beautiful work ! - when I first saw the "120" it made me think of my days with a pair of Dynaco MKVI and their wretched 1-bias pot for 4 expensive output tubes. Are they quiet enough for a full horn rig?
Interesting to see it on an analyzer without the Schade feedback. A lot of moving parts.
For a DHT my preference is no feedback whatsoever…even Schade.
Totally different animal here though.
There is no way you can bring a signal back around perfectly 180° out of phase. Will always be slightly lagging…some frequencies more than others. No way to avoid some phase irregularities. Negligible? Yeah. Audible…? Maybe not, but throw in the other shifts inherent in all of the audio equipment, speakers and cabling… It is additive.
I’ve seen the argument that the human brain has a threshold below which it cannot detect phase shift. No way to know that for sure, only subjective measurements. Also, like anything, that may vary with the individual. They argument could also be made there are things are brain picks up on while listening that can’t be quantified. Why does anyone like listening to one system more than another? Almost impossible to verbalize.
The argument has been made that phase can change by the signal bouncing around the room so anything generated by the amplifier will be below that threshold and undetectable. However, I’m of the mindset that Location and reflection shift are natural occurrences our brain is highly adapted to.
Oddball Electronically induced shifts…Who knows?
Think how many frequencies there are from one pluck of a guitar string. Now add the entire band and vocals… the sheer number of frequencies being generated at any moment is mind-boggling! Now add a slightly different shift to each and everyone of those frequencies. Maybe a reason some prefer zero negative feedback?
Just random unsubstantiated thoughts… I obviously have too much time on my hands!
Again, little to do with this particular amp… Just rambling!
For a DHT my preference is no feedback whatsoever…even Schade.
Totally different animal here though.
There is no way you can bring a signal back around perfectly 180° out of phase. Will always be slightly lagging…some frequencies more than others. No way to avoid some phase irregularities. Negligible? Yeah. Audible…? Maybe not, but throw in the other shifts inherent in all of the audio equipment, speakers and cabling… It is additive.
I’ve seen the argument that the human brain has a threshold below which it cannot detect phase shift. No way to know that for sure, only subjective measurements. Also, like anything, that may vary with the individual. They argument could also be made there are things are brain picks up on while listening that can’t be quantified. Why does anyone like listening to one system more than another? Almost impossible to verbalize.
The argument has been made that phase can change by the signal bouncing around the room so anything generated by the amplifier will be below that threshold and undetectable. However, I’m of the mindset that Location and reflection shift are natural occurrences our brain is highly adapted to.
Oddball Electronically induced shifts…Who knows?
Think how many frequencies there are from one pluck of a guitar string. Now add the entire band and vocals… the sheer number of frequencies being generated at any moment is mind-boggling! Now add a slightly different shift to each and everyone of those frequencies. Maybe a reason some prefer zero negative feedback?
Just random unsubstantiated thoughts… I obviously have too much time on my hands!
Again, little to do with this particular amp… Just rambling!
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Ha! I did have that coming… But you can’t quantify everything. 😁 Maybe someday they’ll develop a quantum computer that can tell me why I prefer my ZNFB 45 SET with single driver speakers over my Mark Levinson with 802D3s! I certainly couldn’t tell you why! Objectively, it just does not make sense. Thus the speculation in the prior post… Just trying to wrap my head around it.
And, oh yeah, DC coupled driver halves! 😉
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My post was not 100% accurate,
For anyone who might know less than me (doubt thats possible lol)
UL/Pentode switch....
I also added a 500k resistor to the lighted power switch to dim down the bulb...
And the neg bias, added a diode and resistor before the last cap which also required one more tag strip...
I can't speak towards a full horn rig as i donk know much about there efficiency, but my Elsinores are 96db at 1w and the amp is dead silent, even putting my ear to the speaker i hear nothing... none of my previous amps came even close...
No problem here in Germany...delivery should be same throughout contiguous EU.
https://www.tubeampdoctor.com/roehr...en-pentoden/kt88-kt90-kt100-kt120-kt150-6550/
Bench Baron
Yeah, I agree on a triode amp, with UL it just sounds WAY too bright/fatiguing to me without some Schade feedback added, and the amount used does change the tone of the amp.