Tube vs. Solid State Preamp
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From: Robert Baer on 3 Apr 2010 13:16 JosephKK wrote: > On Wed, 31 Mar 2010 19:28:24 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: > >> On Wed, 31 Mar 2010 18:04:35 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> John Larkin wrote: >>>> On Wed, 31 Mar 2010 13:36:54 -0800, Robert Baer >>>> <robertbaer(a)localnet.com> wrote: >>>> >>>>> John Larkin wrote: >>>>>> On Tue, 30 Mar 2010 08:56:08 -0700 (PDT), Chris >>>>>> <christopher.maness(a)gmail.com> wrote: >>>>>> >>>>>>> With today's modern technology, is it possible to make a solid state >>>>>>> preamp that is as quiet as a good tube pre? >>>>>>> >>>>>>> I am thinking about building a preamp. >>>>>>> >>>>>>> Thanks, >>>>>>> Chris >>>>>> Tubes are noisy. >>>>>> >>>>>> John >>>>>> >>>>> Try running a 12AU7 with a plate supply of 45V and grid-to-cathode >>>>> voltage of about -1.5V (tweaked for zero grid current). >>>> What are the voltage and current noise densities? >>>> >>> Don't know about the 12AU7 but the 7788 or in civilian E810F could get >>> to around 1nv/rtHz when rigged as a triode (it wants to be a pentode in >>> normal life). >>> >>> I wish Sovtek, Svetlana or one of those companies would make it. In an >>> environment where a big zap to an input is sort of normal these are >>> really useful. Even a real zinger with a blue flash inside the glass and >>> an audible pop typically leaves a tube unfazed. >> We've sort of shot ourselves in the foot with our desire to get >> everything on a single chip... >> >> I'm often puzzled why a hybrid... tubes plus transistors... wouldn't >> be the nicest solution. I've actually made a very HV transistor by >> using a tube with a grounded grid and an NPN in the cathode path. >> >> Size? Ever see a Nuvistor ?:-) >> >> And I can't remember what they were called... a stack of ceramic >> spacers and metal grids... really small. One jokester had the >> "heater" from a blowtorch ;-) >> >> ...Jim Thompson > > I remember a construction like that but it was not small. > Called a lighthouse tube, maybe 2" dia and 4" long. "TIMM"s, i think.
From: Michael A. Terrell on 3 Apr 2010 00:45 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. -- Lead free solder is Belgium's version of 'Hold my beer and watch this!'
From: Paul Keinanen on 3 Apr 2010 02:30 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.
From: krw on 3 Apr 2010 11:54 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.
From: Joerg on 3 Apr 2010 12:40
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. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |