Making a Preamp

[Unkle77]

Hi, I’m new to diy electronics and the workings of amps, I have a bsc in physics and am now doing a masters, and I’ve done a bit of electronic here and there but nothing useful.

Basically my ultimate plan is to make my own amplifier so that I can have total control over the specification and sound it produces.

But first I want to do something to warm myself up and my friend has just the thing.
He needs preamp for connection between his Decks and amplifier.

So what I need to do is find a design for a preamp, I have found the following and was wondering if you experts think this is a good idea or if you have anything to add. All help would be much appreciated.

Links:

http://www.mitedu.freeserve.co.uk/Ci...udio/gmpre.htm
http://sound.westhost.com/project25.htm
or maybe this?
http://www.paia.com/riaa.htm

#I think this was the right thread to post in#

[Bazukaz]

Depending on what you need :
http://sound.westhost.com/projects-2.htm

[lineup]

Originally posted by Unkle77
Hi, I’m new to diy electronics and the workings of amps, I have a bsc in physics and am now doing a masters, and I’ve done a bit of electronic here and there but nothing useful.

Basically my ultimate plan is to make my own amplifier so that I can have total control over the specification and sound it produces.

But first I want to do something to warm myself up and my friend has just the thing.
He needs preamp for connection between his Decks and amplifier.

Audio preamplifier or headphone amplifier
is best 'warm up projects' in amplifier making.
So, your plan is perfect!

- Usual value of voltage gain in preamps is x4 ( +12dB ).
This will take care of most modern sound sources.

- Preamp can have input impedance like 22 - 47 kOhm.

- Good also if it able to drive downto 2.2 kOhm loads, while keeping good sound quality.

- Power supply is often regulated, to give a clean and constant performance.

[latala]

please advise what do you want the preamplifier to do
the decks i assume are turntables? if so what cartridfe are you using moving magnet moving coil
do you require tone controls ?
recording facilities ?
what power amp do you think you will use ?
i try to make a wish list and the approach that ideal
will you want a quick lash up on vero or will you want to make it on a pcb
have you any thoughts re ic or discreet devices
regards
trev

[Leolabs]

Dealing with OPAMPs should be a good choice.

[Unkle77]

Thanks for the responses.

Bazukaz – Yeah was looking at them, trying to work out which one best suites me, don’t really have the knowledge at the mo.

Lineup - Thanks could u give me any more info on power supplies

Latala - I think the cartridges of the turntables are moving magnets, don’t really know as I can't find any damn info on this anywhere!! but they are new and from what I could find I’m guessing MM.

The power amp he is using is a Cambridge Audio A5.

I do note require tone controls as they can be done using the power amp.

I will probably make it on PCB (been doing a bit of research into this) may as well get a bit of practice with this before I do anything more complicated.

I’m not sure if I want to use an IC or discreet devices, the IC will be easier but that isn’t really a plus for me. I want the circuit that sounds better/deforms the input less.

He won’t be needing recording facilities either, that will be something I’ll do later

[lineup]

I thought you were going to build an ordinary preamp.
This is an easy project for a starter.
Gain needs only be x4.


If is a phono RIAA preamp you will build, is totally another thing.
A high quality RIAA phono amplifier (or a good microphone amp) is NOT an easy project.
Why?
Because of the high gain needed.

Instead of x4 you will need x100-400 for MM pickup amplifier.
Because of this high gain, also any noise from power supply
will be amplified with same gain!


There are many different RIAA projects to chose from.
They can be from very simple one Op-Amp to very advanced.
I would go somewhere in between.

And I would say, pick a good existing project.
Follow instructions and pay great attention to the practical building directions,
regarding power supply construction and how to wire everything.

I would say you should pick some good documented variation
at ESP sound projects RIAA phono pages.
I think you already have the link in your first post.

Even for me or some other good with amplfiers,
to make an own RIAA project from scratch is a lot of difficulties.
Both good amp circuit, good power supply design and correct practical build
as well as good component quality is needed to get a performance without troubles.


Before and while study and order components, consult other experienced people here.
Most of them will give you good advices on details, what to do or dont, and avoid you going wrong.

Some of the posters however may (and most surely will)
recommend very advanced, complicated and difficult stuff.
These you do not have to listen to. Not too much.
They are in the high end audiophile league,
where you always should have the best and most extreme setup in your home.
Even if they never have proved they have better sound.
Not that one living soul can hear anyway. And this is what counts.


ESP at http://sound.westhost.com/
is down to earth and still very good quality for us more normal DiyAudio Guys.
Most of his stuff is better, than what you can buy for twice the price,
compared to build it yourself.

[federico moreno]

Hi, Uncle77.
i think that maybe you`re trying to make a line level preamp.
That`s a relatively easy task, as lineup and the other members have told you.
ESP projects are really good; the site have a lot of additional info regarding electronics.
My debut was, a pair of years ago, with a very simple preamp based in only one opamp.
That pre was suited for headphones listening, and also good for feeding a power amplifier.
For starters, and to get some basic info, check out

http://headwize.com/projects/index.htm.
http://headwize.com/projects/showfil...=opamp_prj.htm

The second URL have good info about particularities, tips and tricks to design headphone preamps. The majority of them can be tweaked to be used as simple line preamps, only with a reduction in gain.

Another Diyaudio popular favourite is a derivative of the Burr Brown opamp-buffer combination -something like a turbocharged preamp, capable of drive long cables and heavy loads-.
Check out http://focus.ti.com/lit/an/sboa065/sboa065.pdf
or http://www.pha.inecnet.cz/macura/buffer_en.html
The design of the later URL has no gain -is a buffer, with gain 1, designed to give a little more ooomph to weak or anemic sources, like some cheap cd players-; with some modifications in the gain it can be transmutated into a very good an simple preamp.
You can check some threads here in Diyaudio related to that specific topology, with various tweaks

I´m using currently something very similar, with very nice results.

Enjoy!

[Unkle77]

Heres some questions:

Would a modern turntable such as technics 1210's or and equivalent turntable need a RIAA preamp or just a normal line level preamp.

I believe i need the line level one as what i want is for the signal to just be amplified. I will leave the fancy stuff until i know what i am doing.

So shall i make this:
http://www.pha.inecnet.cz/macura/buffer_en.html

or, this one?
http://www.mitedu.freeserve.co.uk/Ci...udio/gmpre.htm

Or
http://sound.westhost.com/project88.htm

In the bottom on i will not be including the balance or volume controls as my future diy amp will do this.

I will probably do the bottom one, do you guys think this is wise?

Cheers again

[Spev]

Surely the mixer between decks and amp acts as the preamp in this instance? No other pre should be required.