Tubes - How to tell...

[tornandfrayed]

I recently got a Fender Twin amp that we have been using. I really like the sound but for some reason I am not loving it... The condition and age of the tubes in this is unknown, how do I tell if a tube is not functioning or needs to be replaced...

http://www.ampwares.com/amp.asp?id=116

Just looking for some personal experience and insight into this...

Thanks!

[floodcitybrass]

Audible signs:
1) Tone will change while you play : goes louder then softer, or tone changes back and forth
2) The extreme frequencies are gone (highs or lows)
3) Nasty high constant squeal

Physical signs:
1) Color of tube burning is different. It should be orange. If it is blueish then its bad.
2) Broken/burnt tube - Looks like a white or black powdery stuff on the glass.


What exactly don't you like about it?

Take it to Tube Guru in Johnstown. He is the BEST tube repairman around. He can do adjustments, repairs, and modifications. 255-3275

Just curious - what kind of music are you playing with the twin?

[mjb]

i ts a haul for you dave but i second the TUBE GURU...he knows his shit and he'll talk way over your head but i like that in an amp tech. he works on all my amps. and they are perfect when hes done. he'll check things you never even heard of. give him a call and talk to him and he may be able to troubleshoot for ya a little over the phone. tell him Mike borstnar told you to give him a call. what year is your twin?

[bassist_25]

In addition to what FCB said, take a pencil and gently tap each tube. You should get a slight "thump" sound. If you get an echo-like sound or noise, the tube is probably microphonic.

Just looked at the page you posted - The bias is fixed, so switching the tubes yourself should be a snap. www.tubedepot.com has good prices. If you like JJs, www.eurotubes.com has kits. You could probably find a kit selected specifically for the bias of your amp (the Eurotubes site sucks to navigate, though). However, if you suspect other issues with the amp, then take it to a tech, as has been suggested. The nice thing about tube amps is that generally they can always be fixed rather than just junked.

[floodcitybrass]

I have a fender blue junior with a fixed bias. It was way too hot for my tastes. It simply broke up too soon. I added an adjustment so the bias is adjustable.

That's a mod that you may find useful.

[LHSL]

90% of the time if a Twin sounds bad, it just needs turned up louder.

[tornandfrayed]

It does not really sound bad but it does not seem to have any throat in the breakup. I have heard these before and they seem to have different tones up through the volume to about 6 and then they even out.

It is being used for Pop Rock and classic Rock.

My 11 year old Stevie is playing it...

Some of the tubes (power) do look like they have a black spot on the bottom..

I am looking at the 6L6GC tubes and three of them have light through the bottom, the fourth does not. Could be a problem eh?

I have no idea how to find the date of the amp. I have only had it for a little while...

Thanks for all the info, I am fascinated by the tube tech...

[tornandfrayed]

On further inspection of these tubes there are definately some problems. One of the 6L6 tubes does not light all the way, that can't be right. In looking at the 12AX7A tubes two of them look like they have exploded inside, they look full of something..

I am going to go ahead and order the kit from eurotubes, the price was good and they seem to know there shit. There is a Bias/balance adjustment on this thing that I will check out when I get the new tubes...

Thanks again everyone!

[Merge]

Be very careful when you install the tubes. The 12AX7 tubes have glass inputs on the bottom, which can bend and break very easily.

[onegunguitar]

Don't touch them when you put them in,use a rag or gloves,the oil on your fingers will shorten the life of the tube-or so I've been told.

[LHSL]

Don't touch them when you put them in,use a rag or gloves,the oil on your fingers will shorten the life of the tube-or so I've been told.

I know that's true of certain kinds of light bulbs for stage lighting (like metal halide and xeon arc types) but I'm not sure about tubes... Not questioning, I just don't know.

That said, I know they recommend cleaning those bulbs with rubbing alcohol when putting them in to remove any dirt, debris, or oil from your skin. That might work for tubes too if you accidentally touch them.

[bassist_25]

Let us know how the new tubes work, Dave. I just retubed the preamp of one of my amps last week, and it's like I got a whole new head (which, unfortunately, is a lot different than getting head ).

[tornandfrayed]

Come on Paul, we all know that new head is better then old head!

Yeah I will let you know. I am going to do some tracks with this unit the way it is with some documented setting and then try it with the new tubes.

We shall see!

[tornandfrayed]

OK so I replaced the tubes with

5 ECC83S
1 ECC81 standard
1 ECC81 balanced
1 Matched Quad set 6L6GC

I went ahead and cleaned the tube sockets as per

http://www.eurotubes.com/euro-i.htm#1.

I went with the eurotubes because these guys were on the phone with me telling me specifics about my amp! I was very pleased to actually find someone who seemed to give a shit!

I have the tubes ion and the bias is all adjusted. The sound is good. Is it earth shattering? I don't think the change is that dramatic but I do notice a little less "harsh" in the gain.. I am going to play with this a little and see if the y change over time.

Any one have any experience with sound changing over time? Do they "wear in"?

Peace

[songsmith]

My experience is that if you turn up a Twin loud enough to break up, and it sounds bad, your ears are probably hemorrhaging. I'd use a Tube Screamer or something for dirt... they all sound pretty good through that sweet, smushy power tube. I LOVE the Twin sound, but they get a bit loud. I mean-- THEY GET A BIT LOUD!!!--->JMS

[bassist_25]

My experience is that if you turn up a Twin loud enough to break up, and it sounds bad, your ears are probably hemorrhaging. I'd use a Tube Screamer or something for dirt... they all sound pretty good through that sweet, smushy power tube. I LOVE the Twin sound, but they get a bit loud. I mean-- THEY GET A BIT LOUD!!!--->JMS

+1

As is common knowledge, whereas solid-state amps generally even out throughout the volume spectrum until clipping, tube amps sound qualitatively different as you turn the volume pot. What seems loud in your basement or living room may not seem so loud on a stage. What's upbearable in my living room is often a good gig volume. Dave's son may not be cranking the amp enough in a practice or rehearsal situation to really drive the tubes into the classic Twin tone that we all know and love.

I also didn't know that amp took that many preamp tubes. Also, this may be a dumb question Dave, but did you put the preamp tubes in the correct sockets? With different tube types, what you put in the V1 socket is going to have a huge effect on the gain structure and tone of the amp.

[tornandfrayed]

There is a possibility that I mixed the ECC81's up. That is the tube in the V1 socket. I have them switched and I will try it out later on today once the mortals are awake...

It did not specify position in the docs so.... Well you know.. I don't read instructions anyway...

Thanks Paul I will let you know...

[bassist_25]

An ECC81 is a 12AT7, which is a lower gain tube than a 12AX7, so that may be the reason you're not digging the tone. I'm not sure what Fender recommends to go in the V1 socket.

[ToonaRockGuy]

Reading all of this only brought one thought to mind...



Good Lord, I'm glad I'm a drummer.

[whitedevilone]

Reading all of this only brought one thought to mind...



Good Lord, I'm glad I'm a drummer.

Yeah the world need more openly gay drummers.

[ToonaRockGuy]

Reading all of this only brought one thought to mind...



Good Lord, I'm glad I'm a drummer.

Yeah the world need more openly gay drummers.

HAHAHAHAHAHhahahahahahahahah.....right.

At least MY drums work when I set them up. Unlike a certain Carvin guitar player I can think of...

[lonewolf]

Hey Dave, some of the earlier Twins have a pull out switch on the MASTER volume. Its kicks in a smooth overdrive on the preamp tubes.

Try pulling it out and see what happens.

[onegunguitar]

Reading all of this only brought one thought to mind...



Good Lord, I'm glad I'm a drummer.

Yeah the world need more openly gay drummers.

HAHAHAHAHAHhahahahahahahahah.....right.

At least MY drums work when I set them up. Unlike a certain Carvin guitar player I can think of...

Hahaha,at least all his cords worked at the last show

[tornandfrayed]

Yeah Jeff there are actually several of the knobs that pull out and do specific things based on the knob...

It is actually sounding really good but... not quite what Stevie wants to sound like... I think we are going to try a spider 120 for him and see if he is a little more comfortable with all the effects... He is 11 I want him to love this shit!

[onegunguitar]

He is 11 I want him to love this shit!

Then by him a Mesa or an Engl,haha