Finally I have modified this line amp with fully CCS loading for both amplification and buffer stages. I use 7F7 (6SL7 loctal version) instead of 12AY7 in this amp. The power supply is with series 12B4 tube regulated 285V B+.
The first stage is with 2.2K unbypassed cathode resistor and the plate load is with 1mA CCS (with use of 10M45 IC chip).
Now, the second stage is with 1.5mA CCS cathode loading (with another 10M45 chip).
The sound is quite different from using 100K cathode resistor loading. It sound much brighter, less bass but more defined, very airy and clear.
CCS is kind of perfect loading with minimum distortion as mentioned by Morgan Jones. The perfect unity gain line amp designed by him is with Pentode as the CCS sink for the 6C45S tube at the end of his book.
So, what is tube sound.... I am really lost.
Johnny
The first stage is with 2.2K unbypassed cathode resistor and the plate load is with 1mA CCS (with use of 10M45 IC chip).
Now, the second stage is with 1.5mA CCS cathode loading (with another 10M45 chip).
The sound is quite different from using 100K cathode resistor loading. It sound much brighter, less bass but more defined, very airy and clear.
CCS is kind of perfect loading with minimum distortion as mentioned by Morgan Jones. The perfect unity gain line amp designed by him is with Pentode as the CCS sink for the 6C45S tube at the end of his book.
So, what is tube sound.... I am really lost.
Johnny
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Consider this; many years back when tubes ruled, all of the cheap-ish amps (and 'radiograms') had buckets of low even order distortion and a limited frequency response. This was made worse by cheap speakers also with lots of second harmonic distortion. This all lead to a subjectively very 'warm' and 'mellow' sound quality. Some sentiment-driven people latched onto that and kept repeating it until the myth of 'tube sound' was born. It was not tube sound, it was just cheap design using existing (at that time) components to meet a budget. Nothing more.
Tubes themselves have no sound quality. Unfortunately the audiofools and sentiment-driven wusses find this FACT difficult to grasp and hence continue to spread their nonsense. They need help.
Tubes actually have electrical characteristics, not sound quality. The characteristics must be manipulated by the designer to assemble an appropriate circuit. That circuit, when used in an appropriate system (including media, source, power supply, cables, amplification, transducers and listening environment), may be able to reproduce an encoded music signal such that the reproduction can be interpreted emotionally and hence subjectively labelled with a specific sound-quality.
So there is no specific tube sound. There never has been, and never will be.
This may be true in your parallel universe. Where i live all tubes suffer from serious microphony which obviously differs in frequency, amplitude, q-factor between tubes and brands. It is more than sufficient for a specific "tube" sound.
I went to my friend's home for a test drive. It happened that this new line amp has very tense feeling and over emphasis on the high pitches. When we switched to the Marantz 7C, it was much more natural and relax. My friend and I both agree it is very comfortable with the Marantz 7.
I got back home this afternoon and modified the amp to work with 7N7 (6SN7). I believe the local feedback ratio is much less because the amplification factor is only 20 in comparison of 70 with 7F7. It still sounds good clarify, airy, but more relax.
It seems to me that higher the negative feedback, the details will be finer but it will have more tense feeling. It will sound more relax when the feedback is less.
How we could measure the amplifier and what is good sound?? I am lost. However, I am rather confident that this configuration has very good potential and it is just matter we could find the best combination- tube, bias, plate current etc.
Johnny
I got back home this afternoon and modified the amp to work with 7N7 (6SN7). I believe the local feedback ratio is much less because the amplification factor is only 20 in comparison of 70 with 7F7. It still sounds good clarify, airy, but more relax.
It seems to me that higher the negative feedback, the details will be finer but it will have more tense feeling. It will sound more relax when the feedback is less.
How we could measure the amplifier and what is good sound?? I am lost. However, I am rather confident that this configuration has very good potential and it is just matter we could find the best combination- tube, bias, plate current etc.
Johnny
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