these caps are not the same like 866A mercury valve?
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i see,GK71 plate output by screw!
i tink you have KT120 for very good pentode, so this GK71 its very inconfortable for to built audio amps,
wen you made a big power push pull by pentode you need feedback and plate and G2 HV caps to avoid oscillations,
so by triode GM70 no need feedback no anode caps, linearity its perfect and no oscillation ,
OPT secondary windings floating not even need to be grounded so your speakers will be locked no damping factor
and by IT coupling no need of coupling caps and anode resistor, and less of them in audio the best.
only triodes and windings , of course IT and input transformer should be very good quality
i tink you have KT120 for very good pentode, so this GK71 its very inconfortable for to built audio amps,
wen you made a big power push pull by pentode you need feedback and plate and G2 HV caps to avoid oscillations,
so by triode GM70 no need feedback no anode caps, linearity its perfect and no oscillation ,
OPT secondary windings floating not even need to be grounded so your speakers will be locked no damping factor
and by IT coupling no need of coupling caps and anode resistor, and less of them in audio the best.
only triodes and windings , of course IT and input transformer should be very good quality
No, GK71 are very good pentodes. Much better than any so called "audio tetrodes" like KT120 or KT150 or any other derivatives of 6L6 tubes.
i do not tink one tube its "better" of other, and 6L6 807 EL34 KT88 etc etc are the tubes who made audio and instrument amplifier history , the GK71 its made for ham radio if work well in audio its good news but i wont now if its linear an do not oscillate without feedback and others artefacts in push pull mode
if you read the post from the beginning you see it was very heavy but last one its very light, less of 30Kg i go to check lather i use industrial power supply no more two 600w main HT transformers no more 3 very heavy chokes no more seven heather transformers only four 315V500mA industrial modules and two 250W24V smps and four small chokes 1H! photos with old and new psu
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Being wired SE, GK71 typically shows 30% less internal plate resistance, than GM70, this is the main point that sometimes makes GK71 better sounding.
I frequenly heard conclusions, " I've tried to put GK71 instead of GM70 in my SE amp, oh, now it is better, GM70 will not go back"
GM70 its triode, i do not like pentode GK71, and plate cap its not good for home amplifiers.
this tread its for GM70PP, so please forget other power tubes i'm not interested.
this amplifier its a new challenge very small for wath you can get
this tread its for GM70PP, so please forget other power tubes i'm not interested.
this amplifier its a new challenge very small for wath you can get
Vladimir if you have 100Hz noise try 15000uF dual common mode choke
0.8H X2 and 15000uF
or cheaper 15000uF 50/63V then 1ohm 10w resistor and again 15000uF low esr
but the must important thing its groud from katode and HT caps very short by silver plated copper wire 1.5mm for each GM70
0.8H X2 and 15000uF
or cheaper 15000uF 50/63V then 1ohm 10w resistor and again 15000uF low esr
but the must important thing its groud from katode and HT caps very short by silver plated copper wire 1.5mm for each GM70
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I would not advise this way of feeding GM70 heater, a lot of iron and electrolytics in the signal path.
Usually I feed 3A through paralleled j-fet constant current source, with polystyrene cap just on the tube base, shunted with silver-mica cap. No way for lytics on the heater pins.
Also tried 24V SMPS for heater, with RC-RC-RC-RC-RC filter after it. R=0,27 Ohms 5W, C=2u2 film caps, the one on the tube base should be of best quality.
Usually I feed 3A through paralleled j-fet constant current source, with polystyrene cap just on the tube base, shunted with silver-mica cap. No way for lytics on the heater pins.
Also tried 24V SMPS for heater, with RC-RC-RC-RC-RC filter after it. R=0,27 Ohms 5W, C=2u2 film caps, the one on the tube base should be of best quality.
so try to read from the beginning i made first a prototype PP GM70 Sakuma style on open chassis whit standard valves power supply, it was very very heavy so i rebuilt with smps power supply for heathers and HT. now its a "little " amplifiers made by 3 chassis Hammond, smps in the two back chassis before i made 3 i means 3 amplifiers in SE so you like or not no problem. this last PP only need one good cap afther 24V 250W modified smps for two GM70 and this its OK you can put your ears in the 98db Fostex FE2108 and you do not now if amplifier its on or off.no noiseat all. so if you come in France please came home to check. i present my amplifiers i made this last PP very nice sounding
i present my amplifiers i made this last PP very nice sounding
blog to come
the first SE:SE GM70 integré
my personal:SE GM70 deux blocs
the ultimate SE: IT SET GM70
blog to come
the first SE:SE GM70 integré
my personal:SE GM70 deux blocs
the ultimate SE: IT SET GM70
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