C Dixon
From:
Duluth, GA USA
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Posted 11 Feb 2003 12:16 pm |
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Does your Nashville 400 (or other) amp, pop when you turn it on? Does this annoy you? Are you handy at all with a soldering iron? Would you like to eliminate the pop entirely?
If you answered yes to all the above questions, I have designed a simple ciruit that will stop it cold dead in its tracks. And it takes less than a dozen inexpensive parts from Radio Shack.
And, you do NOT have to pull the chassis out; or do ANY modifications to the chassis. The little anti-popper circuit goes between the speaker jack and the speaker!
I have ALL the parts worked out except one. the circuit consists of the following parts:
1. A tiny 5 volt relay.
2. A 1/2 watt resistor.
3. A capacitor.
4. A 4 lug terminal strip for speaker wires.
5. 2 feet of speaker cable.
6. A Small "box" to mount the stuff in.
7. Four "standoffs" and a small ciruit board to mount the relay, capicitor and resistor.
8. A 12 Volt DC transformer.
9. A 12 Volt power jack.
AND,
10. If you do not plug your amp into a power strip, you will need to procure one of these also. It must have a switch on it. Or you can make one from parts bought in the electrical dept of a home center or hardware store. If you want to do this, email me and I will explain how to make a power strip out of electrical parts readily available.
That is all you need to buy. If this interests you, read on. If not, skip the rest. And have a wonderful day. God bless you.
If you are interested:
Theory of the whys and hows. Why do Peavey amps pop when turned on? The reason is they are transistor rather than tube operated. The cause is when the power button is turned on, a transistor turns on immediately. Tubes have a warm up time.
The source of the pop is; large power supply capacitors being charged upon initial power being applied; causes spikes which the transistors feed to the speaker. Or a loud pop! Enough to damage a speaker under certain conditions. Not to mention our precious ears!
In a tube amp, the "pop" has already occured by the time the tubes warm up. So we never hear a pop.
Manufacturers of high-end transitsorized stereos got around this popping problem; by "delaying" the connection to the speakers; until after the power capacitors have fully charged. The delay is quite short. Less that 5 seconds in most cases.
Optimum is to design the delay so that the speakers are turned on JUST after the pop has ocurred. Which is usually less than 1 second on a Peavey.
The little circuit I have designed does just that. It delays the speaker connection for about 3 seconds.
Here is what happens. After building the parts in a a litle box that has been supplied with a 12 Volt transformer (pluged into the power jack on the box), you mount this box to the right inside wall of your amp.
Then disconnect the speaker wires from the speaker.
Using some of the speaker cable connect the speaker to two of the lugs on the 4 lug terminal strip on the box; Then connect the other two lugs to the speaker cable coming from the amp, using some more speaker cable. Use "wire nuts" (or solder if you wish) for this connection.
Also, you must plug BOTH the amp AND the 12 Volt powers supply into a powers strip. And leave the amp in the "ON" position all the time.
Now here is what happens:
1. You turn the switch on the power strip to ON.
2. The amp turns on.
BUT,
3. The speaker is NOT connected because it is in series with the circuit you built.
4. The capictor starts charging. It has a 3 second charge time (approx).
5. When the cap approaches a full charge, the relay operates; and whamo, connects the speaker into the circuit with NO pop. From this point on it is as though you had the speaker connected directly to the amp. Until you turn the power strip to OFF.
Then the process repeats. In other words, the speaker's connection to the amp is being delayed by about 3 seconds ANY time power is applied thru the strip. This even works if you lose power to the amp temporarily.
Ok, what is the one thing I have not worked out yet? It is the value of the cap. I know the value of the resistor and the relay . But not the cap as yet.
The value of the cap plus the value of the resistor plus the voltage applied (in this case 12 Volts) determines the "delay" (charge) time. I need to experiment with different values of caps, until I find one that will give the optimum (or close to it) 3 second delay. My engineering days have fast left me; so I have to do it the ole trial and error way 
When I have done that I will let you know. AND let you know how to wire it so it WILL work the first time. Hopefully I will include the part numbers of all the parts that you need to purchase from Radio Shack. Plus how to build it complete. It should be quite simple.
I am off to Radio Shack to get a half dozen different sized caps to try. A relay, a resistor and a 12 volt DC PS. When I have it working good, I will let you know if you are interested.
carl
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