I am currently chasing down a strange problem with a Trainwreck clone.
When I turn the power switch on, I get a quiet humm from the speakers (the Standby is still off).
How can this be?...
1. There is no power to the OT until the standby switch is on. (switch is wired correctly)
2. Speakers are properly grounded.
3. OT is turned 90 degrees from the PT.
4. 6.3volt heater is center-tapped & grounded. Connections are good at the tube sockets.
I have checked every connection and moved wires around with no change...
It's like a voltage is being induced into the OT from somewhere....
Pulling the EL34's didn't make any diference...
Any ideas???
Otherwise, the amps works correctly and sounds good.
Strange HUM.....
Moderators: pompeiisneaks, Colossal
Re: Strange HUM.....
Do you have a resistor going across the standby switch?
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guitarsnguns04
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Re: Strange HUM.....
is the receptacle your using grounded?
Re: Strange HUM.....
My Express does the same exact thing. Thought this was just normal, since other than that the amp seems to work perfectly.
My Dumble clones do it as well but to a much lesser degree. In other words I have to put my ear to the speaker cab on the Dumbles but it is instantly noticeable on the Express.
Since noticing this hum, I have atleast 40 hours playtime on the Express and have had no problems. Yet!
Todd
My Dumble clones do it as well but to a much lesser degree. In other words I have to put my ear to the speaker cab on the Dumbles but it is instantly noticeable on the Express.
Since noticing this hum, I have atleast 40 hours playtime on the Express and have had no problems. Yet!
Todd
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FUCHSAUDIO
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- Location: New Jersey (you got a problem with that ?)
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Re: Strange HUM.....
Could the power transformer possibly inducing noise into the output transformer ? I'm sure some winds might have a winder hum field than others... the fact the standby switch is on means the amp is not at fault, it could be a magnetic coupling issue.
Proud holder of US Patent # 7336165.
Re: Strange HUM.....
Now that this is in question I will be taking some readings when I get home from work today!
Has anyone else with an Express clone noticed this?
Todd
Has anyone else with an Express clone noticed this?
Todd
Re: Strange HUM.....
Why would there be a resistor across the standby switch?surfsup wrote:Do you have a resistor going across the standby switch?
The only resistor connected to the standby is the 1K 25watter on mine.
Todd
Re: Strange HUM.....
I have had transformers lately that hum badly.
One went back to the manufacturer and they said it was incorrectly built. It works well now (no charge), but myself and the amp owner went through hell with this problem.
Mark
One went back to the manufacturer and they said it was incorrectly built. It works well now (no charge), but myself and the amp owner went through hell with this problem.
Mark
Re: Strange HUM.....
Hey Mark
Was that Hum while in standby?
I know you have built your share of TW's on any of them can you tell audibly when just the power is turned on? Still in standby.
I will also add that mine is using the Mag components TW iron.
This hum is so minor that it in no way affects the sound on this amp, I just want to make sure its not a problem that should be dealt with before something ( expensive ) fails.
Todd
Was that Hum while in standby?
I know you have built your share of TW's on any of them can you tell audibly when just the power is turned on? Still in standby.
I will also add that mine is using the Mag components TW iron.
This hum is so minor that it in no way affects the sound on this amp, I just want to make sure its not a problem that should be dealt with before something ( expensive ) fails.
Todd
Re: Strange HUM.....
I tend to believe the cause is the PT inducing voltage into the OT.
If I place a metal shield between the transformers, I am able to eliminate about 60% of the hum.
The hum is not 'terrible'. Actually, in a normal room, you can barely hear it-that is, if you are actually listening for it.
It just took me by suprise because my other TW clone doesn't do it. They are both using the same transformers, and the transformers are arranged the same way. I will chalk it up to being transformers that are not all created exactly the same way - AND, I will install the shield permamently.
If I place a metal shield between the transformers, I am able to eliminate about 60% of the hum.
The hum is not 'terrible'. Actually, in a normal room, you can barely hear it-that is, if you are actually listening for it.
It just took me by suprise because my other TW clone doesn't do it. They are both using the same transformers, and the transformers are arranged the same way. I will chalk it up to being transformers that are not all created exactly the same way - AND, I will install the shield permamently.
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FUCHSAUDIO
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- Joined: Fri Apr 08, 2005 2:48 pm
- Location: New Jersey (you got a problem with that ?)
- Contact:
Re: Strange HUM.....
it's either a shield or moving the output farther from the power. You can also remove mounting screws and try rotating transformer slightly to find a null if one exists.
Proud holder of US Patent # 7336165.
Re: Strange HUM.....
I dunno about all this. I think that some PTs have a crappy filament wind, such that when you turn the PT on it vibrates loud enough to make you think you are hearing something from the speaker - but you are not.
Q: When you heard this sound, did you isolate the speaker cab with a 20 foot speaker cable?
I had a Heyboer that had this issue, and I love Phil and Heyboer, BTW, and use their product. Apparently it wasn't potted very well and was eventually replaced by Heyboer. If you think about it, some of these TW designed PTs have a 7.5amp filament wind on them - typical - and way way overbuilt for what the Express actually needs. (Blame this on KFs choice of iron perhaps, although Pacific seems to do the job very well.) At any rate, tyically that's a large diameter secondary wire inside the PT, bigger in fact than all the others. As a secondary, converting the 120VAC to 6.3VAC, it is conducting some serious energy. Which translates to heat and, unfortunately, vibration from the AC pulse if it is not built and potted well.
And let's talk about manufacturers for a minute. Mercury goes on about how a good PT can influence an amps TONE? If you think about it, all they are saying is that the best thing a PT can do, besides deliver all the current and voltages needed, is be QUIET. If the PT is quiet, the whole circuit benefits. Which is to say that that filament 'buzz' I ran into impacted the whole amp. It's a bad deal to have any vibrational buzz in any PT secondary because it is right next to all the other PT secondary taps - not to mention the fact that it is strapped onto your chassis and vibrating all your tubes!
Q: Who makes the quietest PTs? Hammond.
I'm not saying that they make a PT that has the voltages I can use for every build because they don't. But I am saying without a doubt, that they produce a PT that produces no vibrational buzz as it operates. This is what you want in an amp like the Express, or any high gain amp, for that matter. Go turn on one sometime, they have figured it out.
Further, I know this goes upstream here, but all this talk about transformer placement/repositioning that occurs whenever someone says they hear a buzz in their Express? Eh, Kenny used the Stancor and then the Pacific. Have any of you that suggest this repositioning thought to determine the brand of PT/OT being used? If it turns out, and it does IMO, that the Express built with Pacific iron does not need this repositioning, what does this tell us? Honestly, I have always thought that this issue came up because somebody had a crappy PT. It may be fun to consider that Kenny did something 'wrong' in his layout, but the fact is he didn't sell amps that had added noise because of tranny placement. Why not instead consider how it was that this was the case? Here, I'll make the answer easy: Good transformers.
Q: When you heard this sound, did you isolate the speaker cab with a 20 foot speaker cable?
I had a Heyboer that had this issue, and I love Phil and Heyboer, BTW, and use their product. Apparently it wasn't potted very well and was eventually replaced by Heyboer. If you think about it, some of these TW designed PTs have a 7.5amp filament wind on them - typical - and way way overbuilt for what the Express actually needs. (Blame this on KFs choice of iron perhaps, although Pacific seems to do the job very well.) At any rate, tyically that's a large diameter secondary wire inside the PT, bigger in fact than all the others. As a secondary, converting the 120VAC to 6.3VAC, it is conducting some serious energy. Which translates to heat and, unfortunately, vibration from the AC pulse if it is not built and potted well.
And let's talk about manufacturers for a minute. Mercury goes on about how a good PT can influence an amps TONE? If you think about it, all they are saying is that the best thing a PT can do, besides deliver all the current and voltages needed, is be QUIET. If the PT is quiet, the whole circuit benefits. Which is to say that that filament 'buzz' I ran into impacted the whole amp. It's a bad deal to have any vibrational buzz in any PT secondary because it is right next to all the other PT secondary taps - not to mention the fact that it is strapped onto your chassis and vibrating all your tubes!
Q: Who makes the quietest PTs? Hammond.
I'm not saying that they make a PT that has the voltages I can use for every build because they don't. But I am saying without a doubt, that they produce a PT that produces no vibrational buzz as it operates. This is what you want in an amp like the Express, or any high gain amp, for that matter. Go turn on one sometime, they have figured it out.
Further, I know this goes upstream here, but all this talk about transformer placement/repositioning that occurs whenever someone says they hear a buzz in their Express? Eh, Kenny used the Stancor and then the Pacific. Have any of you that suggest this repositioning thought to determine the brand of PT/OT being used? If it turns out, and it does IMO, that the Express built with Pacific iron does not need this repositioning, what does this tell us? Honestly, I have always thought that this issue came up because somebody had a crappy PT. It may be fun to consider that Kenny did something 'wrong' in his layout, but the fact is he didn't sell amps that had added noise because of tranny placement. Why not instead consider how it was that this was the case? Here, I'll make the answer easy: Good transformers.
Most people stall out when fixing a mistake that they've made. Why?
Re: Strange HUM.....
TW PT humm's when turned on and no it wasn't my placement or CT grounding.
Mark
Mark
Re: Strange HUM.....
Second from last image under "improved standby switching", and doing this produces a slight output even though amp is not off standby.T Wilcox wrote:Why would there be a resistor across the standby switch?surfsup wrote:Do you have a resistor going across the standby switch?
The only resistor connected to the standby is the 1K 25watter on mine.
Todd
http://www.freewebs.com/valvewizard1/standby.html
I know most here build their TW clones to the "T" but was just asking...
Re: Strange HUM.....
It is hum from the speakers-- NOT vibration from a noisy-loosely built transformer (I have had that problem before). If I unplug the speaker, the hum stops. I have tried isolating the amp from the speaker cab with a long cable. The only thing that seems to work is the metal shield.