Thanks for the informative thread. I have been hearing great things about his designs.
Review: David Berning Co MicroZOTL Tube amp
Category: Amplifiers
I purchased this amp in February 2002 direct from David Berning Co. At my time of purchase, it was only available by factory direct purchase.
This amp was designed to provide access to the Berning ZOTL form of amplification, at a reasonable price. It is intended for high efficiency applications, or bedroom/office systems, or as a headphone amplifier.
All controls are on the top of the unit. It is equipped with a Noble Potentiometer, so it can be used as a single input integrated amp. If you want to use a preamp, you can just turn the Noble pot up full, or bypass it with a soldered jumper. There is a locking headphone jack for its intended use as a headphone amplifier. It also has a power switch that is labled AC/DC which allows ON/OFF switching for either AC or DC power.
The rear of the unit has all of the input and output connectors. Single ended, RCA type input jacks and 5-way binding posts are provided for 1 stereo input and one pair of stereo speaker outputs. Very high quality connectors are used on this unit. Power enters via a removeable IEC connector which allows aftermarket power cords to be used. There is also a DC tip-and-ring connector for 12vdc battery power input.
The MicroZOTL is a small amplifier, about the size of a typical shoebox, and weighs about four pounds. It is very plain in appearance, with a simple bent metal two piece chassis and a glass window in front. Available in 3 colors: olive, red, and blue.
The unique Berning ZOTL circuit is showcased in the MicroZOTL in a Class A no feedback PP triode design. Using 12AT7 as input and 6SN7 as output tubes,to provide the breathtaking 1 watt output of this amp. The linearity of the 6SN7 is really apparent in the sound of this little beauty. You've probably never heard a preamp tube powering a speaker before. It is delicious, using the twin-triodes in each 6SN7 in push-pull within a single tube envelope. One output tube on each channel. This sound goes directly to the speaker with the absence of traditional output transformers. The impedance matching is done by the ZOTL circuit, which uses a 250kHz carrier frequency to piggyback the signal on. The carrier frequency does the impedance matching, and the signal is unaffected, and goes right out to the speaker. It has the best of both worlds. The impedance matching is handled as well as any transformer, and the signal is pure OTL. This circuit is patented by Berning and represents a true quantum leap in OTL design.
I first used this amp as an integrated, with a single source from my Sony 9000 SACD/CD player. It drove a set of single-driver Fostex speakers to reasonable listening levels, but could not get really loud, or handle full symphonic music. The 89db efficiency of the Fostex's was simply not enough for the low power output of the Berning. But, the sonic "goodness" was definitely there. The direct input from the Sony was a little harsh, so I got the preamp, and that was a better setup. This allowed me to then get a turntable rig and use 2 sources. Sound from the analog setup was a clear improvement over CD/SACD. But, the volume level was still too low. I needed more efficient speakers. I settled on the Lowthers, and built Voigt Pipe cabinets with mods. This brought the MicroZOTL into its own.
The sound was awesome, from top to bottom. This has to be heard to be believed. I can get just a few db from real symphonic listening levels with a 1 watt amp. Anyway, 100db is a pretty good SPL for most living rooms. If you stay in the near-field, it's loud. Great dynamics and speed, no grain, crystal clarity, super soundstage and imaging. The only thing is that with direct radiators, you can't get to the 106db level. With horns, no problem. This would be all the amp you'd need with Avant-Gardes or other 106db efficient horns. And for SET fans, this amp is tight right down to the bottom, with no "bloat" or loss of control. The highs soar right up to the sky, with no transformer induced rolloff. No need to sacrifice frequency extremes to get "golden midrange" with this amp.
This is probably the easiest tube amp in the world to live with. It is auto-biasing. Doesn't get hot. Tube life is estimated to be 10-20 years. Uses very little power, and I run mine on battery(2.1 amp draw at 12vdc), for ultra-clean power. It's warmed up after about 15 minutes. You can change tubes in under 5 minutes, when you buy your NOS, which I recommend. Comes with JAN Phillips, and Sovteks. It takes up very little space. Weighs next to nothing. Can put it just about anywhere. No microphonics problems. Plug-and-play. And for a measly $750, you have a killer sounding OTL.
If you can live with 100db or less in your living room, this amp(with Lowthers, or 106db with horns) will give you the best sound possible for anywhere near the price. I have heard higher power amps that cost $5k that would be embarrassed by my little MicroZOTL.
Highly recommended. Twl-ophile Class A component. Best buy.
Associated gear
MFA Magus Tube Preamp with Amperex Bugle Boy NOS Tubes, Cardas Jacks, Cardas Wiring, REL Capacitors, Wonder Capacitors
Sony DVP S9000ES CD/SACD/DVD player
Teres 135 Turntable (Clear Acrylic)
Origin Live Silver 250 Tonearm
Denon DL103 Cartridge
M.A. Cotter phono step-up transformer
Lowther EX3 Voigt Pipe modified
Bybee Ultra Quantum Speaker filters with Nordost SPM tails
DIY interconnects
DIY Speaker cables
DIY Room Lenses
DIY Bass Traps
DIY Wall Panels
DIY 12vdc Battery Power Supply
Similar products
Many tube amps, but none of this low power.
I purchased this amp in February 2002 direct from David Berning Co. At my time of purchase, it was only available by factory direct purchase.
This amp was designed to provide access to the Berning ZOTL form of amplification, at a reasonable price. It is intended for high efficiency applications, or bedroom/office systems, or as a headphone amplifier.
All controls are on the top of the unit. It is equipped with a Noble Potentiometer, so it can be used as a single input integrated amp. If you want to use a preamp, you can just turn the Noble pot up full, or bypass it with a soldered jumper. There is a locking headphone jack for its intended use as a headphone amplifier. It also has a power switch that is labled AC/DC which allows ON/OFF switching for either AC or DC power.
The rear of the unit has all of the input and output connectors. Single ended, RCA type input jacks and 5-way binding posts are provided for 1 stereo input and one pair of stereo speaker outputs. Very high quality connectors are used on this unit. Power enters via a removeable IEC connector which allows aftermarket power cords to be used. There is also a DC tip-and-ring connector for 12vdc battery power input.
The MicroZOTL is a small amplifier, about the size of a typical shoebox, and weighs about four pounds. It is very plain in appearance, with a simple bent metal two piece chassis and a glass window in front. Available in 3 colors: olive, red, and blue.
The unique Berning ZOTL circuit is showcased in the MicroZOTL in a Class A no feedback PP triode design. Using 12AT7 as input and 6SN7 as output tubes,to provide the breathtaking 1 watt output of this amp. The linearity of the 6SN7 is really apparent in the sound of this little beauty. You've probably never heard a preamp tube powering a speaker before. It is delicious, using the twin-triodes in each 6SN7 in push-pull within a single tube envelope. One output tube on each channel. This sound goes directly to the speaker with the absence of traditional output transformers. The impedance matching is done by the ZOTL circuit, which uses a 250kHz carrier frequency to piggyback the signal on. The carrier frequency does the impedance matching, and the signal is unaffected, and goes right out to the speaker. It has the best of both worlds. The impedance matching is handled as well as any transformer, and the signal is pure OTL. This circuit is patented by Berning and represents a true quantum leap in OTL design.
I first used this amp as an integrated, with a single source from my Sony 9000 SACD/CD player. It drove a set of single-driver Fostex speakers to reasonable listening levels, but could not get really loud, or handle full symphonic music. The 89db efficiency of the Fostex's was simply not enough for the low power output of the Berning. But, the sonic "goodness" was definitely there. The direct input from the Sony was a little harsh, so I got the preamp, and that was a better setup. This allowed me to then get a turntable rig and use 2 sources. Sound from the analog setup was a clear improvement over CD/SACD. But, the volume level was still too low. I needed more efficient speakers. I settled on the Lowthers, and built Voigt Pipe cabinets with mods. This brought the MicroZOTL into its own.
The sound was awesome, from top to bottom. This has to be heard to be believed. I can get just a few db from real symphonic listening levels with a 1 watt amp. Anyway, 100db is a pretty good SPL for most living rooms. If you stay in the near-field, it's loud. Great dynamics and speed, no grain, crystal clarity, super soundstage and imaging. The only thing is that with direct radiators, you can't get to the 106db level. With horns, no problem. This would be all the amp you'd need with Avant-Gardes or other 106db efficient horns. And for SET fans, this amp is tight right down to the bottom, with no "bloat" or loss of control. The highs soar right up to the sky, with no transformer induced rolloff. No need to sacrifice frequency extremes to get "golden midrange" with this amp.
This is probably the easiest tube amp in the world to live with. It is auto-biasing. Doesn't get hot. Tube life is estimated to be 10-20 years. Uses very little power, and I run mine on battery(2.1 amp draw at 12vdc), for ultra-clean power. It's warmed up after about 15 minutes. You can change tubes in under 5 minutes, when you buy your NOS, which I recommend. Comes with JAN Phillips, and Sovteks. It takes up very little space. Weighs next to nothing. Can put it just about anywhere. No microphonics problems. Plug-and-play. And for a measly $750, you have a killer sounding OTL.
If you can live with 100db or less in your living room, this amp(with Lowthers, or 106db with horns) will give you the best sound possible for anywhere near the price. I have heard higher power amps that cost $5k that would be embarrassed by my little MicroZOTL.
Highly recommended. Twl-ophile Class A component. Best buy.
Associated gear
MFA Magus Tube Preamp with Amperex Bugle Boy NOS Tubes, Cardas Jacks, Cardas Wiring, REL Capacitors, Wonder Capacitors
Sony DVP S9000ES CD/SACD/DVD player
Teres 135 Turntable (Clear Acrylic)
Origin Live Silver 250 Tonearm
Denon DL103 Cartridge
M.A. Cotter phono step-up transformer
Lowther EX3 Voigt Pipe modified
Bybee Ultra Quantum Speaker filters with Nordost SPM tails
DIY interconnects
DIY Speaker cables
DIY Room Lenses
DIY Bass Traps
DIY Wall Panels
DIY 12vdc Battery Power Supply
Similar products
Many tube amps, but none of this low power.
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