Tube vs. Solid State Preamp

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

Reply to
Chris
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Tubes are noisy.

John

Reply to
John Larkin

I have a guitar amplifier that is all tube. It is very, very quiet compared to the SS amps in the band. I was assuming that they did not suffer from Nyquest noise like SS amps do. However, we have a Alan and Heath sound board, and those are the best sounding boards I have ever heard. Extremely quiet pre's and warm sounding. So, I guess it is possible with SS.

Thanks, Chris Maness

Reply to
Chris

The difference between shoddy and good can be infinite; any difference between tube and solid state pales in comparison.

Take a smart, dedicated audio circuit designer who _believes_ in solid state electronics, give him a big budget and set him loose. Do the same thing with a similarly smart and dedicated audio circuit designer who _believes_ in tube electronics, give him the same budget, and set him loose. When they're done, the differences will be minor, and hugely different (in both price and sound) from something you buy for $100 from Guitar Center.

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Tim Wescott
Control system and signal processing consulting
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Reply to
Tim Wescott

Sure, but it will be shunned by tube-freaks :-)

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.

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Regards, Joerg

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Joerg

Had not transistors had all of the packaging advantages that they did, and the superlative low-power capability that they did, I don't think they would have gotten as far as fast.

It helped not at all that it took _years_ for people to figure out that the design methodology for good transistor circuits is just plain different from that for tube circuits, which means that it took decades for transistors to get as good as tubes in really high-end equipment.

I think the tube mystique stems from those early days, when it was just plain hard to make good transistorized equipment, and when a lot of transistorized equipment really was cheap crap, because "transistors" and "cheap" go together like "Chevy" and "Vega".

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Tim Wescott
Control system and signal processing consulting
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Reply to
Tim Wescott

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. ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Comparing the best tube amp to the worst (new) FET amp?

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Dirk

http://www.transcendence.me.uk/ - Transcendence UK
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Reply to
Dirk Bruere at NeoPax

The topology of preamps actually hasn't changed much. In the HF range the good ones always had "noiseless" feedback, at VHF and up that's difficult to do.

Tubes still have an edge. For example, when I had a rooftop preamp for ham radio two things happened with the transistorized one (active antenna): Every x-th thunderstorm I had to trudge up a mossy and rain-slickened roof to replace the board. Also, full duplex transmissions were a pain. So I replaced it with a tube amp after I lucked out and got a box of army surplus Radar IF tubes -> Both problems gone, for good. Better IP3 as a bonus. Otherwise same performance.

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Regards, Joerg

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Reply to
Joerg

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 :-)

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Regards, Joerg

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Reply to
Joerg

You're still a kid :-)

My record for a solid-state amplifier is 400W (RMS, sustained, fan on a heat-sink "tunnel" :-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Mine's over a kilowatt. But tubes, plus a humongous circus-speaker.

930VDC plate voltage right on the coil, still getting goose bumps about that one. Back then I vowed to never, ever wind a new coil for a speaker again.

Power was also sustained. Well, until this car with the blue light on top showed up ...

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Regards, Joerg

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Reply to
Joerg

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I have decided my fullcoat deck is a little heavy and touchy for field use, so bought a PCM recorder to record film dialog. It has really good sound when you feed it a hot signal so the thing is running at unity gain. However, when you engage the higher gain settings. It gets VERY noisy. I checked my local guitar center, and they have some fairly cheap models. I will swing buy today, and play with them to see if I get acceptable results. If not, I can just build my own, but for as cheap as these things are, I can definitely try them out.

Regards, Chris Maness

Reply to
Chris

Solid state is more ideal than a tube which is why it generally is not good for our ears. The reason is that when it "fails" it does so harshly. When a tube "fails" it does it in a way that is more musical. What makes a solid state amp more ideal also makes it more problematic for audio.

e.g., when a solid state amp clips it does so very good. In audio though it is not good because the harsh clipping introduces harsh odd harmonics. Hence the reason why tube distortion generally sounds better(which takes the clipping issue to the extreme).

For clean sounds a solid state will generally be better because it is much more linear. But tubes generally add these "soft" distortions(or rather non-linearities) that make the audio more musical.

It really depends on what you are trying to achieve. If you want an uncolored clean signal then solid state is the way to go. If you want distortion then tubes are the way to go. If you want that warm tube sound then obviously tubes are the way to go.

You can approximate tubes with solid state but it's always a "fudge". In any case most people don't have the ears to really tell any substantial difference between clean tube and clean solid.

Reply to
George Jefferson

They usually try to pack high gain, and usually try to get distortion in the guitar amp. I tried to denoise one commercial amp once, but its mostly about having so many circuits in series. Its easy to get a low noise design with simple circuits.

greg

Reply to
GregS

A twang filter! :-)

Reply to
ehsjr

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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

Reply to
Chris

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Chris

Reply to
Chris

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

Reply to
John Larkin

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.

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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.

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Regards, Joerg

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Reply to
Joerg

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