Byetheway, I have opened the thing again (these Germans, they make all things like BMWs...) and I tapped the tubes a bit stronger. Most of them remained silent and looking at me like an idiot.
However, one of the 6L6 responded to the tapping with pops. Also, when I gave it a closer look, on of it's sides appears have burn a bit. The filament in the middle is still working. Any ideas?
Talking about Sovteks.....Daved say that
Quote:
"Each (of Robbens) amp currently has a matched quartet of Svetlana 6L6GC tubes and three Sovtek 12AX7EH tubes. "
Marin,
Doesn't the "EH" in "12AX7EH" signify "Electro Harmonix"? I don't believe that the Electro Harmonix is the same design as the Sovtec branded valves. Anyway, it sounds like your problem might be solved with some new 6L6's. Good luck.
Marin,
Doesn't the "EH" in "12AX7EH" signify "Electro Harmonix"? I don't believe that the Electro Harmonix is the same design as the Sovtec branded valves. Anyway, it sounds like your problem might be solved with some new 6L6's. Good luck.
That is the good point. End of the thread .
New thread to come : Do you consider your amp : 1 Male, 2 Female,
3 androgyn,4 a mere machine
Marin,
Doesn't the "EH" in "12AX7EH" signify "Electro Harmonix"? I don't believe that the Electro Harmonix is the same design as the Sovtec branded valves. Anyway, it sounds like your problem might be solved with some new 6L6's. Good luck.
That is the good point. End of the thread .
New thread to come : Do you consider your amp : 1 Male, 2 Female,
3 androgyn,4 a mere machine
Mine is an errant child (gender unknown) whose behavior at any given time is unpredictable. In other words, it's a tube amp.
Joined: 04 Nov 2003 Posts: 886 Location: SF Bay Area
Posted: Thu Mar 04, 2004 9:22 am Post subject:
marinblues wrote:
However, one of the 6L6 responded to the tapping with pops. Also, when I gave it a closer look, on of it's sides appears have burn a bit. The filament in the middle is still working. Any ideas?
Talking about Sovteks.....Daved say that
Quote:
"Each (of Robbens) amp currently has a matched quartet of Svetlana 6L6GC tubes and three Sovtek 12AX7EH tubes. "
Take two Svetlana's and call me in the morning.
There is normally a burn where the getter flashes but any other burns (on the side doesn't sound normal for a 6L6) or funny noises/sparks and get that puppy out of there. If it shorts it will take out several resistors in the amp and could overheat and damage the output transformer.
The is a Sovtek 12AX7 with a long plate structure that was made for the high end hi-fi industry (can't remember the exact designation but I thought it had an "LP" in it). They are much more expensive and comprable to many of the better production tubes today.
Ah the endless discussion of which tubes sound best.
And for the record, my Fuchs is the girlfriend I can't find in real life, sweet, even tempered, and always there. _________________ There are no such things as wrong notes, there's only the look on your face.
My Stuff: www.stevekirbymusic.com
Joined: 18 Jul 2003 Posts: 122 Location: Cherry Hill, NJ
Posted: Thu Mar 04, 2004 10:22 am Post subject:
marinblues wrote:
Lefty, of course that's what I want.....
Talking about Sovteks.....Daved say that
Quote:
"Each (of Robbens) amp currently has a matched quartet of Svetlana 6L6GC tubes and three Sovtek 12AX7EH tubes. "
Thay can't be THAT bad can they?
Thanks to all for helping.
Marin
Marin,
The EH 12AX7 tubes are made in a Sovtek plant but are not branded Sovtek. They don't say Sovtek at all. Just EH. They are 180 degrees different than the Sovtek wa, wb, and even the lps. I have spent hours comparing tubes and the last thing the wa and wb tubes are is smooth and sweet. The EH is actually nice. I use done for a while in V2. I am hooke don JJ now. To my ear, they sound much better than the EH. It is possible Robben has not used the new JJ ECC83S in his Dumble. They are relatively new and better than the JJs of several years ago. Dumble uses JJs too.
I know what you like from your clips and I think you would be pleasantly surprised to try a couple of new 12ax7s in V1 and V2. The other slots are less important for tone. _________________ www.scottlernermusic.com
Joined: 16 Jul 2003 Posts: 328 Location: The Netherlands
Posted: Thu Mar 04, 2004 10:57 am Post subject: Re: A tube amp is female?
elizabeth wrote:
Oooooooh Lefty, I'm not going to say what I am thinking about tube amps being female...
Well........that's it then
Now we will never know.............
And you even cuddled a Dumble? (although it was Robben's) _________________ "Don't play what's there, play what's not there" Miles Davis
"Each (of Robbens) amp currently has a matched quartet of Svetlana 6L6GC tubes and three Sovtek 12AX7EH tubes. "
Thay can't be THAT bad can they?
Thanks to all for helping.
Marin
Marin,
The EH 12AX7 tubes are made in a Sovtek plant but are not branded Sovtek. They don't say Sovtek at all. Just EH. They are 180 degrees different than the Sovtek wa, wb, and even the lps. I have spent hours comparing tubes and the last thing the wa and wb tubes are is smooth and sweet. The EH is actually nice. I use done for a while in V2. I am hooke don JJ now. To my ear, they sound much better than the EH. It is possible Robben has not used the new JJ ECC83S in his Dumble. They are relatively new and better than the JJs of several years ago. Dumble uses JJs too.
I know what you like from your clips and I think you would be pleasantly surprised to try a couple of new 12ax7s in V1 and V2. The other slots are less important for tone.
OK, point taken.
I've checked the manual and I have 4 x 12AX7 in the pre-amp stage (I thought there where 3). I guess I should change all of them with the ECC83S?
Do you agree with Aeolian on the Svetlana 6L6GC for the final stage or do you use JJs as well for this?
Joined: 18 Jul 2003 Posts: 122 Location: Cherry Hill, NJ
Posted: Thu Mar 04, 2004 12:51 pm Post subject:
The Svetlana 6L6 are real nice! Most of my clisp are using them. Ijust tried JJ 6L6 and liek them as well. Both excellent.
Keep in mind that probably only 2 of your 12ax7 tubes are for the preamp. You have 1 phase invertor tube that drives the power tubes and maybe a tube for the reverb or effects loop. Look for V1 and V2 in the manual.
The Svetlana 6L6 are real nice! Most of my clisp are using them. Ijust tried JJ 6L6 and liek them as well. Both excellent.
Keep in mind that probably only 2 of your 12ax7 tubes are for the preamp. You have 1 phase invertor tube that drives the power tubes and maybe a tube for the reverb or effects loop. Look for V1 and V2 in the manual.
Scott
The amp probably has 2 preamps: there is a "clean" channel and a "gain" channel and then there is a preamp that can boost either of the channels. In this way, one can have 4 levels of gain. On top of that there is VLS (Volume level Switch) which allows to set solo/rythm setting. The footswitch has 4 gain switches, VLS switch, reverb switch. Quite a little nifty thing.
Joined: 04 Nov 2003 Posts: 886 Location: SF Bay Area
Posted: Thu Mar 04, 2004 3:12 pm Post subject:
For what it’s worth, to understand the tube layout. 12AX7's are dual triodes, that is there are two tubes in there. Looking at the Dumble schematics I have, one side of the first tube carries the first (input) gain stage and the gain recovery after the passive tone circuit is on the second side of the first tube The high/low gain stuff on your amp probably doesn't use another gain stage but switches levels in this stage. The second tube is used for the OD by running one half the tube into the other. As Scott said, the third tube is probably for reverb or effects loop buffering and the last one (closest to the output tubes) is the phase splitter (takes the single ended signal and makes positive and negative signals from it to drive either of the output tubes in a push/pull system like a balanced microphone, only things like the Fender Champ and some esoteric hi-fi amps are single ended all the way through). This tube needs to have both sides of it evenly balanced so that both positive and negative sides of the output circuit are equal. You went to the trouble to get matched output tubes, this is just as important. Also, the gain of the tube overall should be as the designer expected, so arbitrarily swapping this tube with other things can throw off this part of the circuit. The VLS probably switches a second master volume in and out.
So when you are tube rolling, you can consider what characteristics you want in each section. Something warm here, something brighter and more aggressive there. There’s no end to the fun you can have. Then you forget what it sounded like in the first place and have to start all over again. _________________ There are no such things as wrong notes, there's only the look on your face.
My Stuff: www.stevekirbymusic.com
For what it?s worth, to understand the tube layout. 12AX7's are dual triodes, that is there are two tubes in there. Looking at the Dumble schematics I have, one side of the first tube carries the first (input) gain stage and the gain recovery after the passive tone circuit is on the second side of the first tube The high/low gain stuff on your amp probably doesn't use another gain stage but switches levels in this stage. The second tube is used for the OD by running one half the tube into the other. As Scott said, the third tube is probably for reverb or effects loop buffering and the last one (closest to the output tubes) is the phase splitter (takes the single ended signal and makes positive and negative signals from it to drive either of the output tubes in a push/pull system like a balanced microphone, only things like the Fender Champ and some esoteric hi-fi amps are single ended all the way through). This tube needs to have both sides of it evenly balanced so that both positive and negative sides of the output circuit are equal. You went to the trouble to get matched output tubes, this is just as important. Also, the gain of the tube overall should be as the designer expected, so arbitrarily swapping this tube with other things can throw off this part of the circuit. The VLS probably switches a second master volume in and out.
So when you are tube rolling, you can consider what characteristics you want in each section. Something warm here, something brighter and more aggressive there. There?s no end to the fun you can have. Then you forget what it sounded like in the first place and have to start all over again.
Do you think that I could change them out myself or should I go to a tech. The stuff regarding the phantom currents in the final stage sounds scary...
Also, I guess the final stage would require rebiasing? Correct?
Joined: 04 Nov 2003 Posts: 886 Location: SF Bay Area
Posted: Thu Mar 04, 2004 4:42 pm Post subject:
[quote="marinblues] Do you think that I could change them out myself or should I go to a tech. The stuff regarding the phantom currents in the final stage sounds scary...
Also, I guess the final stage would require rebiasing? Correct?
Thanks Marin[/quote]
Since you have a suspect output tube, the one that sparks, replace it now before something gets fried. The amp will perform best with the bias set optimally but a consumer amp that hasn't been tweaked by someone to have the tubes near frying should work reasonably well as is. There are plenty of fixed bias amps out there. The factory set point is adjusted to be safe. There are "techs" out there who will set the bias so that the tube is on the hairy edge of melting to get the "best sound" from it. In fact there is a "tube amp" book out there that avocates this practice. It is true that an amp biased too "cold" can lose some of the life and magic it could have. So at your earliest convience, take it to a tech and have the bias checked and reset if necessary.
While it could be possible with metallic fingernails to touch the pins on the output tube while it is going into the socket and get the B+ voltage, it would take some effort and ingenuity. Tubes have long been considered "user servicable parts". In the 60's Most grocery stores had a tube tester, with a bunch of GE or RCA tubes in the base, sitting where the ATM machines are now. You went down there with a bag of tubes from your radio, amp, or whatever wasn't working, looked up which socket to use and the settings for a couple of knobs, stuck the tube in there and pushed a button. A meter with green, yellow and red sections told you if you needed to buy an new one. That was the extent of the mystical nature of tubes. My dad, who repaired electrical contraptions for a living, thought nothing of sending his 10 year old kid down to the store to check the tubes out of his amp or the TV.
The preamp tubes should be easy to change and the amp won't need any adjustment there. Just make sure you have the key on the output tubes and the missing pin on the preamp tubes lined up right when you stick them in the sockets. I have seen 6L6's with the key busted off, stuck back in amps before, and the pins on preamp tubes can get bent if you try to force them in wrong.
Welcome to the wonderful world of glass. I'm sure there are some purists out there who will say that you need to use only 30 year old NOS tubes with the filimants hand wound by Hungarian virgins. And then have Howard Dumble himself adjust the bias. I hear more expressive range of tone in one bar of your playing than there is between the variations in good tubes. _________________ There are no such things as wrong notes, there's only the look on your face.
My Stuff: www.stevekirbymusic.com
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Hi Justpassin'By, your's an errant child !!!!!!!!!!!!!!! 
