Negative Feedback pop

[dude]

I searched the pop when feedback is grounded out with an on/off switch. Not too much here except a suggestion is get a "make before break switch", don't know what that is...? And some that used the make before, switch said no help. Was hoping for a cap fix to ground but search here revels not too much info on a fix.


Any suggestions? 

[vampwizzard]

Id assume that the solution would be similar to the standby switch resistor mod from Rob? https://robrobinette.com/Generic_Tube_Amp_Mods.htm#Pop_Reduction


Is it also possible that youre removing the connection to ground when youre taking out the negative feedback circuit?

[Tony Bones]

I don't know exactly what circuit you're talking about; a schematic would help. But, there's usually no reason to ground any part of the NFB when you switch it out; just use a SPST switch to disconnect/connect it.

Seriously, we need a schematic of what you're trying to do.

[dude]

No schematic needed, a simple on/off switch between the Neg. Feedback R and the OT tap. No ground is involved, my mistake. I did add a 5K Presence pot to this amp, wired like a Plexi and 100 other amps and of course with the feedback R cut out, no presence control.


Just a slight pop turning off the switch, Presence pot is not even scratchy. Adding a resistor like on Rob's site for Stdy by switch, I can't see that helping. Would screw with the Presence and FB.   

[shooter]

feedback is grounded out

I don't pay much attention to NFB stuff so I might be all washed up, but don't you just open the NFB loop instead of grounding it?

[dude]

Yeah, Shooter that's what I did, read my last post. I was "out to lunch" saying I ground out the loop in first post, I didn't, ha. I probably wouldn't turn the switch while playing out anyway, my playing out days are over,  . I'm just being a perfectionist, fixing what ain't broke, ha.
Just thought, a cap across the switch or whatever would stop the pop. I'm sure a lot of amp guys have or had this issue. I'll search around.

[sluckey]

There are some amps out there that do actually ground the feedback signal to switch it off. Here's one that I'm very familiar with. No pops...


     http://sluckeyamps.com/november/november.pdf

[jjasilli]

Negative Feedback Pop!  Let's market our own soft dink to amp techs!

[sluckey]

Negative Feedback Pop!  Let's market our own soft dink to amp techs!

Already got one. Oh, wait a minute. Is that what you meant to say?   

[jjasilli]

Not the "Think" Emoji.  Rather, the "Bright Idea" Emoji. 

[sluckey]

I was focused on the "soft dink".   

[shooter]

 
just thinkin bout mine 

just add the soft dink icon, I still need the  one

[jjasilli]

Here ya go!

[sluckey]

Never mind. Sometimes a quip just doesn't connect. That's OK. Ain't worth explainin'.

[dude]

Feedback Pop...? Just give me a beer,  .


Tried that November, FB switch on the ground, still the pop, 11.5 volts at the junction of feeback and PI. That voltage is there which ever way the switch is wired, hence the pop. Some feedback switches I've added have no pop, (cutting FB R or grounding out) some do, just like the presence pot is sometimes scratchy, sometimes not.


Answer: live with the "Feedback Pop" but I prefer beer..

[shooter]

Sometimes a quip just doesn't connect

It connected well, it's a good crop year 

[dude]

Crazy, I took the pilot light out and put the Presence pot there.  The light was right next to the PI so the wiring to Presence was less than an inch, ground too and guess what, no pop, when I turned on/off negative FB. Even with the switch on the back of the amp, taking the feedback R out, not ground.
I have no idea why, when Presence was on the back, I used shielded wire, still had the pop. Nice to have that Presence on the front, usually it's set and that's it but on this amp with the three channel mini toggle in the bright input, I'm constantly changing the Presence when I change channels.


Now back to those 6V6 Plexi's, have 8 Hammond AO43 chassis's. I'll have to make a few Nov's too.


Now time for a Feedback Pop, oh, I mean beer, it's Friday night.