• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Screen driven 6V6 SET a la ZOTL

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On the pictures stil with a power triode but 6v6 in this amp is better still when driven on screen.
 

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JoeAlders

Member
2011-02-12 10:20 am
Had a quick look at that website. Interesting indeed but not much info about those "impedance transformers".
Looking at your amp and having a closer look about the amount of windings around the core, I got the feeling
that those inverters do not have much input/output ratio?
 
Additional images that can help building this amps. I used common mode choke cores for the transformers. 500Khz oscillator and resonator.
The amp itself is very simple. Some of my amps do not even have a phase inverter as my preamp has a symmetrical output. The "power" tubes are sensitive enough, therefore no driver stage is needed as well.
 

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JoeAlders

Member
2011-02-12 10:20 am
Additional images that can help building this amps. I used common mode choke cores for the transformers. 500Khz oscillator and resonator.
The amp itself is very simple. Some of my amps do not even have a phase inverter as my preamp has a symmetrical output. The "power" tubes are sensitive enough, therefore no driver stage is needed as well.


Thanks Lampie519 for this practical info, much appreciated!
So, if I understand you correctly you are using the diff. amplifier as phase shifter with the transistor as current source?
 
Yes, simple isn't it? That is the entire "power" 1W amp (it can drive my B&W Rock Solids easily).
My advise if someone would like to start this "adventure" : Use a low voltage (max 12V) power supply (short circuit proof).
In this headphone amp i have used a 5V PSU. It can be adjusted to about 7V max.
For this amp it is sufficient.
It is the best Zotl project to start with as it needs no High voltage PSU at all.
 
first build a (half) H-bridge and a oscillator. Make sure the square wave form looks good without any harmonics as this would heat up the FET's and could indicate saturation of the ferrite cores. It will burn your FET's in time and the frequency will "run away" causing even more heat dissipation.
 

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JoeAlders

Member
2011-02-12 10:20 am
Yes, simple isn't it? That is the entire "power" 1W amp (it can drive my B&W Rock Solids easily).
My advise if someone would like to start this "adventure" : Use a low voltage (max 12V) power supply (short circuit proof).
In this headphone amp i have used a 5V PSU. It can be adjusted to about 7V max.
For this amp it is sufficient.
It is the best Zotl project to start with as it needs no High voltage PSU at all.


Thanks again lampie519 for this info. The biasing of the current source transistor, I would suggest a resistor in series with the diode to have lesser temperature dependence
of the tail current. Now the tail current increases with increasing ambient temperature (delta Vbe across the 100 Ohm emitter resistor).
I have tried to get an idea what this "zotl impedance converter" is but have to confess that not much data is given here when searching the internet. I have not seen a single schematic so far to
illustrate the idea.
 
Last edited:

JoeAlders

Member
2011-02-12 10:20 am
Status
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