Construction
Pure Tube® OTL – no output transformator or capacitor.
Double mono amplifiers, thus providing stereo. High quality potentiometer. Output power: 0,8W 30 ohm, 1,2W 60 ohm, 1,9W 300 ohm, 1,7W 600 ohm at 1kHz 1%THD Bandwith 10 – 650 000 Hz -3dB Dampfactor > 10 |
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Circuit solution
The dream of creating a tube amp that does not need an output transformer was born back in the 1930s. But it was not until the 1950s that Julius Futterman managed to solve the problem. The real challenge now was to find a practical, working circuit. It has taken a lot of energy to realize Futtermans idea without spoiling its inherent magic.
In order to construct a tube amplifier with low output impedance you need tubes that have low inner resistance. It is not easy to find tubes that match that criteria. For this construction the NOS Russian tube 6C19 was chosen.
The figure shows the main characteristics of the circuit. You will aslo find the theoretical value for the output impedance.
In order to construct a tube amplifier with low output impedance you need tubes that have low inner resistance. It is not easy to find tubes that match that criteria. For this construction the NOS Russian tube 6C19 was chosen.
The figure shows the main characteristics of the circuit. You will aslo find the theoretical value for the output impedance.
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Behind the specs
Nothing was left unattended. Read up on Röcklingers design decisions.
For the experimental Flexible output power 0,8W 30 ohm, 1,2W 60 ohm, 1,9W 300 ohm, 1,7W 600 ohm at 1kHz 1%THD
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For the puritanThe amplifier is Pure Tube® OTL driven– no output transformator or capacitor. THD+N @ 1,0Vrms in @ 1000Hz
0,09 %, 33 ohm 0,09 %, 56 ohm 0,08 %, 330 ohm 0,08 %, 600 ohm |
For the selectiveIn order to construct a tube amplifier with low output impedance you need tubes that have low inner resistance. It is not easy to find tubes that match that criteria. For this construction the NOS Russian tube 6C19 was choosen.
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Read the user manual here
Svenska_HPA1_usermanual.pdf | |
File Size: | 999 kb |
File Type: |
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Output transformerless links
2016-11-09 The first amplifier Röcklinger launched was a headphone amplifer, build with tubes and with OTL technique. OTL stands for Output Transformer Less. To learn more what OTL is we share with you some usefull links for the curious. |
To measure input impedance
2016-10-22 We at Röcklinger always simulate the electrical design first, then we build the circuit measure and improve the design. This loop will continue until we make sure that the final design is flawless. We also like to share and prove our design. So here is a tip on how to simulateinput impedace using LTspice. |