The channel which has this problem also has a 'scratch' noise when turning the volume button, it wasn't doing this before when it had the other transformer and working in UL.
very, very interesting!
only FDA OPA1632, THS4131, ... are begging to be here
then at the output of the "phase inverter" - beauty ...
cathode feedback
- this is the best that can be
true - you need a decent build-up from the phase inverter
but the nature-like feedback is the happiness and charm of the tube sound
Beautiful!!! ,
I removed bypass capacitor and found the problem!!!
I thought it was bad tube, bad ground resistor, bad feedback cap, bad coupling cap.
The problem was a wire touching another one!
AND the feedback loop is inverted somehow, now I removed the contact that touched and I reversed the connection of the output transformer.
I have to draw something to explain it.
Your built is awesome!! Thank you for sharing it with me!
I removed bypass capacitor and found the problem!!!
I thought it was bad tube, bad ground resistor, bad feedback cap, bad coupling cap.
The problem was a wire touching another one!
AND the feedback loop is inverted somehow, now I removed the contact that touched and I reversed the connection of the output transformer.
I have to draw something to explain it.
Your built is awesome!! Thank you for sharing it with me!
I was so distrusting now my abilities to make this amplifier (which was perfectly stable before) , during the modification I must have bent the wires without knowing it.
This made me order two solid state mono power amplifiers.... the only amplifier that I know would be great.
But now the path is clear again to amazing tube sound, nothing like I have heard before. I might even attempt the ultralinear + cathode feedback combination.
This made me order two solid state mono power amplifiers.... the only amplifier that I know would be great.
But now the path is clear again to amazing tube sound, nothing like I have heard before. I might even attempt the ultralinear + cathode feedback combination.
Do you know if it makes a difference if I connect the 8 ohm tap to Ground and the 0 output tap to the feedback,
Instead of reversing the primary of the OT? , I am just lazy and changing 8-0 output taps is easier than reversing all the primaries , which is 6 wires per channel...
Instead of reversing the primary of the OT? , I am just lazy and changing 8-0 output taps is easier than reversing all the primaries , which is 6 wires per channel...
it's time to switch to
6p45s
6p36s
GU50
to have BAS - you need acoustics with high sensitivity on paper diffusers,
a competently tuned circuit and the right output audio transformer
how many pieces of 6p36s will you get for the price of one kt120?
cathode winding feedback - this is the most perfect variation of ultralinear inclusion
ultralinear inclusion itself is worse than cathode feedback
right now I connected the 0 ohm to feedback, and the 8 ohm to ground. Should work...
Svytoslav, I am familiar with 6h9c I use it and it is very good, can't hear anything bad about this nice tube.
I am not familiar with other tubes. I wasn't able to make the 6n6p ever work or the 6n1p, very problematic for me.
Svytoslav, I am familiar with 6h9c I use it and it is very good, can't hear anything bad about this nice tube.
I am not familiar with other tubes. I wasn't able to make the 6n6p ever work or the 6n1p, very problematic for me.
here it is not possible to change the power supply of the second grid relative to the anodesbut in GU50 - it is easyby changing the power supply of the second grid - we change and match the audio transformer with the load at the minimum TND
Ok, I like the sound of the kt120, I don' like warm sound.
Right now I hear the new transformer with cathode feedback and ultralinear, it is very good with UL, it is way better than with my previous transformer, the sound is clearer,
However compared to cathode feedback, UL is more analytical, and tends to place the emphasis on the loudest sound. It is a little bit more analytical, with a more shouting and more bass, it digs into anything and sends it to you, pops, clicks and cracks noises from recording are presented with force and speed.
The CF (cathode feedback pentode) lets more the sounds vibrate without constraints, it has more speed and place the emphasis on the detail of each vibrations, it sound faster but without exposing too much the defects of an LP. However it sound more open with even more details, everything is clearer and it exposes distortions very much, you hear everything.
I didn't expect such a difference. Going from triode el120 to UL el34 is 50% clearer sound and lot less warmth
From UL el34 to kt88 UL finally I can hear the voices without blur and difficulty, then changing the transformer I gain rapidity, even more detail and a great sound, all warmth is gone, then to CF kt88 it is another 20% leap in clarity and speed, everything is exposed.
It is way better than anything I expected, now in the final design I will use kt120 instead of kt88, and I know it will sound the same but even better.
I can only say that the design of cathode followers and 6sl7 gain stage has less texture around instruments , less warmth than using 6sn7 gain stage followed with LTP ecc99. I cannot say which is best and I lost the measurements for the LTP ecc9 amp now gone.
I will measure tomorrow the UL vs CF and try to better understand what I am hearing.
Right now I hear the new transformer with cathode feedback and ultralinear, it is very good with UL, it is way better than with my previous transformer, the sound is clearer,
However compared to cathode feedback, UL is more analytical, and tends to place the emphasis on the loudest sound. It is a little bit more analytical, with a more shouting and more bass, it digs into anything and sends it to you, pops, clicks and cracks noises from recording are presented with force and speed.
The CF (cathode feedback pentode) lets more the sounds vibrate without constraints, it has more speed and place the emphasis on the detail of each vibrations, it sound faster but without exposing too much the defects of an LP. However it sound more open with even more details, everything is clearer and it exposes distortions very much, you hear everything.
I didn't expect such a difference. Going from triode el120 to UL el34 is 50% clearer sound and lot less warmth
From UL el34 to kt88 UL finally I can hear the voices without blur and difficulty, then changing the transformer I gain rapidity, even more detail and a great sound, all warmth is gone, then to CF kt88 it is another 20% leap in clarity and speed, everything is exposed.
It is way better than anything I expected, now in the final design I will use kt120 instead of kt88, and I know it will sound the same but even better.
I can only say that the design of cathode followers and 6sl7 gain stage has less texture around instruments , less warmth than using 6sn7 gain stage followed with LTP ecc99. I cannot say which is best and I lost the measurements for the LTP ecc9 amp now gone.
I will measure tomorrow the UL vs CF and try to better understand what I am hearing.
Your answer is worthy of the highest praise.
If you were sent amplifiers for review, your reviews on YouTube would be a sensation.
Respect to sound connoisseurs!
Bravo!
P.S.: Would you like to fall in love with the sound of the PP GM70 ?
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