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Transformerless valve amplifier

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WATCH RELATED VIDEO: PL36 Handmade Output transformerless tube amplifier by all-audio.pronis

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Many tube amplifiers have a sound described as "warm," "tubey," or "round". This sound can be very nice to listen to.

However, it is the output transformers that produce the "warmth" or the tone of the sound, and it is actually a type of distortion, though pleasant.

The detail of the music can be lost in the "warmth. The ZOTL amplifiers do not have the thicker, warm tone that many tube amplifiers have.

They still have the liquidity and linearity of tubes, but without a transformer's tone. ZOTL amplification achieves neutral accuracy without coloration. This achievement is supported both by listening and through measurement. Switching immediately from other tube amplifiers and solid-state amplifiers designed to be warmer to a ZOTL amplifier can often feel like something has been lost.

What is actually happening is more akin to adjusting the focus of a lens: an increase in clarity accompanies a reduction of haze. While haze can feel like "body" or "weight" that is no longer there, as you adjust to the ZOTL amplifier you realize you are hearing the more accurate weight and body of what you are listening to, and the consistency in performance over varying impedances will allow you to experience this accuracy throughout the frequency spectrum with many different speakers.

ZOTL amplification's neutrality is also transparency. As source components increase in performance, ZOTL amps continue to reflect this, scaling up indefinitely.

After 20 years of designing and manufacturing tube amplifiers, David Berning turned the technology on its ear when he invented ZOTL Zero hysteresis Output Transformer-Less architecture in So radically different from anything around at the time, ZOTL is considered by some to be the most significant improvement to tube amplifier technology since the s.

Audio amplifier design engineers have long sought to eliminate audio output transformers because of the restrictions they impose on amp performance. Leakage inductance and interwinding capacitance limit the high-frequency response of transformers while core saturation and magnetizing current limit their low-frequency response. Transformer-core hysteresis causes specific distortions of non-symmetric and transient waveforms that are characteristic of musical reproduction.

Audio output transformers simply cannot achieve the correct turns ratios as they only max out at due to saturation and hysteresis effects. This leaves much to be desired, which creates and issue that needs to be resolved. This changes the impedance plane to match the impedance of the speaker, so the audio output transformer is no longer required to match the tube to the speaker. An Impedance Converter accomplishes this match up. This super linear amplification process allows the amplifier to have a flat frequency response from 8hz to 50Khz, which is nearly impossible with an output transformer.

However, the real advantage is in the transformer turns ratio. Output transformers are limited to a maximum of about 25 to 1 in turns ratio.

This turns ratio does the matching between the tube output and the speaker. It turns out that the theoretically correct turns ratio for most tubes is typically to 1 and even as high as to 1.

The ZOTL can use the impedance converter to effectively create the ideal turns ratio. This results in the detail and accuracy of the sound.

ZOTL technology involves a linear amplification process using a carrier frequency as well as not having a traditional audio output transformer, instead using air-core Impedance Converters. Noted pioneer of amplifier technology, Julius Futterman, has inspired many different amplifier designs over the years. The two banks are joined in series by connecting the effective cathode of one tube bank to the effective plate of the other tube bank, and driving the loudspeaker in a push-pull fashion directly from this junction point without a transformer.

The output impedance of other OTL amplifiers is nowhere near the actual speaker impedance. In an OTL amplifier, a large amount of negative feedback is required to force the push and the pull to work together properly in order to provide sufficient damping for the speaker. Even with the lowest impedance triodes available, there is still a basic impedance mismatch between the tubes and the speaker in the OTL circuit.

Traditional OTL technology requires a large number of power tubes which need to be driven hard to obtain the required output. This results in drastically reduced reliability and tube life and generating lots of heat. Fans or additional room air-conditioning may be required. Power consumption is typically very high for OTL amplifiers, often exceeding one kilowatt for a stereo pair. Drastically improved tube life due to lower current operation. Distortion by parasitic transformer elements of the audio signal no longer occurs.

Improved bass due to flat, linear bass response to below 10hz. HQ Output Transformer. ZOTL Technology. Featured Products. Z10 Integrated Amplifier. Enter the solution: ZOTL.


SET vs OTL amps - which one offers true "tube" sound?

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Greetings, Looking for some help regarding tube amplifier pushing a His output transformerless tube amps have pretty good bandwidth.

How to protect yourself from Transformer-less amps?


Year of fee payment : 4. Year of fee payment : 8. Year of fee payment : In a high-fidelity, high-power audio amplifier, the power supply makes direct connection is made to the AC line, followed by appropriate rectification and filtering, but without the need for a power transformer. The invention is not limited in terms of the class of amplifier, and may be applied at least to class A and class AB configurations. The input is AC-coupled without the use of a ground potential, preferably using capacitive coupling. To provide voltage levels appropriate for referencing and other purposes, a pseudo-ground is established, preferably through the use of a resistive ladder across the rectified line.

Widowmaker Amps

transformerless valve amplifier

I cannot find any information about who invented the single ended SE amplifier, but for sure that was before the push pull PP amplifier. In Telephony they build SE amplifiers without tubes yes! This can give remarkable AC signal, and power gain from something simple like a carbon microphone. A distance of km could be overcome without using tubes, which number is too optimistic because you had to shout into a horn microphone, and at the other end you can barely hear it. But they did it, and all without tubes.

Regular tube amplifiers have very high voltages in them and by contrast most loudspeakers are low voltage.

ZOTL Technology


Also in we are represented again on the Norddeutschen HiFi-Tage. We are look forward to see you there. For further information click here. Once again EternalArts will be represented at the analog forum in Krefeld. The fair will take place in the Mercure Hotel Krefeld from the 2nd to the 3rd of November

Output transformerless

November 25, , PM Welcome, Guest. Please login or register. Output Transformerless Tube Headphone Amplifier. I wanted something to busy my hands with. I have read this excellent book that I highly recommend: Among other things, it describes how to make an OTL headphone amplifier with a White cathode follower. It is a push-pull circuit and the book gives all the formulas to implement the circuit with the any tube. To get low output impedance, which is needed to successfully drive a pair of 32 ohm headphones, a tube with low plate impedance and high amplification, i.

Output transformerless valve power amplifier. «on: November 08, , PM». Are there out on the forum any members who have built.

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How dangerous are output transformerless tube headphone amplifiers really?


A widowmaker amplifier has no power transformer or fuse. Instead, the two-prong, non-polar power cord is wired directly to the rectifier tube. On the plus? How does a widowmaker amp work?

Fully automatic biasing for either tube. Output Transformerless 60 watts Class A.

Unread post by Firebug1 » Sun Nov 11, pm. Unread post by keepitsimplestupid » Sun Nov 11, pm. Unread post by Thermionic Idler » Mon Nov 12, pm. Unread post by karatestu » Sat Nov 24, pm. Skip to content. Quick links. An Exercise in Daftness.

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