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Ampeg SVT-CL Crackling Sound (video)
- Thread starter zwish
- Start date
- Jun 29, 2006
- 5,148
- 3,217
- Disclosures
- President, CEO, CFO, CIO, Chief Engineer, Technician, Janitor - Reiner Amplification
One fairly common cause with the CL’s is the preamp ground coming loose or making intermittent contact. Pull the preamp chassis out and find the stand-off used to ground the preamp PCB. Remove the screw going through the top of the PCB into the standoff, add a star tooth lock washer that is similar size to the PCB pad/screw head, and reinstall the screw.
Could be a bad tube. I've heard that sound with a bad tube before. Did you do the chopstick test yet? Could also possibly be corrosion in the pre/power jacks. Try sticking an instrument cable in between them and see if it clears up. If so, they need cleaned with either Deoxit or jabbing a plug in and out of them really fast several times. We're all basically spitballing here because we can't check it out for ourselves, but those are the things I'd check first.
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Take a little stick (not a pencil) and tap on the tubes to see if it's a loose tube connection.
Take a little stick (not a pencil) and tap on the tubes to see if it's a loose tube connection.
what if it's a solid state amp with similar crackling?
Gas can and a highway flare? Just asking for a friend
Gas can and a highway flare? Just asking for a friend
Like Jimmy said, try substituting preamp tubes first. It’s an easy thing to try. If any tubes slip in and out of their sockets too easily, there is not enough tension at the tube socket terminals, they should be re-tensioned. It’s a simple process of removing the tune and carefully pinching the tube socket contact inward.
Failing this, you will have to dig deeper to resolve the issue.
what if it's a solid state amp with similar crackling?
Gas can and a highway flare? Just asking for a friend
There are so many possibilities. A lot of bads. A bad connection, a bad component, a bad solder joint, etc.. You have to sweat through a lot of fine details with test equipment to resolve the issue.
and if it's a used amp you got for a buck and a quarter probably not worth the expense to try to suss it out?
Maybe if you're a tech it is, but if you have to pay for it, it could cost that much or more to fix. Depends on the amp if you ask me. Some I'd be more inclined to fix than others.
You get an evaluation, half an hour of bench time. If any work is done the preliminary work’s cost is often waved. It doesn’t need to cost a lot, but part of the price of buying a used amp. This should be factored into the cost of the purchase.
All amps, tube or solid state need service during their life.
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For most part sounds like a bad pre tube.
The plate spacers start to rattle. Or the heater starts smacking against the cathode.
Just typical damage from vibration or alot of hot cold cycles.
Otherwise crickle crackle like that is from bad seated tubes. Bent loose tube socket pins. Or socket to board solder connections need little touch up
Most likely a rattle rocket tube.
Could be pre tube. Or 9pin tube on the power amp.
Just buy one new 12ax7 and new au7
One those tubes be bad. And most likely eventually a au7 will go rattling and cracking and you'll have one when it does
Just figure out what tubes crackling. Replace it. Make sure rest are seated.
Great joke play on guitar players is save working crackling tubes. Pop it in their amp. Watch freak out unplug pedals for 10 mins lol
The plate spacers start to rattle. Or the heater starts smacking against the cathode.
Just typical damage from vibration or alot of hot cold cycles.
Otherwise crickle crackle like that is from bad seated tubes. Bent loose tube socket pins. Or socket to board solder connections need little touch up
Most likely a rattle rocket tube.
Could be pre tube. Or 9pin tube on the power amp.
Just buy one new 12ax7 and new au7
One those tubes be bad. And most likely eventually a au7 will go rattling and cracking and you'll have one when it does
Just figure out what tubes crackling. Replace it. Make sure rest are seated.
Great joke play on guitar players is save working crackling tubes. Pop it in their amp. Watch freak out unplug pedals for 10 mins lol
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I've heard that sound with both but I'd check the pre tubes first because they're cheaper and easier to swap out, although with the bias lights it's not nearly as much of a challenge to swap power tubes in an SVT like it used to be.
your time will come, but I hope it’s not right now.I was looking in the manual to see which 12AX7 and AU7 you were referring to, but I'm not sure if you're talking about the two tubes that are in the preamp that you pull out of the front of the amp, or one of the 3 that are on the actual chassis?
Preamp Tube: 2 x 12AX7
Driver Tube: 1 x 12AX7, 2 x 12AU7
Power Amp Tube: 6 x 6550
Preamp Tube: 2 x 12AX7
Driver Tube: 1 x 12AX7, 2 x 12AU7
Power Amp Tube: 6 x 6550
How I figured out it was a bad preamp tube in mine was to bypass the preamp and see if it still made the crackle. It didn’t so that narrowed it down to the preamp. I snatched the preamp tubes out of my blues jr and put those in and no problems. So I ordered new ones and it’s been great ever since.
