Bcarso, Rbb' is not a normally specified parameter, except when it is ultra low.
I first discovered low Rbb' bipolar devices in 1968, with the introduction of the 2N4401,3,5 series of bipolar transistors from Motorola, but it was NOT on the spec. sheet. I found them by using a QuanTech noise analyzer, and testing with a shorted input and about 3 ma current. This allowed for design of practical transformer eliminators, or pre-preamps for MC cartridges.
Over the years, the Japanese improved on these devices and made a number of ultra low Rbb' complementary devices, about 10 years after Motorola made their 2N440- series, dropping effective Rbb' from perhaps 35 ohms to about 3 ohms. Quite an improvement of about 10dB in potential noise.
Other devices have low Rbb', both American and European, but it is important that the devices are made by a low noise processing facility, so that the 1/f noise is kept at a minimum.
I first discovered low Rbb' bipolar devices in 1968, with the introduction of the 2N4401,3,5 series of bipolar transistors from Motorola, but it was NOT on the spec. sheet. I found them by using a QuanTech noise analyzer, and testing with a shorted input and about 3 ma current. This allowed for design of practical transformer eliminators, or pre-preamps for MC cartridges.
Over the years, the Japanese improved on these devices and made a number of ultra low Rbb' complementary devices, about 10 years after Motorola made their 2N440- series, dropping effective Rbb' from perhaps 35 ohms to about 3 ohms. Quite an improvement of about 10dB in potential noise.
Other devices have low Rbb', both American and European, but it is important that the devices are made by a low noise processing facility, so that the 1/f noise is kept at a minimum.
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It seemed logical to me to have at least a two source selector, probably because I use only two sources, my FM tuner and my CD player. Yeah, it costs that one extra French made Apem switch, but what the hell.
Given the very powerful output stage, again, it seemed logical to include a Line Out par of jacks. Assuming a low power amp imput impedance of just say 10k (which is realistically too low), and a pair of headphones of say 30 Ohms, the composite impedance the amp would have to face is around 29 Ohms, of no consequence, since it was initially developed to be able to drive the Big Daddy of all headphones, the Beyer 48A.
These are said to be the best headphones ever made (though you'd never guess from their specifications), designed by the founder of Beyerdynamics, Herr Eugen Beyer, circa 1937, and used throughout Europe for all sorts of lab measurements. They are supplied by Beyer themselves only, and with no termination - you solder in the plug you need. Their only real caveat - impedance is 5 Ohms. A bitch to drive if you are a headbanger. Take a peek here: beyerdynamic DT 48 E - Studio Headphones - Studio & Stage - Headphones & Headsets - Headphones & Headsets
I have not heard them, but I've been told that until you do, you don't really know what headphones can do for you. So, just in case, I planned for them as well.
To now implement John's last sentence, I'll state the obvious: not all low noise transistors, even when marked the same, are actually the same.
If you are after very low noise complementary trannies, BC 550/560 B (NPN/PNP) are a GREAT choices provided you can find them made by Siemens, Telefunken (a chapter of Siemens) or Philips.
My beloved Motorola is also good, but not as good as usually, their noise is not up to the originals.
Worst of all, there seems to be an inexhaustable supply of Chinese junk trannies marked as low noise transistors, when in fact they are anything but.
At just under 3dB noise figure for a 500 Ohm source impedance, it does not look that good. Very few manu will put accurate ultra low noise plots on the ds.
EDIT - Checked the On-Semi ds the rbb is 160 Ohms or so, not low noise by any measure.
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You should indeed. I think you might be surprised at what you would be hearing.
Set the budget as per the level of your headphone love, the more you love them, the bigger the budget. If you're going to do it, hog it, go to the hilt, or don't bother, mediocre junk is available at similar prices on the Internet.
Just my 2 cents' worth.
Good comment - thank you.
As I said, I have NOT heard them (heck, I haven't even seen them!), all I have is second hand info.
hearing changes with age. Some people develop "gaps" in their hearing that might be compensated by certain headphones response.
Or it's just a matter of taste - some like hot foods, some hate them, some like peanut butter, some feel like barf it (me).
I could find only the Senn HD598 to compare with Grado SR60. The tests look like below. not a huge difference, SR60 display some higher levels in the treble department compared with Senn.
Or it's just a matter of taste - some like hot foods, some hate them, some like peanut butter, some feel like barf it (me).
I could find only the Senn HD598 to compare with Grado SR60. The tests look like below. not a huge difference, SR60 display some higher levels in the treble department compared with Senn.
Attachments
My friend Ben G. at my suggestion bought a bunch of the discontinued Toshiba super-low-rbb' parts for a discrete opamp project. He sold me a couple bags of them. These are the 2SA1316 and 2SC3329. Rbb' is listed as 2 ohms at 1mA (of course the number is only slightly operating-point dependent). I don't believe he completed that project and I may make him an offer for the rest of them, as they seem now to be quite scarce.
IIRC the parts inside Scott's AD797 are around 6 ohms?
Of course, what am I going to do with these anyway? Other than for personal use, what wild and crazy design would be viable in the market, and of what? I told Wes Dooley that I'd contemplated a direct ribbon mic preamp, and he said Oh yeah people keep saying they are going to do that but it never happens. Of course this would require heroic efforts to achieve a <3 dB noise figure from a <1 ohm load, lots of current in paralleled devices, but it does sound like fun. Of course Wes assured me that their transformers work just fine, but as I remarked to SY we don't do this stuff because it's practical, but more because, like a mountain, it's there.
Now the real challenge would be to do this with phantom power
Brad
IIRC the parts inside Scott's AD797 are around 6 ohms?
Of course, what am I going to do with these anyway? Other than for personal use, what wild and crazy design would be viable in the market, and of what? I told Wes Dooley that I'd contemplated a direct ribbon mic preamp, and he said Oh yeah people keep saying they are going to do that but it never happens. Of course this would require heroic efforts to achieve a <3 dB noise figure from a <1 ohm load
, lots of current in paralleled devices, but it does sound like fun. Of course Wes assured me that their transformers work just fine, but as I remarked to SY we don't do this stuff because it's practical, but more because, like a mountain, it's there.Now the real challenge would be to do this with phantom power
Brad
Very true.
I go and have my ears checked out every year. Last year, my upper limit was 16 kHz, and only two years before that, it was 18 kHz. It's a fact of life we all have to put up with. In my case, part of the reason are my inflamed sinuses, which have now settled down, after I purchased and used a Rainbow air filter. Out here, environmental issues don't even exist, except as a nice mention in election campaigns.
Regarding the two plots, although they look fairly similar, in real life the Senn sounds a lot better than the SR60, and that's not just my opinion. Admittedly, they also cost a lot more than SR60, at least locally.
No, that's p**s-poor. Funny to see all those old datasheets talking about "low noise", dating from the days when people were limited to (or thought they were limited to) highish impedances, thus prized high beta.
Of course JFETs were usually cornering at rather high frequencies then as well.
I had a guy who was a o.k. intuitive engineer (BA in music but a ham enthusiast etc.) but who had limited understanding of transistors and noise, and who worked for aerospace circa 1975, in its proverbial "heyday", tell me that I couldn't possibly expect to design anything better than the integrated circuits that he was being showered with samples of in hopes that they'd be specified for war and spacecraft toys. He was trying to get me to try an OP07 as a charge preamp for a capacitive detector, and I told him it was entirely unsuitable. "How can you say that??!! These ICs are designed by PEE AICH DEES!!!" (of course most of the time they are not, but you get his drift. Not that I have anything against people with advanced degrees).
I should have thrown him out of my office at that point, but I suffered fools more gladly then. I did accept a sample of the highest-grade ceramic package -07, and managed to use it somewhere, I recall as some sort of bias source
SoNic, thanks for the graphs, they speak volumes to me. Especially the ~2KHz bump and dip, which is probably key in what I like. The Senns' response likely just fits my ears and ear canals better than the Grados. The upper grunge of the Grados may also have bothered me, hard to say. Those graphs show a very strong correlation of SQ vs Measurements to me.
FWIW, I use a lot of Sony closed back headphones at work which I find have a nice midrange but lack low end. Fine for the monitoring I have to do. Ultrasone is also rather nice.
FWIW, I use a lot of Sony closed back headphones at work which I find have a nice midrange but lack low end. Fine for the monitoring I have to do. Ultrasone is also rather nice.
Last year I did a check up nad "clean" my ears of wax and I was amazed of the improvement. Better than other hardware modes to my players
I might like my music "spicy" and you "mild"
Nothing wrong with that. Maybe, due to my aged ears, the high-end (10-16kHz) profile is exactly what I need - I usually listen without any tone controls. I know that now I can't hear nothing past 17kHz... when i was 18 I tested myself and could hear 21kHz.
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It would be nice if someone did a survey of modern devices for noise. Absent some good work on JFETs recently by Scott W., others with access to Quantechs could do a great service to us all. The old Motchenbacher data, already limited and accompanied by plenty of caveats, was merely reprinted in the newer book with Connelly and is sadly out-of-date.
And of course with counterfeit parts and their ilk, you are, as the preacher says to Sheriff Bart in Blazing Saddles, "on your own".
And of course with counterfeit parts and their ilk, you are, as the preacher says to Sheriff Bart in Blazing Saddles, "on your own".
Last year I did a check up nad "clean" my ears of wax and I was amazed of the improvement. Better than other hardware modes to my players
I might like my music "spicy" and you "mild"
My dear fellow, I clean my ears with cotton swabs each and every morning. And wonder which idiot started the Chinese rumour that this could damage your ears ...
Of course it can if you stick the swab in forcefully, but trust me on this, you'd be feeling some nice, undistorted pain with all its harmonics long before you damaged your ear drums.
And I'm anything but "mild". How mild is a guy who at every moment has in his shoulder bag his "survival kit", consisting of a small can of Nescafe (so I can turn your western black water into actual coffee) and a bottle of Tabasco (by far the greatest American invention after the light bulb, it helps me turn your western mush into something that actually has taste)?
To be fair, USA is still not completely lost, not until it has Cajun food. I thrive on it.
And if anyone starts mentioning French baguette, or Danish muffins, I tell you in all sincerity - the bakers of Europe are Germans. Check it out in Munich, around 9 AM. German national cuisine is far too little known and is far too stereotyped to sauerkraut und wurst .
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The cotton swabs push the wax deeper inside the ear channel and makes a nice packed plug. I did found out that the hard way when I was 30 year old. Vax is supposed to be on sides, not on the eardrum. Also the ear hair cells don't like to be forced rubbed with a swab.
Now I know better. Your milage might vary, since your ears are not the same as mine.
Now I know better. Your milage might vary, since your ears are not the same as mine.
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