Tube vs. Solid State Preamp
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From: Paul Keinanen on 4 Apr 2010 01:54 On Sat, 03 Apr 2010 15:44:45 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >You really need to move to a better neighbourhood. BTW a Finnish friend >of my daughter's (the friend lives in Olu--they met at school in France) >says that during the Winter War, the Finnish government essentially put >the whole adult population on methamphetamine to increase production, >and then cut off the supply cold turkey when the war was over. > >Is that so? Pervitin was administrated to ski/foot patrols operating behind enemy lines http://en.wikipedia.org/wiki/LRRP in the Winter and Continuation war, typically a week at a time. Pervitin was also administered to ordinary ground troops during the massive Russian assault in 1944. I have never heard of any wide spread use of Pervitin by civilians. A massive use of Pervitin would have created a large post war drug problem, however, immediately after the war, the most addicts were due to morphine, which was available without descriptions in the 1920-30's and the use in military hospitals during the wars. BTW, the city is Oulu (not Olu) at 65N at the Bay of Bothnia.
From: Tim Williams on 4 Apr 2010 04:02 <krw(a)att.bizzzzzzzzzzzz> wrote in message news:af6fr5t6iteeoe96r189559vusg7vmco6i(a)4ax.com... > FM wouldn't be as obvious. Wouldn't FM just put a DC bias on the mic > circuit? At school, the school radio station gets into everything. Part of this is because the antenna is on top of the dorms, and who knows, maybe they don't have it tuned very well and it's putting out some AM as it is. But I've been told it's more likely due to multipath, e.g. by reflecting off the building across the street. I installed ferrite beads and ceramic caps. My stereo is now quieter than anyone else's at the school. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: Joerg on 4 Apr 2010 15:44 Michael A. Terrell wrote: > Joerg wrote: >> Michael A. Terrell wrote: >>> Joerg wrote: >>>> krw(a)att.bizzzzzzzzzzzz wrote: >>>>> On Sat, 03 Apr 2010 12:22:27 -0700, Joerg <invalid(a)invalid.invalid> wrote: >>>>> >>>>>> krw(a)att.bizzzzzzzzzzzz wrote: >>>>>>> On Sat, 03 Apr 2010 00:45:27 -0400, "Michael A. Terrell" >>>>>>> <mike.terrell(a)earthlink.net> wrote: >>>>>>> >>>>>>>> Jim Thompson wrote: >>>>>>>>> But they _do_ rectify... just not as efficiently. >>>>>>>> I've seen quite a few tube PA amps that picked up CB radio, and >>>>>>>> police radios into the UHF Mobile band. Some small churches freaked out >>>>>>>> when a police call came through the speakers, at full volume during a >>>>>>>> church service. >>>>>>> Probably not the tube doing the rectification, though. Usually a corroded >>>>>>> wire/contact in a mic was the culprit. >>>>>> Depending on the sermon topic and the nature of that police call it >>>>>> could be a fitting reminder of the consequences of sin :-) >>>>> For communion do you serve coffee and doughnuts? ;-) >>>>> >>>> No, those are for _after_ worship services, even for deputy sheriffs in >>>> attendance :-) >>>> >>>>>> But FM rarely gets in. AM radio from low flying aircraft is another >>>>>> matter. Ham radio as well but since they use SSB most of the time that >>>>>> will sound more like Charlie Brown's teacher ... wah-wa-waah ... >>>>>> ouuah-wah-wah-waaah. >>>>> FM wouldn't be as obvious. Wouldn't FM just put a DC bias on the mic circuit? >>>> Yes, that's why I don't quite understand how police radio could have >>>> gotten in there unless it was through a wireless mike link. >>> >>> How many wireless mikes did you see in small churches in the '50s >>> trough the '70s? >>> >> You hadn't said 70's but I did see wireless mikes back then. Here I must >> confess that I rarely went to church in those days. But we used them at >> school events, at the town hall, and so on. Once as a kid I was a helper >> during some council meeting ballot. They handed me a wireless mike to >> announce results. I felt real important when they gave me that thing :-) >> >>> Any AM detector can demodulate FM via 'Slope Detection'. >>> >> ... _if_ there is a rather steep filter in front of it. That would have >> to be a real coincidence. > > > The input is unbalanced, and not dressed for RF, so it will do slope > detection. I used to put a ferrite bead and a 100 pf capacitor in old > amps to make a low pass filter to keep all the RF from the usual triode > input stage. A lot of the old amps ran the preamp at full gain, with > the gain control after the triode. Some nasty designs, lifted right out > of the RCA, GE and Sylvania tube handbooks. A 5W VHF or UHF commercial > radio would knock some of them out of service at a quarter mile. > That is sad amplifier design. I never had that happen with tube stuff, ever. Back in Europe I once had the antenna on a balcony, blasting close to 100W FM on 144MHz and the old Sachsenwerk radio was maybe 15ft away from it in the living room, separated just by the glass of a window. It didn't even flinch. Same for other tube radios where the record player inputs are always non-balanced. That's how engineering is supposed to be done. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 4 Apr 2010 15:59 Robert Baer wrote: > Joerg wrote: >> Paul Keinanen wrote: >>> On Fri, 02 Apr 2010 10:51:59 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> The not so good ones usually hum. And badly engineered solid-state >>>> ones (meaning a lot of them) go *POCK* when someone turns on a GSM >>>> cell phone nearby. I am not a tube freak but I've never heard a tube >>>> amp do that, even if the design was a bit screwed up. Because it has >>>> no BE junctions. >>> >>> I have hunted down Radio Moscow from several tube guitar amplifiers. >>> There was a large number of short and medium wave transmitters in the >>> megawatt class across the border. >>> >>> Apparently the pick-up coil inductance and the cable stray capacitance >>> formed a parallel resonant circuit that happened to resonate on one of >>> the numerous high power transmitter. Often a quick fix was to use a >>> different cable with different length, which apparently moved the >>> resonance to a quilter place :-). Adding a resistor and capacitor to >>> the input jack usually solved the problems completely. >>> >> >> Well, in Europe propaganda stations from behind the former iron >> curtain were huge in terms of power. Megawatts. In Germany the problem >> was Radio Tirana. It was sad, they were blowing money on propaganda >> and electricity while their people were barely scraping by and often >> didn't have enough electricity. But that's what such political >> "systems" ultimately do to people. >> > ...just watch OBAMAcare, etc... The newspaper today was quite depressing. It's unfortunately a IMHO left-leaning paper (all we've got out here) but they were surprisingly candid when talking about the consequences of tax increases on existing health plans. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Don Lancaster on 4 Apr 2010 23:38
Michael A. Terrell wrote: > >>> I've seen quite a few tube PA amps that picked up CB radio, and >>> police radios into the UHF Mobile band. Some small churches freaked out >>> when a police call came through the speakers, at full volume during a >>> church service. The original tale was that it was a ham radio operator, and the message said "Seek You the Exit!". -- Many thanks, Don Lancaster voice phone: (928)428-4073 Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 rss: http://www.tinaja.com/whtnu.xml email: don(a)tinaja.com Please visit my GURU's LAIR web site at http://www.tinaja.com |