Howabout 1 transistor + 1 chip + 5v (per channel) for a computer preamp?
Is it doable?
P.S./edit:
12v is okay too (5 and 12 are both easily available).
Is it doable?
P.S./edit:
12v is okay too (5 and 12 are both easily available).
Last edited:
Computer/tablet/phone wants to drive singleton input amp with 50k load (there is no need for gain divider to use same resistor values, but it should have same proportion)
Previous efforts of buy another sound card, buy another sound card, buy another sound card, build simple amp with complex supply, build complex amp with simple supply all failed because of LTP caused a shortfall because computer things don't like it at all. Those are steadfast enemies.
So, I thought maybe it would be more doable to do the 'strap on' single transistor integrated buffer in front of a chip (the transistor is buffer for chip and is within global feedback loop). Then the computer/phone/tablet is driving that one transistor and the chip can do the amplification.
Maybe this isn't the best idea, but I've tried the worse ideas already...
And I really DO need a singleton-input preamp.
P.S. Either +5v or +12v is fine.
What is the original signal source?
Level? (in mV) Impedance?
Desired/needed level out?
A humble LM358 can do that, and be happy with +5V single supply, in fact it was designed for that task, over 30 years ago.
That´s the absolute minimum, there are far better ones today, but until you give us more details .....
Please define:
Level? (in mV) Impedance?
Desired/needed level out?
A humble LM358 can do that, and be happy with +5V single supply, in fact it was designed for that task, over 30 years ago.
That´s the absolute minimum, there are far better ones today, but until you give us more details .....
Please define:
in more detail.
Need a singleton-input preamp for computer. Also need doable/easy so that I can use it.
For one case, the android phone/tablet automatically lowers the volume after a period of time (to protect headphones?).
So there is dashing to the phone/tablet for turning the volume back up, really often.
Also, the output of phone/tablet wasn't enough for line level even at max.
So there is dashing to the phone/tablet for turning the volume back up, really often.
Also, the output of phone/tablet wasn't enough for line level even at max.
Asked for more detail, not same twice 😀
Ok.
1) volume going down is a "feature" 🙄
I hate "nanny" software and machines but hey ...... they think they are "helping". 🙄
When it happens I rise volume again, past the nanny warning "you´ll destroy your hearing" and in general it stays there. Oh well.
No preamp can solve THAT
2)
Now we are talking 😉
Try this:
So, I don't know what the output figure is and may vary by phone/tablet. . . but much to the point, being able to use it as a line level device without going past the headphone/ear/nanny level of most new phone/tablet output (which automatically resets back to nanny level periodically). At least it is determined to operate down below distortion levels. . . even though inconveniently not a line level device.
I though that I needed either singleton input preamp or 1-transistor buffer so the phone/tablet/PC need not 'bust a gut' with aggressive EQ settings. I really wish for small-signal version of TDA2003, but don't know if a tiny version was made not the model number for it.
Your example is absolutely brilliant! To get an average chip tamed, either very low current loops with non-inverting; OR!, for the easiest way for practical/useful tonality and low gain as well, just invert it. Awesome! That is another way to use the cheap phone/tablet source devices without overworking their onboard EQ.
I bought an ST version. . . Hope that was right.
358 slew rate may be low for audio...find a device with a rate of at least 8 and preferably 10 us/V, beyond 20 you will have problems.
Basically 5 V / 12 V versions of the TL072 / AD 797 / NEC 5532 / OPA 2134 series.
If not for audio, above circuit is perfectly acceptable.
Basically 5 V / 12 V versions of the TL072 / AD 797 / NEC 5532 / OPA 2134 series.
If not for audio, above circuit is perfectly acceptable.
There are certainly better OPAs on the market now. Considering the limited bandwith of mobile phone out and a line level of 3Vpp a slewrate of about 1V/us with LM358 is a no brainer.
Slew rates in V/us:
358 = 0.2
4558 = 4
5532 = 9
072 = 13
I had made a pre amp for a Thorens turn table, and tried different op amps in the same circuit, as I had put a socket.
358 was dull, which is why I posted above.
The caveat is that the same circuit, and same supply was used for comparison, supply voltages can also affect performance.
Also, for non audio use, the above circuit using 358 is acceptable.
358 = 0.2
4558 = 4
5532 = 9
072 = 13
I had made a pre amp for a Thorens turn table, and tried different op amps in the same circuit, as I had put a socket.
358 was dull, which is why I posted above.
The caveat is that the same circuit, and same supply was used for comparison, supply voltages can also affect performance.
Also, for non audio use, the above circuit using 358 is acceptable.
Here my friends kids use cell phones to stream music in his car, the bandwidth from the phones is good, they use Bluetooth.
Not tried except for earphones on my cell, good enough. Certainly not dull.
Not tried except for earphones on my cell, good enough. Certainly not dull.
LM386?
Or the Chinese version of the 6283, using only one channel, good to about 1.5W/8R?
OP has simply mentioned 2003, not how much power is needed.
Or the Chinese version of the 6283, using only one channel, good to about 1.5W/8R?
OP has simply mentioned 2003, not how much power is needed.
OP is asking for a Preamp, not a small Power Amp.
And as clearly stated in the schematic, the LM358 is a "baseline" component which "will" work happily with only a single +5V supply; in the same schematic user is strongly encouraged to get a better one, BUT it MUST meet the very restricted 5V supply available.
TL072 / AD 797 / NEC 5532 / OPA 2134 do NOT work with +5V single supply and if they do, performance is abysmal.
As of typical Headphone out level, I regularly measure around 200mV RMS; not bad fr a Mixer Line In or Home Audio Aux input, definitely not enough for direct Power Amp drive.
+5V supply is very restrictive in the Analog World, but hey, OP asked for it, so ....
So kids, homework is go searching low voltage Op Amp datasheets and report back findings 😉
And as clearly stated in the schematic, the LM358 is a "baseline" component which "will" work happily with only a single +5V supply; in the same schematic user is strongly encouraged to get a better one, BUT it MUST meet the very restricted 5V supply available.
TL072 / AD 797 / NEC 5532 / OPA 2134 do NOT work with +5V single supply and if they do, performance is abysmal.
As of typical Headphone out level, I regularly measure around 200mV RMS; not bad fr a Mixer Line In or Home Audio Aux input, definitely not enough for direct Power Amp drive.
+5V supply is very restrictive in the Analog World, but hey, OP asked for it, so ....
So kids, homework is go searching low voltage Op Amp datasheets and report back findings 😉
With +5V PS you should use a rail-to-rail (In & out) OPA: OPA1671 (single OPA), LME49721, OPA2376,...
In Post#4:
P.S. Either +5v or +12v is fine.
Post#10:
Basically 5 V / 12 V versions of the TL072 / AD 797 / NEC 5532 / OPA 2134 series.
Basically it seems his line out level is low for the amp, and maybe impedance matching is needed also.
https://www.brighthubengineering.co...le-circuits-for-the-lm386-ic-audio-amplifier/
4-12 VDC, voltage gain can be set from 20 to 200 by changing resistor value.
Should meet OP requirements.
P.S. Either +5v or +12v is fine.
Post#10:
Basically 5 V / 12 V versions of the TL072 / AD 797 / NEC 5532 / OPA 2134 series.
Basically it seems his line out level is low for the amp, and maybe impedance matching is needed also.
https://www.brighthubengineering.co...le-circuits-for-the-lm386-ic-audio-amplifier/
4-12 VDC, voltage gain can be set from 20 to 200 by changing resistor value.
Should meet OP requirements.
Thanks for your help!
The datasheets usually say 'do-all' probably to sell more. But actually if wound up too tight it is unstable/shouts or if too chillaxin then it is dull; And, every chip is that way. I suppose that with small gain, there is not so much risk of getting the 358 overly relaxed/dull. Just sayin--it probably works better as a preamp than it could as a mic/turntable amp.
It is entirely possible to use one on 5v and as a preamp if given some care and supplementary negative feedback (not resembling the datasheet example). I had one like that, but unfortunately have lost it. The sketch for it was on my dry erase board in the hallway for some time, built as same, worked fantastically. But I didn't need it at just that time, so I put it somewhere safe, and just can't find that place. Oops!
358 slew rate is 0.2 v/uS, it is really an instrument amp, for thermocouples and so on, where the signal
is not changing rapidly.
The 386 is used a lot in headphone amps, so it is more suited to audio.
358 sounded dull because it is slow to respond to changes in signal.
is not changing rapidly.
The 386 is used a lot in headphone amps, so it is more suited to audio.
358 sounded dull because it is slow to respond to changes in signal.