I plugged into my friends 2203 and it sounded dreadful. It was overly compressed and the treble is raspy.
The compression was due to the 100K cathode follower resistor measuring 880K. I replaced it and the amp sounded much better. The amp still has raspiness which goes away when I turn the volume up.
I’m wondering if I should consider the Kevin O’Conner mod where you put a 100K resistor in series with the master volume wiper connection.
http://site.triodestore.com/JCM8002203Stock.pdf
This Triode circuit diagram has a 100pF cap across the first stage and I believe that Dave Friedman does put a 0.002uF across the cathode follower 100K resistor.
Thoughts on raspy treble response?
Thanks for your assistance.
Raspy treble from 2203 amp
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Raspy treble from 2203 amp
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Yours Sincerely
Mark Abbott
Mark Abbott
Re: Raspy treble from 2203 amp
Speaker is v30? Change the speaker?
Some other guitar problem?
Some other guitar problem?
Re: Raspy treble from 2203 amp
I used a EVH MIM guitar, and I also used my Strat. The box is a Fender Bassman box with Kendrick Blackframe speakers in it. I have previously used the box with a 1959 and it sounded fine. The speakers aren’t overly bright.
Yours Sincerely
Mark Abbott
Mark Abbott
- Littlewyan
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Re: Raspy treble from 2203 amp
That master volume mod doesn't actually help, I did some tests on this a few years ago with a spectrum analyser and found it made no difference. But YMMV.
Dave Friedman puts a 500pF cap across the cathode follower 100K, lowers the first coupling cap to .0022uF, adds a 22uF to the final stage cathode and lowers the NFB resistor to 47K on 4Ohm tap. This is what he did to the Jake E Lee amp anyway. If you're looking to tame the raspiness I would start with the first and last mods personally, or even try removing the second 500pf treble peaker.
Dave Friedman puts a 500pF cap across the cathode follower 100K, lowers the first coupling cap to .0022uF, adds a 22uF to the final stage cathode and lowers the NFB resistor to 47K on 4Ohm tap. This is what he did to the Jake E Lee amp anyway. If you're looking to tame the raspiness I would start with the first and last mods personally, or even try removing the second 500pf treble peaker.
Re: Raspy treble from 2203 amp
Agree with these. I also would suggest experimenting with potentially adding a resistor to ground after the second peaker (sort of simulating adjusting the normal volume control when plugged into only the bright channel on a 4-hole amp).Littlewyan wrote: ↑Sat Apr 13, 2024 2:09 pm That master volume mod doesn't actually help, I did some tests on this a few years ago with a spectrum analyser and found it made no difference. But YMMV.
Dave Friedman puts a 500pF cap across the cathode follower 100K, lowers the first coupling cap to .0022uF, adds a 22uF to the final stage cathode and lowers the NFB resistor to 47K on 4Ohm tap. This is what he did to the Jake E Lee amp anyway. If you're looking to tame the raspiness I would start with the first and last mods personally, or even try removing the second 500pf treble peaker.
What was the cause of the 880K CF resistor? Was it damaged or was it a mistake? Either way, it might be worth checking other component values also to see if they might be contributing.
Re: Raspy treble from 2203 amp
Thanks for taking time to reply to my thread/post.cdemike wrote: ↑Sun Apr 14, 2024 8:31 pmAgree with these. I also would suggest experimenting with potentially adding a resistor to ground after the second peaker (sort of simulating adjusting the normal volume control when plugged into only the bright channel on a 4-hole amp).Littlewyan wrote: ↑Sat Apr 13, 2024 2:09 pm That master volume mod doesn't actually help, I did some tests on this a few years ago with a spectrum analyser and found it made no difference. But YMMV.
Dave Friedman puts a 500pF cap across the cathode follower 100K, lowers the first coupling cap to .0022uF, adds a 22uF to the final stage cathode and lowers the NFB resistor to 47K on 4Ohm tap. This is what he did to the Jake E Lee amp anyway. If you're looking to tame the raspiness I would start with the first and last mods personally, or even try removing the second 500pf treble peaker.
What was the cause of the 880K CF resistor? Was it damaged or was it a mistake? Either way, it might be worth checking other component values also to see if they might be contributing.
The 100K went high over time. The 100K on the valve socket is measuring 120K so it’s going too.
I think it’s the old Fender issue where they used 1/2 watt resistors on the anode/plates of the valves when they should have used 1 watt resistors. I replaced the resistors with 1 watt ones.
Yours Sincerely
Mark Abbott
Mark Abbott