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A lot of players baby their output tubes. They treat them like better than they treat their significant other! One customer I have kept wearing out his output tube sockets. I found out that he removed them from the amp, placed them in a padded box and neatly tucked them away until he played the next time. All he did was wear out his sockets and give his EL34's more abuse than if he had left well enough alone! I noticed that his early 70's Traynor amp had some of the original preamp tubes! Huh? Don't matter if the outputs are NOS, Superwhatnow hand matched Firebreathers if the preamps are old and tired, the amp will sound crappy! A 20 year old overly used Sylvania 12AX7 will sound worse than a $ 4.00 el-cheapo Chinese tube if its worn out!
My advice is to replace a least the first stage of preamps everytime you replace the outputs. This stage will affect your tone more than later stages because usually it is the most sensitive! Get a good quality tube. For Russian tubes try Sovtek 12AX7WXT+ or 12AX7LP. Both reproduce accurately,quietly and cleanly. Overdrive comes in the later stages.
Hey, give it a try. You might just be pleasantly surprised! Until next tmie, May God bless.- Ken
To modify or not to modify, that is the question. Whether tis nobler in the mind to suffer the sli... OOPS! Slipped into Shakespeare there! A whole lot of guitarists like to have their amps modified. I've installed master volumes, changed tone circuit capacitors, volume control values etc. only to appease customers trying to make those amps sound like a different amp. Master volumes I can see and tone circuits maybe, but I've had Marshall owners request mods from EL34's to 6L6's to make it sound more like a Fender. I've had Fender owners request mods from 6L6's to EL34's to make it sound like a Marshall. I've had pickers ask for an extra stage of output to make it louder!? Huh?
I can understand their feelings. But why butcher a "perfectly good" JCM Marshall to get a Fender sound when there is probably someone willing to trade a Fender for that Marshall because they want a Marshall sound! Buy the sound you want on the front end if you can (OK OK I know tastes change. Sell,trade,don't mod!
Here are my rules for OK mods:
Here is my list of NO NO's:
The main thing to remember is that Leo knew what he was doing when he designed an amp or signed off on the design. If it ain't broke don't #$%@$^ with it. Usually the mods are merely a placebo. You think is sounds better so it sounds better! Later.
A regular customer of mine brought me an amp to go over that he bought at a flea market. It seemed like a real bargain as he only paid $30.00 for it. It was a 50's or 60's vintage Epiphone Constellation or something similar to that. Man, I felt jealous. I never can find anything neat like that for nearly free.
After I tore into it, I found that it wasn't such a great deal. It seems that type of amp used 6EU7's and 6C4's in the preamp stages. Neither the Russians nor the Chinese make these tubes! They are only available NOS! 6EU7's go around $30 to $40 a pop. 6C4's are around $20 to $25 each. Worst case a total retube including 2 6L6's would run $135 to $145 if you do it yourself! All this for an amp that sounds only fair on its best days.
My advice would be to look at the tubes in the amp and see if they are a reasonably standard type. You know 12AX7's, 6L6's, EL34's/6CA7's, EL84's/6BQ5's. These are available from Russia or China for reasonable prices. That way you can afford to fix up that neat old junk amp.
As a warning, those big old SG brand amps from the 70's have oddball output tubes (I can't recall the type) that cost around $45.00 wholesale if you can find them. A dealer would get between $75 to $90 each for them. Unless you are rich, run screaming from those even if the price is too good to be true. Sure, they could be modified to use 6L6's, but that costs too. Until next time, may God bless and keep rockin'!
When I first started playing in the early 70's, the average Joe Guitarist thought tube matching was achieved when you ended up with all of the same brand output tubes! Heck,we generally changed them only when they died and generally only the dead ones! Surprise, surprise! The amps still sounded great!
Now it is the current fashion to replace them all every few months and only with tubes that are "Diamond super what-now gold platinum hand computer matched"! Guess what people, thats all nice, warm and fuzzy but realistically, the tubes are only matched for a short period time. After they have been used,abused and transported around, they are matched as well Pamela and Tommy Lee! Face it guys, they drift. Don't get me wrong, the outputs should be as close as possible for optimum power output(notice I didn't say tone), but a good old hand voltmeter match out of a bulk pile of the same type of tubes, when they are installed in your amp, works just as well as the extra $3 or $4 you pay for the snob appeal matching! Hey Groove Tubes uses the same Sovteks I do so why pay them a bunch extra for what a decent tech can do while he's got it cracked open for a proper bias setting (covered next month).
Let your tech handle your tube changeouts and all should be well! Remember do-it yourselfers, plate voltage on your outputs can exceed 500 volts which can kill your butt! Be safe don't try it at home!
I know it's been more than a week, but I've been real busy. My shop is full! I'm going to give you a tip that will probably get in my back pocket. I make a lot of money by just cleaning amp controls! I get my full labor charge to crack open an amp and spray some juice into the pots. About 15 minutes work for an experianced tech. An amatuer can screw up a whole lot of stuff trying to do it themselves.
The best way to keep them clean is to "swipe" them! No, I don't mean steal someone elses knobs when your get dirty. Just move your controls once a week. I know on my Church rig, the controls never get moved. They will collect dust and oxidize internally and cease to function properly. A least once a week, move the knobs from 0 to 10 (or 11 if you are in Spinal Tap) a couple of times. This will clean the crud out of them. An easy way to save around $40.00! Till next time! Ken
Well people, thunderstorm season is now upon us. It was the time of year my father looked forward
to because the shop could make some fast money replacing the rectifier diodes in T.V. sets. Why, you ask?
It seems storms would rumble through the valley and invariably lightning would strike the power lines! This would
raise the AC line voltage and POW! Fried diodes! Sometimes the juice would fry the switch in a set that
was turned off at the time.Or worse(can you say crispied power transformer). Amps are not immune.
The most fail-safe and fool-proof method of protection is to unplug during a storm. Hey, the evil
voltage can't jump through the air! I realize it's not prudent to unplug during a gig, so just do what I
do. Buy a quality surge supressor. Get one that costs more than a few bucks. You need one that has a light
that tells you if a surge has been encountered. These devices are usually one good for one shot. It will generally fry one
if it gets a good spike. But, would you rather throw away a $30.00 suppressor or fry all of the nice expensive
chips in your prize Line 6(or Fender,etc...). I have one that has protection on the TV cable line, sattelite LNB
coax, phone line to the DSS satellite receiever plus all my home theater AC lines. Cheap insurance.
Modern tube amps such as all of the new Fender tweeds, Marshall JCM-900's and the like have chips in them.
These components won't survive much of a surge. Last summer I did a repair on a Fender mixer/amp that got
nailed with some type of spike. It fried the power transformer plus 30 TL072 op-amps. Ouch!
Hey, it's like the Fram filter commercial, you can pay us now or pay us later! Please buy a surge protector.
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