Tube Amp users..Yeh..you Fender guys...

Tony Prior · From: Charlotte NC

Just an FYI..

During the past couple of weeks I did a re-tube on my Fender Hot Rod Deville which I use exclusivley for my Tele'. First re-tube in several years.

2 new Sovtek 6L6's and 3 new Sovtek 12AX7's.

Dramtatic difference..

So , if your playing thru a Fender amp or another amp which has a few of those glass ,glowing ,hanging upside down things, and you have not changed them in a long while, you may want to consider the option.

New 6L6's will clean up the bottom end at high volumes and the 12AX7's will clean up that little bit of noise that you may hear and will return the preamp gain to where it should be.

If you are playing thru an amp that you bought used, you may not know what you're missing.

Oh yes..I bought all the tubes off of EBAY and saved probably 30% from retail prices.

All tubes were 100% guaranteed by the sellers who obviously were tube dealers.

If you get a chance to by Svetlana tubes , get them, they are premium, the Sovteks are a good second choice and are the exact replacements for tubes used in Fender amps. Fender amps being sold today use Sovtek tubes.

Groove Tubes,( not really a brand ) which are nothing more than highly selected matched pairs are not worth the extra price in my view. You can get highly selected matched pairs of Svetlana for half the price.

And finally, the little Hot Rod Deluxe, single 12"/ 40 watt amp does sound great with the Steel, but not at the volumes that can be achieved with the N1000 or a Twin..

Ok..start bidding...

tp

[This message was edited by Tony Prior on 27 March 2003 at 03:15 AM.]

David L. Donald · From: Koh Samui Island, Thailand

If you play regularly tubes most likely will be on the way out within a year. Sure they'll work, but the gradual fade out might not be really "noticable" until you change them out.
Such seems to be the case here. You might have been compensating with volume and eq etc.
My buddy Bob, nearby here, swaps his out each spring before ther playing season starts up big time.

[This message was edited by David L. Donald on 27 March 2003 at 02:40 PM.]

Smiley Roberts · From: Hendersonville,Tn. 37075

I never could figure out,since heat is a "natural enemy" to electronic equipment, why they would mount vacuum tubes upside-down in amps. This would make the heat "rise" to the bottom of the tube,hence, passing through all the elements of the tube,& even weakening the bakelite tube sockets,over a period of time. Has anyone ever made a tube amp w/ the main amp in the bottom of the cabinet,w/ the tubes standing "upright"? Is this a dumb question?

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  ~ ~


  ©¿©  It don't mean a thang,   


  mm   if it ain't got that twang.


       www.ntsga.com

Ken Fox · From: Nashville GA USA

A lot of 1930's to 1960's amps had the chassis in the bottom of the amp with the tubes upwards. I have worked on several, a Sears Silvertone 2-12(circa 1959), a Thunderbolt with a 15" speaker, even a 1936 National Dobro amp! Unfortunately they don't make them like they used to! Kind of reminds of refrigerators, with the hot compressor in the bottom of the refrigerator!
Don't forget to check the bias on the Fender amp. Fortunately the Hot Rod series has an adjustable bias (unlike their predecessors)
Another great tube company is the JJ/Telsa tubes. They are my personal choice due to their higher power and voltage ratings. They just came out with a nice GZ34 and soon will have a 6V6GT available.

Alvin Blaine · From: Picture Rocks, Arizona, USA

Smiley, you need to get yourself a Marshall Amp. They are made with the tubes pointing up on top of the amp chassis. I have a couple of old Rickenbacher amps from the '30s that have the chassis on the bottom of the cabinet with the tubes pointing up. I think Gibson or Western Electric started making amps with the chassis on top so the controlls would be easier to reach.

Tony, Groove Tube now makes 6L6GE tubes. They bought out the old GE tube factory and moved it to Califonia and started producing USA made tubes for the first time in almost 20 years. Right now they are just making the GT6l6GE and plan to start building an EL34 this year and a 6V6 and 12AX7 next year.
You can get GROOVE TUBE 6L6GE's from Musicians Friend for $69 a matched duet, or $139 for a quad.
Depending on how hot you run these tubes they should last seven to ten years. With the Sovtek's you may get three years of use, so I think the new GT6L6GE would be a better investment.

Bill Hatcher · From: Atlanta Ga. USA

Three years lifespan with Sovtek tubes????---I don't think so.

I just did a 7 week run of the Disney Lion King Broadway show here in Atlanta playing guitar. I used a old Fender Vibrolux. I installed the Sovtek 5881 tubes in that amp when New Sensor first brought them into the country maybe 8 or 9 years ago. NO problems and they still sound great.

Jussi Huhtakangas · From: Helsinki, Finland

Smiley, that is exactly how Standel makes the amps nowadays, power amp is on the bottom of the cab with tubes pointing upwards, preamp is on top tubes mounted horizontally. I don't know if this has anything to do with the tube life though. The separate pre- and poweramp design was pretty common on early Ampegs too and an obvious design in a hi-fi audio world.
Jussi

James Quackenbush · From: Pomona, New York, USA

It's cheaper to keep everything is one place
(the top of the amp ) since the controls are on the top, so is everything else....If the amp lasted too long, you wouldn't go out and buy a new one !!.. That's why the old amps are at a premium !!....They last !!.. What a novel approach !!...Hmmmmmm........Jim

Tony Prior · From: Charlotte NC

Hey Smiley..can you spell McIntosh ?

Alvin, I paid $28 for the pair of Sovteks
and I am thinking that you may not be to far off in the 3 to 4 year quality life.

I find it fascinating that folks have been running to Hi Price Groove Tubes for the past decade. Buying tubes from a company that didn't even make them . Is this a great country or what !

Many of the Guitar players are using the Svet and Sovtek tubes specifically because you can run them wide open and get a tad less gain but more drive.

I would use the Groove tube pairs if I could find a deal on them. Otherwise it will be Svets and Sovteks for me...

tp

[This message was edited by Tony Prior on 28 March 2003 at 04:06 PM.]

Paul Graupp · From: Macon Ga USA

Smiley Roberts · From: Hendersonville,Tn. 37075

Yeah Tony,McIntosh was,w/o a doubt,the best stereo system amp made,but it wasn't a guitar amp.

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  ~ ~


  ©¿©  It don't mean a thang,   


  mm   if it ain't got that twang.


       www.ntsga.com

Bill Hatcher · From: Atlanta Ga. USA

Gain=volume

Drive=break up/distortion.

Tony Prior · From: Charlotte NC

Thank you Bill.
Sometimes the Guitar dudes select output tubes which give a little less overall volume so they can crank up the front end and get more overdrive from the preamp tubes and not kill everyone in front of them with overwhelming volume.

Actually you can do this by swaping out the preamp tubes as well from the 12Axxx family. It just takes a little tinkering to find the comination that works . The guitar forums, talk about this stuff all the time.

And Smiley..I worked in a Band where the Bass player was using MAC Power amp before there were big Instrument amps and it was pretty awesome..pretty heavy too !

I suspect the weight and the cost was a primary factor for a working musician to not use them back then, or maybe even now. With the development of Hi Frequency swithing power supplies that weigh almost nothing, that allows us all to have Hi Power Combo amps that we can at least lift off the ground. I bet those MAC tansformers weiged in at about 30 or 40 pounds each, and there were two on the MAC 275..

We carried a MAC 275 around for a few years for the sound system..We had to get there a week early just to be able to rest up enough to actully play after carrying that beast into the room.

Classic tube amps, with the tubes pointing to the sky..you could heat your house with them..

tp

[This message was edited by Tony Prior on 30 March 2003 at 07:04 AM.]

Bobby Lee · From: Cloverdale, California, USA

The tubes in my Mesa/Boogie Maverick are the same ones it had when I bought it 10 years ago. I don't want to change them because I love the way the amp sounds today more than ever.

The amp has been serviced twice by Michael Bendinelli. Both times he said the tubes were fine. Why mess with a good sound?

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Bobby Lee - email: quasar@b0b.com - gigs - CDs
Sierra Session 12 (E9), Williams 400X (Emaj9, D6), Sierra Olympic 12 (C6add9), Sierra Laptop 8 (D13), Fender Stringmaster (E13, A6),
Roland Handsonic, Line 6 Variax

Gino Iorfida · From: Pittsburgh, Pennsylvania, USA

I've found that SOME tubes do last longer etc... for example, it's not rare to find a preamp tube in an old Fender, Vox Marshall etc that still has a lot of life left in it, and non of the new production tubes can come close to tone, so why change them?

Another good example. I serviced a 1962 Vox AC30 for someone, ALL tubes were original (preamp, power amp and rectifier)... all tested STRONG (suffice it to say as strong as any new production tube)... the guy gave me full blessing to goahead and update the tubes. I could have easily done so and pulled an extra $50+ in profit for myself, instead, I talked him out of it.

Point is, I don't think you can put a 'time' (i.e. every 6 months etc), nor hours playing, rather taek each case individually...

now filter capacitors are another story altogether, I've seen them last anywhere between 5-45 years. however, most mfrs. will rate them at 5-10 yrs max... so if your amp has original caps, or the caps are over 10yrs old, I'd recommend getting them changed, since it would be a case of WHEN they are going to go, not IF... and when they go, they can cause some EXPENSIVE damages when they go...

C Dixon · From: Duluth, GA USA

Having serviced most makes of amps for a long time years ago, I can agree about Fender's decision to mount the tubes upside down.

Fender designed some fine stuff, but that decision was D U M B!.

One of the more serious problems it caused, was severe heat warpage of a fiber separator where all the components were connected inside the chassis.

This fiber would warp so badly in some cases, that it would lift "grounds" completely; as though some one had unsoldered them. This caused one of the more common repairs I had to make. Another common repair was replacing the Silicon rectifiers in the power supply. I could never figure out how often they would go bad, and yet I never ever recall a "call-back" when I replaced them with 600 PIV rectifiers.

Again, the circuity design was superb but mounting those tubes upside down and the way the components were installed and connected was not good, IMO, the best way to go about it.

Also, 12AX7's tend to be quite microphonic and noisy. 7025's CAN be better; but it may take trial and error to get some that are the quietest. When I serviced them, I sometimes would try a half a dozen; trying to get a 7025 that was as quiet as possible, and NOT microphonic.

As I recall, the Sylvania tubes were the best I could find. RCA tubes were often soo noisy as to be totally unacceptable. of course today, one has to use whatever they can get.

One of my major complaints with Fender was them NOT giving a procedure for adjusting the "bias" pot on their bigger amps like the Twins (right on the schemtic). To this day I have never seen a good explanation as to "how" to set that bias; and more importantly "WHY" it is set the way it should be set.

So what I discoverd was, there was as many ways as people I asked. Does ANY one know and please spare me opinion? I mean KNOW for sure. Surely SOME one at Fender knew. But I was never able to find one out that made sense.

carl

Bill Terry · From: Bastrop, TX

Bill Crook · From: Goodlettsville, TN , Spending my kid's inheritance

Bill Terry · From: Bastrop, TX

What Bill describes is the bias balance, the older amps had a single bias supply with no balance. The pot in the older amps' circuit regulated the amount of bias, not the balance. It's one of the first things you do to 'Blackface' a SF amp. I assumed (incorrectly?) that Carl was asking about the older amps and the bias level.

I know of several people who have modified the bias circuit to provide both balance and bias level adjust pots, but the story I hear is that if you buy tubes as a matched pair, (the reseller typically does it before he sells the tubes) the balance is pretty much taken care of. True?

As far as different shops' methods, I'd agree with Bill. I've seen everything from "I adjust it until it sounds good, then check to make sure the plates aren't glowing", to more precise measurements involving measuring cathode current, either directly or indirectly, as Bill described, to looking at a sine wave on a scope and adjusting until crossover distortion is eliminated.

As I said, the Fender forum has many threads on this topic. If you think this bunch is argumentative, check that out...

C Dixon · From: Duluth, GA USA

A minor point. On any quality amplifier, there is NO cathode resistor. Here is why. Any current flowing thru that resistor reduces the amount of power seen at the output. If you eliminate the cathode resistor (to achieve max power), then it creates a problem.

IE, in order to bias the tubes, cathode bias (using a cathode resistor) is by far the most common. (Albeit we lose power in the cathode resistor). The next best option is to use "fixed bias". This is what Fender used back when I serviced them in their larger amps. I have NOT a clue what they use today.

Fixed biasing is by far the best, since there is NO degeneration (loss of power) with fixed bias. The problem fixed bias causes, is getting it set correctly.

Thus the reason for my statement in my other post. AND the verification of my comment that there were as many opinions as people you ask.

For years I assumed you simply adjusted the bias pot for minimum hum with no signal. I was incorrect as so aptly pointed out by a number of more informed people recently. God bless you.

And the post about how the output stages operate, is correct. Because these tubes are operated "class AB*" The star means I have never known whether it was class AB1 or class AB2; or worse yet, a special class that Fender came up with.

I believe this is where the problem lies. Again I feel Fender let the service people down by NOT informing us of the correct procedure to adjust it and the "why's" for adjusting it a specific way.

Finally this; a serious form of distortion can occur in any tube that is NOT operated Class A. This problem is called "crossover distortion". IE, it is distortion caused at the point where one of the tubes is just beginning to turn off and the other one is just beginning to turn on.

Push/Pull amplifiers have this form of distortion as part and parcel of the way they operate, UNLESS some form of correction is used to counteract crossover distortion.

The most common form of compensation is to use negative feedback. In other words, feed JUST the amount of "crossover distortion" BACK (into the grids of the output stages) in the opposite phase to cancel out the distortion. Fender used this all the time back then. I do not know about now.

But here again, a problem can occur IF the correct amount of negative feedback is not used. The end result is it may under or over correct resulting in distortion.

Course, with the rock and roll age, who cares huh?

Oh well,

carl

Jeremy Steele · From: Princeton, NJ USA

All the old Ampeg "PortaFlex" amps had the tubes upright (and caged, since they hung upside down when the amp was in transit).

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