IIC+ Switching / Grounding Help

[Henz]

The changes he made will reduce the reverb level a bit, and will cut bass. The driver stage already cuts bass as the 470n cathode bypass cap creates a shelving filter. I think it would be difficult to notice a difference after his changes.

If it were my amp, and I wanted less reverb drive and didn’t know how much, I’d remove the 220k resistor and wire a pot in its place temporarily. Then you can turn the pot until you’re happy, then remove it from the circuit and measure and replace with a resistor. I wouldn’t mess with the 1M as it connects to the incoming trace underneath the board. I think the 220k has both its connections on the topside.

If you wire a 220k in parallel with the 1M as suggested by the schematic, you’d significantly increase the drive level, hence reverb volume, and may overdrive the driver, or saturate more if it’s already breaking up.

I’ve never got along with the Boogie reverb configuration. I’m not a huge fan of spring in general though either. Boogie verb is before the loop and I tend to like reverb after effects I run in the loop. On all my boogies, I unplug the tank and leave the volume at zero

Thank you! You are very kind and a great help! I completely understand how to take the measurement once pot is dialed to my liking. I'm stumped on how to wire the pot to the two pads once 220k is lifted. One side of 220k is ground obviously and the other to grid with 1 meg. A pot has 3 lugs. Which two lugs would I use? I'm guessing it may not matter on the outer lugs of pot. But the wiper? And since its a 220k resistor, I'm also guessing a standard 250k pot would work? I would just Velcro it in, secure it inside chassis. I need a lil guidance on wiring it to pot . Or, what about changing the value of the reverb pot itself? I believe there's 100k in it. I can double check. I have some 25k audio pots . One more thing too my friend. The author of this schematic , in certain spots, has alternative values seen. My verb circuit uses a 3.3uf as the by pass cap instead of a .47 (C35). Now, does this affect the frequency response of entire amp or just in verb circuit? The other half of this dual triode is the lead tone (V4A). If I was to experiment and put .47uf in, what might I notice? You're A blessing in disguise! Thank you for your time! Jim

 

[Jay Omega]

Thank you! You are very kind and a great help! I completely understand how to take the measurement once pot is dialed to my liking. I'm stumped on how to wire the pot to the two pads once 220k is lifted. One side of 220k is ground obviously and the other to grid with 1 meg. A pot has 3 lugs. Which two lugs would I use? I'm guessing it may not matter on the outer lugs of pot. But the wiper? And since its a 220k resistor, I'm also guessing a standard 250k pot would work? I would just Velcro it in, secure it inside chassis. I need a lil guidance on wiring it to pot . Or, what about changing the value of the reverb pot itself? I believe there's 100k in it. I can double check. I have some 25k audio pots . One more thing too my friend. The author of this schematic , in certain spots, has alternative values seen. My verb circuit uses a 3.3uf as the by pass cap instead of a .47 (C35). Now, does this affect the frequency response of entire amp or just in verb circuit? The other half of this dual triode is the lead tone (V4A). If I was to experiment and put .47uf in, what might I notice? You're A blessing in disguise! Thank you for your time! Jim

I would use any 250k, 500k, or 1M pot that you have on hand. Don't worry about taper as you'll be measuring. If you're looking at the pot like a normal front panel pot from above, wire the terminal on your right to ground, and the middle terminal to the 220k / 1M connection. Turn the knob all the way down (CCW) to start and turn up until you're happy. Don't waste time worrying about changing the reverb pot.

A 3.3 uF bypass on V4B would increase bass frequencies and level for the reverb drive circuit compared to a 470 nF, it will not affect the entire amp. If you feel your verb is muddy on the low end and you'd like to cut bass, swap with something smaller than 3.3 uF, such as 470 nF. If you drop to 470 nF you should have a noticeable difference.

 

[Henz]

I would use any 250k, 500k, or 1M pot that you have on hand. Don't worry about taper as you'll be measuring. If you're looking at the pot like a normal front panel pot from above, wire the terminal on your right to ground, and the middle terminal to the 220k / 1M connection. Turn the knob all the way down (CCW) to start and turn up until you're happy. Don't waste time worrying about changing the reverb pot.

A 3.3 uF bypass on V4B would increase bass frequencies and level for the reverb drive circuit compared to a 470 nF, it will not affect the entire amp. If you feel your verb is muddy on the low end and you'd like to cut bass, swap with something smaller than 3.3 uF, such as 470 nF. If you drop to 470 nF you should have a noticeable difference.

Ty!! And ty for info on bypass cap. . Of course I have a question. Which direction is turning down? Towards ground lug? You are probably pulling your hair out by now with these questions. And I don't know what CCW means. I apologize. After this, I should have a handle on situation and will update you if you like. Sincerely, Jim.

 

[Jay Omega]

Ty!! And ty for info on bypass cap. . Of course I have a question. Which direction is turning down? Towards ground lug? You are probably pulling your hair out by now with these questions. And I don't know what CCW means. I apologize. After this, I should have a handle on situation and will update you if you like. Sincerely, Jim.View attachment 169

Turn down as in turn down the volume. CCW = counter clockwise.

The idea is you want to see the middle lug (grid) shorted to an outside terminal (ground) when you start, and the resistance between those terminals should increase as you turn the pot. Use your meter to see what you’re doing.

You can’t really screw up, pick a middle and outer pot terminal, wire the thing in and turn the knob to see if it sounds better to you.