Conference napalm::guitar

    I had an older marshall (circa 1964)  50 watt lead head....when
    I traded it in in 1982 it still functioned perfectly with the original
    tubes. Of course, it didn't have master volume which eats tubes....
    
    dave

    re -1
    
    Dave, WHY did you trade the amp in?? those old 50WT's are killer.
    
    Re .0
    
    Groove tubes makes the best marshall replacement tube in my opinion.
    They also supply replacement valve sockets if your need those too.
    What's neat is you can buy output tubes from GT for your marshall
    w/o the master vol that actually cut down on the output and
    provide more sustain.                                   
    
    WjB

	I have a 1969 50 watt with EL34's I did install GT's for both power 
and Preamp. I was aware of a performance rating. And I installed #6.? Some 
where around 7 or 8 I get distortion at 6 I do not. I believe the tubes in it
were original and had some problems among other problems the amp had from a
nasty tech who tried to install a master volume. There are also some other
problems with the amp,but I have it to a functional point and it sounds great.
It has a nice warm sound that I can't get out of my Fender(obviously).
	My question to WJB is how often have you replaced your tubes? Every
Marshall I've looked at(inside except this one) seems to have had a fire or
charcoaled tube socket. I don't care to see puff's of smoke and I am trying
to get an idea of preventative maintenance.?? Also what do you recommend for
more distortion and sustain for Groove tubes rating?

							Rick

    Re: Rick
    
    I changed the tubes shortly after I got mine because they literally
    died (I also changed the valve sockets as the old EL34's were rusted
    beyond belief into their sockets!). I wasn't sure which number I
    got, I remember they went from a 'hard' rating (clean) to a 'soft'
    rating (dirty). I just told the tech I wanted the thing to distort
    as much as physically possible. I believe he also changed the bias
    when he did the tube replacement. The old Marshalls are noisy. It
    would be nice to have them rewired, or maybe the connections
    cleaned. I don't like master volumes, but I've heard horror stories
    on MV installations. Mine used to distort great at 6, even better
    than at 8 - 10, where it sounded too grainy. In fact all the freq's
    used to hover around 6.
    
    What do you do to get a warm tone outta yours?
    
    B

    I don't know if you'd find the tube life of another amp interesting
    but...
    
    I have a Mesa Boogie Mark IIB (1980).  I have to replace the power
    tubes about once a year.  The symptom of bad power tubes (6L6C's)
    in my case starts out as a loss of dynamics (unwanted compression),
    then you develop noise, and finally you get what sounds like a cheap
    fuzz box (extreme compression and clipping).
    
    I have never replaced the pre-amp tubes except as an experiment.
    The Boogie engineers have said that pre amp tubes (Boogie's use
    12AX7's) generally last a very long time and that when they "go",
    they GO  (i.e. not gradually).
    
    	db

	I essentially went through the amp,set tube bias,checked the power
supply etc. I still have a 60 cycle hum which should be corrected if I
re-route some wires in the amp. When the previous owner had a master volume
put in it he had it located after the first channel which he overdrove into
the second channel. A real mess and I was lucky that He left the wires hang-
ing around so I could trace it back to the original circuitry. I didn't have
to replace tube sockets,but I did tighten the pins.
	I will check my tone setting to determine how I get a mellow sound
out the amp. I would guess that I run my bass on 4,middle on 10,treble ,on 5 
or6,and presence on 3 or 4. Presently I'm using an old Fender Tremolux 2x10 
Cabinet which I'm going to trade for a 4x12 Cab which I'm going to wire for 
stereo and use 2 12" Celestions for the Marshall and 2 12" for another amp.The
guitar I am using is a Gibson solidbody shaped like a Les Paul which has two 
70's Les Paul Custom humbuckers.
	However I did notice a difference between the two channels that
there is usually a bright channel(higher gain) and a normal channel. Is this 
true? I really don't hear a dramatic difference and since I consider my self
sensitive hearing wise so I suspect that either there is a damaged component 
or something has been rewired which is unrecognizable by sight. I played on
a 1968 50 watt in rough shape which had 6550's which had a drastic difference
between the two channels. I passed up buying this amp due to it's condition. I
also tried a newer JCM amp which I didn't care for. Picky,Picky,Picky!
	There are similiarities in circuitry of a Marshall to Boogie compar-
ision which are primarily found in the power amp,but the preamp sections are 
quite different,so it is hard to go by what a Boogie will do compared to a 
Marshall.(Actually the really old Marshalls used 6l6's(5881's)) Since I don't 
play regularly other than at home I guess it would be safe to replace tubes 
once a year to insure that the amp is reliable and stay's in good condition.

						Thank's for all your help!

								Rick

    I am a Fender Twin Reverb owner, and was surprized to hear
    that Groove Tubes are available in different versions. I would
    like to change the tubes in my Twin to get a slightly overdriven
    sound. Does Groove Tube make 6l6GC's for twins that will give me
    that sound ? Is it nesecary to change the preamp tubes as well ?
    My amp plays fine with the Fender tubes in it. They are about 6
    years old. However it's too clean sounding, partly because it has
    JBL speakers which refuse to distort. How expensive are the Groove
    Tubes and which number should I ask for. Are Groove tubes better
    than Mesa Tubes (better price/performance). I'd appreciate any
    info. 
    
    
    							Mark Jacques
    							LM02/Marlboro
                                                              

    	6L6's are available from Groove Tubes are rated from Soft(S)1 to 10
and Hard(H)1 to 10 and you also can get 5881's which were the old style 6l6's. 
they really have a big variety of replacements for these.
	The soft style tubes distort a little quicker and easier and the lower
the number the easier it is to get compression quicker and distortion.
	Prices on power tubes alone are $100 for a quartet of 6l6's(ouch)and
$50 for a duet. 
	There preamp tubes are $15-20 each.I definately heard an improvement in
sound from the old tubes to the new GT set. I also replaced preamp tube's and
the phase inverter tube. My El34's were rated S-7 which are pretty clean until
the amp is cranked up beyond 6. I'd suggest you find a local dealer who has a
a set of S-4's you can try or even a lower number as most twin's are really
clean. Matching tube performance in pairs and fours insures that you will
get even performance out of your tubes,since it is a push pull tube amp. Also
If you are not using all the power from the Twin you can disable two power
tubes and save some money.
	There expensive ,but I am satisfied with what I hear and that's what
is important.


							Rick

    Has anyone tried Groove Tubes in a Boogie Mark II or Mark III?
    
    Please give a brief review and specify what rating GT (Soft 1 to
    Hard 10) you used.
    
    BTW, one thing I've done to limit the frequency of tube changes
    is buy one of the inexpensive 12 watt practice amp.  This turned
    out to be a good idea.   The tubes I put in about 8 months ago are
    still doing very well, but it also makes practicing much more
    convenient.   I strap on my guitar, plug it into the amp, then pick
    the amp up and move to whatever room I feel like practicing in.
    
    I even brought it with me on vacation last week.
    
    My practice amp even has headphones so I can practice without
    disturbing my SO.  It even has a "distortion" mode although I don't
    use it much (I prefer a clean sound for practice).
    
    	db

    
    re.8
    Rick,
      You mentioned about disabling two tubes, if you don't need the
    power ? 
    I've heard of this before, but have never done it for fear of it screwing
    something up. Does it matter which tubes you pull out, or are you
    leaving the tubes in and disconnecting the pwr lead to the socket?
    MORE DATA NEEDED HERE !!!!
    I had a very depressing experience with an old Marshall Major, when
    I was in college. It smoked, and burned during a gig. The audience
    thought it was great ! I was devastated ! I've been afraid to buy
    another Marshall since. Stupid I know and I shouldn't let one bad
    Marshall experience keep me from buying another one, but I don't
    want to start pulling tubes in my present amp and blow this one
    too !!! One more question, has anyone played, or heard any word
    on the newer 100watt {mosfet} Marshall? I tend to lean towards tubes
    rather than solid state, but was just wondering what the word was
    on it. WJB... what's the deal ? 
    
    Fred
    
    

    re: 10
    
    No way, Rick you used to have a Major??? Those suckers moved
    funature!!! I have an old 100WT marshall super lead and yanked the two
    outter tubes to make it 50WTs (I still need to re-bias). It's more
    bearable. (Check with Rick, he has the word on stuff like that)
    
    The new Mosfet Marshalls?? Well, the all solid state ones sound
    like solid state...what can you say?? they are loud, but its really
    not *the* tube sound. They now have hybrid's too (SS preamp, tube
    output)...I doubt it really helps. I suggest checking out the new
    all valve Jubilee series. they come in 100/50 and 50/25Wt versions.
    
    Have at it...
    
    wjb

                                                                      
 	I answered this offline here's a summary for those interested:   
    
    	There are four power tubes in your 100 watt Marshall of which depending
on what year you buy will be EL34's or 6550's. The two outside tubes (1,4) can
be pulled to reduce volume increase distortion and sustain,and your speaker 
impedance should be changed from 16 to 8 ohms. This is something I got from
the guys at Trainwreck Amp's. Now this does'nt change 100 watts to 50 watts ,but
more of 100 watts to 75 or 80.If this is done and plan to keep it that way 
permanently I recomend you have your power tubes rebiased or at least checked
for biasing. A word on what biasing is... Essentially biasing power tube's is
the equivalent of setting the idle in an automobile. If you use your amp often
then this can impact power tube replacement. Some amps seem to be more sensit
ive to having this done. If you find you replace your power tubes often then it
would be worth your while to have the bias checked the next time you change
power tubes by a qualified repair shop.
	The 100 to 50 watt change can be done on other amp's as well,I install-
ed a switch in a Dual showman to disable it to half power. Any tube amp can 
have this done. Mesa-Boogie offers it as a option to there amps as Seymour 
Duncan and the new Marshall's have it also.

								Rick

    Last night I bought an almost complete set of Groove Tubes for
    my Fender Twin Reverb. I bought a quartet of 6L6GC's (rated H4)
    and 4 7025's. The only thing I didn't replace was the 2 12AT7's
    which drive the reverb and tremelo unit. The reason I didn't 
    replace them is cause I ran out of money. The tubes I bought 
    set me back $135.oo (ouch!) I plan to replace the 12AT7's in
    another week or 2, once my wallet gets done bouncing back !
    According to the diagram inside my amp it takes 1 12AX7. The
    salesman said that a 12AX7 was the same thing as a 7025. Is this
    true ? If so, why the distinction ?                                      
    
    I bought them from Wurlitzers (I know, they suck) because they
    had them in stock and at the right price. Believe it or not a
    complete set for my amp lists for about $200.oo (unreal, in
    1962, you could probably buy a brand new Twin for $200.oo).
                                         
    The guy who sold them to me recommended buying power tubes rated
    H6. I asked about the soft tubes S1-? and he said they didn't 
    recommend them for twins since a Twin is supposed to have a clean
    sound. With the soft tubes I would be limited to only one sound,
    dirty. I told him that my Twin was really too clean, partly because
    it has JBL speakers in it. He said if I wanted a little more edge
    to go to an H4 but no lower. So that's what I bought.
                                    
    	Did I make the right choice ? The amp does sound a little bit
    punchier, with more sustain, and was certainly due for new tubes
    (It's been 5 years), however I never imagined spending that kind
    of money for tubes in my wildest fantasy. If you look at it in the
    context of $/watt (I know totally eroneous) I paid about 64cents/watt.
    I haven't had a chance to crank my amp up loud yet with the new tubes,
    since it was midnight by the time I got home from nightschool and got 
    around to swapping them. That will be the true test of any sound 
    improvement resulting from the change.
    
                
    						Mark Jacques
    
    

	Boy! where do I start? No a 12ax7 is not a 7025 is not a 12at7.
All three tubes have different tonal,gain characteristics. The first
two tubes when facing the back of a twin are 7025's usually,according to
schematics this is true also. The 7025 has more gain and edge than a 12ax7
which has less bite and gain. It will work in your amp,but be aware of the
change. The next 3 tubes moving to the left are reverb and tremelo tubes.
I can list them later. The 12at7 tube which is right next to the power tubes
is a phase inverter tube and should be replaced when replacing power tubes.
	The reason he recommended H6's is correct if you want the Fender
twin sound. Also if you change power tubes it is recommended you have the 
tube bias checked. I think I explained why somewhere else. This is a fairly
easy and inexpensive procedure for a repair shop who has a scope,frequency
generating device,and loads. If your bias is incorrect you will see the 
groove tube's label on the glass turn brown. Or you will get an excessive
amount of crossover distortion. Your tube's will wear quick also. 
	Did you make the right choice? Only you can answer this. If it sound's
good to your ear that's what's important. The price does really take a bite
out of the wallet,but What's the end result? Maybe this will be answerable
in a year. I've heard a twin with H7's in it and it was incredibly clean.

							Rick

    
    I believe there must be a few different versions of Twins out
    there, because mine is different than others I've seen. Inside
    the back of the amp, it has a tube location diagram. Off the top
    of my head I believe the order is from left to right:
                                                        
    	4 6l6's in a row
    	1 12AT7
    	2 7025
    	1 12AT7
    	1 12AX7A
    	1 7025
    
    	I could be wrong about the order. I'll write it down tonight,
    and write it in tomoro.
    
    	Anyway's I'll probably get the 2 12AT7's this weekend, and complete
    the set. As far as any adjustments on the amp is concerned, there
    are two adjustment pots on the back panel, Hum balance, and Output
    tube matching. I adjusted both to produce the least amount of hum
    with my Telecaster plugged in to channel 2 (Reverb channel), with
    the reverb turned up to about 5.
    
    	I may end up having it checked out by a repair shop, because
    I get this sound when I turn it up load, kindy like thunder about
    a mile off in the distance. I believe if I let it warm up for 
    an hour or two, it doesn't do it, but usually I only use the amp
    for a hour here and there, since I'm not currently using it for
    playing out. Any idea what the thunder sound could be ?
    
    
    							Mark J.
    
    	 

    I was off a little on the tube diagram. It should be
    
    (4) 6L6GC's	12AT7	12AX7A	7025	12AT7	7025	7025
    
    	I picked up the 2 12AT7's last night and popped them in.
    I don't hear the noise I was getting before, so maybe I had
    a bad 12AT7. I also noticed that if I keep the Tremelo in the
    on position on the footswitch, it clicks. I was cranking my
    pots up and down. Both channel volume pots were noisy. After
    cranking channel 2 a few times, it sounds cleaner. The channel
    1 volume pot is continuously noisy after several cranks up &
    down. I may need to replace the volume pots on this baby. You 
    know that damn Fender reliability. I've only had the amp a measily
    10 years and already I have to have it repaired (sarcasm) !!
    
    	After using the amp for a few hours with the new tubes, my
    conclusion is that it sounds "warmer". It has a sweeter sustain
    than before. Before it was so clean that a single coil pickup
    couldn't make it sing. Now it sings better ! The reverb sounds
    much better than before which leads me to believe one of the Reverb
    tubes was on it's way out. I am gonna check with the repairman
    at Union Music about having it checked out. 
    
    	Does anyone know if there are any books out there about
    repairing tube amps. I'm sure I could check the biasing myself
    if I had a book to refer to. Do you have to use a scope, or
    can you measure the bias voltage with an AC voltmeter ?
    
    
    							Mark J.
    

	Biasing the power tubes in an amplifier requires the following
test equipment:

1. Voltmeter
2. Oscilloscope
3. Sine wave generator 
4. Resistor decade/subtitution box(in some case's)
5. Speaker Load

	The process is fairly simple,but the scope is absolutely necessary
in order to determine if the tubes are properly biased. ie.Can you set the idle
of your car 1200 RPM by listening to it? (you need a tach) There are books 
which are available which get into tube theory,some new,some out of print 
some old. They usually spend very little time on biasing itself,but get into
alot of other stuff. If you have access to the necessary test equipment I'll
type in the process or start another note on how to do it.
	The 12at7 to the left of your second channel preamp tube(7025)
    is right before the Reverb springs transformer the 7025 next in
    line is the output. The 12ax7 is used for the tremelo and then the
    12at7 is the phase inverter. Scratchy pots some times can be cleaned
    with tuner cleaner(lubricated). Finding replacement's of equal quality
    is both expensive and hard to find. 
    
    							Rick

    	I think I missed the point about S VS. H tubes.
    
    	Is 'Soft' a dirty sound and 'Hard' a clean sound?
    
    	Which would you recommend for my 50W Fender Bassman?
    
    
    			Tom G.

    	Soft at a lower rating(1-10) distorts easier and Hard is
    cleaner (also rated 1-10) I use S6's in my Marshall for the
    distortion/comp sound and ordered H7's for my Fender for a clean 
    sound.
    	I'd recomend H7's to maintain or improve what you have,anything
    else will not be drastic enough unless you use and H3-4 for distortion
    which I assume you don't want. If want the H7 type sound and need
    more clean I'd suggest you replace the GZ34 or 5ar4 rectifier tube
    also.

    
    Re: .18
    
    For a bass amp, particularly a Bassman, I would go for harder
    tubes...in fact I did when I retubed mine, also got the solid state
    replacement for the rectifier tube.

               
    

    
    re: .-1
    
    > also got the solid stae replacement for the rectifier tube..
    
    	Huh? (I feel SOOOO uninformed!! :-))
    
    		Tom G.

    re:.20, .21
    
    Oops, sorry if I confused you.  Some old Fender amps use a tube
    rectifier in the power supply instead of a solid-state (diode).
                                 
    Nowadays, with tubes becoming more scarce and more expensive, Groove
    Tubes has come out with a can that fits into the tube rectifer socket
    but actually is solid-state, so it won't need to be replaced later.
    
    The easiest way to tell if you have a tube rectifier is count the
    large tubes (the small ones are for your preamp).  In a Bassman,
    there are two 6L6 tubes and if there is a third large tube, it should
    look different than the other two, this is the rectifier.  
    
    There are arguments that solid-state rectifiers produce cleaner
    power to the amp, thus allowing less "mush" when you are playing
    hard.  I don't know for sure, I just figured why keep putting a
    tube into the power supply every couple of years.  
    
    My Bassman is an old one, with blond tolex and brown face.  I would
    think that all the later black and silver faced amps used solid-state
    rectifiers.
    
    
    
    

    A word of warning on replacing a tube rectifier with a solid state.
    Groove Tubes warns that the DC voltages generated by a new solid
    state rectifier may be slightly higher than those from an aged
    tube rectifier.  This increase in voltage may cause old, mariginal
    components in the amp to fail.  Be prepared to make some repairs
    if you do this upgrade.
    
    /rick

    	I'd also be careful to power up your amp slowly,like in standby
    mode first each time. The amount of time delay in tube warmup as compared
    to solid state power up is significant and I'm sure this may impact
    your other tubes.(wear and tear?) I considered the SS5u4b Rectifier
    tube that GT distributes,but was inclined to stay with the stock
    design rather than change and risk damage or getting a different
    sound out of the amp the way it is. 
    
    							Rick
    

    Do any of you know if any of the mail-order music places (Stewart
    McDonalds, etc) sell tube sockets.  I noticed in one of the earlier
    replies that GT markets them, but when I go to the local music stores
    (some of which SELL Groove Tubes...).  They just go, "Huh? whydoncha
    try an electronics store?...".  None of the local electronics stores
    have the socket types I need (they have little hoods) for my preamp
    tubes.
    
    I have a HiWatt 100 watt combo that got damaged in shipment when
    I moved here and a couple of the tube sockets were bent/broken.
    Maybe they were that way before, I always noticed a funny buzz (from
    the amp, but not out the speaker).  In any case, I'd really like
    to fix it and can't for the life of me find the parts.
          
    Any help will be appreciated GREATLY!
    
    Greg
        

    I don't understand your description, but I've had luck in similar
    "hopeless" situations at Stark Electronics, Franklin St., Worcester.
    
    Jon

    
    I think that it is not the *socket* you are having trouble finding.
    
    The socket is still plastic.  The metal hoods are two separate pieces,
    the base mounts to the chassis, the hood clips to the base with
    a bayonet action.                                                    
    
    

    re .26
    
    Sorry about the description, I'm not feeling well today and my mind is
    pretty foggy (...when I was a child, I had a fever.  My hands felt just
    like two balloons.  Now I have that feeling once again.  I can't
    explain you would not understand, this is not how I am...).  I'll try
    to clarify. 
    
    re .27
    
    In a way you're right...I can find the little bakelite sockets. The
    problem is that the original ones have the chassis mount and hood mount
    as an integral part of the socket housing.  Ie. the bakelite socket is
    surrounded by a metel ring that has the screw mounts to hold it to the
    chassis and also the bayonette mount for the shields.  It's this metel
    part that's broken.  The tubes are ok and the amp still operates!  But
    one of the tubes is loose because the screw flanges on the socket are
    broken off and it's just being held in there by the wires to the
    socket.  There's another that's bent over at about a 20 degree angle. 
        
    What happened to the amp was:  It laying on it's back during shipment
    and the heavy EV-II speaker pulled the screws out that hold the
    speakerboard.  The speaker then contacted the preamp tubes.          
    
    Hope that's more clear.
    GReg    

      
    re: .17 
    
    Rick,
    
      Did you ever enter a note explaining the processes of
      biasing power tubes???
    
      I have a fender vibrolux reverb amp that needs it and I'm
      a little unsure about what to do.  I am *assuming* that
      biasing the tubes is done to set the output stage idle
      current and elimate the crossover distortion.  I have done
      this alot in school on transister amps, so I figured it must
      apply to tube amps too.
    
      If my assumtions are correct, there is one peice of information
      that I am lacking in order to do this, and that is the amount
      of idle current.  Does one simply adjust it until the crossover
      distortion is gone?

      Somewhere, I think I read that if tubes are glowing blue or some
      such thing, they are biased incorrectly.  Is that true, or what??
      
    Thanks,
    Frank
    

    	I get back to you,I'll need to find what I wrote or write something
    up.
    
    								Rick
    

			Power Tube Biasing

Tools required:

Screwdriver (with an insulated handle.)

Sine wave Generator cable of 1 to 2khz

Voltmeter

Scope

Resistive Load 4 or 8 ohms

Resitor Decade box(maybe)



	Underbias - Tubes are running too hot
	
	Overbias - Tubes are running too cool and you will get crossover 
	distortion and loose that nice harmonic distortion.

WARNING: Tube amplifier's have voltage's which typically are around 400v
	and caution should be taken when working with them.

	Dis-assemble amplifier by disconnecting the speaker,and reverb in/out
cables. Take four chassis screws/nut out of case and don't forget the strain
relief for AC input cord. Pull metal chassis out of wood case and stabilize
on you workbench. Take the insulated screwdriver and discharge capacitors to
chassis to eliminate potential shock hazards,when facing the rear of the amp
the discharge area is near the left side of the amp and not far from the power
transformer. The power supply caps are actually located under the amp chassis
covered by a metal pan.(for safety)

	Attach volmeter to pin 5(red probe) and ground to chassis(black) remove
power tubes,plug into ac,power up amp and adjust variable pot to the highest 
negative voltage possible.(anywhere from -30 to -50) turn off amp and 
discharge cap's.
	Replace Power tubes and put a load of 4 to 8 ohms depending on your
requirements and power up amp. Put a 1 to 2khz sine wave into the input and
increase volume to 75%. Monitor your sine wave at the output stage with a scope
and it should be only different from the input in amplitude. At 75% volume you 
may see the sine wave as a square wave. Crossover Distortion indications will 
be seen at 50% or half the peak as a break in the sine. You adjust your bias pot
until it disappears from the scope picture. I usually let it run for awhile to
make sure that the Power supply has reached a steady state. This is dependant on
your time. Power down the amp,disconnect meter,discharge capacitors and put the
chassis back in the wood case. 
	I'd recomend you replace the 5u4 Power supply rectifier tube
and the 12at7 phase inverter tube also if you are going to go to trouble of 
doing some amp maintenance. If your amp doesn't have a biasing pot you will 
need a Resistor decade box to get the right resistor value.

	A Blue glow is not an indication that your tubes are mis-biased,but
if they start turning cherry red inside then you have biasing problems. And
Yes biasing power tubes is current/voltage adjustment. Matching tubes will
get the best performance out of your amp.

	I can't stress safety enough in doing this kind of work,and hope I
have not forgotten anything as this was from memory. 

						
							Good Luck,

								Rick

    Rick,
    
     Thanks for taking the time to enter .32.  I will give
     it a try as soon as the opportunity presents itself.
     Oh, and I promise to be careful.
    
    Frank
    

    Does anyone have the number to Groove Tubes handy ?

    I looked thru all my old guit-magazines, and can't find the add/number
    anywhere !
    
    jc

    I don't know Jeff...I replaced all the tubes in my twin last year
    with GT's (at great expense, I might add) and I really do think
    they're fine tubes.  But, a quartet of matched 6L6's cost me $80
    and the preamp tubes were $12 a piece (there's 6 of 'em).  Prices
    now are even higher.  Let me say that as much as I like the GT's,
    I wouldn't do it again.  Just can't be *that* much better than good
    ol' RCA or Sylvania or ?? tubes.
    
    I know you're considering the EL34 mod on your Marshall, so maybe
    you have to buy GT's...
    
    If you're trying to get a free "Tube Book" (or whatever it's called),
    forget it.  They charge you for it and it ain't cheap -- well, you
    can try to get them to send you one for zip, maybe you'll do better
    than I did.  Although GT does sell their tubes direct, you get much
    better prices at your local distributor (i.e. music store).  The
    number is (818)-362-1551.  I've been through this all once before
    along with Mark Jacques, and Dennis Moreau to name a few.
    
    joe.

Reprinted without permission from "The Tube Amp Book"  distributed by Groove
Tubes

"The EL34 is widely used in HiWatt, and older Traynor amps.  It was also
stock equipment in Marshalls sold here up until 10 years ago when the
distributor in the US requested that their amps be outfitted wwith a heavier,
more reliable tube, the US made 6550.  The 6550 will last longer in the
average Marshall and that translates into less cost and hassle for the
distributor.  However the 6550 will not sound like an EL34 and they WILL
NOT cost you less (the price of an EL34 is about 1/3 less than 6550's).

The Marshall company has recently change distribution in the US and as of
mid-1986 (old book eh?-jc) are shipping their new amps with EL34's as standard
equipment.  Marshall amps with 6550's can easily be converted to GT-EL34's
(little plug for GT!  The schematics and directions are included in the
book-jc).

The EL34 is stock equipment on Marshalls sold every where but in the US
and Japan.  In other words a Marshall with EL34's is THE guitar sound on
records recorded in Europe, Canada and Australia over the past 30 years.
If you've tried to duplicate those sounds with your US Marshall, chances
are you haven't been completely satisfied.  Perhaps the EL34 conversion
is for you.

The reason our GT-EL34's sound so unique is a result of their design and
construction.  The EL34 has smaller components than the 6550 and they are
sealed in a thin bottle with a softer vacuum.  This means they run hotter,
and distort sooner when you attack the string.  They kind of act like a
light gauge string in that they "bend" easier and so the distortion character
is more controlable and less penetrating.  Strait rockers and R&B players
usually prefer the soft, compressed tone of the EL34, while bass players
and Heavy Metal guitarists will liek the powerful and tight sound of the
6550's (Oh really ?-jc).

For what it's worth, Jim Marshall dislikes the 6550's in his amps and is
a strong promoter of the GT El34's.  We label our EL34's a soft style tube 
because of their soft clipping  character and are availble in Duets, Quartets
and Sextets with performance ratings from 1-10.

    BTW - This book is very informative.  I gave $10 to GT to own it...
    they have a little blurb like in -.1 for each tube they sell, plus
    some history on Marshall, Fender, Orange, Park, HiWatt, Carvin
    etc...etc...  As well as modifications for popular tube amps (no
    kitty stuff though... :).
    
    The main modification that I noticed was for Marshall 6550 to EL34
    conversions...and vise-versa.  They also had mods for Fenders if
    you wanted to change tubes to EL34's or 6550s.
    
    In a nut shell, Cool book !
    
    jc

    Eddie Van Halen likes the sharp transients that the 6550s provide.
    Of course, with his Variac, sharp transients is the key word here!
    I like EL34s because they provide a soft, warm distortion.  6l6s
    are cool, too.  I had 6550s once and hated them!
    

    My Marshalls had 6550's in them.  I recently replaced the 6550's
    with GT 6550-S4's...But the Marshall seems to be sick.  I've got
    Field Service working on it now...I think I may have burnt a coupling
    cap or a filter cap or something...This may be why I think Marshalls
    are so lame...   ;^)
    
    BTW - This the 2205 I'm refering too...

    Oh Buck, tell me what Variac does...  I've heard of them, and I
    though they were voltage pots that allow you to pump in more volts
    or something ??
    
    jc

    Yeah, voltage pots...they regulate the voltage running through the amp.
    Back when Van Halen was a sick puppy, he'd crank up the voltage to 400
    or 500 volts and watch the tubes melt!  This process provides a very
    distinct sound from a Marshall...very transient.  You either like it or
    you don't.  Of course you need to be wireless if you are running a
    Variac due to the high risk factors involved with the voltages.

    Yeoch !!
    
    That would be fun.  A variac and a fist sufll of tubes...
    I love his early tones...Runnin' With The Devil etc...
    
    jc (C for Crunch)

    Having just purchased a tube replacement kit for my Mesa Bass 400 at a
    cost of $109.00, which included (6 - power and 4 - pre-amp, plus an
    assortment of fuses, a spare knob, some resistors and capacitors and a
    fuse cover) I was wondering if any of you tubular experts could answer
    a tube type question for me.
    
    I've been running my rig since May of 1988, (a little of 18 months) -
    and running it fairly hard and heavy - - meaning, lots of rehearsal
    time - lots of gig time - lots of load it in/load it
    out/crunch/bang/jar/drop kick type of activity.
    
    The bass still sounds fine to me.  Mesa says, "replace the tubes every
    six months if you're gigging regularly or at least once per year if
    not."  
    
    So I can't figure it - - how does one "really" know when to replace the
    tubes?  Sure - if the a tube blows big time - then that's obvious - but
    my rig has all its tubes burning - seemingly fine - - so why should I
    pull them and put new ones in???
    
    Any advice would be welcome......Thanx .... Dan

        
    Dan,

	Mesa's recommendation may be based on what they believe will give you
optimum performance out of your amp. Plus it indicates that perhap's the  
most useful period of time in the life a tube is 6 months to a year and 
after that period of time performance of the tube drops drastically enough
to degrade the performance of your amp. Since your amp is not a high gain
model,I would assume that once a year for your play schedule would be adequate.
to insure the optimum. 	However,also you might want to note that I have 
seen alot of 20 year tube amp's with the original tubes,some sounded fine
and sounded even better after getting new tubes.
	How does one really know? I listen too every sound which comes out 
of the amp(noise too!) and when I hear something inconsistent,in tone or
volume,then I check out what the problem is. You may not have the time
you need to invest into troubleshooting your system. But then again if
you change your strings regularly it's just like any other maintenance
expense. What's it worth to you for someone else to do the work? 
	I would investigate and find a reliable repair tech.


							Rick	

    Even thou I've replaced my 6550's with EL34's, I still remember that
    hard sound. Once I had the thing WIDE open , all the knobs up.
    The thing sounded like a Grand Piano to me, unreal.
    
    My fun got cut off when the Xformer snuffed and took all the tubes with
    it. 
    
    

	.-1 - what where you doing that got a "grand piano" sound. There's
	this ideal whole-band tonality that I have in my head that requires
	a bass rig that sounds dead-on-the-money like a concert grand.

	Thanks
	Charlie B

    
    
    --------------------
    |			|
    | 100W MV Marshall	|
    |			|
    ---------------------
       |   |    |  |
      /     \  /    \                            Only 1 of these speakers
  ___________________________   Floor            is connected
    
    
    No Cab , speakers sitting onm floor, marshall sitting on speakers
    EV SR0-12's, 16# sheilded magnets, 
    Monster cable 1' long
    
    Linoleum floor
    LIVE plaster walls ( none of this sheetrock. Plaster on metal lathe.
    Nice sunny morning with the window open. 
    
    
    

    
    
    	I think its time for new tubes in my JCM900 50 Watt Duall Reverb
    M word amp...
    
    	This unit was purchased new in June of 88,.. and purchased used by
    me in December of 91 (Merry Xmas Cat!),... and itys my first tube
    amp and my first serious amp in general. So anyway,.. I'm starting to
    notice a strange and annoying buzz... Based on that and sopme previous
    notes I'm guessing it needs a tube or two,.. but if I'm going to muck
    with it,.. I'm just going to do them all.
    
    	Some questions for the filer:
    
    	1) Do you agree that the symptoms (buzzing) are probably due to a
    fried tube somewhere?
    
    	2) Do you agree that Marshall amps burn tubes faster and that 4
    years is way long (4 1/2 actually) for a set of tubes to last in this
    amp?
    
    	3) I think what I need (haven't looksed inside yet) is 3 12AX7's
    and 2 EL34's yes? Wheres the best place to get tubes these daze?
    
    	4) I like to be able to stay clean at louder volumes,.. so I
    presume I'd be wanting a pair of (matched of course) "HARD-8,9,10"
    EL34's? 
    
    	5) Buck said he'd sell me a set of 3 12AX7's,.. how much should
    I give him? :-) :-)
    
    	Thnaks
    							/Bill
    

    re .49
    
    Buck, give 'im the dam tubes will ya. You're a hi paid deccie! Don't
    the rest of you boys and girls agree? C'mon Buck! Don't be such a 
    materialist. You're into enlightened ideas like brotherhood, eh?
    Give 'im the tubes!
    
    :^)
    
    "sakman"
    

Why go with "Hard" tubes in a Marshall - go for mediums 5's ?

12AX7's can be had bnew for as little $4.5each, and a pair of EL34's
will cost $30-%50.

My experience says stay away from GT stuff.  A load of crap.

>12AX7's can be had bnew for as little $4.5each, and a pair of EL34's
>will cost $30-%50.
    
    Where are *you* buying tubes, man?  I've never seen 12AX7s for less
    then about $7 each, usually more like $8-$9.  And you can get
    (unmatched) EL34s for as low as $12 each.
    
    I guess you could save somewhat by buying a whole bunch of 'em...
    
    Greg

I bought four AudioGlassic 12AX7's from Rice for my Quattro for $20 and 
a contribution to uncle sam (not Sam Lambert  :).

jc

    Then they must have charged you the wrong price, not charged you for
    one of 'em, or given you a substantial discount, because they charged
    me $7.50 each for the three I put in my KH M3 just before I sold it to
    Dave Russo.
    
    Greg

U-Do-It Electronics in Needham has 12AX7's for about $6.50 and $7 (two
different quotes from 2 different manufacturers).

adam

    
    You guys should put the electro_notes conference in your notebooks, if
    it's not there already.  Last week some guy was giving away mass
    quantities of tubes...no good for me, since he was on the least coast.
    

    Rice always gives me substansial discounts.  :)
    
    jc

>    Rice always gives me substansial discounts.  :)
    
    Rice *used* to give me substantial discounts, at least Walt did.  Now? 
    Who knows...  Guess I'm lucky to get anyone to say "hi" when I go in
    there.
    
    gh

Saw Walt the other day, BTW.

He's been #1 broker at his office since he started!  We're supposed to get 
together and jam some bluez next week...

jc (Who needs to brush up his bluez chops...BAD!)

    
    	Umm,.. well,.. this is what happened:
    
    	I went to Daddy's today and bought a pair of EL43/6CA7 "green dot"
    Mesa-Boogie matched tubes for $24,...
    
    	They are selling 12AX7's for $4.80 a piece right now (all tubes
    are 40% off)
    
    	So I think I'm going to grab the 12AX7's there tonight as well
    unless Buck gives me a call pretty quick...(hint hint)
    
    	So can anyone relate what these "green dots" would be rated
    as (hard/soft) compared to whatever the standard EL34's Marshall
    put in the JCM900's? Any comments on the pricing? From what I've read
    in here,.. even though I'm buying them retail,.. the price doesn't
    seem bad at all...
    
    	The reason I wanted "hard ones" is because I get plenty of
    distortion out of this amp and as I understand it hard tubes
    wil stay cleaner at higher volumes,.. so,.. I guessed I wanted
    hard tubes,..certainly nothing softer than what I had in there,..
    
    	Yes? 
    						/Bill

See - I'm NOT crazy !!
:)

Best o luck dood !!
jc

    WOWOWOWOWW!
    
    	My new amp sounds great,...
    
    	Well,.. its the same old Marshall with new tubes but man o man
    what a difference,.. before the thing was barely in puberty,..
    just a little peach fuzz,.. but NOW,.. it has to shave and
    everything,..I mean the balz are back in this unit,.. its definitely
    better than when I bought it...
    
    	The differences I noticed with the new tubes right away were
    increased "punchiness/presence" feel to the whold sound. The buzz
    in the mid range is gone. The highs are there like they never were
    before. I was beginning to think there was a problem with my guitar
    as far as the highs went,.. but not so,. it was the amp.,. or rather
    the burnt tubes that caused the loss of high end,.. me high E string is
    now just as loud (well almost) as my other strings,.. I have backed
    way down on the presence control and brought up the bass on the
    EQ (you were right about that Buck!) now that the highs are there I
    can enhance the bass a little,..
    
    This is only after a five minute test drive this morning,.. Got a gig
    tomorrow and one on Friday so by this weekend I'll know for sure.
    
    So anyway,.. if anyone knows I'm still curious as to how these
    EL34 Mesa Boogie "Green Dots" would be rated by GT,.. Hard,.. Soft
    or whatever,.. I like them,.. they do seem to be pretty clean/hard
    tubes,.. but I'm only comparing to what a possible very tired duet
    of 34's used to sound like,.. 
    
    Play your thang..
    
    							/Cat
    

    re .62
    
    I know the sensation. I had an old Fender for 10 years or so. I never
    changed the tubes thinking that tubes were like light bulbs, they
    either work or they don't. Then as a result of this very notesfile,
    I decided to change the tubes once and man was I surprised! Tone and
    presence for days!
    
    "sakman" 

    Well,..
    
    	A few days after the new tubes andss the buzzing is back...
    
    	:-(
    
    	What a bummer eh?
    
    	Not really,.. turns out the buzzing is at least partly the guitars
    fault,.. a little contact cleaner in the switc/pots and ... boing,..
    its noce and clean,. now I can really hear the high end on these new
    tubes,.. adn for a second I thought,.. well,.. you can guesss..
    
    						/Cat_still_a_happy_tuber
    

    Filter caps next dood.  :)