I am generating audio test signals in software and need to raise the soundcard output to 15Vpp. It will provide input for a single stage vacuum tube amp. Can anyone recommend a suitable circuit for this?
Prefer single supply. Output impedance to be less than 10K.
Thanks for any advice.
David
Tricky when +12V is the highest in the PC !
Can you tap into the -12V too ?
Graham
You've almost answered to your question. You need a single power supply AC coupled amplifier. If your PC sound card delivers say 1Vrms, the amplifier must be supplied somewhere about 20Vand have again around 10...11. Any ancient
741 will do it.Vasile
Since you're driving a tube, just slap a transformer on the output of the audio card. Find a transistor radio output transformer, and use it in reverse. The input of a tube is typically high-impedance, so you don't need a lot of amps. (maybe microamps, or milliamps at most, if you're running class B or C.)
Good Luck! Rich
In message , dated Sat, 2 Sep 2006, Rich Grise writes
Rich, you DON'T EVER use Class C in audio, and you don't use Class B in low-level stages.
-- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
How badly do you "prefer" a single supply?
If you must use only a single supply, it will need to be something greater than 15v.
I'm not an expert, but, ONE way you might be able to do it, then, with two opamps, would be to use one opamp to make a sort of power supply "rail splitter", and the other opamp to make an audio amplifier.
The following circuit assumes that the soundcard's output is 2V p-p (+/- 1V). If it's not, then the output amplitude can be adjusted by changing the value of either the 6.49K R or the 1K R that's on the - input of the same opamp. You could make one of them a potentiometer. (>6.49K or
Of course, you could just eliminate that first opamp (and the 1K R on its - input and the 15K R and .01uF C) and connect the junction of the
22K resistors directly to where the opamp's output was connected (and increase the R from the 18v supply's - to GND, to something large, or eliminate it (shorted) if the soundcard's - output doesn't share ground with the 18v supply or the load).- Tom Gootee
In message , dated Sat, 2 Sep 2006, snipped-for-privacy@fullnet.com writes
Clearly. I haven't checked whether your circuit will work or not, but it's far more complicated than necessary.
-- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
If you did keep the first opamp, then the 220uF cap on the output of the second opamp wouldn't be strictly necessary. But if you eliminated the first opamp, then you would have to have the 220uF cap on the output.
- Tom Gootee
It works in Spice.
Simplifications were already noted in a subsequent post.
- Tom Gootee
AAaaaaaaaaarrrggggghhhhhHHHHHHHHHh !
What has the world come to ?
Graham
I KNEW(!), as I typed that, that it would probably elicit that reaction, from someone. (Are you guys, perchance, all really Bob Pease, using several different noms de plume?)
I consider Spice (LT-Spice, in particular) to be an extremely-valuable tool. But I do also have stacks of breadboards, some power supplies and test equipment, and hundreds of tiny drawers of components, next to my simulation computer. And, actually, nowadays, I often prefer to "breadboard" using a PCB, since they can be made in less than an hour.
- Tom Gootee
As it happens I rarely breadboard but that has perhaps more to do with my confidence in my design skills than anything else. In fact when I declined to breadboard a new design for the first time about 12 yrs back quoting the unwanted parasitics of breadboarding my colleagues looked aghast at me. They got used to the idea in the end. For me, the prototype pcb normally *is* my breadboard.
Simulation's great too but beware of its limits. It's entirely possible to simulate a 'nonsense circuit' and draw false conclusions from it.
Graham
got
It would be quite nice to be able to do that.
Thanks. I agree, and think that I am aware of many of the limitations and pitfalls of simulation, but am always trying to learn more about everything, as I go along.
- Tom Gootee
[snip]
There are only three limitations to simulation...
(1) Most important... The component models are inadequately devised, or you concocted them yourself... note that I said "your", mine are perfect ;-)
(2) You are clueless that components are less than perfect and don't know that you should do some component sensitivity analysis before building it.
(3) Or you are simply clueless in general and shouldn't be attempting circuit design at all ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Jim,
Thanks for the reply.
I realize that, compared to you, people like me probably ARE clueless when it comes to circuit design. But I have to admit that it's still a little disconcerting to read "You are..." in a direct reply to my message, even though you were (I hope) using the "You" in the general sense, regarding limitations to simulations done by "anyone". ;-)
- Tom Gootee
Sorry... I meant the "editorial you" :-(
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
to
Jim,
No apology was necessary. I'm sorry I even mentioned it "out loud". But thanks for the official clarification.
- Tom Gootee
"He who lives in a glass house should not invite he who is without sin."
In message , dated Sun, 3 Sep 2006, snipped-for-privacy@fullnet.com writes
It is reported that a Colonial Power (a long time ago, of course) tried to eliminate the 'chief' system in the colony. To do this, it confiscated the ceremonial chairs that were a key part of the appointment of a chief.
The people responded by hiding the very heavy chairs in the roof structures of their huts. Unfortunately, in the rainy season, the excess weight caused the huts to collapse.
People who live in grass houses shouldn't stow thrones.
-- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
Groan! That's almost as bad as the old joke punch line, "Leave no tern un-stoned" ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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