Hum Neutralizer
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Hum Neutralizer
Hi guys,
I stumbled upon this video as I had some hum in an my 18 Watt Superlite TMB:
https://www.youtube.com/watch?v=epQUVJ--JZY
I tried it on my amp and it did reduce the hum quite a bit, however, not completely. What are your thoughts on this "mod"? Anybody else tried it?
I could not try the amp loud yet, but do you think the tone has changed?
Thanks and best regards!
I stumbled upon this video as I had some hum in an my 18 Watt Superlite TMB:
https://www.youtube.com/watch?v=epQUVJ--JZY
I tried it on my amp and it did reduce the hum quite a bit, however, not completely. What are your thoughts on this "mod"? Anybody else tried it?
I could not try the amp loud yet, but do you think the tone has changed?
Thanks and best regards!
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- JMPGuitars
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Re: Hum Neutralizer
That appears to be a modified version of elevated heater wiring. I'm not sure what connecting it to the PI cathode does, but I didn't really watch the video yet. This method likely only gets rid of hum due to the heater wiring.
If you're still having hum/noise issues, it's more likely lead dress, grounding, or possibly not paying attention to the direction of capacitor foils, or a million other things that can add to amp noise.
Which version Superlite TMB did you build?
If you're still having hum/noise issues, it's more likely lead dress, grounding, or possibly not paying attention to the direction of capacitor foils, or a million other things that can add to amp noise.
Which version Superlite TMB did you build?
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- TriodeLuvr
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Re: Hum Neutralizer
This technique has been used commercially for many years, although I've never seen it applied to the phase inverter. Here's a Stromberg console amp from the '60s:
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Re: Hum Neutralizer
Thanks for the replies guys!
I was aware of heater elevation too, but this method of noise canceling was new to me. And to be honest, I did not fully understand the logic behind it as explained in the vide. The way I understood it was that ALL hum getting into the power stage can be cancelled by it and not only heater hum (as opposed to common heater elevation). I guess I was mistaken.
Josh, it is just the regular Superlite TMB (newest version from the downloads here). I recycled used parts and had to make some tradeoffs due to very short wire lengths of the transformers I used. This has led to suboptimal lead dress.
I was aware of heater elevation too, but this method of noise canceling was new to me. And to be honest, I did not fully understand the logic behind it as explained in the vide. The way I understood it was that ALL hum getting into the power stage can be cancelled by it and not only heater hum (as opposed to common heater elevation). I guess I was mistaken.
Josh, it is just the regular Superlite TMB (newest version from the downloads here). I recycled used parts and had to make some tradeoffs due to very short wire lengths of the transformers I used. This has led to suboptimal lead dress.
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Re: Hum Neutralizer
I would say that's probably your answer right there. If the leads are too short, you can extend the leads and double heat-shrink tube the connections. That's fine as long as you're not planning on selling the amp. That said, I would be surprised if it's all in the PT area causing your noise. BTW- this is one reason why I stick with solder lug PTs. Harder to avoid on OTs, but wires can still be extended if done correctly.
Post some build photos so we can take a look. Also a sound sample so we can hear the issue.
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Re: Hum Neutralizer
JMPGuitars wrote: ↑Thu 12/17/20 4:49 pmI would say that's probably your answer right there. If the leads are too short, you can extend the leads and double heat-shrink tube the connections. That's fine as long as you're not planning on selling the amp. That said, I would be surprised if it's all in the PT area causing your noise. BTW- this is one reason why I stick with solder lug PTs. Harder to avoid on OTs, but wires can still be extended if done correctly.
Post some build photos so we can take a look. Also a sound sample so we can hear the issue.
You are right. I have to make the leads of my OT longer so I can place my board better with regards to the tube sockets. I have rather long leads to the PI tube from the board and they cross wires of the power tube socket. I will fix that and if the problem still remains post some pictures. Btw, the hum is tolerable but I still like my amp as quiet as possible. I will keep you updated, thanks!
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- TriodeLuvr
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Re: Hum Neutralizer
I often re-purpose vintage transformers that have been removed from older gear. The leads are almost never long enough. I just mount a terminal strip directly under the transformer and wire all the leads to that. Then I add new wiring to the terminal strip. Looks neat and solves the problem.Riffmonster wrote: ↑Thu 12/17/20 1:40 pm
You are right. I have to make the leads of my OT longer so I can place my board better with regards to the tube sockets.
Jack
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Re: Hum Neutralizer
That is actually a smart idea, thanks for the tip!TriodeLuvr wrote: ↑Fri 12/18/20 10:15 amI often re-purpose vintage transformers that have been removed from older gear. The leads are almost never long enough. I just mount a terminal strip directly under the transformer and wire all the leads to that. Then I add new wiring to the terminal strip. Looks neat and solves the problem.Riffmonster wrote: ↑Thu 12/17/20 1:40 pm
You are right. I have to make the leads of my OT longer so I can place my board better with regards to the tube sockets.
Jack
I did rework the amp a bit today. I moved all tube socket one position to the PT direction after making the leads of my OT a bit longer. This made it possible to shorten most wires going from the board to the tube sockets. The hum is significantly lower now, when you play at bedroom level you can basically not hear it. There is a bit of hum and white noise when I turn it up, but I think it is not too bad.
I attach you two photos. It is not a neat looking amp, I know. As I said it was made from parts I used years ago over an over again. If you have some tips for making it even more quiet, please go ahead. I could, for example, try carbon comps on the PIs. Thanks
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Re: Hum Neutralizer
Carbon comps are the noisiest option. They're only beneficial at the PI plates. If you want less hiss, metal film are the best option.Riffmonster wrote: ↑Fri 12/18/20 12:23 pmI did rework the amp a bit today. I moved all tube socket one position to the PT direction after making the leads of my OT a bit longer. This made it possible to shorten most wires going from the board to the tube sockets. The hum is significantly lower now, when you play at bedroom level you can basically not hear it. There is a bit of hum and white noise when I turn it up, but I think it is not too bad.
I attach you two photos. It is not a neat looking amp, I know. As I said it was made from parts I used years ago over an over again. If you have some tips for making it even more quiet, please go ahead. I could, for example, try carbon comps on the PIs. Thanks
But I doubt it's the resistors from the look of the build. Your lead dress is a mess, and you should chopstick it a bit. Sloppy lead dress = noise.
Your heater wires are also an issue. They should all be tight together, including the separate runs going between the tubes. For example, both connections to Pin 9 on your preamp tubes should not be separated. Use a zip tie to join them if you need to. I twist and heatshrink.
Thanks,
Josh
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Re: Hum Neutralizer
Riffmonster wrote: ↑Fri 12/18/20 12:23 pmThat is actually a smart idea, thanks for the tip!TriodeLuvr wrote: ↑Fri 12/18/20 10:15 amTube Town parts? I recognize the silicon wiresRiffmonster wrote: ↑Thu 12/17/20 1:40 pm
You are right. I have to make the leads of my OT longer so I can place my board better with regards to the tube sockets.
I often re-purpose vintage transformers that have been removed from older gear. The leads are almost never long enough. I just mount a terminal strip directly under the transformer and wire all the leads to that. Then I add new wiring to the terminal strip. Looks neat and solves the problem.
Jack
I did rework the amp a bit today. I moved all tube socket one position to the PT direction after making the leads of my OT a bit longer. This made it possible to shorten most wires going from the board to the tube sockets. The hum is significantly lower now, when you play at bedroom level you can basically not hear it. There is a bit of hum and white noise when I turn it up, but I think it is not too bad.
I attach you two photos. It is not a neat looking amp, I know. As I said it was made from parts I used years ago over an over again. If you have some tips for making it even more quiet, please go ahead. I could, for example, try carbon comps on the PIs. Thanks
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Re: Hum Neutralizer
I use metal films, but if you were inclined to use CC and believe RG Keen, they would be OK on the PI plates in a non-NFB amp like the 18 Watter, and on the output tube grids too. And also at the first stage plate, which Keen says is "ideal".JMPGuitars wrote: ↑Fri 12/18/20 12:48 pmCarbon comps are the noisiest option. They're only beneficial at the PI plates. If you want less hiss, metal film are the best option.
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Re: Hum Neutralizer
Yeah, we mostly use the same stuff.crgfrench wrote: ↑Sat 12/19/20 12:38 amI use metal films, but if you were inclined to use CC and believe RG Keen, they would be OK on the PI plates in a non-NFB amp like the 18 Watter, and on the output tube grids too. And also at the first stage plate, which Keen says is "ideal".JMPGuitars wrote: ↑Fri 12/18/20 12:48 pmCarbon comps are the noisiest option. They're only beneficial at the PI plates. If you want less hiss, metal film are the best option.
But for other people's reference:
http://www.geofex.com/article_folders/c ... oncomp.htm
http://www.aikenamps.com/index.php/resi ... -it-matter
I thought Merlin had a thing about it too, but I can't find it.
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Re: Hum Neutralizer
Thanks guys. I implemented a proper star ground and the hum is gone now.
I did not do the heater elevation in the end. Maybe I will try the carbon comps on the PI plates, but I am quite how it sounds now. This showed me once again how important proper grounding an lead dress is.
I did not do the heater elevation in the end. Maybe I will try the carbon comps on the PI plates, but I am quite how it sounds now. This showed me once again how important proper grounding an lead dress is.
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