One such thread that fits Itsallinmyhead’s description, is 6L6s AJ build guide. He puts it in a 5U, then measures and selects a sweet spot. Pictures and all.
Better yet wrt the deeper scheme of things, is Papas articles about the subject. On the FW site.
Better yet wrt the deeper scheme of things, is Papas articles about the subject. On the FW site.
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The bias thing, that always appeared to me as a method to squeeze the last bit from a mosfet, until the system becomes current limited - meaning at some point you're just making heat instead of power. ...but to hot-rod the part is to increase its linearity. Like everything I'm sure there is a sweet spot from which there is a diminishing return (enjoyment vs. waste). Sweet spots... how very Pass.
There is a sweet spot as far as diminishing returns go and safe operating temps…but as far as performance goes I do t believe anyone would prefer a class a amp biased at say 1.3 amps vs the same amp biased at 2 amps. More bias is almost always better if you have the heatsink and the devices are in safe dissipation zone.
Where it gets tricky is one MAY prefer a simpler amplifier with less output devices and therefore less bias. Or one MAY have 16 ohm speakers that are not current demanding and the increase in bias won’t make much difference.
Really, more bias is making the devices more linear but more importantly increasing the class A envelope into low ohm loads. Those of us with conventional speakers with say a 4 ohm minimum will appreciate this.
Where it gets tricky is one MAY prefer a simpler amplifier with less output devices and therefore less bias. Or one MAY have 16 ohm speakers that are not current demanding and the increase in bias won’t make much difference.
Really, more bias is making the devices more linear but more importantly increasing the class A envelope into low ohm loads. Those of us with conventional speakers with say a 4 ohm minimum will appreciate this.
Very good points. To comment on the last remark, my Fyne 502s sounded significantly better once the dissipation of my BA-3 got so high that I barely dared take the garbage out without switching it off. So I sold the speakers 
I turned cheap too.
But heavily beaten by your brain and gold-finding talent keeps me in non audiophile retirement-ready status either forever, or for a long time to come
So for now I am just a cheap greenhorn. Still looking for brains and talent.
But heavily beaten by your brain and gold-finding talent keeps me in non audiophile retirement-ready status either forever, or for a long time to come
So for now I am just a cheap greenhorn. Still looking for brains and talent.
This is one of those things all of us tweakers hope is a shortcut to better sound.
I think of tube gear that people would run at the ragged edge and feel sure the thing sounded so much better and then there were manufacturers who in the interest of not having to deal with angry customers would run the tubes at reasonable levels and get sound quality that was very highly regarded,
I think of ben mah writing on the SINGING BUSH topics and finding his version of the amp sounded better with ZM's recommended bias; finding he preferred the sound with the lower bias.
This is a hobby that is a rigorous education in compromise and learning how to balance them within your system. Balance and proportion are not classical values without reason.
Nonetheless, one never knows without trying. But this is a place where I would bet expectation bias is very difficult to control.
I think of tube gear that people would run at the ragged edge and feel sure the thing sounded so much better and then there were manufacturers who in the interest of not having to deal with angry customers would run the tubes at reasonable levels and get sound quality that was very highly regarded,
I think of ben mah writing on the SINGING BUSH topics and finding his version of the amp sounded better with ZM's recommended bias; finding he preferred the sound with the lower bias.
This is a hobby that is a rigorous education in compromise and learning how to balance them within your system. Balance and proportion are not classical values without reason.
Nonetheless, one never knows without trying. But this is a place where I would bet expectation bias is very difficult to control.
I have been known to wear out the threads on the screws for my chassis top covers. Yes, I like to button up the whole chassis each time after making an adjustment to one or more of the components on the PCB. My VFET amp needs a whole new set of screws at this point. As said above, bias current is just one of the knobs we have to adjust the operation of the circuit.
I definitely preferred a lower bias with my F6. Once it started approaching the ‘sweet spot’ for cancellation, it became too much of a 3rd dominant machine for me.
If the bias is high enough to soften the hot glue holding down the top, then I know I'm good. Who needs thermometers or screws? 
Cheap? Nope, you are smart enough to merely have best ever made fullrange drivers RCA LC-1A and big Tannoys! 😛
Sometimes I take the cover and don’t make any adjustments - I just stare. Usually if I stare long enough, I’ll find something I could’ve done different or better. That’s how new projects are born at my house. 😀
do not worry, I'll look for 12" Fyne in decade or so, when they go cheaper
or even better - 15" Fyne, if they start to make them
🙂
oh yeah, I'm accepting free specimens, for extremely subjective evaluation
shipping expenses theirs, logically
🙂
shipping expenses theirs, logically
🙂
In fact, I have an agreement with him to take the J Zen to his shop for listening tests once it is up and running.
But beware, last persuasion in Scotland took a lot of whiskey and nagging. For 15s, I fear persuasion must be done with a combination of tools, including au naturél perhaps. Best find a suitable candidate for that
But beware, last persuasion in Scotland took a lot of whiskey and nagging. For 15s, I fear persuasion must be done with a combination of tools, including au naturél perhaps. Best find a suitable candidate for that
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