Weird note decay - Express build
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- Reeltarded
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Re: Weird note decay - Express build
If you tap the input wire with a stick is the wire hyper microphonic? Try this with nothing plugged into the input and with a guitar plugged in and guitar volume @ zero.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
- Reeltarded
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Re: Weird note decay - Express build
I am too ultra focused on the input stage. Chopstick every stage grid until you find something that seems related in frequency to the frittering note tails. Really examine shielding on wires and the dress as bepone said. Curl around seperate and snug flat against the chassis.
Swap all preamp tubes with any other position. Swap them in order 1-2 2-3 3-1 if the response changes we can maybe find the problem if it follows a weak of very strong tube..
Swap all preamp tubes with any other position. Swap them in order 1-2 2-3 3-1 if the response changes we can maybe find the problem if it follows a weak of very strong tube..
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
- Ledvedder5150
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Re: Weird note decay - Express build
I've already started dismantling it, so I can't test anything else
Yesterday, I tried tracing it with a signal generator and my oscilloscope. With just a resistive load in the output, I could hear the signal noise from one of the tone capacitors. I think it was the 500pf treble cap. To make sure I wasn't going crazy, I changed the signal generator to different frequencies, and the sound followed suit.
I used a layout from Modulus to build it. I'm not sure if Michael would appreciate me sharing it here.
Yesterday, I tried tracing it with a signal generator and my oscilloscope. With just a resistive load in the output, I could hear the signal noise from one of the tone capacitors. I think it was the 500pf treble cap. To make sure I wasn't going crazy, I changed the signal generator to different frequencies, and the sound followed suit.
I used a layout from Modulus to build it. I'm not sure if Michael would appreciate me sharing it here.
Check out my band: https://www.facebook.com/ungluedband
- Ledvedder5150
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Re: Weird note decay - Express build
What type of caps are recommended for the treble cap and the bright caps? Right now I'm using mica. Would ceramic be better?
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- Littlewyan
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Re: Weird note decay - Express build
It’s normal to hear some sound without a speaker. I think it comes from the OT.
Use Silver Mica, don’t use Ceramic.
Are you rebuilding it as an Express again?
Use Silver Mica, don’t use Ceramic.
Are you rebuilding it as an Express again?
- Ledvedder5150
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Re: Weird note decay - Express build
Yeah, I think so. I liked the Komet 60 sound, but it's not all that different from a few of my Marshall type amps.Littlewyan wrote: ↑Sat Dec 02, 2023 11:51 pm It’s normal to hear some sound without a speaker. I think it comes from the OT.
Use Silver Mica, don’t use Ceramic.
Are you rebuilding it as an Express again?
Check out my band: https://www.facebook.com/ungluedband
- Ledvedder5150
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Re: Weird note decay - Express build
I found a pic I took before I started ripping it apart. Ignore my attempt at the split load switch, and the few component additions. That was my attempt at converting the preamp to a Komet 60. That odd noise was happening before and after those changes.
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- Reeltarded
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Re: Weird note decay - Express build
Silver micas have a reputation for one in many being shit. Possible.
FLY the switch wires ALL THE WAY to the deck of the headbox. That situation is not great, there are also some safety reasons to use the Farady coil instead of shield there depending on wire prep and voltage capacity.
FLY the switch wires ALL THE WAY to the deck of the headbox. That situation is not great, there are also some safety reasons to use the Farady coil instead of shield there depending on wire prep and voltage capacity.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
- Ledvedder5150
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Re: Weird note decay - Express build
I'm probably gonna remove the switch anyway. Although I like what it does for my Liverpool, I don't care for it much in this one.Reeltarded wrote: ↑Sun Dec 03, 2023 1:39 am Silver micas have a reputation for one in many being shit. Possible.
FLY the switch wires ALL THE WAY to the deck of the headbox. That situation is not great, there are also some safety reasons to use the Farady coil instead of shield there depending on wire prep and voltage capacity.
Check out my band: https://www.facebook.com/ungluedband
- Reeltarded
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Re: Weird note decay - Express build
It is rarely something worth doing. That variable cathode tail I described is hundreds of times more useful for a similar but better action with infinite degrees.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
- Ledvedder5150
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Re: Weird note decay - Express build
Yeah, can you explain that variable cathode tail thing?Reeltarded wrote: ↑Sun Dec 03, 2023 3:10 am It is rarely something worth doing. That variable cathode tail I described is hundreds of times more useful for a similar but better action with infinite degrees.
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- Reeltarded
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Re: Weird note decay - Express build
So, you simply add 25k pot on cathode tail to ground. It is that simple and you dial in how much fire overall.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
- Littlewyan
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Re: Weird note decay - Express build
Only things jumping out in that pic are:
- Your grounds, looks like you’re using the jack sockets as ground points.
- Spare secondary is a bit close to the split wiring.
- Maybe what appears to be your OT primary is very long.
I haven’t been able to listen to the recording yet (soundcloud is forcing me to login and I don’t have an account).
Are you using an attenuator by the way?
- Your grounds, looks like you’re using the jack sockets as ground points.
- Spare secondary is a bit close to the split wiring.
- Maybe what appears to be your OT primary is very long.
I haven’t been able to listen to the recording yet (soundcloud is forcing me to login and I don’t have an account).
Are you using an attenuator by the way?
- Littlewyan
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Re: Weird note decay - Express build
Ah, found a way to listen. Yes sounds like instability or maybe a bad connection somewhere. Will have to see once you’ve finished rebuilding.
- Ledvedder5150
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Re: Weird note decay - Express build
Maybe I'm just dumb but I'm not sure what you mean by cathode tail.Reeltarded wrote: ↑Sun Dec 03, 2023 7:14 am So, you simply add 25k pot on cathode tail to ground. It is that simple and you dial in how much fire overall.
Check out my band: https://www.facebook.com/ungluedband