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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: How to restore a not so great 1977 amp? posted by SiBurning on June 29, 2005 at 21:18:14:
One of the biggest bangs you can get for your buck is upgrading the power supply. Why ? Simply because you are, in the end, listening to your power supply. All that neat circuitry does is modulate your power supply. If you look at any audio schematic you will see that the input signal does not pass beyond the first active device, usually a transistor. From that point on the signal is an analog of the input signal, and that analog comes from your power supply. Replace the rectifier diodes with Hexfreds and install a Pi Filter. about 1K uF after the rectifiers followed by a 2-5 mH choke followed by as much additional capacitance as you can cram into the space available. Remember, "Qualitat uber alles ". If you're really ambitious bypass all the 'lytics with 0.01 uF silver micas. Also, if you have AC coupling (a capacitor at the input and output, it probably does) replace these with quality film caps. If you can identify it, replace the feedback R's with Rikenohm CF R's. These are 2 R's with 1 connected from the amp's output to the input of the first stage, and the 2nd R connected from the 1st stage input to ground. (one set in each channel). These act as a voltage divider and determine the amount of amplification of the input signal, ususally 10x, or 20 dB,. The replacement R values need not be the same as long as their ratio is the same : 10:1. The 10x R value goes from output to input, and the 1x R goes from input to gd. A good set of values is 2.70K & 270 ohms.Happy Llistening !
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Follow Ups
- Re: How to restore a not so great 1977 amp? - pkell44 11:11:56 06/30/05 (1)
- What value of diode for an amp? - Rayax 16:15:32 06/30/05 (0)
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