hoffy
New Member
Posts: 35
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Post by hoffy on May 13, 2023 4:00:14 GMT -7
I have found out my Cure amp produces quite some hum at higher volume levels, esp. with the Volume (=gain) knob turned up. Here is a sound file I recorded: soundcloud.com/phtady/humThe sample is recorded without any guitar or cable plugged in. First part is with all knobs at noon, 2nd is Volume, Master and Level at 3 o'clock and finally Volume, Master and Level almost full. But it is coming mostly from the Volume pot, this influences it the most. Is yours doing that too? Is that normal for this amp? It is 100 Hz, so I guess something to do with 50 cycle hum? I have tried to swap preamp tubes in every position with a new one, one at a time, rectifier tube and power tubes as well and the hum has not changed. The Cure is the first version from 2017 and I am in Europe so it has an EU transformer if that helps. Thanks!
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Post by DRZ on May 13, 2023 5:21:30 GMT -7
Check your input jack for tightness to the chassis. 1/2 inch nut on the jack , needs to be very tight.
Z
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hoffy
New Member
Posts: 35
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Post by hoffy on May 13, 2023 9:40:32 GMT -7
Check your input jack for tightness to the chassis. 1/2 inch nut on the jack , needs to be very tight. Z Thanks Doc! Jack seems to be tight. Anything else worth checking?
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Post by daddyelmis (Greg) on May 13, 2023 13:31:15 GMT -7
Hoffy - check this out
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Post by Don A on May 13, 2023 18:59:27 GMT -7
I just tried those settings and my 2019 Cure doesn't hum like that. Hiss, but not hum like that.
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Post by scottyc13 on May 14, 2023 4:14:08 GMT -7
It sounds like a ground or earth loop to me. Is the amp plugged in by itself with no other amps?
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hoffy
New Member
Posts: 35
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Post by hoffy on May 14, 2023 10:58:25 GMT -7
It sounds like a ground or earth loop to me. Is the amp plugged in by itself with no other amps? Yeah, just Cure by itself. No other amps. It is 100 Hz so it may be related to ground - 50 cycle hum?
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Post by scottyc13 on May 14, 2023 13:25:11 GMT -7
It sound like earth loop hum. Did you try it on a different outlet or place?
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klmn
New Member
Posts: 26
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Post by klmn on May 14, 2023 13:50:33 GMT -7
I have found out my Cure amp produces quite some hum at higher volume levels, esp. with the Volume (=gain) knob turned up. Here is a sound file I recorded: soundcloud.com/phtady/humThe sample is recorded without any guitar or cable plugged in. First part is with all knobs at noon, 2nd is Volume, Master and Level at 3 o'clock and finally Volume, Master and Level almost full. But it is coming mostly from the Volume pot, this influences it the most. Is yours doing that too? Is that normal for this amp? It is 100 Hz, so I guess something to do with 50 cycle hum? I have tried to swap preamp tubes in every position with a new one, one at a time, rectifier tube and power tubes as well and the hum has not changed. The Cure is the first version from 2017 and I am in Europe so it has an EU transformer if that helps. Thanks! Any possible external sources of the hum, like a neon lamp or a dimmer switch?
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hoffy
New Member
Posts: 35
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Post by hoffy on May 15, 2023 0:15:23 GMT -7
I have found out my Cure amp produces quite some hum at higher volume levels, esp. with the Volume (=gain) knob turned up. Here is a sound file I recorded: soundcloud.com/phtady/humThe sample is recorded without any guitar or cable plugged in. First part is with all knobs at noon, 2nd is Volume, Master and Level at 3 o'clock and finally Volume, Master and Level almost full. But it is coming mostly from the Volume pot, this influences it the most. Is yours doing that too? Is that normal for this amp? It is 100 Hz, so I guess something to do with 50 cycle hum? I have tried to swap preamp tubes in every position with a new one, one at a time, rectifier tube and power tubes as well and the hum has not changed. The Cure is the first version from 2017 and I am in Europe so it has an EU transformer if that helps. Thanks! Any possible external sources of the hum, like a neon lamp or a dimmer switch? Not that I am aware of. The point is, my other amps do not have it. It is not as pronounced when playing, but it is there in the background. When I crank the gain, it becomes quite audible.
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Post by scottyc13 on May 15, 2023 4:03:25 GMT -7
There are a couple of ground points in most amps. The input jack is one and the other is usually one of the power transformer mounting screws. Dr Z marks the point with a green sticker. Can you check to see if the PT feels loose at all? It may be that the ground just needs tightening. If you’re not experienced working inside an amp, I would recommend taking it to a tech. Amps can be dangerous (lethal) if you don’t have experience. The capacitors hold lethal voltage and need to be discharged before working inside the amp.
If you have other tubes, you could try substituting a know good tube in each location. Also check the jacks in the back of the amp for speaker and foot switches and make sure they are tight. Remove the knobs on the front panel and make sure the pots are tight.
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Post by frankie on May 15, 2023 9:53:32 GMT -7
I have found out my Cure amp produces quite some hum at higher volume levels, esp. with the Volume (=gain) knob turned up. Here is a sound file I recorded: soundcloud.com/phtady/humThe sample is recorded without any guitar or cable plugged in. First part is with all knobs at noon, 2nd is Volume, Master and Level at 3 o'clock and finally Volume, Master and Level almost full. But it is coming mostly from the Volume pot, this influences it the most. Is yours doing that too? Is that normal for this amp? It is 100 Hz, so I guess something to do with 50 cycle hum? I have tried to swap preamp tubes in every position with a new one, one at a time, rectifier tube and power tubes as well and the hum has not changed. The Cure is the first version from 2017 and I am in Europe so it has an EU transformer if that helps. Thanks! After checking that the jack is tight and other points on the amp are tight like in the maintenance video (good to do regardless of if this solves the issue), the first position preamp tube can be a source of noise. Another source is mismatched power tubes, like in the instance one is weak and beginning to fail. To determine where in the circuit the hum is potentially coming from, pull the phase inverter (preamp tube closes to the power tubes). If the hum stops, it would tell you that it's more than likely the issue is in the preamp. Try swapping the first preamp (V1, closest to the input jack) with the second (V2). Often times noisy preamp tubes in V1 will not exhibit the same noise in V2. If the hum is still there with the phase inverter pulled out of the amp, this may be a power tube issue like described above.
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klmn
New Member
Posts: 26
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Post by klmn on May 31, 2023 21:44:40 GMT -7
I have found out my Cure amp produces quite some hum at higher volume levels, esp. with the Volume (=gain) knob turned up. Here is a sound file I recorded: soundcloud.com/phtady/humThe sample is recorded without any guitar or cable plugged in. First part is with all knobs at noon, 2nd is Volume, Master and Level at 3 o'clock and finally Volume, Master and Level almost full. But it is coming mostly from the Volume pot, this influences it the most. Is yours doing that too? Is that normal for this amp? It is 100 Hz, so I guess something to do with 50 cycle hum? I have tried to swap preamp tubes in every position with a new one, one at a time, rectifier tube and power tubes as well and the hum has not changed. The Cure is the first version from 2017 and I am in Europe so it has an EU transformer if that helps. Thanks!
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klmn
New Member
Posts: 26
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Post by klmn on May 31, 2023 21:47:09 GMT -7
Check out this video. He is talking about 120 cycle hum - of course he is in America, where we have 60 cycle current. I think in Europe the same issue would result in 100 cycle hum.
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Post by cfidave on Oct 31, 2023 8:04:37 GMT -7
I had a hum coming from the Cure. Steady volume, does not change with volume knob. I switched out both 6v6s to the original JJs and the hum disappeared. It was coming from one or both of my so called NOS 6v6s. Try to determine if the volume knob effects the hum. That will tell you where it is most likely coming from i.e. preamp or power side.
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