Coming from a perspective of SET amplifiers, the Zen Torii is a unique minimalist design in a push-pull pentode amplifier with zero negative feedback. It has the liquidity and micro-detail of our SET amps but with a bit more than 25 watts per channel. Although rare, it's proof that a well engineered push pull design can sound as good as a single ended design and even surpass it in some areas. Fully tube voltage regulated power supplies ensure a smooth linear response without having to use feedback. There are very few pentode amplifiers in the world that don't require feedback to have a flat frequency balance. This is the exception. Imagine your favorite SET with unusually electrifying speed and control, and that's what this amp sounds like.  

Using a 6N1P (6922) as the input stage and direct coupled phase inverter, this push pull design requires only the minimum possible number of parts in the signal path... 1 capacitor and 2 resistors. Of course the motivation behind this amp was to get the sound of single ended amps but with more power. You can build a 25 watt single ended amp, but you will need an additional tube stage to drive the larger output tube, leaving you with twice the parts in the signal path and consequently less transparency. This push pull design was the only way to keep the same short signal path as our smaller SET amps. The nice benefit is that you have the transparency of a good single-ended amp but with the absolute slam of push pull. This amp's speed in the bass makes good solid state amplifiers sound slow.

WHY DOES THIS AMP SOUND SO GOOD?

Of course there are no circuit boards and no Chinese parts.  There IS a lifetime warranty though.

There is a bias switch that allows you to adjust the weight and warmth of the amp on the fly while you listen.   Matched pairs are suggested for the EL34's, but the amp is self biasing so there are no adjustments to make, ever. The input tube for each channel is your choice of 6N1P, 6DJ8 or 6922's.  The four voltage regulation tubes besides looking really cool don't really wear out, nor do the rectifier tubes.  They can however be rolled with alternates to achieve subtle but significant changes to how the amp sounds.

Voltage regulators can be ignored, or used to take the tube rolling experience to a deeper level. The four voltage regulator tubes below all modify the operating points of the output tubes they regulate. This in turn changes the way the output tube sounds.

FEATURES

The TORII MK III has a volume (gain) control located on the front so it may be used without a preamp. We recommend if you own a preamp to try both using and not using it to see which is actually better.  There are also two pair of inputs with a selector switch mounted just behind the gain control.  Output impedance is selectable with a switch from 4 to 8 ohms or from 8 to 16 ohms (please specify).   Additionally, there is a treble control for each side to assist with fine tuning channel balance between speakers.  This is also a handy compensator for aggressive speakers or bright rooms.  It is a simple shunt to ground circuit so it is not in the direct signal path and does not effect fidelity.

Additional features are listed later in this page.

STYLES:

The amplifier was designed with a machined aluminum plate featuring a high gloss piano finish with a baked on powder coat making it impossible to rust or even scratch.  This in turn is set into a solid wood base.  The amp comes standard with the base shown at the top of the page, however we offer alternate bases with a more contemporary profile in a variety of solid hardwoods and even exotic woods.

Shown in optional hardwood base.

This amplifier requires no adjustments or maintenance other than changing output tubes every couple of years.  It is a self biasing design.  

INPUT TUBE CHOICES: 6922, 6DJ8, 6N1P

OUTPUT TUBE CHOICES: EL34


INPUTS: 2 RCA TYPE INPUT JACKS FOR EACH CHANNEL

OUTPUTS: 1 PAIR HEAVY Gold  BINDING POSTS PER CHANNEL

OUTPUT STAGE TOPOLOGY: GND-CATHODE TRANSFORMER RK

RLOAD PLATE TO PLATE: 6600 OHMS

IDLE CURRENT: 47 MILS PER OUTPUT TUBE

HIGH B+ VOLTAGE: 410 VDC CHOKE REGULATED PER CHANNEL

INPUT IMPEDANCE: 100 K OHMS

INPUT SENSITIVITY: FULL POWER @ 2.0 VOLTS

POWER INTO 3.5 OR 8 OHMS: 24.6 WATTS RMS PER CHANNEL

NOISE: -90dB

OPERATION: CLASS A1

GRID REGULATION: ONE OA3-OD3 PER CHANNEL


INPUT STAGE REGULATION: ONE VR75~VR150 PER CHANNEL


RECTIFICATION: ONE 5Y3GT or 5AR4 or 5U4 PER CHANNEL

INPUT STAGE: ONE 6N1P or 6922 or 6DJ8 PER CHANNEL

OUTPUT STAGE: TWO MATCHED EL34 PER CHANNEL

SIZE: 19-1/8 " WIDE x 13-3/4 " DEEP x 7-3/4 " HIGH

NET WEIGHT: 36.8 lbs.

WARRANTY: LIFETIME TO ORIGINAL OWNER / 90 DAYS ON TUBES

SHIPS WITH:

PREMIUM MATCHED WINGED "C" EL34 OUTPUT TUBES
SOVTEK 5Y3GT or 5U4 RECTIFIERS
6922, 6DJ8, 6N1P PREMIUM INPUT TUBES
N.O.S.  VOLTAGE REGULATOR TUBES
REMOVABLE POWER CORD


 



 

PERFORMANCE

Measured specs into a pair of 94dB loudspeakers (with a difficult impedance curve) at normal listening levels:

Above summary of specs.

Frequency response of both channels overlapped.  Tone control at 1/2 way point.  The minus -3dB point at low frequency is 6Hz.

Frequency response and THD.

Noise test.

Dynamic Range.

THD test.

Inter modulated Distortion.

VOLTAGES


This amplifier comes standard with our World Voltage Compatible Transformer. Your amp will be automatically wired for the correct voltage for your country and be supplied with the correct removable power cord. 

TUBES:

This amp is shipped with graded premium quality RUSSIAN EL34 output tubes.  These winged "c" Russian tubes are the top grade of what we came to know in this country as the SVETLANA EL34.  The TORII MK III has been optimized for EL34's.  While you can also use 6550's, KT77's and KT88's without any damage to the amplifier, the amplifier will only sound "correct" with EL34's in most cases.  NOTE:  This is a big change from the TORII MK II which used any of the above mentioned tubes and all of them sounded great.  Now with the Hazen grid technology and new voice coil bias technology, EL34's sound superior in this amp, so much so, that using anything else is a waste of time.

The input tube is a single 6N1P, 6922 or 6DJ8 - your choice.  6N1P's have the warmest tone, 6922's have the best dynamics, 6DJ8's have the most air and micro-detail with a touch less bass.  Again, a powerful tool for voicing your amplifier to your particular tastes.

The rectifier is a 5U4G and can be substituted with a 5AR4 or compatible rectifier.  Many owners of this amp like using the 274B.  Each rectifier change will also make audible differences in the sound and performance of the amplifier.

The voltage regulating tubes can also be changed to effect the bias and sound of each different output tube.  You can use an OA3 which gives the highest grid voltage and usually the most low end performance.  You can use an OD3 which gives the lowest grid voltage and usually the tightest bass.  If you wished it to land somewhere in between, there is the OB3 and OC3.

The smaller seven pin regulating tube is cleaning the power for the input stage.  There are also four tubes you can use here, starting with the stock OC2 also know as VR75.  This gives the input stage the highest gain.  Changing to a VR150 lowers the gain of the input stage.

With the stock tubes we ship in the amp, it gives ideal performance in most applications.  It's just that you CAN tweak it to a very fine level if so motivated.

REVISION HISTORY

	TORII / Manufactured from 2002 to 2004 This was our first Torii, at 12 watts per channel with solid state regulation using EL34's or KT77's.
	TORII MKII / Manufactured from 2004 to 2009. New chassis, tube rectification, tube regulation, and twice the power at 25 watts x 2.  Feedback was eliminated.
	TORII MKIII / New for 2010 New chassis, more tube regulation, several tweaks, Hazen Grid Mod.  This amp has become our flagship amplifier for 2010.

IDEAL SPEAKERS

CABLES

This amplifier is so transparent that differences between cables will now become big differences. If you don't have good interconnects or speaker cables or just not sure how good yours are... we offer reference quality cables that will let you hear its full potential. It is important to us that you hear what your new amp is capable of and most customers, even those with expensive cables, find that ours sound better.

SUPPORT

This amplifier is hand built in the USA by DECWARE / High Fidelity Engineering C0. It comes with a lifetime warranty to the original owner. If you purchase one second hand and ever have questions or technical problems we WILL be happy to check it out for you and service it if needed for a very reasonable rate.

We also have a support forum with many people who own this amplifier who's experiences you may benefit from. 

REVIEWS

You can get a military-grade waterproof/shockproof case customized to perfectly form-fit your amp for transport and or shipping.  The amp fits upside down into foam.  Case features wheels and a pull out handle so anyone can easily move it. - $299.00

 

The owner manual for this amplifier can be viewed on line or printed:
TORIIMK3 Owners Manual.pdf

ADDITIONAL FEATURES:

1/8 INCH THICK LASER CUT DUAL MONO CHASSIS 
MIRROR IMAGE SYMMETRICAL AMPLIFIER LAYOUT
DESIGNED TO ENSURE CLEAN INCOMING POWER
USA MADE PROPRIETARY POWER TRANSFORMERS
TUBE RECTIFICATION FOR EACH CHANNEL
CHOKE REGULATED POWER SUPPLY FOR EACH CHANNEL
LINEAR OPERATION WITH ZERO NEGATIVE FEEDBACK
PURE CLASS A OPERATION AT ALL TIMES
TOP GRADE ATOM SPRAGUE FILTER CAPS
TUBE VOLTAGE REGULATION FOR EACH CHANNEL
SYMMETRICAL SOLID COPPER GROUND BUSS
SINGLE TRIODE DIRECT COUPLED INPUT/DRIVER STAGE
BASIC WIRING POINT TO POINT / MATCHED LENGTHS
ONLY ONE COUPLING CAP PER CHANNEL
SELF BIASED TUBES MEANS NO ADJUSTMENTS NEEDED
OVER SIZED HIGH QUALITY OUTPUT TRANSFORMERS
ADJUSTABLE TOP END FREQUENCY BALANCE ON EACH CHANNEL
HEAVY GOLD BINDING POSTS
FRONT MOUNTED VOLUME/GAIN CONTROL MAKES PREAMPS OPTIONAL REMOVABLE POWER CORD
ON/OFF SWITCH FOR EACH CHANNEL
2 PAIRS OF INPUTS WITH SILVER SELECTOR SWITCH
SELECTABLE OUTPUT IMPEDANCE 3.5 OHMS / 8 OHMS / 16 OHMS
CCE / Hazen Grid Mods
Voice Coil Cathode Bias
OC2 input stage regulation

RELATED INFO

STEVE'S DESIGN NOTES on the TORII MKII amplifier - the foundation of this amplifier and worth reading.  Specific design notes for this amplifier can be found in the TORII MK III owners manual.

Some of our loudspeakers to match with your Zens

Steve's papers for audiophiles