Classic 100 Head crackle at low frequencies

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ZachC137
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Joined: Wed Apr 26, 2017 8:17 am

Classic 100 Head crackle at low frequencies

Post by ZachC137 » Wed Apr 26, 2017 8:40 am

I purchased a used Classic 100 Head about 6 months ago, but recently have noticed that the amp crackles when I play notes in the lower frequencies. This problem has gotten progressively worse over the last several weeks. Initially it seemed to go away when I turned the volume down a tad but now that doesn't suffice. The amp now crackles even with no signal going in.

This is my first prolonged experience with a tube amp, but my first thought is that the tubes are going bad. The preamp tubes don't seem microphonic, and I've checked that none of the cables/guitars were the issue through testing them on another amp. So that leaves the power tubes. Is there any other issue it could be?

Classic54
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Joined: Tue Aug 14, 2012 12:46 pm

Re: Classic 100 Head crackle at low frequencies

Post by Classic54 » Wed Apr 26, 2017 9:03 am

I had a similar problem with low frequency notes and it was indeed a microphonic valve. Have you tried the pencil test tapping the valves?

ZachC137
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Joined: Wed Apr 26, 2017 8:17 am

Re: Classic 100 Head crackle at low frequencies

Post by ZachC137 » Wed Apr 26, 2017 9:14 am

Classic54 wrote:I had a similar problem with low frequency notes and it was indeed a microphonic valve. Have you tried the pencil test tapping the valves?
Thank you for the reply. I did, but I'm not certain I really know what to look or hear for. The preamps all sounded the same, and the power tubes all similar to each other as well. I could try to record it later in the day if it would help though!

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