audioguru

February 23 above on this page has the latest schematic of the revised 3A lab power supply.

February 23 above on this page has the latest schematic of the revised 3A lab power supply.

About 53 years ago the CD4046A was introduced but it had many problems. It was replaced a few years later by the improved CD4046B and MC4046B and HEF4046B.
Your CD4046A must be one of the very old ones with problems.
Look on the datasheets of an A and of a B to see the differences.

Hi Maliki,
National Semi doesn't have a spicy ( ;D) model for their LM3914.
I looked on Google for Spice and then Pspice Model For LM3914 and found many people asking for a model too. One guy found a similar model to pspice online at a university.
There are many French links. Parlez vous francais? Not me, and I hate Google's horrible translator. ;D

It is probably an Oriental 2SC828 transistor. Go to www.datasheetarchive.com to see its spec's and to see substitution guides.

The TDA2003 does not bridge well because the output offset voltage are not matched for the two amplifiers like a monolithic bridged amplifier IC. But you might be lucky so try it.

With a 14.4V supply the bridged output at clipping into 4 ohms is 14 watts.
If your speakers are 8 ohms then the power is 8 Watts.
If the supply voltage is less than 14.4V then the power is less.

You should make an active crossover circuit.

Pin 8 of the IC should be 5.0V which is the output of the 78L05 voltage regulator or the 6V battery voltage. If you use the voltage regulator and D1 in series with it, then the minimum input voltage is 8.2V. Don't use a 9V battery because its voltage quickly falls lower.

The micromitter has an attenuator of 3 resistors at its output to reduce its range. Remove the attenuator for much greater range.

1) The first opamp is inverting with such a low input resistance of 1k ohms that it kills most of the signal from the higher resistance electret microphone. This opamp should be non-inverting with a much higher input resistance.
2) The coupling capacitor C4 between the opamps couples positive and negative AC to the input of the second opamp. But the maximum allowed negative input voltage is only -0.3V so the much higher negative part of the signal will probably damage the input.
3) The entire output current of the second opamp slams into the bases of the transistors without any current limiting that overloads the opamp and might damage the bases of the transistors.  

Hi Gruber,
The current-setting pot in this project has a tolerance of 20% and the values of the resistors were chosen so it provides 3A if the pot's resistance is 20% high. If your pot's resistance is 20% low then with it set to max, the project will try to produce 4.2A.
Such a high current will overload the transformer and cause its core to saturate. A transformer with a saturated core isn't a transformer anymore, it is a piece of wire across the mains, blowing fuses.

You should add a trimpot in series with the current-setting pot. Adjust the trimpot so the project supplies a max of exactly 3A when the current-setting pot is at max.

Your main filter capacitor value is much too low for an output of 10A. use at least 20,000uF.
The transformer voltage is too high for a maximum output voltage of only 20V and its current rating is much too low.
The poor little BD139 driver transistor will smoke and die if you are unlucky to find those very old output transistors with low current gain.
Q1 is completely wrong. Its maximum allowed reverse bias on its base-emitter is only 5V.   

Thanks for the freelancing job recommendation but I am a 70 years old government worker (I am retired with a government pension and some stocks and bonds) so I do not need more income. I do whatever I want whenever I want. 

Distortion can blow out a tweeter because distortion has strong high frequency harmonics.
Try feeding an input directly to the power amplifier without connecting the preamp.

The output of a preamp will produce clipping distortion if the input level is too high. The pickup from an electric guitar produces a level much higher than an FM tuner, a CD player or an MP3 player. Most preamps for a guitar pickup use a Jfet because of its very high input impedance with a gain of only about 1.4 times.   

Nobody makes an LA4058. You got the numbers mixed up, the schematic shows a Sanyo LA4508.
Your 13.6V transformer must feed the rectifiers on the Power Part of the schematic. Maybe you fed the transformer wrongly to the amplifier instead of to the rectifiers? Then probably many parts are destroyed. Your 13.6V transformer will produce a peak of 19.2V and the rectifiers reduce it to +17.2V.
With a 17V supply the LA4508 produces about 6W at clipping into 4 ohms per channel. Who told you 100W? It has fairly high distortion at low and high frequencies and it cuts frequencies above only 5kHz.
Your amplifier probably uses one LA4508 for left woofer and left tweeter and the second LA4508 is probably used for right woofer and right tweeter. 

The TIP41 has an fT of only 3MHz so it is slow and its delays will probably cause the output amplifier to oscillate and have transient problems. The BD139 that should be used is very fast with an fT of 190MHz.

The hFE is not important because the minimum hFE of one of the two 2N3055 output transistors at 1.5A is 41 then the collector current of the BD139 must be a maximum of only (1.5A/41) x 2= 73mA where its minimum hFE is about 70 so the maximum output from opamp U2 must be only 73mA/70= 1mA but the minimum output from a TLE2141 opamp is much more at 20 so there is plenty of hFE available.