Yes, that's what I do too.
Whenever there's two cascaded gain stages with polarity flips, then any coupling will likely be positive and mitigation to reduce that coupling should be considered.
Rather than do it mentally, as a first off, actually mark up the schematic with the polarity flips, and then transfer that to the layout.
I find this a very powerful tool.
No squealing with no guitar, but squeals at 4-6 with guitar
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Re: No squealing with no guitar, but squeals at 4-6 with guitar
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him!
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Stevem
- Posts: 5144
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- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: No squealing with no guitar, but squeals at 4-6 with guitar
Test
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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titser_marco
- Posts: 131
- Joined: Tue Mar 13, 2007 3:08 pm
Re: No squealing with no guitar, but squeals at 4-6 with guitar
UPDATE:
I tried moving some wires around and it seemed that the plate and cathode wires on V1 had the most effect. Couldn't try moving them completely far away so what I did was switch the sides used for each gain stage, i.e. first gain stage is now v1b and second is v1a. I also had to change the grid stopper resistor going into the second gain stage from 150K to 270K as that was all I had. The schematic called for a 180K but these were the only values I had when I first built it and earlier this morning.
The squeal is now gone, which makes me happy, but a part of me wants to tinker around with the grid stopper resistor to see whether that was the culprit or whether the new layout was key.
I tried moving some wires around and it seemed that the plate and cathode wires on V1 had the most effect. Couldn't try moving them completely far away so what I did was switch the sides used for each gain stage, i.e. first gain stage is now v1b and second is v1a. I also had to change the grid stopper resistor going into the second gain stage from 150K to 270K as that was all I had. The schematic called for a 180K but these were the only values I had when I first built it and earlier this morning.
The squeal is now gone, which makes me happy, but a part of me wants to tinker around with the grid stopper resistor to see whether that was the culprit or whether the new layout was key.