Audio Pre Amplifier

[StevenStanleyBayes]

Read only the addendum. This is where the audio stuff is.

"Electronics for Musicians" is not a novel but fun. The book is at the very beginning. I do not know when I will be ready. The book is published on the web site on "Publish As You Do" "PAYD" basis.

Originally Posted by SY

I clicked on "Electronics for Musicians," and I must say it's... novel.

[StevenStanleyBayes]

There isn't much to discuss but I will try. Before, so, I must say again: the schematic is very simple and I have been thinking to publish the schematic may be rather an insult to the readers but I decided to do it because I found the pre amplifier to be rather useful.

I have purchased an inexpensive yet a very good quality microphone from Active surplus as well as some other microphones from dollar shops and even a reputable Sony from the reputable "Best Buy". All of them have been incredibly low signal and one must literally shout to get some sound out of them while they are rather stuck in the mouth of the singer/talker. To address this problem, I have decided to make the pre amplifier. The main application was to connect the microphone to the PC Audio Card's analogue microphone input and to get some sound recorded. Worked pretty fine.

Another advantage of the preamplifier is the microphone and the preamplifier can be plugged to any amplifier and there is no need to have a specific microphone input of this amplifier. Without a specific microphone input, the signal of some microphones can be low enough to be properly amplified by the general purpose amplifier. The pre amplifier works as a breeze mainly when the 10KOhm input resistor is not installed.

Then I got hold of some fancy speakers JBL Creature (II most likely). These have Bass and Treble potentiometers at the subwoofer. As stupid as I am, I have not realised there have been a + and - keys on the right satellite speaker which are, as you can think of, used to increase/decrease the volume. So, I have thought the speakers' volume cannot be increased. Hence the stereo input output to pre amplify the level of the analogue output of the PC audio card and boost the signal supplied to the amplifier of the speakers to a good level and hopefully not higher than the maximum. This worked pretty fine too but I have discovered the volume control thereafter so, the preamplifier may seem to be redundant in this case but may be useful with amplified speakers which may need a higher level than the PC Audio Card can give, in case there are such at all.

The guitar output is boosted by the pre amplifier to a good level to be displayed to the analogue input of the PC Audio card. Thus one may wish to hook the microphone to the microphone input of the PC Audio card and the guitar to the two inputs of the stereo analogue input of the PC Card. Or to plug the microphone to one and the guitar to the other input of the PC Audio Card which would give a "stereo" recording of the singing on one of the channels and guitar on the other.

The pre amplifier may seem to be redundant when the guitar is connected to the PC through a distortion in case the distortion has a preamplifier and most of them do. When distortion is not needed, one can reduce the level of distorting to 0 and thus the distortion would work as a simple pre amplifier. The question is whether all distortions can go to 0 distorting. Should be true. Another question would be the level noise of some of the distortions.

Another application would be to plug the guitar through the pre amplifier to a microphone input of an amplifier or a PC audio card. Some audio cards have been said on the Internet to have as tiny as 1KOhm input resistor and the guitar may be rather quiet. I believe, they put low input resistor at the input to improve the performance of the "discharge" of the microphone coil (linearity) as well as to decrease the noise. However, I tested the pre amplifier (without input resistor, just straight non inverting amplifier with a very high input impedance) and the noise seemed to be non detectable (I couldn't hear any noise). I do not know what happens with the non linearity of the microphone as well as how linear the rest of the circuitry on the path of the signal is.

Of course, in case any of you is a great fan of an input resistor than a resistor of value 1KOhm to 20KOhm (as cited by the Internet) can be put in parallel to the input.

I don't know what else to say except I am sick and tired of typing for now and, as the documentation says, the pre amplifier can be used as a general purpose pre amplifier or mili power amplifier with a gain from 8 to ~2750 and frequency range of 0 to 25KHz. The frequency range can be bumped very easily to more than 200KHz at the same gain as well as the gain can be bumped sky high at the expense of the frequency range. At the standard audio range of 20Hz to 25KHz, the maximum gain with a minimum adjustments to the circuit can reach 3375000 tanks to the high ft (unity gain bandwidth a. k. a. frequency of transmission) of TL084. This gain at audio frequency range can be used to listen to Martian songs for free, for example.

As I said, I found the pre amplifier very useful. I have been trying to purchase one all over Europe and North America (from the general purpose stores) and I have not been able to find one. I will be happy in case you find the pre amplifier useful or in case you find some applications. Yes, I do take good jokes as you may now be tempted to reply so I high gain recording of a fart is rather useful and possible with this pre amplifier.

However, think a bit: if you need a pre amplifier and if you make a big noise, the Chinese will be able to manufacture one for $3 or around. Thus, I would be able to walk to the dollar store and get one for a few bucks next time instead.

I did not make the pre amplifier. Texas Instruments did.

Originally Posted by Pano

You can do either. We encourage attachments for several reasons, but you can also insert images from elsewhere.

Your jpeg came across just fine, thanks! Do you want to discuss your design choices and reasons?

[StevenStanleyBayes]

There are updates on the documentation published on www.Steven-Stanley-Bayes.co.cc (click on the link "Pre Amplifier").

A description of the pre amplifier circuit has been included as well as a schematic for a 72W stereo/mono/guitar amplifier.

Please, note, I have been in a hurry and I have not made the 72W amplifier circuit as yet. May have made some mistakes which I will correct when I do it. The circuit is pretty standard and elementary and I do NOT expect problems there but there may have been something with the additional considerations. The pre amplifier has been done, though, and works fine.

I understand you are used to have something published as an attachment. I have tried to satisfy this requirement but the "Upload Attachment" window said: "This format is not recognised". I tried to upload Word 2010 .docx file and I do not want to open it and save it as a simple .doc because I have to check it out after the conversion because of graphics standard and other incompatibilities.

[StevenStanleyBayes]

I would also like to take a few seconds to say something more general:

The main function of a pre amplifier is to provide an equal opportunity for every device to work with any amplifier instead of having a million "dedicated" amplifiers to a given task. For example, one can plug a guitar in a stereo amplifier of any stereo device by short connecting the two stereo inputs of the amplifier and putting the signal through the two channels of the stereo simultaneously thus doubling the power. WHY DOES ONE NEED A GUITAR AMPLIFIER? Some say something of power supplies but I do not want to accept this.

This example is not very good because the home stereo would perform much better than a guitar amplifier even by the same company and with the same guitar, even without a pre amplifier. However, there may be more cases as for example with microphones and with two amplifiers interconnected with insufficient signal level, etcetera. How many times have you plugged something into something and either of these works?

This is why, instead of having a bunch of lousy amplifiers all over the house, one would rather have one or a few and plug different devices into as per the desire. For this reason, one better has a pre amplifier.

Also the device would be less expensive, tiny and very light when purchased without an amplifier and speakers.

One has an amplifier in the TV, radio, CD/DVD player, MP3 docking station and many more devices around. What for? How many does one use in parallel. Sometimes two? OK than have two amplifiers and two sets of speakers. The amplifier is a separate device and has got nothing to do with the amplified device. There aren't specially matched amplifiers to a given device. They are all general purpose and the manufacturers may say otherwise just to get your money. Otherwise, the amplifiers go by parameters not by "designed for".

The only matching I've heard which makes some sense is people match the power supply to the speakers resistance.

How many of these amplifiers one has at home have the same parameters as the parameters of the fewer amplifier one would have in case one would switch to an option to have a few but high performance ones?

Which one would you chose? A super quality amplifier from the 70's or 80's for $5 or the newest iPod amplifier for $150?

Another good point: with a pre amplifier you will be able to be heard and to hear. Without a pre amplifier, one needs the director of the Vienna Philharmonics to translate from device to English.

Try and see!

[DF96]

Originally Posted by StevenStanleyBayes

"Donations" from Nigeria are welcome as long as these are in convertable currency or in Nigerian girls.

'Donations' from Nigeria usually end up costing the 'recipient' lots of money. I hope there is a diode on your bank account.

[jacco vermeulen]

On the other hand, donation of a West-Nigerian girl may have a decent HIV Internal Rate of Return.

[StevenStanleyBayes]

I would love to have a transistor in the bank account to amplify the money. Even a pre amplifier would do!

Originally Posted by DF96

'Donations' from Nigeria usually end up costing the 'recipient' lots of money. I hope there is a diode on your bank account.

[StevenStanleyBayes]

Not to worry, I will drink a lot of vodka with the return.

Originally Posted by jacco vermeulen

On the other hand, donation of a West-Nigerian girl may have a decent HIV Internal Rate of Return.

[StevenStanleyBayes]

I LIKE THE SENSE OF HUMOUR OF DF96 AND JACCO!

[StevenStanleyBayes]

Everything on max, microphone boost on max:

No pre amplifier:
https://www.youtube.com/watch?v=aRu0...kcdZv2Rm2zYUEb

Pre amplifier to ~50%:
https://www.youtube.com/watch?v=pO3a...WTMFQ1e3CcrJw7

Preamplifier to 100% (Gain=14):
https://www.youtube.com/watch?v=dpn8...K3mCzHjeTxPkBW