Matthew Cattle's Website

The time is and it is

DIY Audio
The website where I got most of the information that allowed me to make my 'Gain Clone'. My nickname there is matttcattt.

Texas Instruments
The website of Texas Instruments. This is where I got my free samples of the OPA541, OPA548 and OPA549 High Power Operational Amplifiers.

This site is a member of WebRing. To browse visit here.

This is Matthew Cattle's website. My hobbies include electronics, robotics and HiFi. This website is about these hobbies. This page is about HiFi as this is my most active hobby at the moment.

First of all, a little introduction to my page. I was going to write this page as a tutorial for people, but I cannot be bothered, and their are many websites that already do this. Instead, this page is just to show what I have built.

I have finished making my first amplifier, a stereo 'Gain Clone'. I chose to make this amplifier due to its simplicity (only 7 components per channel and a simple unregulated power supply) and price, as I got the amplifier chips free as samples from Texas Instruments. I first started using the OPA548 High Power Operational Amplifier as this was the least powerful of the chips that I got as samples. I made a simple Gain Clone using the circuit below and used my bench power supply to power it.

Fig.1

The amplifier worked first time and I was impressed with the results. I though that, for such a simple circuit, the amplifier was very good. I do not have a detailed opinion on the quality of sound as I am not an audiophile. If you were looking to make a simple amplifier as a first project, I would recommend a 'Gain Clone'.

I decided then to make a more powerful copy of this amplifier using the OPA541 High Power Operational Amplifier's that I got as free samples. I was impressed with the results of this amplifier as well, considering the low- quality components I used. A picture of this amplifier is below.

Both the above amplifiers were power by my bench power supply for testing, with the positive supply of one for the positive rail, the 0v of this supply, and the positive supply of the other for ground, and the 0v of the second supply for the negative power rail. This gave me +/- 0-30v supplies, of up to one amp, easily enough for testing purposes.

I then found two 15v 5A supplies, and used these as the above. I am still in the constructional stages for my final power supply. This will be a large supply of +/-40v. This supply shall be able to provide my amplifier with enough power.

At the testing stage, I used 4,700uf per rail as I had these capacitors lying around at the time of construction. Soon after finding the two 15v supplies, I found four 33,000uf capacitors and I am now using two of these per rail, giving 66,000uf total per rail. This amount of capacitance, in my opinion gives much better bass. This is because bass uses more power that treble, and with large capacitor banks, the capacitors help provide the required power.

I have just made a Gain Clone using the circuit below. This circuit uses two OPA541/9 Power Operation Amplifiers, in parallel configuration, to allow the use of 4ohm speakers with the amplifier, unlike one using a single IC, which could not handle a 4ohm load.

Fig.2

After this, I tried the circuit below, which uses the same method as the one above, but using 4 OPA541/9 Power Operation Amplifiers to allow the amplifier to theoretically power 2ohm speakers safely (not having any 2 ohm speakers, I paralleled two 4ohm ones).

Fig.3

I also tried the two circuits below, which use two, and four OPA541/9 Power Operation Amplifiers to achieve two and four times the power of a single IC, respectively, using bridged configuration. I used the Texas Instroments DRV134 for IC1.

Fig.4

Fig.5

I am now in the process of making a 6 channel Gain Clone for use in my car (When I get one :D). 4 channels will use Fig.4, and 2 channels will use Fig.5. this is a total of 16 OPA541/9 Power Operation Amplifiers. :D The four channels will be for my two front and two back speakers, and the two, more powerful channels will be for two sub woofers.

I was planning on making a large power supply for this amplifier, but it would have cost me upwards of Ł80 to build. When I finally install the amplifier into my car (when I get one :( ), I will have to use two separate 12v batteries to, get the +/-12v supply required, so I have decided to buy the batteries and a charger (or two), and use them to power the amplifier before, and after I have installed it.

I have put my car amplifier project on hold as of the 15th February 2002, as I wish to build an amplifier to test, and then permanently power my subwoofer, which is also a work in progress (see my other pages, when they are built :P). It will use four OPA541s in bridge and parallel configuration, to provide ~100W, and should also be able to power 2 ohm loads. I have now completed the basic amplifier section of the sub amp, and it really adds some low frequency output to my system. The 100Hz Low Pass Filter (LPF) is completed, and my sub is now actually working as a sub. Or at least a woofer, as it only handles frequencies from 65-100Hz. :P

Here are some photos of my prototype, and the final amplifier:

My first test setup. You can see the amplifier in the top right, the star ground in the center, the star +V and -V connections at the bottom, and in the top left corner, two large electrolytics (33,000uf). +V is red, -V is black, and ground is yellow. The wires in the bottom right are the speaker outputs.(~9/03)

Two large input caps. Also, the other channel to the right. (~9/03)

The whole amp, mounted on an old PCB. (~9/03)

My whole setup. Including CD player and CDs. (~9/03)

My test setup of the 'Bridged', and 'Bridged and Paralleled' circuits, on top of the amp's case. (~10/03)

The front of my car amps case. Not finished yet (3 more potentiometers to add), and propped up by test speaker :D. (~10/03)

The Back of my car amps case, notice the very badly drilled holes for the biding posts, also not finished. :( (~10/03)

Another shot of the case. (~10/03)

A shot of the front, this is taken with a new, better camera. :D (~21/12)

A shot of the back. (~21/12)

A shot of the top, this is soon to have a clear acrylic cover over it. (~21/12)

A shot of the underside. (~21/12)

My latest amplifier, my subwoofer amplifier, the heatsink attached to the case. (~20/02)

The case, without heatsink, with grommets, to protect the wiring. (~20/02)

The heatsink after drilling. (~20/02)

The chips (OPA541), fully wired. (~20/02)

The chips mounted on the heatsink. (~20/02)

The mess of wiring :P. (~20/02)

The case, partly assembled, with the lid removed. (~20/02)

A really bad photo, with the lid attached. (~20/02)

Another really bad photo, also with the lid attached. (~20/02)

Sorry for the poor quality of the photos, it is due to my lack of ability when taking photos, not my camera :(.

Figs 2 to 5 originally drawn by carlmart (of DIYaudio).

If you have any questions, E-mail me at matttcattt (at) yahoo.co.uk (change the (at) to an @) or talk to me on DIYAudio (my nickname is matttcattt). Try to include the word "amplifier" or "robot" or something to help me see your e-mail amongst the several hundred spam e-mails that I recieve each day.