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hello
I have a question about power tubes
like 45, 2a3, px25 or 300b.
If you take a tube opration from the paper
is ther a common rule what happens with the sound if you increase or lower the b+?
And what is happen soundwise as you play with the current ?
what gives a brighter sound and what gives a warm and more body to the sound.
Follow Ups:
That higher currents is better sounding in output filamentary triodes, and I built and listened like this for 35 years.However, I have recently found that lower voltages and currents in triode output stages sounds better to me. Far less STRAINED!!!!!!! sounding, with more freedom and ease of musical delivery. Ask ace custom amp builder and audio guru, Jeffrey Jackson, how much current he LISTENS to at home, in his own triode rig !!
You see, the technoboys look at tube curves and distortion plots ALONE to answer your query, and their usual ( boring ) answer " by the book " IS technically correct, but not practically correct. They totally fail to consider that the tube is in a circuit with OTHER components, and when you reduce the current through, say, a SE output transformer, from say 60 mA ( the "book" on a 2A3 ) to 45 mA. truly MAGIC things happen sonically to the overall delivery of the music, IF, ( a big word ) all else is optimized in the SE amp !!
Of course, all else is SELDOM optimized in 97% of the SE amps out there, so, they typically " push " the tube to get some clarity, and to make up for their very poor wiring implementation, and ludicrous high DCR, C and HY power supplies, implementations that are now obsolete, .... but few understand this.
The very few however, the 3% ( or less ) who DO build in the new style however, they are all digging it. I do come off sounding elitest here, but frankly, thats just the way things sound to me now in 2007, the truth - in MY latest set of audio experiences.
OK flat-earthers, have a really good "go" at me now. I've left you a large target. But IF you've heard what I heard, you cats will whistle a different tune. How many have I OFFENDED with this post? Better and far more important yet, who will openly consider what I've reported, try the newer implementation, LISTEN to it, and build even better gear?? Time will tell. Cheers to all.
...when did this become a competition? I like it better when sharing means something simpler. My discoveries are mine, yours are yours... Input is just input and nothing more. It's no fun when we have to pick sides, and it's definitely no fun when we are forced to follow *anyone* else's methodology. That sucks all the joy out of the hobby.
Not always. I meter everything and have consistently found that most tubes run 'high and cold' compared to classical op points show more of the least objectionable 2nd harmonic distortion and greatly reduced distortion compnents above the 3rd or 4th. It's almost certainly the reason for sounding less strained. The effect is easy to see on a spectrum analyzer. Within reason a side benefit in output stages is the increased grid bias means greater plate swing and increased output, which can be traded off with a higher turns ratio OPT for any even greater reduction of upper distortion components. Meters are the reason I end up running oddball points like a 6CW5 SE at 260 B+ and ~35ma into a 5k OPT instead of the classical ~150 VDC at 75ma. And yes, along with reducing the DCR in the PS, to my ears it results in terrific sounding amp.
> ...a side benefit in output stages is the increased grid bias means greater plate swing and increased outputCan you provide more details regarding your meaning on this point? Increasing the grid bias moves the tube further toward cutoff. That limits the positive-going swing at the anode. More bias = less zero-signal current = less swing = less power.
> ...a side benefit in output stages is the increased grid bias means greater plate swing and increased outputAgree that this is not entirely true. All output stages produce their max power within a range of bias voltages which is dependant on load, HT and topography (lower impedance narrows the range as does higher HT voltage). 0V is generally the limitation for Class A1 but obviously not so for A2. More negative bias will produce greater power in PP amps but only at the expense of driving deeper towards Class B.
Sorry about that, the statement was a little too general. It was in comparison to low and hot, where unless the driver is designed to supply grid current it's usually the limiting factor.
Thermionically addicted.
JeffI agree with you on this topic.
Although I would also stipulate that a
higher ratio OPT is also necessary
for a lower distortion output.
Yes, apart from greater linearity higher currents tend to provide more body, generally without loss of HF response. However in SET amps the driver's interaction must be taken into account. For instance lower current in the driver produces higher distortion, which is also mainly 2ndH if a triode is used. This usually reduces overall distortion due to some cancellation with distortion in the OP stage (which is in anti-phase and also mainly 2ndH). To my ears this translates to noticeably sweeter sound. So IME higher current in the OP stage and lower current in the driver works best, the caveat being that all systems are different and system balance may dictate different settings for best results.
Take a look at this page. Generally speaking, raising the current and load impedance reduces distortion.
Mike
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