Welcome to Decware

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a dual-mono purist-designed push-pull masterpiece from Decware

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The Zen Mystery Amp

Model ZMA

The Zen Mystery Amp is for People who
want MORE than to just hear the music…
they want to float in it!

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"Edgar Winter’s They Only Come Out at Night was the first record in my collection, so to say I’m intimately familiar with it would be an understatement. For old times’ sake, it’s the first album I place on the turntable when critical listening begins for the Zen Mystery Amp (ZMA). Wow! Just when you think you’ve heard it all and you know a piece of music inside and out, this amp whacks you upside the head—which is enlightening and it’s what keeps this reviewing game interesting. The first cymbal crash on Radiohead’s “High and Dry” further convinces me that I’m listening to something magical. There’s more air and delicacy everywhere. The ZMA is all about nuance and finding more information lurking in the details."

 

-- Tone Audio Magazine's Jeff Dorgay                                    Read the Full Review

FEATURES

  • Dual-Mono design where the only thing shared between the two halves is the power cord.

  • Purist Design is hand built point-to-point with no circuit boards.

  • Vacuum tube regulated power supplies for each channel.

  • Rare harmonics that sound and feel like an SET amplifier.

  • No global negative feedback used.

  • 40 watts / channel

  • Compatible with 6L6, 5881, KT66, 7027. 

  • Optional Transformer-coupled XLR inputs.

  • Boutique internals including Miflex Copper Foil capacitors and F&T electrolytics.

  • The best tube bias system ever designed.

SPECIAL FEATURE

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One of the things that makes the Zen Mystery Amp unique is it's insane power supplies.
 
A typical tube amplifier this size uses power supply capacitors totaling about 80 micro-farad. 

The dual mono Mystery Amp has thousands of micro-farads per channel.  In fact it's about 40 times more than normal for this cost-no-object power supply design and the massive capacitors come with some huge sonic benefits.  The ZMA power supplies have enough stored energy to start your car and melt all four tires to the garage floor!

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In fact, these capacitors are so large that the amplifier sounds as if it's being run on batteries. It is where the liquidity comes from in the sound.  Clean power is everything with transparent amplification, so when you consider the cost of a power re-generator is more than this amplifier -- the value becomes obvious.

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Zen Mystery Amp

SUPERIOR TUBE BIASING 

My first tube amp was a "fixed bias" design that required a screwdriver and a voltage meter to set the bias.  The bias always drifted.  When you adjusted one tube the others changed.  When you set it wrong, the tube plates got cherry red and started to melt. This is how a lot of tube amps are designed and likely the reason why so many people who tried a tubes for the first time ended up going back to solid state.

This amplifier needs no tools and is ingeniously designed with the ability to not only set the bias for each pair of tubes, but also set the balance between the two tubes.  You just look at the meters and adjust the knob until the they match.

 

This means you have basically a tube tester that allows you to see if the matched tubes you purchased actually do match as well as the ability to adjust the balance to make them match if they don't.

The meters also show you if a tube is acting up, or getting ready to fail, or has failed.  There is no guesswork with this amplifier.

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Steve Deckert / DECWARE

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WHAT ELSE SETS THIS AMP APART?

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"The two biggest things other than no circuit boards or solid state parts, would be this:

1) Tube Regulation - shown left.

2) Even Order Harmonics - discussed below.

Both are unheard of in the vast majority of push-pull amplifiers, tube or solid state alike.

This beautiful tube is a variant of the OA3 regulator tube. It is a VR90 which drops the voltage to the input stage by around 15 volts.  This can be just enough to tickle your exotic N.O.S. 6922 or 7DJ8 inputs tubes into a new level of nirvana.  There are actually three of these tubes you can work with that will give you three different sounds.

Harmonics

Even order vs. Odd order harmonics is basically a discussion comparing the sound of SET amps to common Push-Pull designs.  Push-Pull designs, both tube and solid state typically have odd-order dominant distortion whereas the SET (Single-Ended-Triode) amp designs have even-order dominant distortion.

Even-order distortion is found in nature.  It actually can make things sound better rather than worse.  Odd-order distortion is like hitting the wrong notes on a piano, and is never enjoyable in any amount.

 

We designed the Zen Mystery Amp to have similar harmonics to our low power SET amplifiers.  The output stage in the ZMA  uses relatively lower voltages with an adjustable bias for long tube life. 

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Even Order

ZEN MYSTERY AMP

ZEN TRIODE SET

Shown above are the harmonics of both the ZMA and our SET amplifier side by side.

A typical push-pull amplifier's distortion graph looks like this:

Odd Order

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Unlike the Decware -- the 1K tone doesn't generate an even harmonic at 2K, instead it is at 3K, 5K,  and 7K (A,B and C)

OPTIONS

Wood Types

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Shown above from top to bottom is:  Maple, Cherry, Black, Walnut, Black Victorian. Custom hardwoods and or finishes are available upon request for additional costs.

Knobs

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From left to right is; Ebony, Gold, Black Chicken Head,  Cream Chicken Head, Walnut.

Anniversary Mods -

 

This amplifier can be upgraded with full Anniversary Mods which include Miflex Copper Foil bypass caps in the power supply and Nichicon NXF mains caps.  These mods take the resolution of the amplifier further for those with more serious listening rooms.

 

XLR Inputs -

You can add transformer-coupled balanced XLR inputs to this amplifier in parallel with the existing RCA jacks for each channel.  That means you use either RCA or XLR but not both at the same time.

Voltage

The amp has a CE rated world voltage compatible pair of power transformers. You can select your voltage you want from within the shopping cart.

DESIGN NOTES

The Mystery Amp came directly from our signature Zen TORII Mono-Blocks which are an impressive reference with 88dB hi-fi speakers.  But we wanted something in a single chassis and with a reduced voltage for a more musical experience with high efficiency speakers.  By building two mono amps in a single chassis, eliminating the fancy transformer covers, reducing the power a bit, using smaller meters and finally by making balanced XLR inputs optional ~ it was possible to maintain the same cost-no-object design goals in a more affordable amp.

The Mono-blocks are unique in that they have a massive power supply with caps so large it is possible to eliminate the choke and any dropping resistors feeding the output stage.  Unless you see an amp with similar size caps, you can be certain that it has at least one if not both of these current limiting necessities.  This is why the Mono's sound better than almost everything.  Well, on that note, the Mystery Amp explores this zen approach a little further by doubling the capacitor size and eliminating the dropping resistor that feeds the input stage.  Instead a vacuum regulator tube was used to drop the voltage with no heat and 20 times the ripple rejection of the resistor it replaces.  This was a personal goal of mine because it makes this the first tube amp power supply in the world that doesn't use a choke or any current robbing resistors to supply both the input and output stages of the amp.  Consequently there is no heat or parts to fail.  The real impressive part however is the liquidity and speed that results from eliminating these parts.

This is about as close to pure DC power as you'll ever get in a 500 volt amplifier.  As a result, the Mystery Amp will have strong immunity to dirty power from your wall outlet.

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The other nice thing about this amplifier is how it handles the output tube bias adjustments.  We've all seen tube amps that have blown up due to "bias runaway" when the plate inside the tube gets red hot and causes the tube and sometimes the amp to fail.  This happens because many amplifiers share a bias supply between more than one tube.  Setting the bias wrong, or using mismatched tubes can trigger this event.  It's a big reason people who like cathode biased amps, like cathode biased amps better than fixed bias amps.  Anyway, an adjustable fixed bias amp can actually be as reliable and sound as good or better by simply doing it right.  

In the Mystery Amp, I created independent bias supplies for each output tube so that when you adjust one tube, it does not affect the other tubes.  That way you only ever have to adjust it once, instead of ten times until you happen to hit it just right.  Also a lot of time was spent defining windows of adjustment that worked with all the recommended output tubes without allowing the user to get into too much trouble should he/she miss adjust it.  In fact, most of the time it will impossible to get into trouble ensuring long happy tube life.  

The biggest thing is output tube matching in push pull amplifiers for linear output and max power, so to that effect rather than have a bias adjustment for each tube, we have one for the pair and one as a balance control located between the meters so that the user can perfectly match the meters at any time in less than a second. Each channel is set up this way. You'll find this handy since tubes drift with temperature and this allows you to counter it on the fly as you listen without tools.  It takes all the pain in the ass out of owning a fixed bias amplifier.  Of course the meters make great tube testers and clipping indicators allowing you to see if any one tube is prematurely clipping relative to the others despite being perfectly matched at idle.

Another delightful thing about this amplifier is that is has zero negative feedback so the imaging and sound stage depth are unrestricted and capable of rending whatever is on the recording or whatever is permitted by the acoustics and speaker placement.

In the end, it is every bit the fidelity and performance of the Zen TORII Mono's with a bit sweeter top end.  On most speakers greater than 86dB there was no noticeable difference in power between the Mystery Amp and the Mono's.

The OA3 feeding the input stage combined with double the capacitance of the Mono's gives the Mystery Amp unparalleled accuracy and liquidity. 

NOTE:  There is also a forum thread on the Mystery Amp that I started early in the design process.

SPECIFICATIONS

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  • World Voltage compatibility 50/60Hz

  • INPUT TUBE Compatibility: 6N23P, 6922, 6N1P, 6DJ8, 7DJ8

  • OUTPUT TUBE Compatibility: EL34, 6CA7, KT77, KT66, 7027, 5881, 6L6G

  • INPUTS: OPTIONAL TRANSFORMER BALANCED XLR INPUTS

  • INPUTS: SINGLE-ENDED RCA INPUT 

  • OUTPUTS: 4 & 8, or 8 & 16 OHM SPEAKERS

  • IDLE CURRENT: 40~70 MILS PER OUTPUT TUBE - ADJUSTABLE

  • HIGH B+ VOLTAGE: 410 VDC WITH LOAD

  • INPUT IMPEDANCE: 100 K OHMS

  • INPUT SENSITIVITY: FULL POWER @ 2.0 VOLTS ON RCA INPUT

  • POWER INTO 4 , 8 or 16 OHMS: 38 WATTS PER CHANNEL

  • NOISE: -90dB

  • PRECISION CURRENT METERS 0 to 100 MA

  • WINDOWED BIAS CONTROL to ADJ OUTPUT TUBES

  • DYNAMIC BIAS BALANCE CONTROL FOR PERFECT MATCHING of EVEN UNMATCHED TUBES

  • COPPER FOIL MIFLEX - SIGNAL CAPACITORS

  • OPTIONAL 20 POS STEPPED ATTENUATOR w/ GOLD CONTACTS for INPUT LEVEL (GAIN) CONTROL

  • 4400 UF 500V LABORATORY GRADE POWER SUPPLY CAPS

  • GOLD TEFLON INPUT JACKS

  • RECTIFICATION: ULTRA FAST RECOVERY 3 AMP 1000V 

  • MACHINED STEEL CHASSIS with POWDER COAT FINISH

  • HI-GRADE FUSED IEC CONNECTOR for REMOVABLE POWER CORD

  • SOFT START- NO STANDBY NEEDED

  • SHIPS WITH:

  • PREMIUM GRADE KT66 OUTPUT TUBES

  • PREMIUM GRADE 6N1P-EV INPUT TUBES

  • OA3/VR75 REGULATOR TUBES

  • SIZE: 19-1/8" WIDE  x 13-3/4" DEEP  x  8-3/4" HIGH

  • NET WEIGHT: 43 lbs.

  • WARRANTY: LIFETIME TO ORIGINAL OWNER / 90 DAYS ON TUBES

REVIEWS

SUPPORT

Since we don't have dealer's and we sell our amplifiers directly to the customer, our customers have a direct line to us.  As a result, Decware support is legendary for over 20 years.

Support is not only a phone call or email away at any time, but when you purchase this amplifier you join a huge family of customers who also own one and enjoy supporting each other on our support forums.

 

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Owner's Manual is in a .pdf format

TRY ONE AT HOME FOR 30 DAYS!

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Return IT if not satisfied FOR 10% RESTOCK FEE !

MODEL ZMA

40 WATTS x 2 

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Made by hand in the USA and sold wholesale to the public with a 
L i f e t i m e   W a r r a n t y  !

Amps are hand-built to order.  There are presently lots of orders on our real time build sheet.   A 10% deposit secures your place on the list with today's date and time stamp.  Balance is due when it's ready to ship. You will be sent a final invoice with the total price including actual shipping costs by our office during your wait.   

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Listen to one and find out what you've been missing!

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40 WATTS of LIQUID HONESTY

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