specified different valves and a completely different DAC. These changes apparently necessitated some small changes in the amplifier’s circuitry, but essentially it’s the same basic design that’s available in other markets as the Dared i30. Richter calls its re-worked version the ‘Mystique’.

The equipmenTIn the flesh, the Richter Mystique is surpris-ingly small, measuring 160mm high, 380mm wide and 300mm deep (this last measure-

were labelled ‘ECC835’ and were made in the Slovak Republic by JJ Electronic. The ECC835 is electrically the same valve as the 12AX7, but if you’re new to the world of valves, it might be confusing that the label on the amplifier says 12AX7 while the one on the valve itself says ECC835. Don’t be confused, and be aware that many other differently-named valves can be used instead of a 12AX7. One you may care to try, for example, is the famed ECC803S… but sit down before you get a price! (But don’t worry about the cost of small-signal valves, because 12AX7/ECC835 valves can be had for around $20–30 depending on the manufacturer and whether you want extras, such as gold-plated pins.)

As for the output tubes, they too were completely unmarked on our sample, so we asked Richter about them, and were told that they were made exclusively for this model by Chinese company Shuguang, which is a company that sells its own valves under the audiophile ‘PSVANE’ label. While we were asking, we enquired about the unlabelled 12AU7s on the Mystique and it turned out that these are also made by Shuguang, but are not part of the upmarket PSVANE series.

• great sound• Smart appearance• USB input

• location of aux input• design of valve shield• no remote

laB repOrt

By way of explanation, Shuguang is not only China’s largest valve manufacturer but also oldest, having been founded in 1958. The company makes a wide range of valves, and supplies them either with the usual clear glass envelopes or with carbon compound coatings (carbon-coated valves are known as ‘black bottles’). The company is most famous for its ‘Treasure Series’ of valves, released to commemorate its 50th anniversary.

While we’re on the subject, valves do wear out, but they do so only very slowly. According to high-end US manufacturer Audio Research, which has been designing and building valve amplifiers for more than half a century, its service records show that output valves generally last around 2,000 hours, while small signal valves go for at least 5,000 hours or so. So if you listened to the Richter Mystique for two hours every night of the week, every day of the year, you could expect around three years’ life from the 6L6Gs, and more than six years from the 12AX7s and 12AU7s. And, contrary to popular belief, valves are pretty rugged. Almost all guitar amps use valves, and they get moved from gig to gig almost every day, in the process of which they’re dumped into the backs of vans, bumped up and down flights of stairs, and yet they still manage to perform reliably every night. But in the event you do need to replace a valve, because you broke one, or it simply wore out, it’s simply a matter of pulling out the old one and pushing in a new one—it’s no more difficult than replacing a house-hold light bulb.

So when the valves in the Mystique do finally wear out, what’s a replacement going to cost you? If you decided to replace the PSVANE 6L6Gs with well-known and highly-regarded ‘Ruby’ valves, you could pick up a set of four hand-matched Ruby 6L6GCMS-TRs for around $100 the set at the time of writing. However, if you wanted NOS (New Old Stock) valves made by famous European or US manufacturers that have been stored away by collectors for twenty or thirty years, you could pay that same price for just a single valve. Why would you want to change from the PSVANE brand? Probably for the same reason that most owners of valve amplifiers change their valve brands, which is to experiment with replacement valves made by different manufacturers to see if they can get better sound quality or, sometimes, just a different sound quality. The pursuit is known as ‘valve-rolling’ or ‘tube-rolling’.

The front panel of the Mystique has a single volume control at the far right, to the left of which is an input selector with positions for Line 1, Line 2, Line 3, Aux and USB DAC. The input selector has only a thin

The speaker terminals are extremely high-quality, gold-plated, colour-coded WBT lookalikes, with 4Ω and 8Ω taps positioned either side of the ‘0’ (negative, or common) terminal. The USB input (with a red LED above it) is a standard Type A USB connector, which leads to a 24-bit/96kHz USB DAC. The 240V input socket is an IEC-standard three-pin type with an integrated fuse.

Our photograph of the Richter Mystique shows it without the casing that would normally go over the valves to protect them (as well as to prevent anyone from touching the valves, which get very hot). The casing on the Mystique is a perforated steel cage that’s fitted with a large Perspex ‘window’ at the front, so that you can see the valves. To attach or detach it from the amplifier is simply a matter of removing or installing

Power Output: Single channel driven into 8-ohm and 4-ohm non-inductive loads at 20Hz, 1kHz and 20kHz. [Mystique]

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Power Output: Both channels driven into 8-ohm and 4-ohm non-inductive loads at 20Hz, 1kHz and 20kHz. [Mystique]

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IntegRAted VAlVe AMplIfIeR

Richter Mystique

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ON TEST Richter Mystique Integrated Valve Amplifier

two hex-head screws. It’s not a particularly attractive example of the genre, so we suspect most people won’t use it at all.

peRFORmAnCeYou’d want to have your eyes checked before trying to install the Mystique, because we found the screen-printed labels on the rear panel were very difficult to read. It’s partly the colour of the paint (grey paint on a black background—why not gold paint, the same as on the front panel?), partly the style of lettering (all capitals, which is more difficult to read than upper and lower case) and, in the case of the ‘Left’ and ‘Right’ labels for the speaker outputs, the positioning of the letter-ing (underneath the speaker terminals, where it’s all but impossible to see them if you’re leaning over the amplifier from the front).

Another trap for young players is that the speaker terminals are mirror-imaged, so that the 8Ω tap is to the right of the ‘0’ terminal on the left channel, but to the left of the ‘0’ terminal on the right channel, so if you’re not careful it would be very easy to accidentally connect one speaker to the 4Ω tap and the other speaker to the 8Ω tap.

OK, so all these inconveniences will all be annoying only the once, when you first install the amplifier, but they’re such obvious inconveniences—and so easy to fix—that we found them annoying. Since we’re speaking of the amplifier speaker taps, we’d recommend that irrespective of the nominal impedance of your speakers, you connect them to the 4Ω taps, because with all the speakers we tried, this tap sounded better than the 8Ω tap.

We auditioned the Mystique over a period of a week, during which we followed our own long-standing advice about the operation of valve amplifiers, which is to turn them on a few minutes prior to listening, and to turn them off after each listening session. The Mystique warmed up very quickly (we had the valve cage fitted, which tends to contain the heat) and although we heard

some very minor improvements in the sound quality after the amplifier had been playing for an hour or so, we didn’t find they were significant enough that we’d feel the necessity to switch the amplifier on well in advance of planning to use it.

As for the sound quality, it was a case of ‘love at first listen’! The sound that issues from the Mystique is beautifully sweet and mellifluous, with not a trace of harshness, even when the amplifier is being pushed to its limits. The bass is beautifully tuneful, and we were able to follow bass lines with ease, for example the incredible bass intro to Queen’s Another One Bites the Dust, which has the advantage (from an auditioning point of view) of also having a nice clean kick drum in the mix as well. The six repeated notes after the two-note run are E2 (so although it sounds pretty low, it’s actually 82Hz), so we also tried out Michael Jackson’s Billie Jean (from ‘Thriller’). The lowest note in this bass riff is an impressively low 43Hz, very nearly as low as an electric bass (or double bass) will play. Yet even with notes this low, the power and precision of the Mystique were clearly audible, and the tension induced by the music is palpable… just as it should be.

The string sound was rich, yet at the same time tonally pure, so if the Mystique was adding anything to the sound, it was all good!

The oh-so-sweet sound continued through the audio range, right across the midrange and through to the highest treble. Particularly across the midrange, music played through the Mystique seemed to ‘sing’ and sound more fluid than we hear from solid-state amplifiers. And it wasn’t from any differences in response: the tonal balance of the Mystique was perfectly accurate, right across the audio band. The difference this makes when listening to vocal harmonies, for example, is absolutely magic: you’ll feel a shiver go through your spine.

If the Mystique has an Achilles’ heel, it’s its power output, which is most definitely on the low side. (Newport Test Labs later measured as delivering a maximum of 16-watts continuous per channel at 1kHz and slightly less at very low and very high frequencies. A full laboratory test report can be found on page 40. It means that unless you only ever play your system at very low volume levels you will definitely need to use speakers with a sensitivity rating higher than 87dBSPL. (So you won’t be at all surprised to learn that all Richter’s loudspeakers are rated at 88dBSPL or higher… even up to 90dBSPL). However, in the event that you drive the Mystique into clipping you will find that, like all valve amplifiers, it clips so gracefully that the amplifier will appear to sound ‘louder’ rather than the sound suddenly becoming harsh, which is what happens when solid-state amplifiers go into clipping.

We should point out at this juncture that you should not depend on the Mystique’s front-panel VU meter to tell you if the amplifier is clipping: the needle’s movement is far too slow to be able to indicate peaks in the music signal. It is for this reason that some VU meters also have peak-reading LEDs built in, which flash when the amplifier is clipping. It would be nice if the Mystique’s VU meter had such an LED… but it doesn’t.

COnClusiOnIf you’ve never heard music played through a valve amplifier, we have to tell you that it’s worth taking the time to listen to the Mys-tique just so you can hear why music-lovers rave about the sound of valves, and why valve amplifiers are now ‘all the rage’ right around the world, selling in unprecedented numbers. But be warned… follow the lead of Odys-seus and leave your credit card with a trusted friend, lest you be lured by the beauty of the sound and end up buying Mystique the very first time you hear one. (But if you do suc-cumb, rest assured that you will be the proud owner of a very fine amplifier indeed.)

lAB RepORt On pAge 40

Power Output: Single and both channels driven into 8-ohm and4-ohm non-inductive loads at 20Hz, 1kHz & 20kHz. [Mystique]

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ValVe-rOllIng dOS and dOn’tSIf you are valve-rolling, be a little cautious because some of the so-called ‘valve substitution’ charts on the internet are incorrect. for example a few appear to suggest that you can replace a 6l6gC valve with an el34, but these valve types have different requirements. for example, the el34 has the suppressor brought out on pin 1, which must be connected in the amplifier, whereas the 6l6gC has the suppressor internally tied to the cathode, so no amp connection is required. (there are other important differences, but they’re beyond the scope of this brief note.) One of the most reliable sources of what’s compatible with what can be found at www.audiotubes.com. to be 100 per cent certain that a valve you’re buying is an exact replacement, you only have to ensure that the letters and numbers on the valve you’re buying are exactly the same series of numbers and letters as the valve you’re replacing so, for example, a valve with the letters 6l6g can be used to replace a valve with the same letters and numbers, no matter what brand it is, or in which country it was made. If you are in any doubt about the suitability of a particular valve for use in the mystique, contact richter acoustics.

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Richter Mystique Integrated Valve AmplifierRichter Mystique Integrated Valve Amplifier ON TESTON TEST

COntInUed fROM pAge 38

TesT ResulTsAs I have pointed out almost every time I have had to write a report on the test results for a valve amplifier, it’s extremely difficult to quantify the output power of a valve ampli-fier due to the fact that the output waveform will distort significantly (more than 3.0%) before the tops and bottoms of the waveform start to ‘clip’. Presumably the 30-watts per channel out-put that Richter claims for the Mystique is at the point of the waveform clipping, at which point distortion levels would be in excess of 5.0% THD. Newport Test Labs measured the power output just before the 3.0% distortion level was reached, under which conditions the Mystique returned the highest output power of 18-watts per channel into 8Ω, right across the audio band. Interestingly, these figures were returned only for one condition, which was when the amplifier was driving 8Ω loads from the 4Ω speaker output tap. If the same 8Ω load were connected to the 8Ω tap, the amplifier delivered 16-watts at 1kHz, 15-watts at 20Hz and just 10-watts at 20kHz. Connecting a 4Ω load to the 8Ω tap saw outputs diminish to 11-watts per channel at frequencies up to 1kHz, dropping to just 7-watts per channel at 20kHz. When a 4Ω load was correctly con-

nected to the 4Ω taps, the power output was lower than when an 8Ω load was connected, as you can see for yourself from the tabulated results. And if you’re wondering what that VU meter shows, if you’re playing music at an output level of around one watt, the needle will hover around the –15VU (20%) mark. If you’re at the limit of the amplifier’s power capabilities, it should be hovering around the 0VU (100%) mark.

In Newport Test Labs’ frequency response tests, the Mystique only just managed to meet its specification, rolling off a little early to be 1dB down at 20kHz and 3dB down at 30kHz. The low-frequency response was, however, very extended, with the amplifier being only 1dB down at 1Hz. This puts the normalised frequency response of the Richter Mystique at 1Hz to 20kHz ±0.75dB, using a standard 8Ω non-inductive test load (shown as the black trace on Graph 6), slightly better than specification.

Into a simulated loudspeaker load the Mystique’s frequency response was not quite as flat, with Newport Test Labs measuring it at 1Hz to 20kHz ±1.25dB, slightly out of spec. However, both these responses would be audibly flat, since the human ear cannot detect such small variations in level, particularly over such a wide bandwidth.

Channel separation was measured by the lab at an excellent 93dB at 20Hz, 82dB at 1kHz and 56dB at 20kHz. I reiterate: these are excellent figures for a valve amplifier. Interchannel phase was also excellent for a valve amplifier, returning figures of 1.9º at 20Hz, 0.4º at 1kHz and 4.6º at 20kHz. The balance between the two channels was exceptionally good: 0.04dB. This is far better than some of the best solid-state amplifiers.

Overall distortion levels were quite low for a valve amplifier design, with THD+N measuring just 0.05% at one-watt output levels, and 0.42% at an output level of 16-watts.

The finer detail of the harmonic distortion picture is shown in the first four graphs, which show distortion at 1-watt into 4Ω and 8Ω loads, as well as distortion into these same loads at 16-watts (8Ω) and 11-watts (4Ω). At one watt you can see that the second harmonic is the most prominent, reaching –68dB (0.039%) with 8Ω loads and increasing to –59dB (0.112%) with 4Ω loads. Regular readers will know that the second harmonic is not troublesome, since it’s effectively the ‘octave’ of the fundamental and therefore very pleasant-sounding to the ear (though not strictly accurate to the original). Into 8Ω loads all the remaining harmonic distortion components are more than 81dB down (0.008%), with the third and fourth almost exactly at –80dB, the fifth and sixth at –90dB (0.003%) and all the others (out to the 20th) at or below –100dB (0.001%). Whereas normally I would have expected the even-order harmonics (2nd, 4th, 6th, etc) to dominate in the output, the levels of even-order and odd-order (3rd, 5th, 7th, etc) are approximately even. When driving 4Ω loads, the third harmonic sits at –70dB (0.031%), the fourth at –76dB (0.015%), the fifth at –88dB (0.003%) and the sixth at –84dB (0.006%). All higher-order harmonics are down at around –100dB (0.001%). (Ignore the signals near 16kHz, they’re breakthrough from a nearby video monitor.)

Distortion levels are obviously much higher when the amplifier approaches its rated power output level. For brevity I’ll look only at the 8Ω result, which has slightly lower overall distortion than at 4Ω. You can see the second harmonic component sitting at –61dB (0.089%), but this time the third harmonic component is higher, at –44dB (0.631%). The fourth and fifth are around –63dB (0.071%), while the next three harmonic distortion components, the 6th, 7th

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Graph 1: Total harmonic distortion (THD) at 1kHz at an output of 1-watt into an 8-ohmnon-inductive load, referenced to 0dB, using 8-ohm output tap. [Richter Mystique Amplifier]

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Graph 2: Total harmonic distortion (THD) at 1kHz at an output of 1-watt into a 4-ohm non-inductive load, referenced to 0dB, using 8-ohm output tap. [Richter Mystique Amplifier]

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Graph 3: Total harmonic distortion (THD) at 1kHz at an output of 16-watts into an 8-ohmnon-inductive load, referenced to 0dB, using 8-ohm output tap. [Richter Mystique Amplifier]

Newport Test Labs

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Graph 4: Total harmonic distortion (THD) at 1kHz at an output of 11 watts into a 4-ohmnon-inductive load, referenced to 0dB, using 8-ohm output tap. [Richter Mystique Amplifier]

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Richter Mystique Valve Amplifier - Power Output test ResultsChannel load (Ω) 20Hz

(watts)20Hz

(dBW)1kHz

(watts)1kHz

(dBW)20kHz

(watts)20kHz (dBW)

1 8Ω (8Ω tap) 15 11.7 16 12.0 10 10.0

2 8Ω (8Ω tap) 15 11.7 16 12.0 10 10.0

1 4Ω (8Ω tap) 11 10.4 11 10.4 7 8.4

2 4Ω (8Ω tap) 11 10.4 11 10.4 7 8.4

1 8Ω (4Ω tap) 18 12.5 18 12.5 18 12.5

2 8Ω (4Ω tap) 18 12.5 18 12.5 18 12.5

1 4Ω (4Ω tap) 15 11.7 16 12.0 10 10.0

2 4Ω (4Ω tap) 15 11.7 16 12.0 10 10.0

note: figures in the dBW column represent output level in decibels referred to one watt output.

and 8th, are all around –77dB (0.014%). The presence of a low-order odd-order harmonic (the third) is not bothersome, because in musical terms, it’s a fifth which, like the octave is pleasant-sounding to the human ear…though again, not strictly faithful to the original.

Noise levels were acceptably low, and good results for a valve amplifier, with the unweighted signal-to-noise ratio referred to 1-watt being measured at 63dB. The ratio

increases to 71dB with A-weighting. Referred to rated output, the signal-to-noise ratios again improve to 72dB (unweighted) and 81dB (A-weighted). These ratios are around 10–20dB less than I’d expect from a well-designed solid-state amplifier, but good for a valve amplifier design.

Input sensitivity for one-watt output was 73mV, while you’ll need 300mV at the input in order to be able to drive the Mystique to rated output. This will be easily achievable

for any source component I’ve encountered that’s fitted with a line-level output. The output impedance of the Mystique was measured at 1.5Ω, which means that when it’s driving 8Ω loads, the damping factor will be a very low 5.3, so the impedance of the speakers you connect to the Mystique will affect the final sound quality, just as their sensitivity will affect the maximum undistorted SPLs you will be able to achieve in your listening room.

Balance between the channels was exceptionally good...far better than some of the best solid-state amps

Richter Mystique Valve Amplifier - test Resultstest measured result Units/Comment

frequency response @ 1 watt o/p 1Hz – 16kHz –1dB

frequency response @ 1 watt o/p <1Hz – 30kHz –3dB

Channel Separation (dB) 93dB / 82dB / 56dB (20Hz / 1kHz / 20kHz)

Channel Balance 0.04 dB @ 1kHz

Interchannel phase 1.9 / 0.4 / 4.6 degrees ( 20Hz / 1kHz / 20kHz)

tHd+n 0.05% / 0.42% @ 1-watt / @ rated output

Signal-to-noise (unwghted/wghted) 63dB / 71dB dB referred to 1-watt output

Signal-to-noise (unwghted/wghted) 72dB / 81dB dB referred to rated output

Input Sensitivity (Cd Input) 73mV / 302mV (1-watt / rated output)

Output Impedance 1.51Ω

damping factor 5.3 @1kHz

power Consumption n/a / 142 watts (Standby / On)

power Consumption 143 / 160 watts at 1-watt / at rated output

mains Voltage Variation during test 242 – 255 minimum – maximum

Heatsink temperature (degrees C) 89 @ 1-watt and 5-watts output

41 Australian

Richter Mystique Integrated Valve AmplifierLAB REPORT

Square wave testing revealed excellent performance for a valve amplifier—or any other type of amplifier, actually. The 100Hz wave shows a very slight tilt revealing that the low-frequency response does not extend down to d.c., and some slight curving showing a little phase shift, but is otherwise excellent. The 1kHz wave is certainly not quite perfect, but it shows only a little rounding on the leading edge. The 10kHz wave exhibits considerable rounding, and the

ripples on the leading edge indicate some high frequency irregularities, but it’s very stable. The 1kHz capacitive load image proves the Mystique will be unconditionally stable into any loudspeaker load, including electrostatic loudspeakers… indeed it appears that a slight capacitive loading (as will occur with even ordinary dynamic loudspeakers) will actually improve the amplifier’s performance. As I’ve noted on previous occasions, good performance with a capacitive load correlates well with amplifiers that are reported to ‘sound good’ in listening sessions.

Mains power consumption was, as you’d expect, relatively high, with the Mystique pulling 142-watts from your 240V supply whenever it’s switched on and a bit more when it’s playing music at normal levels. Maximum draw is 160-watts, so for reasons of economy and in the interests of extending the life of the valves, I would suggest switching the amplifier off between listening

Square wave testing revealed excellent performance for a valve amplifier—or any other type of amplifier

sessions unless they take place on the same day. Most of the power is lost as heat, of course, and Newport Test Labs measured the temperature of the cage immediately above the output valves at 89ºC during ‘normal’ use. Because of this, I would recommend leaving plenty of space above the Mystique, so don’t install it in an enclosed rack or closed shelving. Steve Holding

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