@JeffYoung -
I can't comment too deeply when it gets into a material's use within an application.
What I can definitively say is that polyethylene =/= Mylar.
I can also definitively say PE (Polyethylene) =/= PET Polyethylene Terephthalate
Things get shortened frequently and vernaculars are often used. I couldn't be certain if what some refer to as a polyethylene cap is actually a cap containing Mylar. I can be certain that if the cap contains Mylar as its selling point / defining material, then I'd personally use a more accurate / correct term.
If you happen to have a few clear examples of part numbers, I may be able to help further.
I can't comment too deeply when it gets into a material's use within an application.
What I can definitively say is that polyethylene =/= Mylar.
I can also definitively say PE (Polyethylene) =/= PET Polyethylene Terephthalate
Things get shortened frequently and vernaculars are often used. I couldn't be certain if what some refer to as a polyethylene cap is actually a cap containing Mylar. I can be certain that if the cap contains Mylar as its selling point / defining material, then I'd personally use a more accurate / correct term.
If you happen to have a few clear examples of part numbers, I may be able to help further.
@ItsAllInMyHead, it was more just general curiosity.
I do note that Epcos/TDK call their "metallized polyester film" capacitors "MKT". I wonder if the 'T' is a reference to terephthalate?
Some of their MKT datasheet get more specific:
But others just say:
(Check out the parenthetical though, could you get more in-specifically specific?)
I do note that Epcos/TDK call their "metallized polyester film" capacitors "MKT". I wonder if the 'T' is a reference to terephthalate?
Some of their MKT datasheet get more specific:
But others just say:
(Check out the parenthetical though, could you get more in-specifically specific?)
@JeffYoung -
It seems marketing takes over at some point. With the technical expertise I've seen that you have - I'd go by spec sheets for the specific part vs. a generalization in hierarchy of materials. As an example, my previous company made over 50 unique PETs that were ongoing SKUs, and I did R&D on many, many more. Not all PET is created equal. Metallized polyester... well, I dunno? I've put everything from metals including silver (for antimicrobial properties) all the way to ceramics (for all sorts of fun things) into PET products. Then you have not only the characteristics of the polymer and the additives that are "bound" within the physical structure, but whatever "finishes" you might apply to the surface for both product attribute and manufacturing performance. You wouldn't (generally) use the same PET polymer for textiles that you would for bottle resin that you would for films.
tl;dr - I'd rather go by how something performs on the spec sheet vs. "Polypropylene > PET > Mylar > Polyethylene > Magic Widget dust" as generalizations. I'd generally trust the manufacturers to post relevant and accurate specs for the products they sell, and for the engineers to choose the correct part for the application. Myself, I don't even know how capacitors actually work, and I only barely understand what they do. So I wouldn't have the foggiest idea what the best material choice might be.
Sorry to be of so little help. I know the materials themselves very well, but I know nothing about suitability or even relative performance differences for use as the dielectric material in a capacitor or what specs re: the polymers actually "matter" in this application.
Complete guesswork... but I'd imagine that within the "PET family" of choices available to the capacitor manufacturers; many choices are made for manufacturability vs. performance of the final product or some compromise. Some wonderfully performing materials can be a total PITA to work with in automated industrial settings.
More trivia than useful information. But it may sate a bit of your curiosity.
It seems marketing takes over at some point. With the technical expertise I've seen that you have - I'd go by spec sheets for the specific part vs. a generalization in hierarchy of materials. As an example, my previous company made over 50 unique PETs that were ongoing SKUs, and I did R&D on many, many more. Not all PET is created equal. Metallized polyester... well, I dunno? I've put everything from metals including silver (for antimicrobial properties) all the way to ceramics (for all sorts of fun things) into PET products. Then you have not only the characteristics of the polymer and the additives that are "bound" within the physical structure, but whatever "finishes" you might apply to the surface for both product attribute and manufacturing performance. You wouldn't (generally) use the same PET polymer for textiles that you would for bottle resin that you would for films.
tl;dr - I'd rather go by how something performs on the spec sheet vs. "Polypropylene > PET > Mylar > Polyethylene > Magic Widget dust" as generalizations. I'd generally trust the manufacturers to post relevant and accurate specs for the products they sell, and for the engineers to choose the correct part for the application. Myself, I don't even know how capacitors actually work, and I only barely understand what they do. So I wouldn't have the foggiest idea what the best material choice might be.
Sorry to be of so little help. I know the materials themselves very well, but I know nothing about suitability or even relative performance differences for use as the dielectric material in a capacitor or what specs re: the polymers actually "matter" in this application.
Complete guesswork... but I'd imagine that within the "PET family" of choices available to the capacitor manufacturers; many choices are made for manufacturability vs. performance of the final product or some compromise. Some wonderfully performing materials can be a total PITA to work with in automated industrial settings.
More trivia than useful information. But it may sate a bit of your curiosity.
The short answer is yes, that resistor sets the gain.
The long answer:
Gain is R13/R10. R10 is 22R. 2k/22R = 90. Not a good idea.
Something in the 500-1K range would be better. Or try paralleling the 2K to make 1K. Even then you have altered the circuit and it may become unstable (and likely sound worse since you are effecting the degeneration I am guessing) Also, watch the dissipation on R13.
Ok. I can get my hands on some 1K resistors. If I just swapped them with the stock R13, would I need to re-bias the circuit or it’s a straight swap and plug in my F4?
Listening to the F4 and BA3 now with the stock 220 ohm resistors. It’s a great combination but needs a tad more headroom as max volume is a little over my normal listening level. . I’m thinking just swap R13 with 500 ohm as 10db more may be all I need.
Can anyone else comment on their R13 size for F4?
Can anyone else comment on their R13 size for F4?
I am totally new to diyaudio and attempting to do an F6 with BA-3 pre build. My head is swimming with 400+ ages of forum threads but want to especially give a shout out to 6l6 for all his work that gets somebody like me going. And all the others. My question is, I expect to make mistakes and don't want to trash my small hoard of matched Toshibas so am looking for suggestions for relatively inexpensive and replaceable JFETS that I can use to debug the boards. Then when I get things right I will remove them and replace with the Toshibas. Obviously it helps me if I don't have to make other board changes to go from one set to another. Thanks for any help and advice.
I don't know what debugging you could do with different transistors in there. You could always leave them out until you're sure everything else is verified to be correct. Really all you can do wrong in this simple build is get the orientation of the JFETS/MOSFETS backward, which is a common mistake.
I finally got around to experimenting with the BA-3 and O2 combo. As you suggested I lifted the O2's hi-gain resistors for unity gain, and put it on the BA-3's output. I actually have a second O2 so I connected that one to the source, and went back and forth with several kinds of music.
In the end, the BA-3 with the O2 as a buffer sounded superior, with deeper, tighter bass and better sense of space. I added a parallel set of output jacks to the BA-3 and now have the O2 (desktop version) permanently connected. No more pulling plugs for headphone usage.
