Tube vs. Solid State Preamp
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From: krw on 3 Apr 2010 15:47 On Sat, 03 Apr 2010 15:28:39 -0400, "Michael A. Terrell" <mike.terrell(a)earthlink.net> 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. > > > No, it was usually on an unused mic input, where someone forgot to >screw the shorting cap back on. That was one of the reasons that >Switchcraft developed the shorting version of their 2501 series chassis >mount connector. The problems (with phones, too) I've found were lousy connections.
From: Joerg on 3 Apr 2010 16:48 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. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Michael A. Terrell on 3 Apr 2010 17:35 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? Any AM detector can demodulate FM via 'Slope Detection'. -- Lead free solder is Belgium's version of 'Hold my beer and watch this!'
From: Michael A. Terrell on 3 Apr 2010 17:37 "krw(a)att.bizzzzzzzzzzzz" wrote: > > On Sat, 03 Apr 2010 15:28:39 -0400, "Michael A. Terrell" > <mike.terrell(a)earthlink.net> 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. > > > > > > No, it was usually on an unused mic input, where someone forgot to > >screw the shorting cap back on. That was one of the reasons that > >Switchcraft developed the shorting version of their 2501 series chassis > >mount connector. > > The problems (with phones, too) I've found were lousy connections. Early tube audio amps were high impedance and unbalanced inputs, which made them easy to disturb. Kind of like Phil or dimbulb. -- Lead free solder is Belgium's version of 'Hold my beer and watch this!'
From: Jim Thompson on 3 Apr 2010 18:39
On Sat, 03 Apr 2010 09:40:25 -0700, Joerg <invalid(a)invalid.invalid> 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. Welcome to America :-( ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy |