help! need tube knowledge!

N

natbot

New member
Alright, so over the weekend me and the band are driving from brooklyn to somewhere in massachussets for a gig, and along the way one of my tubes falls out and busts... "hmmm," i think, "i don't know shit about tubes!" i'd like to use this opportunity to get a set of better tubes that will help my sound along...

right now i'm playing a mexican strat custom tele through (my know semi-dead) fender twead re-issue 4x10. i like to play clean most of the time. bright, twangy, warm, clean. can anyone recommend some mid-price-range tubes for me?

also, i like to use the twead's overdrive option occassionally, but it really sounds like shit (ie. compressed, thin, no good mid or low end)... does that have to due with the tubes?
and of course the reverb is well used as well...

any opinions, war stories, or educational urls welcome!
 
You didn't say which tubes you were looking for, preamp or power.

As I have found out the hard way, Sovtek tubes are generally junk unless they've been run through some additional QC. The ones that come from unsorted sources like Musician's Friend and other mass music retailers are at least 25% bad in terms of noise and other defects. I ordered six recently and two were definitely, unusably bad, and none were quiet enough for me.

I suggest getting them from Lord Valve, who rejects about 40% of the Sovtek preamp tubes he gets from the importer. Other outfits reject about 10%. Audiophile tube stereo people reject about 90% of the 12AX7LPSs.

Lord Valve is a total putz, but he's got the best Sovtek tubes for the price. Don't have a URL, but you'll find his page on any search engine or any flamewar in the tube/amp newsgroups on Usenet.
 
Tubes,...??

Hey Natbot,.. I have a little knowledge about tubes, and what they do to the amps 'Tone"
for example, most of the tubes in stock somewhere, all have varying degrees of defects, basedc on how they where shipped, etc, and finding a 'Matched ' pair, or language like that makes a difference in cost, as well.......
There are also available thru many sources, New,Old Stock , or the same tubes that were in the old fenders, or Vox amps, or old Ampegs, etc etc They are available in a large variety by Brand, GE, RCA, RAYTHEON, SYLVANIA, and some of the 'Premium' Names, are Mullard, Amperex, , and a couple of others,........ They all sound diferent from one another.... and also many come in a military version, which is built a little heavier, so can take a little more abuse.....

The original numbers on the tubes, can also be replaced , even if only temporarily with several other ones with the same voltages, and pin arrangement. Such as Lots of amps use 6L6 power tubes, This could be temp. replaced with a 6V6, or a 6K6, with dramatic results in getting a differant sound........

And the smaller tubes, like the 12AX7s can be (even if only temporarily) with others like 12AU7, or 12AT7,

Then bring in the differance in sound from one brand or another,........
You have TONS of choices man, just depends on what 'Tone' you are lookin for....

If you go on E-Bay, and go to a search there, Vacuum Tubes, there are lots of links to venders.

I also have a few 'Old' tubes myself, and plan on trying a few differant ones in my 'Univox' amp, to see the differance from the Mullards that are the Pre-amp tubes.....

Maybe I'll do a report on the results, kinda like a book report......

Yeah,..... Thats what I will do......

Stand-by...

Testing,......

Testing..............

Testing,............

HEY,.. IS THIS THING ON,..... tap tap ,.. bloww blow,... tap tap,.....

Testing.....


Yeah, thats what I'll do

Upstate :D
 
I dont want to contradict upstate but unless the tube is a direct replacement do NOT use a different tube than what is called for. For example if you use a different tube that draws more current you can fry everything in that circuit.
 
dragonworks said:
I dont want to contradict upstate but unless the tube is a direct replacement do NOT use a different tube than what is called for. For example if you use a different tube that draws more current you can fry everything in that circuit.
Click to expand...
You have some flexibility with preamp tubes, but do NOT monkey around with power tubes. Even "exact" replacements frequently require rebiasing of the circuit.

Getting a bunch of 12AX7 variants of different vintages and swapping them out in your preamp stage is usually harmless and can make a huge difference in sound quality. Finding some excellent vintage 12AX7s in old equipment permitted me to make an enormous difference in the sound quality and noise level on my Ampeg V-50H head when I bought it. Dutch-made Amperex "Globe" tubes I found made a night-and-day difference in the sound compared to both the no-name Chinese 12AX7As that came in the amp and the Sovtek 12AX7LPSs that I bought to try out as replacements. The Sovteks were unacceptably noisy, worse than anything I have yet tried.
 
ok, so...

cool. thanks for all the help gang, but i'm still unsure of what move to make...

as stated before, i'm playing through a fender tweed re-issue 4x10. there are two power tubes (i think).

and does anyone know what kind of tubes these would take? the one i have left is a Sovtek, but the number is worn. seems to be something ending in "...600" i purchased the amp used, so they may not be the original tubes.

i'm looking at the Sovtek 6L6WXT+ tubes... they seem like they would fit me well. i'm considering ordering through tubestore.com as i feel i could blindly trust their quality control. is this a bad idea?

any and all help is greatly appreciated. thank you.
 
Dragonworks,....

Hey Jerry,

I am looking at a book called : H.H.Cisin's TUBE REPLACEMENT GUIDE published in 1959, inside is the following quote

"All tubes suggested for substitution have characteristics similar to the tubes they are to replace. WILL FIT INTO THE SAME SOCKET, and DO NOT REQUIRE ANY CHANGES WHATSOEVER IN WIRING. In a number of instances, where no domestic substitute exists, foreign replacements obtainable in this country have been listed."

" In most cases, it is preferable to replace with the original type,if this can be obtained.

In some instances, certain tubes may only be substituted, in a parallel connected circuit, these will be marked with an asterick. (*). In cases where an asterick is shown, it is neccessary to know whether the heaters or filaments are connected in series, or parallel. This information may be obtained readily without consulting a diagram or tracing the circuit. Remove a tube, while the power is off, when the power is turned on, if the remaining tubes are lit, the heaters are in parallel."

With this being the case,....... turning to the page with the 6L6 tubes, the list of possible replacements is as follows;

6L6, Replace with,
6F6*,6K6*,6U6*,6V6*,1614, KT66(f),5881, 1621* ,1622,5932,6550,7027*,6L6G,6L6GB,6L6GC

The one with the (f) is a foreign replacement.

Going to a different place where another type of tube is listed, The 12AX7, the book suggests;
12AT7, 12AU7,12AY7,12AV7*,12BH7*,12AZ7*,12AD7,5751,6057,6681,
ECC83(f).

Also, in the back part of this same book, is a chart with USA replacements for foreign tubes, and the chart reads;

B339,replace with,12AX7
B329, " " ,12AU7
B309, " " ,12AT7
B152, " " ,
ECC81, " " ,12AT7
ECC82, " " ,12AU7
ECC83, " " ,12AX7
EL37, " " , 6L6
KT66, " " , 6L6*
5881, " " , 6L6


Now, as far as I know, according to this, and the other tube books that I've read, as long as the voltages are the same,and the pin arrangement is the same, and the basic function of the tube is the same, IE: Power tube VS pre-amp tube, etc and you follow the guide as to parallel VS series heater wiring, then I think this replacement guide is valid,.....
As I stated earlier in this thread, I will do an experiment based on this info, and do a report to further explain the results.

Of course the report will include such things as, the difference in the same tube number, ( like a 12AX7) but different manufacturers, like Mullard VS GE, VS Sylvania,VS Raytheon, and on and on.

I also will report on the others, if I find that my Univox will allow for parallel plug-ins.( such as replacing a 6L6, with a 6V6)


Be posting results ASAP.


Upstate













:D :D :D :D
 
All tubes have specific plate voltages, bias volatages, grid voltages (depending on the number of grids), transconductance, load resistace, etc. The circuits in amplifiers are designed around specific tubes and unless those tubes match the circuit design you will obtain less than optimum results if not downright frying.
Upstate noted that a 7027 is a replacement for a 6L6. The 7027s were used in ampeg vt22s and v4s and v2s and the 6L6s were used in most of the old fenders. Try substituting those tubes for one another without changing the circuit design, namely the bias voltage, and I guarantee you will fry your amp.
 
I am gonna start my tests with just the pre-amp tubes, and report the diferences from Mullard, GE, SYLVANIA, etc, I think that I'll skip any power tube replacing till I have more info on tube structure, I think the stuff Dragonworks is talking about comes from later amp, and tube designs, after the 1959 publish dates of the book I was taking my info from.
Jerry, what are some titles of more recent tube replacement guides,...??

I think I have access to one more, a little newer, but there has to be a 'current' one of some sort.

Upstate:D
 
natbot, to answer YOUR question......

You seem to have a Fender Blues Deville amp. It's not really a reissue, just the pre-HotRod series of the amp line. Your stock power amp tube type for that amp is a 6L6GC, or a 5881, and yes, there are two of them. When replacing power tubes, you will want to have the bias set to that of your new tubes. If you want more gain out of the OD channel, you can ask the tech who sets your bias to set it a little hotter than it was. I did this to my Blues DeVille and it really made a big change.

I currently am running Fender Groove Tubes in this amp. They are now stock for the Hot Rod line and they do a fine job for this amp.

As far as pre-amp tubes. You should buy several 12ax7's to experiment with which ones you like. They are pretty cheap, and are always a good thing to have around in case one blows on you. And you do not need to do any other adjustments when changing preamp tubes, just smack them in and fire it up. I keep about 10 of them around at any given time for all my amps. The stock preamp tube for your amp is a 12ax7a (for all 3 sockets). If you would like any more information on your amp or tubes for it specifically, just let me know.

Thanks,
H2H
 
Just dont substitute 12ax7s with 12au7, or 12at7, etc. An ECC83 is a direcet replacement for a 12ax7 and can be used. A 12ax7 is acutually 2 tubes in one having two plates and cathodes and two grids one for each section. One tube can be used for two purposes such as two channels, one channel and the reverb circuit, etc. Without reviewing your amplifier schematic you run the risk of experimenting with two different circuits using one tube.
12ax7 AF amplifier and phase inverter
max plate voltage 330 volts
max plate dissipation 1.0 watt
max positive dc grid voltage 0 volts
max negative dc grid voltage -55 volts

Characteristics and typical operation
Class A1 amp each section
plate voltage 100 250 volts
grid voltage -1 -2 volts
plate current 0.5 1.2 milliamps
plate resistance 80,000 65,000 ohms
transconductance 1250 umhos
amplification factor 100
Note
section number 1 connects to pins 6,7 and 8
section two connects to pins 1,2 and 3
 
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