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In Reply to: RE: SE 2A3 biasing : non-linear vs. linear biasing ...graphs posted by deathtube 667 on March 30, 2014 at 10:48:04
"Q: is there any valid technical reason to use the non-linear/reduced current/golden ratio current biasing method?"
A valid technical reason? The way I look at it....no.
To me, our job as designers is to operate the tubes in the most linear way possible.
The "subjective, ear-valuation, that proves nothing" reason would be the "unique harmonic profile......that some builders seem to enjoy".
I believe that proves that some people like the sound of distortion which is what makes this hobby (that, IMO, should be an objective one) so subjective.
BTW, Keep up the good work!
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Follow Ups:
I feel it is virtually impossible to make any sort of purely objective statements when it comes to audio. People cloak their subjective beliefs with the objective but the underlying goals are still subjective in nature.
Using the objective is a slippery slope that can easily take you places you don't want to go. Just consider where chasing the objective goal of "low distortion" took us years ago.
dave
" People cloak their subjective beliefs with the objective but the underlying goals are still subjective in nature."This may all be a matter of semantics but the goal is objective. To Reproduce the source.
We just don't have an objective way to determine if that's being accomplished.
We are left with our subjective senses to try to ascertain if the objective goal is being reached.
This is why it's so important to educate our ears as to the sound of acoustic instruments.
"Using the objective is a slippery slope that can easily take you places you don't want to go. Just consider where chasing the objective goal of "low distortion" took us years ago. "
That was due to mis-guided science.
The real science shows us that the human ear interprets upper ordered harmonic distortion as more noticeable/objectionable than lower ordered harmonic distortion by a large margin.
Years ago serious people purposed that harmonic distortion be weighted to better represent the way the human ear interprets distortion WRT order.
If that method would have been followed we would not have fallen into that rabbit hole.
Therefore THD is almost completely meaningless except, it is almost certain that if the THD is ultra low, it won't sound very good.
The methods used to achieve low THD increase the number of upper ordered harmonic distortions. The result is the antithesis of the goal.
"Norman Crowhurst wrote a fascinating analysis of feedback multiplying the order of harmonics, which has been reprinted in "Glass Audio," Vol 7-6, pp. 20 through 30. He starts with one tube generating only 2nd harmonic, adds a second tube in series (resulting in 2nd, 3rd, and 4th), and then makes the whole thing push-pull (resulting in 3rd, 5th, 7th, and 9th), and last but not least, adds feedback to the circuit, which creates a series of harmonics out to the 81st. All of this complexity from "ideal" tubes that only create 2nd harmonic!"
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 03/30/14 03/30/14
This may all be a matter of semantics but the goal is objective. To Reproduce the source.
No that is your subjective goal. If you want to only converse with people who have the exact same goal then you are fine. However a community like this is filled with all kinds of people with all kinds of goals. My goal is an illusion of what I think the live event might have been like. I have yet to find any measurements that tell me I am going to get with a system but I have found specific patterns of things that put me in the direction I like.
We just don't have an objective way to determine if that's being accomplished.
Agreed.... but then why do we still insist on justifying the subjective with facts?
We are left with our subjective senses to try to ascertain if the objective goal is being reached.
Isn't the "objective goal" different for everyone? doesn't that simply mean it is subjective? I like hip hop and rap (old skool) and never really got into metal. Many out there don't consider either to me music at all.
This is why it's so important to educate our ears as to the sound of acoustic instruments.
I don't buy this. If you want to set the goal to be acoustic music so be it. To insist this is some kind of goal or standard is fine for the people who listen to that particular type of music. To suggest that if a system does this well it will also handle everything else is a bit of a stretch.
"Using the objective is a slippery slope that can easily take you places you don't want to go. Just consider where chasing the objective goal of "low distortion" took us years ago. "
That was due to mis-guided science.
how do we know that we are not using mis-guided (or better selective) science today? I seriously question the use of the word Objective in relation to musical tastes or reproduction.
The real science shows us that the human ear interprets upper ordered harmonic distortion as more noticeable/objectionable than lower ordered harmonic distortion by a large margin.
Then there should be some magical distortion spectra that everyone agrees on. Hell the people here cannot agree on SE vs. PP The SE guys bark out about the higher odd harmonics and the PP guys talk molasses like 2nd order.
Years ago serious people purposed that harmonic distortion be weighted to better represent the way the human ear interprets distortion WRT order.
so what is the right distortion spectra? PP or SE?
If that method would have been followed we would not have fallen into that rabbit hole.
sure we would have... it would have just been a different type of rabbit hole and don't forget there are many people still happily living in the rabbit hole you escaped.
Therefore THD is almost completely meaningless except, it is almost certain that if the THD is ultra low, it won't sound very good.
I see the lumping of all distortions together to be problematic but others may not. To boil it down to one specific spectra is right sure makes a lot of assumptions in my book.
The methods used to achieve low THD increase the number of upper ordered harmonic distortions. The result is the antithesis of the goal.
Doesn't PP decrease the total THD at the cost of high order harmonics?
re: crowhurst
measurements and theory are fine but the fact that everyone likes something different sort of makes them meaningless to anyone who doesn't hold your identical subjective tastes.
dave
What do you mean "My goal is an illusion of what I think the live event might have been like."
Like a live rock concert with a PA and everything?
First of all, with most recordings there never was a live event.
The players weren't even in the same room at the same time.
I've mixed a lot of live shows on really good PAs in really good venues.
And they sounded good in a relative way.
But let's start with the mics.
If I had those same players, playing those same instruments and those same parts in the studio I would have some really good mics (u67, u47, AKG C12, etc.) on them and would record multitrack and spend time on the mix.
The mix down, played back on my home stereo would sound much better than any live show using stage mics and a PA system.
So again, what do you mean "My goal is an illusion of what I think the live event might have been like."
Now if you were talking about a live, unamplified acoustic concert.....I'm right there with ya.
See, for me, after working in a professional recording studio for 15 years, recorded music (or at least the bits and pieces) are a live event and I don't have to imagine what it sounded like. I was there. I set the mics. I listened to the sound, with my own ears, of our 9 1/2 foot Baldwin concert grand piano with professional players as diverse as Roger Kellaway and John Ondrasik (Five For Fighting) and Andy Street (music director of American Idol) playing it, electric bass and acoustic bass of Randy Tico, singers---lots of great singers Dave Mason and Kenny Loggins and Ann Kerry Ford, Hammond BV with a Leslie speaker, Phil Salazar's Fiddle, Bobby Nichol's drum kit, John Cowsill's drum kit, Dave Mason's electric guitar and amp, Robbin Ford's electric guitar and amp, Virginia Kron's Cello, harp (not a mouth harp), John McEuen's (Nitty Gritty Dirt Band) banjo and Martin Guitar, Jonathan McEuen's Martin guitar, Chris Hillman's acoustic guitar, JayDee Maness' petal steel guitar and amp, Jim Capaldi's drum kit, Jim Capaldi's congas..............and more.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hey,
as I said.
Illusion.
Those instances where there was not a "live event", I still want the illusion of one and I strive for my system to give me what i think the artists intent would be.
It is subjective and everyone hears and interprets differently.
To try to put this subjective experience into an objective box just limits the audience it appeals to.
Don't get me wrong, I use and trust the objective all the time. There are some goals that I find need to be objectively met prior to considering the subjective. Those goals are very soft and cover basic functionality of the system. I realize it is comforting for many to rely on the science as justification for their sound and that is fine. They just have to understand that when they make the science "theirs" they have subjectified it by attaching their biases.
dave
I get what you are saying Tre, that it is impossible to create a live event if the original recording was not live but a studio creation. Conversely, each 'track' has to be played live in any case and then all stitched together. So surely all music is live, just not played as a one off gig.
Anyway, my experience with my DC45 amp is I CAN have the illusion of a live event in my music room. Daft Punk at 95db, yes I know that's a little low, have you heard David Guetta live? But I do have neighbours. Sarah Vaughan hitting those long sustained high notes with no sign of compression or distortion. Jason Isbel being intimate and emotional with acoustic guitar.
What my amp, and all the credit should go to Jeff and Dennis, gives me is that live event with see through soundstage, hearing the whole acoustic of the recording studio and the heart of the performance.
These amps are are running at milliwatts and probably have low distortion at these levels plus lower op. point output tubes and overspec transformers and higher output loads and in my opinion MUST be used on high efficiency speakers. Mine 117dB!
There are many ways to achieve live performance in the home, this is one way not the only way. Works for me and others, try it.
Side note, my best friend, Dogman Dave, check him out on souncloud, a British Neil Young came to stay the other week and he played some songs using my standard Vintage guitar not his Martin and after we cranked the volume up on the system and played one of his recorded tracks. He was blown away as to how close it came to his live version he'd just played. That for me was mind blowing.
Please don't let this thread descend into another Jeff bashing outlet.
Thanks for listening.
Smart845
117dB 1w/1m seems a bit far fetched IMO , most large format compression drivers manage around 110dB 1w/1m . I seem to remember you mentioned you had Avant Garde speakers . The Uno and Duo are around 104dB 1w/1m sensitivity . I think the Trio is around 109dB 1w/1m
Al
That's right, Avantgarde Duo with the Omega drivers which were 16ohm and I thought 117dB but I may be wrong on that as I believe the sensitivity should be the overall sensitivity and not just the drivers alone.
Cheers
I like this.
Be careful with 95db. Anything longer than 4 hours and you will permanently damage your ears. (some experts say 1 hour)
BTW, I agree. With your speakers a 45 is more than enough power. But I'll never understand why you don't operate the driver tube in a linear spot and/or use a driver tube that has the output impedance that's needed to drive the Miller fully.
Your speakers are so sensitive that you could use a 6sn7 or a 5687. You don't need that high gain driver stage. Try it.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hi Tre,
Planning on another amp later in the year with more compact chassis and using all I've learnt so far. Maybe this is the chance to give a 6ns7 a try and push the op point higher for the 45.
Out of interest I was told by a respected transformer designer to run the 45 filaments at 3v. Sounds like tube suicide to me, opposite of starved filaments.
I do have to say though that lower gain 12ax7 do not have that amazing jump factor that I get from a Golden Lion 12ax7. The Psavane are nice but less gain and without that special dynamic freedom.
Cheers
Smart845
That's really interesting. Especially a 45 with 3vac on the filament. I would think it would just kill the tube?
It seems, these days, everyone wants to re-invent the wheel.
I will say that the "amazing jump factor" you speak of almost has to be some weird adoration. Gain is gain and if you have enough, you have enough.
But who am I to tell you what to listen to?
In my system I don't even have enough gain to clip my output tube but I have enough to play my system at the levels I want.
Take care,
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Can't seem to get the video to imbed...The CD of this performance is one of my reference tracks. Listen to the brushes on the snare. This is a beautifully recorded album.
https://www.youtube.com/watch?v=it1NaXrIN9I
Edits: 03/31/14
Very nice recording.
You have to use the old codes.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
No embeds on the ipad but got the you tube.
The DK track is wonderful and again I get that reality of the live concert as though sat at her feet hearing all the clacks and coughs from the audience.
Cheers
Here's a nice, somewhat dry recording that puts Mark's vocal right in the room with you.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Maybe the post linked below will help. Maybe not.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Nice post Dave.What if its a vacuum tube's "thermal stress" our ear subjectively responds to, and NOT THD, IMD, etc ??
Several good amp builders I know find that a tube with a relaxed op point, a "sweet spot" may subjectively sound better, "more relaxed" to them, than when pushing the plate dissipation.
Of course, we won't read about thermal stress sounds in tubes in any EE book I know of, do we ?? Morgan Jones, Radiotron??? Nope, not at all. Nor is it typically considered.
Only on this Forum, search word "Tube Wrangler".
The proof of the pudding.
I liked your post Dave. Science or ART ????
Jeff Medwin
Edits: 03/30/14
within a defined subsection of circuits, in this case, direct coupled 2 stage SE amp with a 2A3, seeking results that "measure better" by changing a few basic variables (admittedly amidst many more) is still useful stuff IHMO.
The small parts count in an amp like this (except for those that prefer multiple bypassing) puts more percentage per part as being responsible for the final sound/performance. So, if by tuning the operating variables for measure best, the remaining parts are then the only areas where something "might" be able to be improved, example cap quality, or wire or other things not likely to make a "big" change.
The only other thing is that maybe loading higher to lower distortion
at a point starts to sound "less good", even though it measures better.
I've not heard too many complaints from others about this, again, specifically regarding this type of circuit.
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