Dear Tony,
Congratulations
I am awestruck by your knowledgeand ability
Best regards,
Sam
thanks...
with fuses installed, power to the output traffo and output tubes are complete....the 3 minute delay timer shorts out the 12k/5W soft start resistor...this resistor is in series with the main B+ ac supply....voltages ramps up to about 100 volts and stays there until the 3 minute timing period is reached, this protects the output tube from thermal run-away, at the same time that the plate B+ is ramping up, the negative bias voltage is likewise ramping up and settles to a value around -75 volts....these steps ensures successful turn on of the amp....
at the end of the 3 minute timing period, the relay closes and the 12k resistor is shorted out thus the B+ finally ramps up to around 210volts dc.....it takes another 5 minutes for the plate current to reach about 200mA....i recommend to wait for 10 minutes before music is played to give time for the amp to settle down to business....
i set the bias pots for this plate current level and bias drift was observed...i am happy to report that drifts were minimal and after 2 hours the bias current actually goes down a bit by around 10mA....this is normal as plate voltages in triodes have an effect on plate currents.....
i also observed that bias changes were caused by changes in line voltages.....
set-up for final adjustment to bias the output tubes.....
with my power meter monitoring the ac input to the amp, power factor was at 92%.....
total watts measured at 218watts...
line current....
thermal scan of the bulb at socket side underneath the chassis, i have installed fans running of 7 volts dc to move a bit of air underneath the amp when bottom plates are installed...
at the end of the 3 minute timing period, the relay closes and the 12k resistor is shorted out thus the B+ finally ramps up to around 210volts dc.....it takes another 5 minutes for the plate current to reach about 200mA....i recommend to wait for 10 minutes before music is played to give time for the amp to settle down to business....
i set the bias pots for this plate current level and bias drift was observed...i am happy to report that drifts were minimal and after 2 hours the bias current actually goes down a bit by around 10mA....this is normal as plate voltages in triodes have an effect on plate currents.....
i also observed that bias changes were caused by changes in line voltages.....
set-up for final adjustment to bias the output tubes.....
with my power meter monitoring the ac input to the amp, power factor was at 92%.....
total watts measured at 218watts...
line current....
thermal scan of the bulb at socket side underneath the chassis, i have installed fans running of 7 volts dc to move a bit of air underneath the amp when bottom plates are installed...
thanks guys, i am excited about this design....the final operating points and power consumption predictions were spot on, computed versus actual.......i am happy....
the power trafffo is a little warm even after 3 hours, only the tubes are hot....
as predicted, the total power consumption was around 220 watts...so that at 20 watts music output, overall efficiency is a mere 10%...
the power trafffo is a little warm even after 3 hours, only the tubes are hot....
as predicted, the total power consumption was around 220 watts...so that at 20 watts music output, overall efficiency is a mere 10%...
Hi Tony,tube compliments: 6C33 output tubes, 6P15P voltage amplifier/driver, 6N1P buffer, CG13 150v gas regulator tube......as you can see these are all Russian tubes....
do you have any concerns about that?
Otherwise... my congrats! Great build!
Hi Tony,
do you have any concerns about that?
Otherwise... my congrats! Great build!
none, i have grown to respect Russian tubes ever since i made my first 6H23 preamp....over a year ago.....
and after over 30plus years haitus, i ma making tube amps again, i am retired now and i know that i have to keep challenging my mind....an this is my way of doing it...
AJT thanks a lot to let us to see your amazing work.
It looks 100% DIY project, congratulations
Also i did a couple of tube project but coudnt find a chance to deal with 6c33 but i am planing to do.
If posibble can you compare 6c33 SE amp's sound to the 300b because i have listened a couple of times 300b
Thanks
It looks 100% DIY project, congratulations
Also i did a couple of tube project but coudnt find a chance to deal with 6c33
but i am planing to do.If posibble can you compare 6c33 SE amp's sound to the 300b because i have listened a couple of times 300b
Thanks
4P1L parallel SET
2nd Russian set with the 4P1L paralel singel ended triode...
paralleled tubes were baised to mimic a single 2A3 tube,
input tube was 6j9 triode wired, buffered by a 6N1P in a broskie cathode follower driving the palralleled finals grids...
the 4P1l filaments are run DC at about 4 volts...
and was very quiet and no hint of microphonics....
2nd Russian set with the 4P1L paralel singel ended triode...
paralleled tubes were baised to mimic a single 2A3 tube,
input tube was 6j9 triode wired, buffered by a 6N1P in a broskie cathode follower driving the palralleled finals grids...
the 4P1l filaments are run DC at about 4 volts...
and was very quiet and no hint of microphonics....
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