Tube vs. Solid State Preamp
in [Design]
|
Prev: How do you call
Next: Internet via Cellular
From: Jim Thompson on 1 Apr 2010 18:34 On Thu, 01 Apr 2010 11:35:25 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Jim Thompson wrote: >> On Thu, 01 Apr 2010 10:30:26 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> Jim Thompson 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. ... >>> >>> Well, that can most certainly be arranged: >>> >>> http://ixbtlabs.com/articles2/aopentube/ >> >> That's just plain dumb audiphoollery. >> > >But it'll sure turn some heads during a party :-) > >>> >>> I've actually made a very HV transistor by >>>> using a tube with a grounded grid and an NPN in the cathode path. >> >> I needed a 1000V device with characteristic curves much like an ideal >> CMOS transistor... no ability to get feedback in there. Piece-a-cake >> with an NPN in the cathode circuit of a pentode (with local feedback). >> > >1kV is a white knuckle ride with most tubes unless you use a ballast >triode or something. Although most tubes will stomach the voltage even >if the abs max says 700V or 800V. It was a HV shunt regulator. I'm trying to find the original paperwork, but the tube was quite happy. > > >>>> 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. >>> >>> >>>> 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 ;-) >>>> >>> That I don't remember. I'm not _that_ old :-)) >> >> Yeah, You are! You just don't admit it :-) >> > >But it was you who called me young buck and yourself old buck :-) I'm just yanking your chain :-) ...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: Jim Thompson on 1 Apr 2010 18:35 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. ...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: Phil Hobbs on 1 Apr 2010 18:36 On 4/1/2010 2:11 PM, Tim Williams wrote: > "Phil Hobbs"<pcdhSpamMeSenseless(a)electrooptical.net> wrote in message > news:4BB4AA5D.4060007(a)electrooptical.net... >>> ....I had wonderd if a device using positive ions might work... >> >> The mass ratio between even a proton and an electron is about 1800:1, >> which makes holes in silicon look very speedy! > > I'm going to have to make one, if I ever get access to the equipment (and > glassblowing expertise!) to do it. > > There's something fundamentally wrong about making a tube with gas, though. > It can work, but it can't work very well. It's very difficult to pump the > electrode section low enough so that it's only ions, no electrons and > definitely no secondary ionization taking place. And as soon as those ions > hit the plate (= cathode), they become hydrogen again. The plate material > has to resist atomic hydrogen, which is rather acidic (literally, 100% > Bronstead-Lowry acid). Plus, ions carry enough momentum to sputter the > cathode, which is even worse. > > Even if your P-tube has a tranconductance ~2000 times lower than a 12AX7 > (i.e., about 1umho), it's worth considering because hey, a current mirror is > a current mirror. > > Tim > one possibility would be a gallium field emitter, as used in focused ion beam milling machines--you make a needle with a dimple in the end, and the electric field pulls it into an atomically-sharp point. A very cool demonstration of electrostatics! Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: Tim Williams on 1 Apr 2010 18:49 "Phil Hobbs" <pcdhSpamMeSenseless(a)electrooptical.net> wrote in message news:4BB51FFB.40407(a)electrooptical.net... > one possibility would be a gallium field emitter, as used in focused ion > beam milling machines--you make a needle with a dimple in the end, and the > electric field pulls it into an atomically-sharp point. A very cool > demonstration of electrostatics! Oh yeah, those are neat! Gallium ions would be even lower 'mobility' though (or since it's ballistic rather than resistive trajectory, should that be 'ballisticity'?). What happens when it runs out, though? I've got 12AX7s that have conducted more than a few farads of charge. Eventually you get a cathode spattered with gallium (or amorphosized with gallium deposition competing with sputtered substrate). Just let it drip to the bottom like the old mercury toobs? What's the vapor pressure of molten gallium, anyway? Lesse, 'Pedia says 1Pa at 1310K... probably not a big deal at 25C. Actual operating temperature could be high or low, depending on how you seal the thing... if you build it like an ordinary tube and dissipate real power, it could get quite hot. Or you could make it like a TO-247 with a small bell jar, keeping the cathode arbitrarily cold. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: Jim Thompson on 1 Apr 2010 18:53
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. >>> >>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 :-( ...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 |