Zesto Audio
Explore Zesto Audio
We have looked for a long time to find a line of quality US made tube gear that we think is really special. Zesto Audio is just that. It is an American made line of very high quality separates that competes with the best products made. We have been following George & Carolyn since they introduced their first phono stage 10 years ago and have been consistently impressed. They now have a full line with a world class tube preamp, two state of the art Class A tube power amplifiers as well as 3 phono stages and a superb Step up Transformer.
Leto Ultra II Preamplifier
State of the art stereo preamplifier$11,900.00
See the great Feb 2021 Stereophile review. They say:
"When your reference preamplifier regularly bests all comers, ticking off the reasons why lesser equipment can't compete becomes commonplace. The Zesto Audio Leto Ultra II preamplifier was a welcome deviation from that pattern. It blew out my preconceptions and expectations."
Must be heard to be fully appreciated."
"Highly recommended."
Read the entire review at: https://www.stereophile.com/content/zesto-leto-ultra-ii-line-preamplifier
In the 11.23.23 review Positive Feedback they said:
Read the full review here: https://positive-feedback.com/reviews/hardware-reviews/zesto-audio-leto-ultra-ii-preamplifier/
In the Feb 2020 review by Positive Feedback Robert Levi says:
"The Zesto Audio Leto Ultra Preamplifier is Zesto Audio's ultimate statement of preamplifier perfection. It is made 100% in America. The all-tube unit is chock full of useful and creative features a dedicated audiophile and music lover will enjoy, styling which would be right at home at MoMa, a flexible remote control without flaws, and Zesto's best overall musical performance to date. Sonically superior to anything solid state I have ever heard, you would have to spend a ton more to equal its high definition and many features in the tube world."
"No tube preamp at any price is quieter or has better facilities to manage hum and noise in your entire system like the Leto Ultra. The Leto Ultra is one superior innovative product, and right at home in the Zesto line. My highest buy recommendation!"
Here are a few other quotes from the review:"George created a preamplifier that is neutral with a bullet, remotely changeable to enhance lesser recordings or sources, has remotely adjustable outputs that provide unity gain with no editorializing, and uses fully balanced tube circuitry throughout...all on one normal-sized chassis. Plus, it is a 100% ultra-quiet advanced tube circuit super easy to roll. Joining the Bia amplifier and the Andros Deluxe phono, the new Leto Ultra preamplifier premiers in excellent company—the three most innovative and dramatic advances to date of AFFORDABLE state of the art musical reproduction in the home."
"The Leto Ultra soundstage is grand. From ceiling to floor and wall to wall, and front to infinity, the speakers disappear and the music flows. With a state-of-the-art source, expect a state-of-the-art performance from the Leto Ultra."
The new 2019 Ultra version replaced the extremely well reviewed Leto 1.5 and the new 2020 Leto Ultra II is even better with upgraded power dupply:
Zesto has announced their newest, all analog product - the Leto Ultra II preamplifier, which replaces the Leto 1.5 and original Leto (which is now discontinued). Of particular interest are the 'tone controls', the new Presence Control. George Counnas says, “This was born out of my frustration that the more resolved my system became, many of my favorite new and old recordings, became unlistenable due to the inconsistencies of the Mastering, regardless of the source. I realized the part that bothered me was the harmonic balance of the mid and high frequencies, the region that can be considered too bright, edgy, aggressive or fatiguing.” The 6 position Presence control easily allows you to dial it back without any technical knowledge required, just listen for the most enjoyable tonal balance for every song. George says, “It works great for your mood too, because sometimes I’m in the mood for lots of detail and sometimes I want it laid back and I can do it from my sofa with the remote.
Top 7 New Features of the Leto Ultra Preamplifier
1. New upgraded circuit topology delivers more musical detail with a tighter bass. It has a robust input design to handle higher output sources. Dynamic range is expanded by new circuitry that produces a higher output before distortion. Still 100% Analog tube circuitry throughout the signal path.
2. New tube configuration with the 12DW7 allows for the smoothest transition from the input section to outputs, providing the cleanest and most musical path for your signal.
3. New 3 gain positions 3dB, 6dB and 9db make the Leto Ultra one of the most versatile preamps available. It easily accommodates the many volume
differences from all your sources such as a high output DAC, as well as a low output phono. Your preferred gain settings are saved on each input and can be conveniently adjusted “on the fly” with the Remote or Manual control.
4. New 6 inputs for your many sources include 3 true dedicated transformer Balanced Inputs and 3 Single Ended. All are high quality, gold plated connectors for better conductance and less corrosion for the most reliable connection.
5. New 6 Position Presence Control adjusts the harmonic balance in the mid and high frequencies allowing you to dial back what you may consider to be too bright, edgy or aggressive. This is an exceptionally useful tool that addresses the inconsistencies of mastering from any source. It’s easily adjustable “on the fly” with your remote or manually for each piece of music.
6. New 9 button Remote control to conveniently adjust “on the fly” settings including Input, Volume, Presence, Mute, Mono and Gain. In case you misplace your remote, all features can be adjusted manually.
7. New LED indicators on the front panel clearly display all your adjustments.
In the first review of the original Leto Positive Feedback summed with:
"The Zesto Audio Leto 1.5 Vacuum Tube Preamplifier bests the 1.0 in features and in every parameter I can think of. It hosts improvements in the highs, mids, and bass which will mightily please audiophiles. It has improved definition and neutrality. It makes the music live in your high-end system. Plus, it is not more expensive, just improved and perfected! It even sports an excellent headphone output jack on the front panel for added pleasure. The 1.5 is a real keeper in my book and worthy of any system no matter how expensive.
This new Ultra preamp is another step forward in sounics and features
My congratulations to Zesto Audio. They did it again! Most highly recommended."
Stereophile summed the original Leto review with:
"I was very impressed with the Leto. Zesto Audio has produced a well-made, stunningly gorgeous product that gave me hours of pleasure as I listened to a wide range of recordings. In this crazy market of ever-increasing prices, a tubed line stage with so many strengths, so few and negligible weaknesses, and that can produce this level of musical satisfaction without costing somewhere in five figures, is commendable. In that sense, the Zesto Leto line stage is a veritable bargain."
Other Important Features you may want to know about:
- No solid state devices are used for switching the signals, only relays. This reduces noise and provides the most musical detail.
- The wide frequency response allows you to hear the finest passages in your music.
- Left and Right ground switches allows you to control the grounding of the outputs.
- The low impedance output transformers prevent the Power amp from affecting the line amp, thus providing the strongest and cleanest signal to your power amplifier.
- Recessed RCA and XLR connectors are premium quality, gold plated, with an isolated ground.
- All connectors are durable and will hold up to the typical Audiophile who loves to change their configuration.
- Automatically goes to mute when turned on or off, preventing any pops which could damage your speakers or surprise the hell out of you.
- The remote Mono feature helps you to trouble-shoot your system, especially phase issues, center balance and sound stage.
- Each preamp receives 50 hours of factory burn in on all circuits and vacuum tubes.
- Elegantly designed 16 gauge zinc plated steel enclosure to help isolate the electronic “chatter” from nearby equipment.
- On/Off power switch conveniently mounted on front side panel.
- Each unit is hand built “Made in the USA”.
Andros Spirit phono stage
$2997.00 Now shipping
$3997.00 with MC transformer upgrade
Positive Feedback Online - 03-22-2024 - By Robert H. Levi - Issue 132
"Congratulations to Zesto Audio for the Andros Spirit, the everyman all-tube audiophile phonostage.
My Highest recommendation."
Read the full review here: https://positive-feedback.com/reviews/hardware-reviews/zesto-audio-andros-spirit-phonostage/Immerse yourself in the rich, detailed sound of the new low cost phono stage with high performance definition. Discover the all tube sonic experience of the newest addition to Zesto Audio’s award-winning audiophile line!
Zesto Audio has a long history of producing award-winning Phonostages since the company launched the original Andros PS1 Phonostage in 2010.
George Counnas, Founder, and Chief Design Engineer of Zesto Audio says, "I designed the Spirit so it would retain only the essential features of its predecessors, while still offering the Zesto Audio signature sound." George admits how challenging it is to design a high-quality product that sounds good at a lower price point."
Key Features of the new Spirit
- Available in 2 versions MM only or MM/MC
- Standard MM unit is easily upgradeable to MM/MC
- 100% Analog tube circuitry without any solid-state devices in the signal path, because tubes are inherently more musical.
- The tube complement is a quad of 12AX7s, which provides sufficient gain with minimal noise.
- Safety switch to discharge the high voltage for your added safety when changing tubes.
- Robust, built-in ESP toroidal power supply for better dynamic range and lower noise.
- The high-quality built-in MC step-up transformers are designed for better phase linearity. This translates to better stereo imaging.
- Three of the most popular loading positions are 100, 250 & 500 so you can dial in the best match for your cartridge. Easily adjustable MC “Load on the fly” without clicks or pops so you can hear the change.
- All MC loading is on the secondary of the MC step-up transformer. This allows all the delicate signal from the cartridge to pass through to the main circuits for the most musical detail.
- Dual mono circuit which creates better stereo separation
- All switches and knobs are easily accessible, with nothing hidden inside to adjust.
- Full size 17″ x 12″ elegantly designed 16-gauge steel enclosure for better grounding and to help isolate the electronic “chatter” from nearby equipment.
- Illuminated tubes for a more sensual musical experience.
- Each unit is hand built “Made in the USA.”
- 50-hour factory burn-in on all circuits and vacuum tubes.
Made in California, USA.
Priced at $2997 for M version or $3997.00 for MC
Andros Deluxe II Phonostage
$8,300.00
"The Zesto Audio Andros Deluxe II Phono Stage receives my highest recommendation. It is an outstanding and stunning work of audio art."
Read the entire review here: https://positive-feedback.com/reviews/hardware-reviews/zesto-audio-andros-deluxe-ii-phonostage/
Read the entire review at: https://www.theabsolutesound.com/articles/zesto-andros-deluxe-ii-phonostage
Our favorite Zesto phono stage and we think the best sounding at anywhere near its price.
Key Features
- The high quality built in MC step-up transformers are designed for better phase linearity. They are also large enough to accommodate all the extra windings and the Mu-metal shielding that reduces noise. This translates to better stereo imaging.
- Independent ground switches affect both the MC-XLR and the MC-RCA inputs and reduce or eliminate hum by breaking those pesky ground loops.
- Balanced transformers reduce noise in two ways, by providing a true differential signal and allowing the ground to float, making the noise level very low.
- The MM-RCA connectors are always grounded to reduce noise from your cartridge.
- The dedicated output transformers are driven by the 12DW7 output tubes providing an accurate balanced signal to your preamp.
- The output RCA connectors have a floating ground and the XLR are grounded to reduce ground loops.
- The tube compliment is a pair of gold pin, high gain, low noise 12AX7’s and a pair of gold pin, high current, low noise 12DW7’s.
- Dual mono circuit which creates better stereo separation.
- A low Noise level of -80 dBv below maximum output allows the quietest passages of you music to be heard.
- 10 position MC load 1000, 800, 700, 600, 500, 400, 300, 200, 100, 50 Ohms so you can dial in the best match for your cartridge.
- Easily adjustable MC “Load on the fly” without clicks or pops so you can hear the change.
- The gain switch applies to both MC and MM inputs, to better match your cartridges.
- 100% Analog tube circuitry without any solid state devices in the signal path, because tubes are inherently more musical.
- All the RCA and XLR connectors are Gold plated for better conductance and lower corrosion.
- Recessed RCA connectors are durable and will hold up to the typical Audiophile who loves to change their configuration.
- All switches and knobs are easily accessible, nothing hidden inside to adjust.
- Each unit is hand built “Made in the USA”
- 50 hour factory burn in on all circuits and vacuum tubes
- Elegantly designed 16 gauge steel enclosure to help isolate the electronic “chatter” from nearby equipment
Bia 200 Class A Stereo Power Amp
Modern Tube Design for the 21st Century Listener
100 Watts per channel Dual mono Class A amp with a 3 Position Bias Switch
The new Bia 200 delivers 100 watts per channel of dynamic Class A power, plus one of the most unique features in a tube power amp, a 3 position “Auto Bias Select switch”. The Bia 200 ships with KT150 output tubes, but has the auto bias that can accommodate KT88, KT120 and KT170.
In the Positive Feedback review they sum with:
"In my experience, the Bia 200 Select is the most mellifluous and realistic-sounding amplifier, tube or solid-state, currently produced anywhere within its power rating, and with only two output tubes per channel. It is an absolutely breakthrough design, fabulously flexible, and capable of maximizing current and NOS tubes for decades to come. As a Class A tetrode design, it never runs out of gas, and never disappoints the listener. It is more neutral and quieter than any amplifier with tubes made by anyone I've heard, and that would hold true for most solid-state designs that I know, too."
"The Bia 200 Select is a wonder. It is well worth its not inconsiderable price. Most highly recommended by me, regardless of your predilection for tubes or solid-state. The Zesto Audio Bia 200 Select Stereo Amplifier is state of the art."
Read the entire review here: https://positive-feedback.com/reviews/hardware-reviews/zesto-audio-bia-200-select-stereo-amplifier/
Stereophile said:
"Maybe it's the top end that seems to go out for miles, or the sonorous bass, or how it steps out of the way of recordings and lets them shine on their own terms."
Read the Stereophile review: https://www.stereophile.com/content/zesto-bia-200-select-power-amplifier
Key Features
- The Bias Select switch is engineered with 3 bias settings for 4 different output tube
- Compatible with KT88, KT120, KT150 and KT170 output tubes
- Bias Select switch is easy to use, change on the “Fly” so you can hear the difference
- Auto Bias is safe, consistent and settings are always perfect
- Class A power is fast for a more lively, immediate response to your music
- 4, 8 & 16 Ohm taps gives you options for your speaker preference
- Dual Mono gives you less cross talk and better stereo imaging
- Choice of high quality gold plated Single Ended RCA or Balanced XLR connectors to suit your needs or cable preferences
- True transformer differential balanced XLR inputs for the best noise rejection
- Independent Left and Right ground switches on the XLR balanced inputs to eliminate ground loops and hums
- No Negative Feedback design does not modify or compress the musical signal
- Large custom Toroid is higher voltage for increased performance and lower noise
- Global mains power supply can work all over the world
- Provides plenty of gain for your system
- Push-Pull/Ultra Linear circuit design provides lower distortion, more power, and a better performance out of your tubes
- Low noise levels allow really dark black quiet musical passages
- Non-inverting polarity retains the same phase as the input (so your trumpets blow and don’t suck)
- Gold pin sockets are more reliable because gold doesn’t oxidize when it heat cycles
- Matched quad KT150 output tubes retain the stereo balance and lower noise
- Elegantly designed, heavy duty 14 &16 gauge zinc plated steel enclosure to accommodate the extensive grounding scheme
- The optimized frequency response provides the best musical range to benefit the natural harmonic structure of the instruments
- All fuses are easily accessible
- Each unit is hand built “Made in the USA”
Specifications (based on KT150 tubes)
Output
- Class A
- KT150 = 100 Watts per channel into 8 Ohms
- 4 Ohm, 8 Ohm and 16 Ohm output taps
- 10A, 7A and 5 Amp 6mm x 32mm Slow-blow speaker fuses for outputs
- Eight 5-way binding posts
- Non-inverting output polarity
- Push-Pull Ultra-Linear design
- Transformer floating ground differential balanced XLR inputs
- Left and right balanced inputs (pin 2 hot), impedance 10K Ohms
- RCA single ended inputs Left and Right with impedance of 47K Ohms
- Independent ground lift switches on left and right Balanced inputs
- 5 Volts RMS input to reach rated output
Detailed Specs
- Dual Mono
- Auto bias
- No negative feedback
- Frequency response 20Hz to 30Khz ~ 3dB
- Total Harmonic Distortion ~ 0.22% at 1W into 8 Ohms
- Gain of 24dB
- Noise level > 2mV -RMS into 8 Ohms with input shorted
- 1% metal film resisters throughout
- Polypropylene capacitors throughout the signal path
Power
- Custom Toroidal power transformer with global mains
- 15 Amp IEC power mains connector
- 120 Volts AC mains with 8 Amp 5mm x 20mm slow blow fuse
- Optional factory installed 220V, 230V/240V 50/60Hz with 4-amp slow blow fuse
- Power consumption at rated output 517 Watts
- Front panel on/off switch with green LED indicator for high voltage and amber LED for low voltage
Active Components
- Matched quad set of four (4) KT150’s vacuum tubes
- Four (4) Gold pin ECC82 (12AU7) vacuum tubes
- High quality gold plated ceramic sockets
Other Features
- Each unit is made by hand
- 50-hour factory burn in on all circuits and vacuum tubes
- Dimensions 17″ W X 20″ D X 10″ H
- Weight 64 (29Kg)
- Shipping box = 27” x 27” x 13” (5 cm x 68.5 cm x 33 cm)
- Shipping weight: 80 pounds (36 kg)
- 16 and 14 gauge Zinc plated steel enclosure
- Two year limited warranty
- Six months warranty on Vacuum Tubes
Voted Best Sound at Axpona 2023
Zesto Audio is pleased to announce the launch of their new Eros 500 Select Monoblocks, quite possibly the most powerful Class A tube amps available. Each amp has 250 watts of dynamic Class A power. The Eros 500 Select ships with KT150 output tubes, but has the perfect auto bias settings to accommodate KT88s, KT120s and KT170s.
See the amazing first review where they sum with:
"Congratulations to George Counnas and Zesto Audio for bringing to us, the audiophiles of the world, the best tube amplifier (and maybe any amplifier) ever. You must hear the Zesto Audio Eros 500 Select Class A monoblocks if you are even contemplating cost-is-no-object or high-end high-powered amplifiers for your system. These are the best amplifiers yet devised, in my humble opinion."
Read the entire review at: https://positive-feedback.com/reviews/hardware-reviews/zesto-audio-eros-500/
George Counnas, President and Chief Design Engineer of Zesto Audio says, "I was excited to find that my new circuit design using KT150 tubes produced so much power that they didn't even break a sweat creating such beautiful, effortless musical detail from my speakers." George continues, "I really love the way these amps allow all the components in my system to live up to their potential."
The Eros 500 Select has options
- RCA or true floating transformer balanced XLR connectors.
- Independent ground switch to eliminate hum.
- Subwoofer Speak On connector is Rel Acoustics compatible for a safe and reliable connection.
- 2 different taps, 4 Ohm and 8 Ohm to better match your speakers.
Eros 500 Select Key Features
- Sextet of KT150 output tubes create 250 watts of Class A musical power.
- Class A power is fast for a more lively, immediate response to your music
- The Bias Select switch is engineered with 3 perfect auto bias settings for KT88, KT120, KT150 and KT170 output tubes.
- The Bias Select switch is safe and easy to use, change on the “Fly” so you can hear the difference.
- 4 Ohm and 8 Ohm taps gives you options for your speaker preference. 4 Ohm may give you more base and the 8 Ohm tap may sound more open.
- The optimized frequency response provides the best musical range to benefit the natural harmonic structure of the instruments
- The SpeakOn cable connector provides most reliable hookup for your subwoofer.
- Transformer balanced true differential XLR input offers noise cancelling and rejection, as well as providing ground isolation from your preamp.
- Should you need to eliminate a hum? The Eros 500 has a XLR ground switch installed for your safety. This eliminates the dangerous temptation to lift the ground from the mains.
- The combo Push-Pull and Ultra Linear circuit design provides lower distortion, more power, and a better performance out of your tubes.
- No Negative Feedback in the circuit design provides better dynamic range because it doesn’t compress the music.
- Non-inverting polarity retains the same phase as the input (so your trumpets blow and don’t suck)
- Large Custom Toroid power transformer provides plenty of available power.
- Toroids have lower noise because they concentrate the magnetic field and are very efficient in the 50 to 60Hz mains range.
- Choice of high quality gold plated Single Ended RCA or Balanced XLR connectors to suit your needs or cable preferences
- Gold pin sockets are more reliable because gold doesn’t oxidize when it heat cycles.
- An extensive grounding scheme is designed into the power supply, wiring and all tube circuitry.
- Elegantly designed, heavy duty 14 & 16 gauge zinc plated, fully grounded steel enclosure isolates external noise and vibration.
- All fuses are easily accessible
- It’s ready to enjoy with 50 hours of factory burn in on all circuits and vacuum tubes.
- Each unit is hand built “Made in the USA”
Andros 2 Phonostage
The new Andros 2 verson uses an upgraded power supply
The Best of the Best! Andros 1.2 Phonostage
The 12th Annual PFO Writers’ Choice Awards for 2015 by Mark Pearson
“The Andros 1.2 just does everything right. It is dynamic, it has gorgeous tonal colors, it throws a big and deep soundstage, and it’s super quiet. .”
Andros 1.2 Phonostage
Mark Pearson – Positive Feedback – August 11th 2015
“I have had lots of phono sections in my system(s) over the years, but I have never had one this good or this quiet.” Read entire review
Andros 1.2 Phonostage- Positive-Feedback Online – April 2015…..
Robert H. Levi
“The new Zesto Audio Andros 1.2 Phonostage Preamplifier clobbers the original, and may just be the best piece of audio gear designed by George Counnas to date. ”
Michael Fremer – Stereophile Analog Corner – March 2013
“…The Zesto had an addictive, warm overall sound, with plenty of impact, detail and grace. It’s among the more enjoyable and satisfying phono preamplifiers I’ve auditioned at any price …”
Key Features
- The Circuit is specifically designed to provide sufficient amplification to match your cartridge with the rest of your system.
- Each unit is hand built “Made in the USA”.
- 50 hour factory burn in on all circuits and vacuum tubes.
- A low Noise level of -75 dBu below maximum output allows the quietest passages of you music to be heard.
- The output circuit is designed to drive your cables and isolates the output from the influence of the next stage.
- RCA connectors are high quality, Gold plated, recessed with an isolated ground.
- Isolated ground RCA connectors plus the Ground On/Off switch will allow you to choose the best ground configuration.
- Recessed RCA connectors are durable and will hold up to the typical Audiophile who loves to change their configuration.
- All switches and knobs are easily accessible, nothing hidden inside to adjust.
- Two position MM switch 47K and 15K Ohms to accommodate more cartridges.
- 10 position MC load switch from 20 to 1000 Ohms and more in the sweet spot above 200.
- Accommodates both high and low MC output cartridges
- Elegantly designed 16 gauge steel enclosure to help isolate the electronic “chatter” from nearby equipment.
- On/Off power switch conveniently mounted on front side panel
- Easy to read large type on back panel
Specifications:
Inputs per channel
- Separate MM and MC inputs
- MM/MC switch
- MM impedance switch 47K or 15K Ohms
- MM capacitance 200pf
- MC Single Ended RCA with isolated ground or Balanced XLR3F
- MC ground on/off switch
- MC load impedance adjustable 1000, 800, 600, 500, 400, 300, 200, 100, 50, 20 Ohms
- MC Internal step up transformers
- MC High/Low switch with ~ -3dB gain for high output MC cartridges
Outputs per channel
- Impedance 10K ohms
- +6V max output level
Active Components
- Four (4) Gold pin JJ ECC83S/12AX7 vacuum tubes with high quality gold pin ceramic sockets
Power
- Ground binding post
- Power consumption 27W , 0 drain when off
- Voltage 110/120V AC 60Hz
- Optional factory installed 220V or 230/240V AC 50/60Hz
- Standard 3 pin IEC power connector
- ON/OFF power switch conveniently located on the front side
- Two internal high quality linear regulated power supplies, 250V and 12V
Detailed Specifications
- Gain MM input 47dB
- Gain MC input 67dB
- Noise – 75dBu below max output level
- Frequency response complies with the original RIAA curve within +or- 0.5 dB
- RIAA curve is achieved using a passive filter
- 1% metal film resisters throughout
- Polypropylene capacitors throughout the audio path
Other Features
- “Made in the USA” using US and imported parts
- Each unit is built by hand
- 50 hour factory burn in on all circuits and vacuum tubes
- Dimensions 17″ W X 12″ D X 5″ H
- Weight 20 lbs.
- 16 gauge zinc plated steel enclosure
- Two year limited warranty
- Six months warranty on Vacuum Tubes
$35,000.00 the pair
Zesto Audio Eros 500 Select Class A Monoblocks
Awarded by Robert H. Levi
"I have grown tired of expensive tube amplifiers designed by committees utilizing ancient circuits like class AB and triode that are full of warmth and color when the sources are not. Well, guess what?"
"The new Zesto Audio Eros 500 Select Class A Monoblocks are, in my judgment, the most advanced and powerful all-tube amplifiers with unique full-time class A operation and zero feedback on the market today. Someone tell me who else does this? With a circuit exclusively designed by the award-winning George Counnas, these monoblocks are audiophile heaven able to drive any speakers on the planet to their fullest potential."
Eros 500 Select Key Features
- Sextet of KT150 output tubes create 250 watts of Class A musical power.
- Class A power is fast for a more lively, immediate response to your music
- The Bias Select switch is engineered with 3 perfect auto bias settings for KT88, KT120, KT150 and KT170 output tubes.
- The Bias Select switch is safe and easy to use, change on the “Fly” so you can hear the difference.
- 4 Ohm and 8 Ohm taps gives you options for your speaker preference. 4 Ohm may give you more base and the 8 Ohm tap may sound more open.
- The optimized frequency response provides the best musical range to benefit the natural harmonic structure of the instruments
- The SpeakOn cable connector provides most reliable hookup for your subwoofer.
- Transformer balanced true differential XLR input offers noise cancelling and rejection, as well as providing ground isolation from your preamp.
- Should you need to eliminate a hum? The Eros 500 has a XLR ground switch installed for your safety. This eliminates the dangerous temptation to lift the ground from the mains.
- The combo Push-Pull and Ultra Linear circuit design provides lower distortion, more power, and a better performance out of your tubes.
- No Negative Feedback in the circuit design provides better dynamic range because it doesn’t compress the music.
- Non-inverting polarity retains the same phase as the input (so your trumpets blow and don’t suck)
- Large Custom Toroid power transformer provides plenty of available power.
- Toroids have lower noise because they concentrate the magnetic field and are very efficient in the 50 to 60Hz mains range.
- Choice of high quality gold plated Single Ended RCA or Balanced XLR connectors to suit your needs or cable preferences
- Gold pin sockets are more reliable because gold doesn’t oxidize when it heat cycles.
- An extensive grounding scheme is designed into the power supply, wiring and all tube circuitry.
- Elegantly designed, heavy duty 14 & 16 gauge zinc plated, fully grounded steel enclosure isolates external noise and vibration.
- All fuses are easily accessible
- It’s ready to enjoy with 50 hours of factory burn in on all circuits and vacuum tubes.
- Each unit is hand built “Made in the USA”
Specifications per amp (based on KT150 tubes)
Output
- Pure Class A, Push-Pull Ultra Linear design
- 250 Watts per amp
- 4 Ohm and 8 Ohm non-differential output taps
- Three 5-way binding posts
- 10 Amp and 7 Amp Slow-blow speaker fuses (6mm x 32mm)
- Non-inverting output polarity
- SpeakOn connector for a subwoofer
- SpeakOn subwoofer cable specs: Pins +1 and +2 go to the 8 Ohm output and pin -1 goes to ground
Power rating for Auto Bias Select Switch Settings
Low Bias (Left switch Position)
- KT88 = 150 Watts per channel
- KT120 = 150 Watts per channel
- KT150 = 150 Watts per channel
- KT170 = 150 Watts per channel
Medium Bias (Middle switch position)
Most feel the best sonics is medium bias
- KT150 = 200 Watts per channel
- KT170 = 200 Watts per channel
High Bias (Right switch position)
- KT150 = 250 Watts per channel
- KT170 = 250 Watts per channel
Inputs
- Transformer true balanced differential input
- XLR gold pin balanced input with pin 2 hot, impedance 12K Ohms
- RCA gold pin single ended input, impedance of 12K Ohms
- XLR ground lift switch
- 3.3 Volts RMS input to reach rated output
Detailed Specs
- Monaural
- Auto bias
- No negative feedback
- Frequency response 20Hz to 30Khz ~ 3dB
- Total Harmonic Distortion ~ 0.07% at 1W into 8 Ohms
- Gain of 27dB
- Noise level > 4 mV RMS into 8 Ohms with input shorted
- 1% metal film resisters throughout
- Polypropylene capacitors throughout the signal path
Power
- Large custom Toroidal power transformer
- 120 Volts AC mains with 10 Amp 5mm x 20mm slow blow fuse
- Mains fuse located in drawer compartment of IEC power connector
- 3 pin 15 Amp IEC power inlet connector
- Optional factory installed 220V, 230V/240V 50/60Hz with 5 Amp slow blow fuse
- Power consumption at rated output 756 Watts
- On/Off switch conveniently located on front panel
- Amber LED low voltage and green LED high voltage indicators
Active Components
- Six (6) KT150’s vacuum tubes
- Two (2) ECC82 (12AU7) vacuum tubes
Other Features
- Each unit is made by hand
- 50 hour factory burn in on all circuits and vacuum tubes
- Dimensions 17″ W X 20″ D X 10″ H (43.1 cm x 25.4 cm x 50.8 cm)
- Weight 79 lbs. (35.8 Kg)
- Shipping weight 96 Lbs. (43.5 Kg)
- Shipping box 27″ W X 27″ D X 13″ H (68.5 cm x 68.5 cm x 33 cm)
- 16 and 14 gauge Zinc plated steel enclosure
- Two year limited warranty
- Six months warranty on 12AU7 Vacuum Tubes, 90 day warranty on KT150 power tubes
Andros Allasso Step Up Transformer
Create the perfect match between your cartridge and any phonostage with 40 options!
Michael Fremer | Stereophile | April 2019
…”Zesto’s George Counnas designed the Allasso (Greek for change or transform) to be both incredibly flexible and easy to use…
Best of all, rather than overload your primary and secondary coils, Counnas says that “it’s about the best sound, not the math.” He suggests beginning with the middle load position (5). I’d still use math to set the gain, based on the cartridge’s output, but you’re free to experiment while listening. Turning the Andros Allasso’s knobs produced no thumps or bumps through my speakers….”
Zesto Andros Allasso Step Up Transformer – Quite Possibly The Last SUT You’ll Ever Need!
Michael Corsentino | Positive Feedback | March 2019
“From my cold, dead hands!” - Charlton Heston, describing the only way anyone would be able to take away his guns. I’ll state right up front that after a month in my reference system that’s exactly how I feel about the Zesto Andros Allasso step up transformer. In fact I was completely smitten with this little sonic marvel in a matter of hours, we bonded that quickly…”
Key Features
- Allasso in Greek means to change or transform one thing to another.
- It’s very versatile! Will accommodate the widest range of cartridges with 40 adjustments in Mono and 40 adjustments in Stereo.
- It’s flexible to allow you to control the 4 step up ratios/gain settings, each having 10 load positions.
- Designed with the highest quality MC transformers. They are quiet, with extra shielding and large enough with the multiple windings to handle even your high output cartridges.
- It’s easy to use as all the adjustments are on the front, nothing is hidden inside.
- All adjustments can be done on the “fly” without clicks or pops.
- No math skills are required; it’s just you and your ears.
- Enough adjustments to tailor it specifically to your cartridge or your next one.
- Works with any standard MM input on any phonostage.
- Designed to reduce “Hum” with 2 ground lift switches and 2 ground binding posts.
- The Mono switch is specifically designed to reduce “Hum” in your Mono cartridge.
- A unique feature of the Mono switch is it takes a single input and sends to both outputs.
- It’s quiet, with extensive grounding in the circuit design and enclosure.
- RCA connectors are high quality, Gold plated, recessed with an isolated ground.
- Recessed RCA connectors are durable and will hold up to the typical Audiophile who loves to change their configuration.
- Elegantly designed 18 gauge steel enclosure to help isolate the electronic “chatter” from nearby equipment.
- Easy to read large type on back panel.
- Each unit is hand built “Made in the USA”.
Specifications:
- Frequency response -3dB at 0.4Hz to 100 KHz
- Phase deviation 1° typical at 20Hz
- Transformer noise 2 dB @ 20 Ω, 1.8 dB @ 12 Ω
- Hum rejection 125 dB @ 60 Hz
- Voltage gain 12dB, 16dB, 18dB and 22dB
- Step up ratios 1:4, 1:6, 1:8 and 1:12
- MC load 40 positions in Mono, 40 positions in Stereo
- Recommended output load 47KΩ @ 200pF (MM input)
- Inputs Balanced and Single Ended MC
- Outputs Single Ended
- Grounds Independent input ground-lift switches
- Grounds Two ground binding posts
- Mono Takes one input and sends it to both outputs
- Dimensions 4”H X 6”W X 8”L (101.6mm X 152.4mm X 203.2mm)
- Weight 5lb (2.27Kg)
- Shipping weight 8lb (3.63Kg)
- Box dimensions 7”H X 9”W X 13”L (177.9mm X 228.6g X 330.2g)
Andros Téssera Reference Phono stage
Zesto Audio Andros Téssera Reference Phonostage: Quadruple Your Input
The new Tessera Reference phono stage is Zestos all out assault on a state of the art design.
In the Positive Feedback Review they sum with:
"Though one might consider the Reference expensive, it delivers the musical goods, and does accommodate four tonearms simultaneously (Téssera is four in Greek) with accompanying adjustments for everything, and memory set, too. For the first time in years, I can rightly say you get your monies worth with the Téssera Reference (or the "T Ref," as George Counnas calls it)."
"Congratulations to Zesto Audio for a stellar Reference phono offering for the pickiest audiophiles! I extend my most humble and sincere statement: the Zesto Audio Andros Téssera Reference Vacuum Tube Phono stage Preamplifier is most highly recommended, without reservations."
Key Features For A Quieter and More Musical Phonostage
Musical Features
- Completely new 100% tube analog circuit design with optimized components.
- Dynamic range increased from 108dBV to 116dBV, so the quietest parts are quieter, louder parts are louder.
- Loading on the secondary of the MC transformer to capture the most detail from the cartridge.
- 12 position MC load per channel with more finessed adjustable options like 1000, 800, 700, 500, 400, 350, 300, 250, 200, 150, 100, 50 Ohms
- Two completely independent dual mono channels, with LED indicators for A and B
- Gain is improved up to 7dB, which increases the output volume to better match your cartridge to your system.
- The voltage increases from 250V to 300V for more headroom.
- The power increases from 52W to 60W to provide more energy needed to reproduce the highs and lows of music accurately.
- The amps increase from 3.4 A to 8 A to provide more current to the tubes.
- Maximum output improved from 8V RMS to 12V RMS increases the headroom to allow more musical peaks like trumpet and drums.
Quieter Features
- New 12DW7 tubes improves the amplification to better drive the output tubes which gives you lower noise, more headroom and lower distortion.
- Dual chassis external power supply
- New Toroid design ESP Supply replaces the linear regulated power supply which generates significantly less noise by concentrating the magnetic fields.
- The dark black noise levels went from -90dB to -95dB.
- New PCB layout with significantly more grounding for lower noise.
- Dual chassis with 3-meter RFI filtered umbilical cable to eliminate external noise.
- Dedicated output tubes driving high quality output transformers to create a true differential low impedance output for lower noise and ideal transfer of power to the preamp.
- True floating ground, transformer balanced XLR inputs and outputs
- New grounding throughout to further reduce the internal and external noise.
- Switching on relays so there’s no digital chatter.
- Easily adjustable MC “Load on the fly” without klicks or pops so you can hear the change
- Elegantly designed 16-gauge steel enclosure to help isolate the electronic “chatter” from nearby equipment
- Ground lift switches on the MC inputs on each channel to prevent noisy ground loops
- All the RCA and XLR connectors are Gold plated for better conductance and lower corrosion
Other Features
- Accommodates 4 tonearms, 1 MM and 1 MC per channel
- All settings are saved when you switch between channels
- More energy efficient Standby power that reduces the drain from 7w to 0.5W.
- All switches and knobs are easily accessible, nothing hidden inside to adjust
- Recessed RCA connectors are durable and will hold up to the typical Audiophile who loves to change their configuration
- Each unit is hand built “Made in the USA”
- 50-hour factory burn in on all circuits and vacuum tubes before final testing
