I have redesigned my old 25W IRON-AMP cancelling the IPT (10dB) and make it more clean and powerful.
This easy DC adjustable 0dB Power DB with Sziklai BJT (or POWER MOSFET) is based on LH0033 as a JFET
source follower plus Power Diamond Buffer, low noise, high speed and NO output stage thermal problem.
The new amp uses cascode DN3545 + 2N5458 to replced old 2SK246 for higher voltage supply from +/-38V
to +/-70V, the bias current of SANKEN 2SC2922/2SA1216 is about 60mA and 100mA using 2SK1529/2SJ200.
With a good pre-amp followed by this unity-gain power DB will make it a very good non-global-NFB amp!🙂
This easy DC adjustable 0dB Power DB with Sziklai BJT (or POWER MOSFET) is based on LH0033 as a JFET
source follower plus Power Diamond Buffer, low noise, high speed and NO output stage thermal problem.
The new amp uses cascode DN3545 + 2N5458 to replced old 2SK246 for higher voltage supply from +/-38V
to +/-70V, the bias current of SANKEN 2SC2922/2SA1216 is about 60mA and 100mA using 2SK1529/2SJ200.
With a good pre-amp followed by this unity-gain power DB will make it a very good non-global-NFB amp!🙂
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Here is my other version with MOSFET output stage using TOSHIBA 2SK1529/2SJ200.
Compare with BJT version, I may not choose the MOSFET version because of the Vgs
are hard to control, I have measured one pair, 2SK1529's Vgs is about 2.03V at 50mA,
but 2SJ200 is only 1.66V about 0.37V difference.
I can adjust the 2N5458's Id current to get the suitable Vgs in the first stage to keep
output DC level almost 0V. And I have to choose the right R26 R27's valuse times 1.8mA
setting current to get the right idle current of the power MOSFET I want.
Choosing the right sound between BJT and MOSFET is not so easy, but I think that the
output impendance BJT's version will be lower than the MOSFET's and that is very
important for the non-NFB 0dB amp.
I love my new 0dB amp more than my 29dB 150W EU-152 now, I think they are not
the same type of Power Amp,though my ears are not good but still can tell some
small details are different.
Compare with BJT version, I may not choose the MOSFET version because of the Vgs
are hard to control, I have measured one pair, 2SK1529's Vgs is about 2.03V at 50mA,
but 2SJ200 is only 1.66V about 0.37V difference.
I can adjust the 2N5458's Id current to get the suitable Vgs in the first stage to keep
output DC level almost 0V. And I have to choose the right R26 R27's valuse times 1.8mA
setting current to get the right idle current of the power MOSFET I want.
Choosing the right sound between BJT and MOSFET is not so easy, but I think that the
output impendance BJT's version will be lower than the MOSFET's and that is very
important for the non-NFB 0dB amp.
I love my new 0dB amp more than my 29dB 150W EU-152 now, I think they are not
the same type of Power Amp,though my ears are not good but still can tell some
small details are different.
