Hi newbie here.
While I have built a couple of guitar pedals and mic pre's I know jack about tube guitar amps.
I got a Peavy Valve King Royal8 5 watt class A design tube amp for recording used.
It only has two tubes, the pre/ pwr amp.
I'd like to be able to mod it a little but right now it has the Scratchy rattling resonance when I hold a chord or play the low end strings. It sneaks in after the initial strung pluck.
If I back the gain and volume down it is clean and sounds okay. Turn up to not even half way and in comes the resonance.
The volume brings out this rattling noise more than the gain, so too the tone control shunt to ground.
I have new tubes in it. They aren't vibrating. The amp is connected to a larger ext speaker.
I was hoping someone might know what this is a symtom of or a ball park idea on what to check as I need to fix it before making mods.
The cost of decent amps is beyond me and I don't really need lots of watts and weight for recording.
Thank you for reading
While I have built a couple of guitar pedals and mic pre's I know jack about tube guitar amps.
I got a Peavy Valve King Royal8 5 watt class A design tube amp for recording used.
It only has two tubes, the pre/ pwr amp.
I'd like to be able to mod it a little but right now it has the Scratchy rattling resonance when I hold a chord or play the low end strings. It sneaks in after the initial strung pluck.
If I back the gain and volume down it is clean and sounds okay. Turn up to not even half way and in comes the resonance.
The volume brings out this rattling noise more than the gain, so too the tone control shunt to ground.
I have new tubes in it. They aren't vibrating. The amp is connected to a larger ext speaker.
I was hoping someone might know what this is a symtom of or a ball park idea on what to check as I need to fix it before making mods.
The cost of decent amps is beyond me and I don't really need lots of watts and weight for recording.
Thank you for reading
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Sorry, I'm not musician, so I ignore the meanings of terms as scratchy, hash, etc.
Then, if when no cable to guitar the trouble disappears, then:
1) there is any undesirable interaction between them,
2) there is a short or open cable then receiving some kind of noise from the amplifier or any other source (AM FM Station for example), the causing the amp to oscillate.
Then, I suggest to test the amp with any other audio source: a radio, a microphone, etc, to test the amp itself.
Then, if when no cable to guitar the trouble disappears, then:
1) there is any undesirable interaction between them,
2) there is a short or open cable then receiving some kind of noise from the amplifier or any other source (AM FM Station for example), the causing the amp to oscillate.
Then, I suggest to test the amp with any other audio source: a radio, a microphone, etc, to test the amp itself.
Thanks kevin, there is a possibility that the amp is a few years old though looks as new.
i guess if I replace them I can think about changing values to get a better tone.
Osvaldo, I have shielded my guitars and it does it on any I try with any cable I use. It also does it if I use an isolating transformer on the mains power or not.
I don't think it is an interference on the mains power line into the amp.
There is a fluro light in the kitchen down the hall. I'll turn it off and see just to make sure. Also I am on a completely different electrical circuit to the rest of the house
i guess if I replace them I can think about changing values to get a better tone.
Osvaldo, I have shielded my guitars and it does it on any I try with any cable I use. It also does it if I use an isolating transformer on the mains power or not.
I don't think it is an interference on the mains power line into the amp.
There is a fluro light in the kitchen down the hall. I'll turn it off and see just to make sure. Also I am on a completely different electrical circuit to the rest of the house
I should also describe this rattling scratchy ticking buzz.
It comes in after a single strum on the strings holding the chord and stops before the final decay of the strum.
With no fluro lights it is still present.
most likely a failing component.
Looks like the solution is to upgrade components and make some mods.
I'd be better off building a better design! LOLOL.
It comes in after a single strum on the strings holding the chord and stops before the final decay of the strum.
With no fluro lights it is still present.
most likely a failing component.
Looks like the solution is to upgrade components and make some mods.
I'd be better off building a better design! LOLOL.
I had to sign up just to reply to this thread because I was dealing with this exact problem in a filter I built recently!
The resonance in my filter is acheived by adding feedback at a certain point in the signal path which increases Q factor and morphs the filter type into chebyshev, if your circuit is in any regard similar to this we may have had the exact same problem!
Although I can't tell for sure without a schematic.
The problem was that I was overdriving the amplifier portion of the filter. The waveform was hitting the rails and this caused no resonance to happen. Additionally when the input waveform peak to peak voltage exceeded the voltage fed back, less resonance happened. This was due to feedback limitation acheived with diodes.
Basically it's all down to overdriving your resonant parts.
When things were on the edge of resonance attenuation due to overdriving, it got really rattly and scratchy just as you described! I've adapted my filter to encorporate this- it's a feature now, not a bug
Things also got pretty raw when I had some offset voltage fluctuations in a previous design. Sometimes a signal present would cause certain parts of the circuit to become biased up, resulting in the waveform hitting the rails again and loosing resonance and getting all rattly. This happens especially when the input waveform has unequal high and low portions.
To overcome it, I simply attenuated the input signal a lot and amplified the output. This was fine for my specification and didn't even use that many more components but I can see how it would be undesireable for many applications.
The resonance in my filter is acheived by adding feedback at a certain point in the signal path which increases Q factor and morphs the filter type into chebyshev, if your circuit is in any regard similar to this we may have had the exact same problem!
Although I can't tell for sure without a schematic.
The problem was that I was overdriving the amplifier portion of the filter. The waveform was hitting the rails and this caused no resonance to happen. Additionally when the input waveform peak to peak voltage exceeded the voltage fed back, less resonance happened. This was due to feedback limitation acheived with diodes.
Basically it's all down to overdriving your resonant parts.
When things were on the edge of resonance attenuation due to overdriving, it got really rattly and scratchy just as you described! I've adapted my filter to encorporate this- it's a feature now, not a bug
Things also got pretty raw when I had some offset voltage fluctuations in a previous design. Sometimes a signal present would cause certain parts of the circuit to become biased up, resulting in the waveform hitting the rails again and loosing resonance and getting all rattly. This happens especially when the input waveform has unequal high and low portions.
To overcome it, I simply attenuated the input signal a lot and amplified the output. This was fine for my specification and didn't even use that many more components but I can see how it would be undesireable for many applications.
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