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Guide to getting and playing better gigs


   

Amp Safety

     
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1. Always make sure the speaker is plugged in properly before turning on the amplifier. Failure to do so may cause expensive or even catastrophic results.

2. Turn on the main power switch and wait at least 30 seconds before turning on the standby switch to extend your tubes` lives. If your amp uses 6550 type output tubes, wait about 60 seconds before switching on the stand by switch.

3. Use a grounded AC outlet and don`t defeat the ground pin on the three pronged AC plug on the end of your power cord. Better hardware stores sell a device for testing the integrity of the AC receptacles to see if the building`s ground wiring is connected properly. This is a wise investment in your safety and future. If the testing device indicates a faulty or missing ground path, you may be in danger of severe electrical shock.

4. Have your power output tubes changed (6V6, 6L6, 6BQ5, 6550, 6CA7, EL34, EL84 etc.) about once a year, or more often if you play every day for roughly six or eight hours, or if you notice a dullness in your sound. Always purchase matched pairs, or quads, of output tubes; they will sound and work much better than unmatched output tubes. Even if you only need a pair of matched output tubes, it is very wise to buy a matched quadruplet set so you will have a pair that is ready to use without a big change in tone . If you see glowing red plates in your output tubes, STOP! You either have failed tubes or circuitry trouble, and failure to shut the amp off usually results in major blown parts (£££s). The pre-amplifier tubes, the 12AX7`s and 12AT7 smaller type tubes might last for several changes of output tubes, but this is not a rule. If you hear jingles, rattles, pops, squeals or if the gain or attack decreases, it may be time to have these tubes changed out.

5. Transport your amp on a padded surface. Amps transported on the bare metal floor of a van or unpadded boot of a car may have the elements in the tubes shaken loose and cause microphonic rattles or worse, short out when next powered up at a gig. Treat the amp gently and it will last longer. Consider the purchase of a professional flight case if you plan to transport your amp frequently. If you are going to place your amp on a plane, a professional flight case is a must.

6. Carry a spare fuse or two with you and tape them to the inside of the amp cabinet. Always unplug the amplifier from the power source before changing any fuses. Follow the amplifer manufacturers recommendations about fuse changing. Never, ever use a fuse of a higher rating than called for, or you may wind up with a (£££s) blown power or output transformer.

7. Do not plug your amp into an AC outlet where heavy appliances or industrial equipment are also plugged in, such as refrigerators, freezers, heaters. Their off and on transients may cause severe voltage spikes on the power line which could take out weak components. Your amp will not like the brownout condition a 15 amp heater will cause if plugged in together.

8. If your amp has an impedance selector, such as Marshall, HiWatt, some Ampegs, etc., place the amp in standby before changing the impedance. Also, be sure to select the correct impedance for the type and number of speakers being used.

9. To determine the impedance of the speakers used, follow these general guidelines; two 16 ohm speakers in parallel equal 8 ohms; Two 8 ohm speakers in parallel equal 4 ohms and two 4 ohm speakers in parallel equal 2 ohms. And 2 ohms is about as low an impedance as any amp can withstand. Many solid state amps will fry with a 2 ohm load. If there is an impedance stated near the amplifier speaker output jack, do not use a speaker combination lower than this stated value.

10. Use a thick wired cord for speaker hookup (the orange 'lawn mower' cable is ideal). Don`t use thin coaxial guitar cables as speaker wire if possible. This is specially true for bass, where damping factor, tone and watts could be easily lost. However, if your are experiencing radio or TV interference, a shielded guitar cable might help out with this problem, as the culprit interfering radio frequency energy could enter your amp through a speaker cable, as well as through the input cables. Additionally, shielded coaxial cables used in the speaker path might cause some amplifiers to break into uncontrollable and dangerous oscillations. Caution is advised here. If the amp doesn't sound right or if it behaves oddly after installation of a shielded coaxial speaker cable, go back to using the zip cord type.

11. If you hear the amp cutting in and out, reduce the amp volume then wiggle the speaker cord. If this influences the cutting in and out, STOP! An intermittently open or shorted speaker connection or lead might blow up your amplifier. This one is very important.

12. Keep all cable ends clean. Dirty input jacks cause intermittent crackles and hums sometimes attributed to more serious problems.

13. Don`t unplug your guitar from the guitar end of the input cable while the amp is powered up. The loud hum you will hear could be the death knell of some component or speaker if the sun is not shining well on you that day. Some otherwise well informed people think this is an old wives tale, but if you have several hundred watts available, the results could be catastrophic. If you believe in trial by fire, then this one`s for you.

14. After powering up your tube amp, look at the output tubes. If the tubes' plates are glowing red hot, STOP! You could be in big trouble if you continue to operate with tubes running away, as red hot plates are called. This symptom takes moments to show up and just a few more moments to destroy the output transformer or other parts. The problem could be as simple as worn out tubes, or you could have other trouble, such as bias supply failure. A new set of output tubes plugged into a seriously malfunctioning amplifier can be ruined in a very, very short time. When in doubt, have your amp tested by a competent technician.

15. NEVER PLAY ON A WET OR DAMP CONCRETE FLOOR OR WET WOODEN STAGE! (That's the support bands job!). If a shock potential exists, you will be bitten badly, especially if you wear leather bottomed shoes. Wet or damp leather is a fairly good conductor of electricity, and hand to foot shocks can be quite fatal. Don't play in the rain. Beyond the obvious shock potential, your amp and particularly your speakers may be ruined. If using an extension AC cord outdoors, be absolutely sure you are plugged into a grounded outlet and that all the ground pins on AC plugs are intact or else.....

16. Never touch the grounds (input jacks) of two amplifiers at the same time. One may be properly grounded and the other amplifier may have any number of dangerous volts present waiting to shock you. Hand to hand shocks are the most dangerous type. Avoid them like the plague.

17. Use moderate sound volume levels. Sustained high levels of amplified sound (above 80 D.B. S.P.L.) can cause permanent and irreversible hearing loss. You may want to purchase a sound pressure level meter (and learn how to use it properly by carefully reading its instruction manual), to protect your very precious hearing capabilities.

18. Give the amp plenty of ventilation. A fan blowing on the output section of the amp will keep things cooler and generally increase the service life of the electronic components in the amp greatly. An easy way of accomplishing the cooling process is to purchase a small table fan at a discount store and place the fan behind the amp blowing into it. The cooler your amp runs, the longer it will run. Your capacitors will especially love you if you keep them cool. Never place the amp with its back against a wall. This will severely limit the natural ventilation the manufacturer has hopefully built in.

19. Do not move the amplifier immediately after switching it off. Let the amp cool down for a few minutes before moving or transporting it. It is also a very good idea to switch off the standby switch first before turning off the mains AC power switch. This extends tube life.

20. Do not take your amplifier apart. Do Not remove the chassis (the metal box containing all the electronic components) from the cabinet. There are no user serviceable parts inside your amplifier. There are capacitors in amps which store 500 deadly volts long after you switch it off. Contact with these lethal voltages will lead to only one outcome. You could be playing harp with Jimi immediately upon contact with many parts in your amp. Some amps have bleeder resistors in them to automatically discharge the caps within a few minutes of switching off the amp, but many amps do not have this feature (especially older amps like tweeds and most black tolex Deluxes). BEWARE! DON`T EVER GO INSIDE YOUR AMPLIFIER! Leave all amplifier work up to your trusted technician. He knows how not to get killed by the 500 or so volts in your amplifier. (Ampeg SVT's top out above 650 volts at about three amps capability).

21. A little knowledge can be a dangerous thing. What may start out as a simple problem can turn into an expensive repair when you have a well meaning friend "who knows something about amplifiers" try to fix your amp for you inexpensively. I can attest to this situation personally, as I have repaired several amps which started out with a simple problem, and which turned into a catastrophe when some well meaning novice let his meter probe slip off the desired test point and caused a smoky short blowing several expensive tubes and other parts. Bring your troubled amp to a qualified technician only. If you are new to an area and do not know who`s good and who`s not, either ask fellow musicians or call a music store and ask for a referral.

22. Use common sense at all times. Follow your first mind. I have helped many musicians who said something like, " I thought that hookup might blow my amp up (speakers, tubes, transformer etc.). I wish I had done what I thought was right instead of blowing it up"

23. Never, ever, plug the speaker output of one amp into the guitar or line level input of another amp. There is a way to do this without harm, but you need a special interface. This can be a very expensive mistake if not avoided. If your amp has a line output jack, this is a safe signal level to plug into another amplifier's line input. The line output of some amps is fairly large (a volt or more) and may distort the guitar level input of your amplifier. Try using the second input jack on your input channel which is typically 6 db less sensitive, and therefore, less likely to distort the preamplifier stages when a large input signal is presented.

24. Never try to parallel the output of one amp with the output of another amp. Never try to connect two amps to the same speaker. (These two "nevers" are exactly the same). This is the best way of generating the most smoke and most expensive repairs I know of.

25. Amplifiers which have been sitting unused for many months may have their power supply electrolytics deformed to a lower voltage than required for proper operation. Bringing the amplifier slowly up to 120 volts with a variac is a good idea. (Your amp tech should have a variac.) Amplifiers which have been unused for years usually have dried out electrolytics. Powering up one of these amps frequently has one outcome: smoke. Electrolytic capacitors have a useful life of about ten years. (Although many last much longer, some have much shorter lives.) Any old tube amp with its original electrolytic capacitors should have those power supply caps changed out by your tech promptly if you intend to plug the amp in and use it. If you are a collector of amplifiers and are never going to plug the amp in and use it, then you may forego this vital maintenance. While collectors want to see all original components in an old amplifier, players should have the proper maintenance performed on an old amp before any appreciable use is given to it. This is because old electrolytics may seem to be performing sufficiently, but may be leaking current and imitating a resistor. The current may not be enough to blow the fuse, but could be enough to overheat and burn up the old, often very hard to find (=£££s) power transformer.

Remember: "Too old to rock---Too young to die!"

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