Tube vs. Solid State Preamp
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From: Chris on 30 Mar 2010 17:56 On Mar 30, 2:12 pm, Chris <christopher.man...(a)gmail.com> wrote: > On Mar 30, 12:39 pm, ehsjr <eh...(a)nospamverizon.net> wrote: > > > > > Joerg 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 :-) > > > A twang filter! :-) > > I went down to guitar center, and found that they don't actually sell > solid state pre amps. I picked up a cheap one -- 12AX7 pre -- as I > found that it had a fairly low noise floor. I am not trying to go > high end, I just wanted something that was markedly quieter than the > stock pre amp on the digital voice recorder. The nice thing is now I > have manual gain control, and the line level input on the digital > voice recorder does not have AGC which is a good thing. I hate that > pumping sound from the AGC. > > Thanks, > Chris Maness Here is a sample of the audio. http://podcast.rccoc.org/podcasts/100330_010.mp3 Chris
From: John Larkin on 30 Mar 2010 18:14 On Tue, 30 Mar 2010 09:49:03 -0700, Joerg <invalid(a)invalid.invalid> 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? >>> > >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. Well, now RF fets can hit noise temperatures around 40K. Try that with a tube. I think a good tube runs in the ballpark of 10 nV/rthz voltage noise at audio frequencies. A good opamp or a discrete jfet can hit 0.8. John
From: Joerg on 30 Mar 2010 18:40 John Larkin wrote: > On Tue, 30 Mar 2010 09:49:03 -0700, Joerg <invalid(a)invalid.invalid> > 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? >>>> >> 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. > > Well, now RF fets can hit noise temperatures around 40K. Try that with > a tube. > > I think a good tube runs in the ballpark of 10 nV/rthz voltage noise > at audio frequencies. A good opamp or a discrete jfet can hit 0.8. > Nah, the good old PCC88 can compete when using both triodes in there in parallel, around 1.5nv/rtHz at audio. With pentodes configured as triode you could supposedly get even lower but I've never tried that. http://www.r-type.org/pdfs/pcc88.pdf The German text in there is rather funny. For "low noise" they use the expression "niedriges Geraeusch". That words normally describes a noise such as the squeal of a bearing that's about to go bad. Of course, you won't get an energy start rating for an amplifier with one of those. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Adrian Tuddenham on 30 Mar 2010 18:47 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. You may have difficulty beating the L.F. noise level of Nuvistors with any normal solid state device, but above 1Kc/s there are many solid state devices that are as good as the best valves. The circuit design is critically important, especially the method of matching the input impedance to the source impedance. If you throw away signal at that point, no first stage valve or transistor, however exotic, will achieve the best S/N ratio. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
From: Tim Williams on 30 Mar 2010 20:12
"Joerg" <invalid(a)invalid.invalid> wrote in message news:81fcueF1c9U1(a)mid.individual.net... > Nah, the good old PCC88 can compete when using both triodes in there in > parallel, around 1.5nv/rtHz at audio. With pentodes configured as triode > you could supposedly get even lower but I've never tried that. .... > Of course, you won't get an energy start rating for an amplifier with one > of those. Why not? They're 100% efficient space heaters. That's as efficient as it gets, riiiight? http://www.thevalvepage.com/testeq/tek/545a/545a.htm Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms |