Tube vs. Solid State Preamp
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From: VWWall on 1 Apr 2010 21:01 Jim Thompson wrote: > On Thu, 01 Apr 2010 14:48:57 -0700, John Larkin > <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >> On Thu, 01 Apr 2010 14:34:37 -0700, VWWall <vwall(a)large.invalid> >> wrote: >> >>> Joerg wrote: >>>> Jim Thompson wrote: >>>>> Size? Ever see a Nuvistor ?:-) >>>>> >>>> Yup, used them. In fact, one of my RF tools here (a dipmeter) has one in >>>> there except they called them acorn tube in them's days. >>>> I just looked at a grid-dip meter I built about fifty years ago. It used a 9002 triode and could oscillate up to 250 MHz. I think the selenium rectifier has gone west or it may just be the resistor line cord which dropped the line to heater voltage. Might be worth rebuilding! >>> Acorn tubes and Nuvistors were very different things. Acron tubes were >>> used in a direction finder loop pre-amp that I used in the U. S. Army >>> Signal Corps in 1943-1945 in North Africa and Italy. They were 954 and >>> 955, glass envelope tubes with element connections out the side and top. >>> They *were* in the shape of acorns. >> Here's one: >> >> ftp://jjlarkin.lmi.net/Acorn.JPG >> >> I have some nuvistors around here somewhere too. They're not as >> pretty... metal cans that look a lot like an overgrown TO-5 >> transistor. >> >> John >> > > See... > > http://analog-innovations.com/SED/Nuvistor.JPG > > 0.2" Grid. > > (Gotta work on my lighting techniques :-( Looks great. I assume this is with a digital camera. My last serious photography was with a 4 X 5 Speed Graphic. This whole thing is worth a read: http://www.smecc.org/creative_thinking_-_john_r__pierce.htm "Another example is provided by the development of the 416A triode. The original and startling germ of a creative idea was that after all these years a triode might still be the best amplifier for microwaves, if only the spacing were close enough and the grid fine enough. An auxiliary idea was that close enough spacings could be attained and held by grinding the cathode and a surrounding ceramic co-planar, and then supporting the grid from the ceramic. These were, however, mere germs of an idea. Something real and complete was brought into existence only after years of concentrated effort, including the inauguration of a program of cathode studies which is still being pursued for other purposes." I knew John Pierce at Bell Labs. When he needed a little more money for a vacation trip, he'd whip up a science fiction story for Amazing Stories, writing as J. J. Coupling. -- Virg Wall
From: Jim Thompson on 1 Apr 2010 21:35 On Thu, 01 Apr 2010 17:40:14 -0700, VWWall <vwall(a)large.invalid> wrote: >Jim Thompson wrote: >> On Thu, 01 Apr 2010 14:34:37 -0700, VWWall <vwall(a)large.invalid> >> wrote: >> >>> Joerg wrote: >>>> Jim Thompson wrote: >>>>> Size? Ever see a Nuvistor ?:-) >>>>> >>>> Yup, used them. In fact, one of my RF tools here (a dipmeter) has one in >>>> there except they called them acorn tube in them's days. >>>> >>> Acorn tubes and Nuvistors were very different things. Acron tubes were >>> used in a direction finder loop pre-amp that I used in the U. S. Army >>> Signal Corps in 1943-1945 in North Africa and Italy. They were 954 and >>> 955, glass envelope tubes with element connections out the side and top. >>> They *were* in the shape of acorns. >>>>> 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 ;-) >>>>> >>> A Nuvister was a small ceramic vacuum tube. The last one I saw was used >>> in my garage door opener receiver. When it failed, I couldn't find a >>> replacement and had to replace the whole receiver with a transistorized one. >>>> That I don't remember. I'm not _that_ old :-)) >>>> >>> I was at Bell Labs when transistors were young, and have taught >>> transistor electronics at UCLA Extension, but most of my career has >>> included vacuum tubes from magnetrons to traveling wave tubes. >>> >>> I'm older than either of you! :-( >> >> Not by much! IIRC you said something like 74?? I'm 70. >> >How old do you think I was when being shot at in North Africa with the >Signal Corps? I did enlist at seventeen, but that was almost 70 years ago. > >My brother's 15 months younger, and lives in Scottsdale. He owned the >Ethan Allen furniture store in Phoenix and Mesa. Have we ever met? You name sure sounds familiar. What company halls have you "haunted" ?:-) I did Motorola SPD, Philco Ford (Santa Clara), Dickson Electronics and GenRad (Phoenix), besides being independent for 37 years. ...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
From: Robert Baer on 2 Apr 2010 17:52 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? > > John > Never bothered to measure; lack of proper equipment for starters - but seems to be a heck of a lot lower than common commercial tube stuff ("heck of a lot lower" naturally is a highly technical term).
From: Robert Baer on 2 Apr 2010 17:59 Chris wrote: > On Mar 31, 2:45 pm, Robert Baer <robertb...(a)localnet.com> wrote: >> Jim Thompson wrote: >>> On Tue, 30 Mar 2010 10:41:07 -0700, Joerg <inva...(a)invalid.invalid> >>> wrote: >>>> Jim Thompson wrote: >>>>> On Tue, 30 Mar 2010 09:49:03 -0700, Joerg <inva...(a)invalid.invalid> >>>>> wrote: >>>>>> John Larkin wrote: >>>>>>> On Tue, 30 Mar 2010 08:56:08 -0700 (PDT), Chris >>>>>>> <christopher.man...(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? >>>>>> Sure, but it will be shunned by tube-freaks :-) >>>>>>>> I am thinking about building a preamp. >>>>>>>> Thanks, >>>>>>>> Chris >>>>>>> Tubes are noisy. >>>>>> Not at all. I remember when I was young and those super low noise RF >>>>>> FETs came out. Everyone (who had the dough to buy those) jumped on them, >>>>>> only to find out that the old nuvistor preamp was in about the same >>>>>> ballpark noisewise but had a dynamic range from here to the Klondike >>>>>> while them thar newfangled trainsistahs didn't. >>>>> If you know how to bias BJT's for low noise, you can make phenomenally >>>>> low audio noise preamp's. >>>>> Sheeesh! Back when I was a kid I could make a reasonably low noise >>>>> preamp with Ge devices... low current and low VCE. >>>> When I was a kid that wasn't needed. The "lowest noise" audio source >>>> were 45rpm records and even that didn't matter. Because in our time it >>>> was all rock music. The louder the better. So the race was on who could >>>> build the biggest honking amplifier. My limit was reached when the >>>> breaker on a typical European 230V/16A circuit would trip off upon a >>>> heavy-handed twang on the electric guitar :-) >>> You're still a kid :-) >>> My record for a solid-state amplifier is 400W (RMS, sustained, fan on >>> a heat-sink "tunnel" :-) >>> ...Jim Thompson >> A lot better than my record for a tube amp at 100W RMS sustained, >> with total hum and noise under -60dBmW. >> Do not remember how far down it was, but cranked up all the way it >> made no difference open input or shorted input, one could not hear noise >> and/or hum with ear right at speaker. > > Do you still have the schematic of your amp? Also, did it have a mic > level pre? or just a line level input? > > Chris It was line level; schematic gone - it was made over 45 years ago using midnite requisition military parts. One of the tricks was the filaments were run from a DC supply, another was all power was regulated in a different chassis (no AC to amplifier); the only commercial part was the Dyanaco output transformer made for a part-Williamnson, part cathode feedback circuit. Push pull parallel KT66 (i think), plate supply used a cascode regulator with regulation about 1v no load to 0.5A full load (??350V??).
From: JosephKK on 2 Apr 2010 08:05
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. |