Hi everyone,
I had a problem with one channel of my Tubelab SSE amp the other day. A little bit of backstory:
I built the amp about 6 months ago. It's worked flawlessly until this recent issue. About 2 weeks ago, the amp was inadvertently switched on without being connected to speakers. An input signal was connected. I think it was like this for a few hours, but I don't know for sure. Once I noticed, I shut it down, and the next day turned it on w/ the speakers connected and all seemed to work well. A few days later I took out those power tubes (Gold Lion KT77's) and switched in some TungSol EL34b tubes. All still ok. A few days after that, I put the KT77's back in and shortly after turning the amp back on, there was a crackling noise in one of the KT77's and the light inside was kind of flickering on and off. It wasn't making very bright fireworks, just crackling and switching between no a dim light and normal light. There was no smell near the amp when this happened. I shut it off quickly.
I looked inside the amp last night and all seems to be OK. I didn't notice any obvious damage to components. The only 2 possible but small issues I noticed were that the wrapping on the Auricap coupling caps looks to be peeling a bit, and the wires coming out of the choke seem to be losing some of their black coloration. Just on the off chance these are indicative of something, I've attached images.
I understand that running the amp without a speaker load connected can cause problems. I want to get the amp back up and running, but what should I check for before putting in new tubes and flipping the switch? Did I possibly damage my output transformers? Could other parts be damaged even if not visibly? I don't want to do any further damage to the amp or blow more tubes.
Thanks for your help!
Dan
I had a problem with one channel of my Tubelab SSE amp the other day. A little bit of backstory:
I built the amp about 6 months ago. It's worked flawlessly until this recent issue. About 2 weeks ago, the amp was inadvertently switched on without being connected to speakers. An input signal was connected. I think it was like this for a few hours, but I don't know for sure. Once I noticed, I shut it down, and the next day turned it on w/ the speakers connected and all seemed to work well. A few days later I took out those power tubes (Gold Lion KT77's) and switched in some TungSol EL34b tubes. All still ok. A few days after that, I put the KT77's back in and shortly after turning the amp back on, there was a crackling noise in one of the KT77's and the light inside was kind of flickering on and off. It wasn't making very bright fireworks, just crackling and switching between no a dim light and normal light. There was no smell near the amp when this happened. I shut it off quickly.
I looked inside the amp last night and all seems to be OK. I didn't notice any obvious damage to components. The only 2 possible but small issues I noticed were that the wrapping on the Auricap coupling caps looks to be peeling a bit, and the wires coming out of the choke seem to be losing some of their black coloration. Just on the off chance these are indicative of something, I've attached images.
I understand that running the amp without a speaker load connected can cause problems. I want to get the amp back up and running, but what should I check for before putting in new tubes and flipping the switch? Did I possibly damage my output transformers? Could other parts be damaged even if not visibly? I don't want to do any further damage to the amp or blow more tubes.
Thanks for your help!
Dan
Attachments
The amp was run without speakers. If the volume was low enough that clipping never happened, nothing bad should happen. Clipping in an amp without speakers happens at a much lower volume level than with speakers, so if the volume was less than half your normal listening level, nothing bad likely happened. An amp at full crank without speakers usually results in a fireball inside the OPT. It is possible that one of the output tubes was damaged by a tube arc or other high voltage event during this moment.
You connected up the speakers and the amp seemed OK. Did you play it loud enough to get near or into clipping since running with no speakers? If so did it still seem "normal"? If so it probably wasn't damaged by the no speaker moment.
You swapped in some different tubes, and then one tube "crackled" and the light inside "flickered." It's kinda hard to pin this one down.
There is a glowing cathode rod in the center of the tube. It is normally red hot, and takes several seconds to cool even if all power is abruptly removed, so I assume this was not the flickering light.
Any white light flashes or sparks inside the tube is a bad thing and that tube should not be used again if that was the case. It could have been damaged during the no speaker moment.
Many of today's new production tubes have enough residual gas inside to ionize producing a light blue-purple-pink glow inside the plate structure. If this was flickering on an off, I would assume the the sound was also going on an off, or maybe the crackling sound came from the speakers?
If this glow is changing in intensity, what's happening to the sound at the same time? If the sound is cutting out when the glow gets dim, then something is affecting the current through the tube. This started when you changed tubes, so the likely place to look is the soldering on the tube sockets or the sockets themselves. The screw terminals on your cathode resistors should be checked too, as well as all the screw terminals for the transformer wires.
A slightly risky experiment would be to swap the output tubes and try the amp again. If the problem follows the tube, that tube is bad. If the problem stays in the same channel, there is something wrong with the circuitry in that channel.
The coating peeling from the choke wires is normal. The bobbin gets dunked in an insulating varnish after it is wound. The coating is stiff when dry, but the wires are not. The coating will crack and fall off. Normal.
The tape peeling from the caps.....I would expect something stickier for what they charge for those things, but one of my Auricaps is peeling too....but it is 14 years old. It has been partially peeled for about 10 of those years....still works fine.
You connected up the speakers and the amp seemed OK. Did you play it loud enough to get near or into clipping since running with no speakers? If so did it still seem "normal"? If so it probably wasn't damaged by the no speaker moment.
You swapped in some different tubes, and then one tube "crackled" and the light inside "flickered." It's kinda hard to pin this one down.
There is a glowing cathode rod in the center of the tube. It is normally red hot, and takes several seconds to cool even if all power is abruptly removed, so I assume this was not the flickering light.
Any white light flashes or sparks inside the tube is a bad thing and that tube should not be used again if that was the case. It could have been damaged during the no speaker moment.
Many of today's new production tubes have enough residual gas inside to ionize producing a light blue-purple-pink glow inside the plate structure. If this was flickering on an off, I would assume the the sound was also going on an off, or maybe the crackling sound came from the speakers?
If this glow is changing in intensity, what's happening to the sound at the same time? If the sound is cutting out when the glow gets dim, then something is affecting the current through the tube. This started when you changed tubes, so the likely place to look is the soldering on the tube sockets or the sockets themselves. The screw terminals on your cathode resistors should be checked too, as well as all the screw terminals for the transformer wires.
A slightly risky experiment would be to swap the output tubes and try the amp again. If the problem follows the tube, that tube is bad. If the problem stays in the same channel, there is something wrong with the circuitry in that channel.
The coating peeling from the choke wires is normal. The bobbin gets dunked in an insulating varnish after it is wound. The coating is stiff when dry, but the wires are not. The coating will crack and fall off. Normal.
The tape peeling from the caps.....I would expect something stickier for what they charge for those things, but one of my Auricaps is peeling too....but it is 14 years old. It has been partially peeled for about 10 of those years....still works fine.
All,
Thank you for the helpful responses. I have a few digital multimeters, but unfortunately not much knowledge of what to do with them to diagnose this problem. I have a few follow up questions:
Again, thanks to all for your help. I'd be grateful to if you have any suggestions on how to test the coupling caps, output transformers, and tube. I'll inspect all of the solder joints George mentioned and will reply with any updates.
Thanks! Best,
Dan
Thank you for the helpful responses. I have a few digital multimeters, but unfortunately not much knowledge of what to do with them to diagnose this problem. I have a few follow up questions:
- Is there a good way to check the coupling caps? Just a visual inspection? or something I can do w/ a multimeter?
- How does one check the output transformers? The amp did work for a while after the incident -- is that possibly good news for the OPT? Evidence of no "fireball" inside the OPT during the no-speaker-event?
- George, thank you for the very detailed and comprehensive reply.
- I'll begin by inspecting the solder joints of the tube sockets and terminals for the transformers (I did check the solder joints on the screw terminals of the cathode resistors and those passed).
- What I remember of the crackling-noise incident is: I put the KT77's back in, turned the amp on, and pretty much right away there was this issue in one of the output tubes. it was flickering (I think it was the cathode rod, but maybe not?) and as it flickered there was a crackling noise. I think the crackling noise came from the speaker, but the tube might also have been making noises. Sorry; it was a traumatic moment.
- I don't remember seeing any white flashes inside the tube.
- Regarding volume levels: I don't know what level the volume was set at when the amp was running without being connected to speakers. Probably at 'normal' listening level, which is nowhere near clipping. I did turn the amp up pretty loud after the no-speakers-connected event, but "pretty loud" is usually less than 3/4 on the dial and I don't notice any clipping at that level. Just gets too loud for my circumstances.
- Is there a way to test the tube? I visually inspected it and nothing looked out of ordinary. I took it out of the socket and gently shook it and didn't hear anything rattling around (as old lightbulbs would do after they popped).
- I will wait to do the test you mention, George, of swapping the output tubes.
Again, thanks to all for your help. I'd be grateful to if you have any suggestions on how to test the coupling caps, output transformers, and tube. I'll inspect all of the solder joints George mentioned and will reply with any updates.
Thanks! Best,
Dan
Hi everyone,
I wanted to let you know what's happened w.r.t. my SSE amp and the one crackling channel. [It's been a while...; I had to take some time off for the holidays, etc.]
I inspected the components on the board, the terminal connections, and the tube socket solder joints. I found a few issues:
The only downside here is that I don't really know what went wrong or what to take away from this. It seems like the OPT connections at the screw terminals being loose could have been the issue. I'd appreciate input from anyone with more experience and knowledge.
One additional question: I'm not sure if the tube that was in there when it started crackling is ok or not. Maybe it was a tube issue and it's bad and I should throw it out. But is it possible that the tube is OK and I could continue to use it? If so, how can I check the tube?
Again, thank you all for your help! I'm really glad to have the amp working again. It just sounds better and listening to music on it is more enjoyable than on my Onkyo receiver.
Thanks,
Dan
I wanted to let you know what's happened w.r.t. my SSE amp and the one crackling channel. [It's been a while...; I had to take some time off for the holidays, etc.]
I inspected the components on the board, the terminal connections, and the tube socket solder joints. I found a few issues:
- A few of the wires going into terminal sockets were not very tightly secured. I was able to kind of jiggle them gently and get the wires to pull out of the terminal socket. This was most prevalent on the two terminals indicated inside red circles in the attached picture. I pulled the wires out, stripped off some fresh sections, twisted the ends and put a little solder on to hold them together and then re-installed and tightened very well.
- I got rid of the screw terminals on the cathode resistors. I thought they were a good idea initially b/c I wasn't sure what value cathode resistor to use, but I've been worried that they don't allow for a really good connection between the resistor and the board. So they're gone and the resistor is connected to the board directly.
- The tube sockets looked good, so did their solder connections to the board. I didn't see any other issues with any of the other components or their solder joints.
- I changed the tubes; put in some sort of Electro Harmonix big bottle el34 type that's relatively cheap to replace.
The only downside here is that I don't really know what went wrong or what to take away from this. It seems like the OPT connections at the screw terminals being loose could have been the issue. I'd appreciate input from anyone with more experience and knowledge.
One additional question: I'm not sure if the tube that was in there when it started crackling is ok or not. Maybe it was a tube issue and it's bad and I should throw it out. But is it possible that the tube is OK and I could continue to use it? If so, how can I check the tube?
Again, thank you all for your help! I'm really glad to have the amp working again. It just sounds better and listening to music on it is more enjoyable than on my Onkyo receiver.
Thanks,
Dan
Attachments
Hey Dan,
Congrats on tuning up your amp!
There are some simple tube tests you can do with a DMM Simple tests for Tubes with a Multi Meter - YouTube
Of course a tube tester is miles better, but I thought you might be interested.
Congrats on tuning up your amp!
There are some simple tube tests you can do with a DMM Simple tests for Tubes with a Multi Meter - YouTube
Of course a tube tester is miles better, but I thought you might be interested.
All,
Again, thank you very much for the help! I have a few updates and I'd be very grateful for any insight you may have.
As I said previously, since this problem w/ the crackling tube, I got the amp working again w/ different tubes. In my initial excitement about getting things working, I think I missed some kind of weird channel imbalance issue. While listening to a jazz trio album (Money Jungle!) over the weekend, I noticed things sounded a little off (piano and bass all in left channel which was very much more prominent, drums in the other channel, and everything sounded kind of disjointed). I disconnected the Tubelab amp and connected my SS integrated amp and played the song again, and indeed the stereo image was different. The piano was right in the middle, the bass to the left, and the drums to the right, and it sounded much more cohesive.
I've been low-key worried that there was something a bit off, possibly in the input jacks --> volume pot --> board wiring -- I didn't do a great job on the wiring, maybe there's a problem w/ the volume pot, possibly the grounding, etc. So anyways, today I took all of that out and just wired the input jacks directly to the board (keeping a ground connection on one of the jacks). I think, again (ha!), that it sounds much better. The stereo image sounds more cohesive, the piano is more in the center in Money Jungle, etc.
But even though it sounds better, I'm worried that one channel is still favored over the other. The stereo image doesn't seem centered between the speakers, but pulled more to the left channel. Is this possible? If so, is there a more formal way to check for it? [I don't think its an issue of my room -- I've tried switching the speaker cables and the issue follows the cables.] It kind of looks like the cathode rod is glowing a bit more in one of the tubes, but maybe that's just psychosomatic. Is there a good way to test the power output of each channel?
cogitech: thanks for the video! I did the suggested continuity test on my KT77 tubes, and both checked out OK. As I understand it, that doesn't show that they're definitively OK, but rather that there is no lack of continuity b/w heater pins and no continuity where there shouldn't be.
Another question for the experts: do you think it's OK to put the KT77 tubes back in and see if they work? What risks would that entail? Or should I just trashcan them.
Thanks again for all of your help!
Best,
Dan
Again, thank you very much for the help! I have a few updates and I'd be very grateful for any insight you may have.
As I said previously, since this problem w/ the crackling tube, I got the amp working again w/ different tubes. In my initial excitement about getting things working, I think I missed some kind of weird channel imbalance issue. While listening to a jazz trio album (Money Jungle!) over the weekend, I noticed things sounded a little off (piano and bass all in left channel which was very much more prominent, drums in the other channel, and everything sounded kind of disjointed). I disconnected the Tubelab amp and connected my SS integrated amp and played the song again, and indeed the stereo image was different. The piano was right in the middle, the bass to the left, and the drums to the right, and it sounded much more cohesive.
I've been low-key worried that there was something a bit off, possibly in the input jacks --> volume pot --> board wiring -- I didn't do a great job on the wiring, maybe there's a problem w/ the volume pot, possibly the grounding, etc. So anyways, today I took all of that out and just wired the input jacks directly to the board (keeping a ground connection on one of the jacks). I think, again (ha!), that it sounds much better. The stereo image sounds more cohesive, the piano is more in the center in Money Jungle, etc.
But even though it sounds better, I'm worried that one channel is still favored over the other. The stereo image doesn't seem centered between the speakers, but pulled more to the left channel. Is this possible? If so, is there a more formal way to check for it? [I don't think its an issue of my room -- I've tried switching the speaker cables and the issue follows the cables.] It kind of looks like the cathode rod is glowing a bit more in one of the tubes, but maybe that's just psychosomatic. Is there a good way to test the power output of each channel?
cogitech: thanks for the video! I did the suggested continuity test on my KT77 tubes, and both checked out OK. As I understand it, that doesn't show that they're definitively OK, but rather that there is no lack of continuity b/w heater pins and no continuity where there shouldn't be.
Another question for the experts: do you think it's OK to put the KT77 tubes back in and see if they work? What risks would that entail? Or should I just trashcan them.
Thanks again for all of your help!
Best,
Dan
Hey Dan,
A couple of ideas to check channel balance.
1 - I am sure you tried this, but swap the tubes and see if the imbalance follows the tubes.
2 - If not, you can test channel balance by playing a test tone (1kHz sine wave is what I would use) at a normal listening level and then use your DMM (set to AC, low range) to measure the voltage across each set of speaker terminals and compare.
If you have a PC as a playback source, there are test tone generators on the interwebs.
A couple of ideas to check channel balance.
1 - I am sure you tried this, but swap the tubes and see if the imbalance follows the tubes.
2 - If not, you can test channel balance by playing a test tone (1kHz sine wave is what I would use) at a normal listening level and then use your DMM (set to AC, low range) to measure the voltage across each set of speaker terminals and compare.
If you have a PC as a playback source, there are test tone generators on the interwebs.
Thanks for the note.
Dan
- The problem does not seem to follow the tube.
- I have a question about the 2nd suggestion: Is this done w/ the speakers connected? That's how I tried it, but I couldn't measure any AC voltage at the speaker terminals.
I have a tone generator app on my phone. I hooked it up to the input of the amp, played a 1k hz tone, and tried to measure on the speaker terminals any AC voltage. My digital multi meter only has 600V and 200V AC, so I used the 200V setting. But it just read 0 when I touched the probes to the speaker terminals. Am I missing something? I didn't play the tone _too_ loud b/c I read online that blasting a constant tone can be bad for your speakers. But it wasn't super quiet either, just kind of normal listening level.
Dan
It sounds like you are doing it right. Always have speakers attached when powering up your amp.
Odd that your DMM doesn't get anything. Maybe it is a sensitivity issue. You can try just playing some music and turning it up louder to see if the DMM will pick up the VAC. It'll be all over the place and not settle, so it'll be useless except to verify your method and DMM is working.
Odd that your DMM doesn't get anything. Maybe it is a sensitivity issue. You can try just playing some music and turning it up louder to see if the DMM will pick up the VAC. It'll be all over the place and not settle, so it'll be useless except to verify your method and DMM is working.
So I tried measuring AC voltage on the speaker terminals again, this time with music blasting. With the DMM on the 200V AC setting, I was getting readings of 0.0 - 0.7 or so, and fluctuating wildly as expected. It just doesn't seem like the meter is sensitive enough to make this measurement accurately.
I think maybe I'll just try tilting my head a little bit to the side, or moving the couch sideways, and see if I can't deal w/ the issue that way for a while.
Thanks!
Dan
I think maybe I'll just try tilting my head a little bit to the side, or moving the couch sideways, and see if I can't deal w/ the issue that way for a while.
Thanks!
Dan
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