5F2 to 5F1 Tonestack Cutout

[charisjapan]

Hey all,

Got my 5F1 board kit from Boot Hill , but like the idea of a 5F2 tone knob. Can the tonestack be cut out just by a switch between the volume center lug and the tone pot?

And yes, Keithb7, I will be considering a NFB cutout as well!

Thanks,

charisjapan

[keithb7]

Looking at the lay out, I would think the same. Putting it between the two pots. Seems to me from V1, lower end frequencies take a hi-way straight to the volume pot. Higher end frequencies go to the tone bleed off, then via that connector wire between the pots, go back to the volume knob to re-join the tone that by-passed the tone knob.

Have I been waving the NFB flag a little high as of late?
I am looking forward to hearing your report on the mod.

[charisjapan]

Originally Posted by keithb7

Looking at the lay out, I would think the same. Putting it between the two pots. Seems to me from V1, lower end frequencies take a hi-way straight to the volume pot. Higher end frequencies go to the tone bleed off, then via that connector wire between the pots, go back to the volume knob to re-join the tone that by-passed the tone knob.

Have I been waving the NFB flag a little high as of late?
I am looking forward to hearing your report on the mod.

Just kidding, man!

I got a replacement MOSFET from Dave, so if I get my VVR fixed, I'll be waving my own banner soon.

[tubeswell]

Ideally you want to lift it in 2 places at the same time (with a double pole switch) - one at the junction of the treble cap and the vol pot wiper/2nd stage grid, and the other at (say) the junction of the vol pot input and the tone wiper.

[TurtleFang]

Originally Posted by keithb7

Have I been waving the NFB flag a little high as of late?

You have! In fact I'm pretty sure that I will put a NFB switch on my Boothill 5f1 build that I'm hoping to start soon.

Does the 5f2 tone control give you something that an EQ foot pedal or a guitar's tone control can't?

Honest question... I ask as there is no "outside influence" way to engage/disengage NFB, but my thinking was that there are ways to trim your tone externally. So therefore maybe I would keep the amp as simple as possible 5f1 mod-wise?

Thanks,
-Turtlefang

[printer2]

Originally Posted by tubeswell

Ideally you want to lift it in 2 places at the same time (with a double pole switch) - one at the junction of the treble cap and the vol pot wiper/2nd stage grid, and the other at (say) the junction of the vol pot input and the tone wiper.

Done it this way and removed the switch. I found that running without the tone control did not give me anything more than I could get with it in. Mind you I am using a 15CW5, similar to a EL84 so there is more gain on tap.

The NFB switch I like.

[charisjapan]

Originally Posted by printer2

Done it this way and removed the switch. I found that running without the tone control did not give me anything more than I could get with it in. Mind you I am using a 15CW5, similar to a EL84 so there is more gain on tap.

The NFB switch I like.

O~~K~~

So Printer (or anyone else), do you think a 6V6 with a tonestack cutout will make a difference?

And to you and Keithb7, what effect can I expect with the NFB?

Finally, yes, Tubeswell, I can see that a DPST cutting out the tonepot altogether is a good way to make sure there's no connection whatsoever.

I want to work this all out before I start building!

[boredguy6060]

I'm with Keith on the NFB.
I've tried single coils, P-90, and several humbuckers, they all sound better without the NFB for R&R .
It adds a little gain and a raw-er sound.
I still use the NFB for a lot of sounds, that's why I like in on a switch.

[tubeswell]

Me manglin' Jimi Page with a 5F2A circuit I made with a NFB lift switch (lifted) - about 4 years back. Speaker is an old 15W 12" Goodmans

http://music-electronics-forum.com/a...ay-heaven-.mp3

[printer2]

Originally Posted by charisjapan

O~~K~~

So Printer (or anyone else), do you think a 6V6 with a tonestack cutout will make a difference?

And to you and Keithb7, what effect can I expect with the NFB?

Finally, yes, Tubeswell, I can see that a DPST cutting out the tonepot altogether is a good way to make sure there's no connection whatsoever.

I want to work this all out before I start building!

Just because I am using a different tube in mine I can not say what will happen with a 6V6. But I have more than enough gain right now so the minimal loading going on will not bother me.

[Telenut62]

Originally Posted by tubeswell

Me manglin' Jimi Page with a 5F2A circuit I made with a NFB lift switch (lifted) - about 4 years back. Speaker is an old 15W 12" Goodmans

http://music-electronics-forum.com/a...ay-heaven-.mp3

Nice, amp sounds like it has plenty bite

[TurtleFang]

But does having a tone pot bleed in the 5f1 board do things that can't be done with a guitar's tone control or an eq pedal?

[keithb7]

The removal of NFB in my 5F2A, makes the amp more raw, and in your face sorta. It's brighter, I end up with the tone knob down around 3-4 with the NFB turned off. I also find it breaks up a little more. A little hair-ier or fuzzier and louder I think. (maybe just perception on volume) With the NFB on, the amp seems to get more polite, milder. I end up rolling the tone knob up. I like to play harder driven rock and dirty blues so the NFB is off almost all the time. It's a perfect fit for me. Very good chance that will be putting a NFB switch in any future tweed amp builds with NFB.

[charisjapan]

Well, I thought it was a pretty simple question with a definite answer... And the method is pretty simple, cut out both leads to the tone pot.

But now the issue is the necessity of switching to a 5F1. A search here and several other places tells me that the majority think the additional gain is no biggie. On the other hand, I am seeing a majority that praise the NFB switch as a means of getting a raw 'unleashed' sound out of a 5F2a, which kind of describes a 5F1!

So I guess since I want a lower-volume, quicker breakup amp, it's either a straight 5F1, 5W PT, 8" speaker or a 5F2a, 5W PT, 8" speaker w/ NFB cutout. If I want more bass with either, a larger cab. If I want more volume, a bigger cab w/10" speaker. And if I want more clean, a larger PT. Does that just about sum things up?

Oh, and if I want to use a humbucker guitar, go with the 5F2a, right?

(But whatever I do, never, under any circumstances, ask about specific trannies, tubes, speakers, caps, resistors, jacks, pots, cables or solder ... )

[hackworth1]

Lots of guys build 5F1 with no NFB. My guess is that most 5F1 Players would probably prefer not to have NFB, if they knew about it. That is to say if they knew that it existed and that it is easily disconnected.

In addition to no NFB, another way I found to get more from a 5F1 or 5F2A is to install a 22uF 50V or a 25uF 25V bypass cap on the cathode resistor (pin 8) as is done on the other side of the 12AX7 Twin triode cathode (pin 3).

[charisjapan]

Originally Posted by hackworth1

Lots of guys build 5F1 with no NFB. My guess is that most 5F1 Players would probably prefer not to have NFB, if they knew about it. That is to say if they knew that it existed and that it is easily disconnected.

In addition to no NFB, another way I found to get more from a 5F1 or 5F2A is to install a 22uF 50V or a 25uF 25V bypass cap on the cathode resistor (pin 8) as is done on the other side of the 12AX7 Twin triode cathode (pin 3).

Hackworth,

Well now, I'm thoroughly confused. Not even sure what a NFB switch is?!

Looking at Weber's 5F2a layout:

1) You're suggesting a bypass cap on the 'other' 1.5K resistor, right? And...

2) A NFB would be an 'ON/ON' switch that bypasses the 22K resistor between pin 8 of V1 and the tip of the speaker jack?

charisjapan

[hackworth1]

No switch. Don't need a NFB switch. Omit the 22k resistor that connects to the speaker output jack tip. That's the NFB connection. You're left with a 1.5K cathode resistor just like the one on the other side of the 12AX7 double triode.

The 12ax7 is two tubes in one envelope. The two sides of the triode Pins 1,2, and 3. Are the plate, grid, cathode. Respectively pins 6,7, 8 are plate, grid cathode.

Treat pin 8 the same as pin 3. Put a bypass cap on it.

[Telenut62]

Originally Posted by hackworth1

No switch. Don't need a NFB switch. Omit the 22k resistor that connects to the speaker output jack tip. That's the NFB connection. You're left with a 1.5K cathode resistor just like the one on the other side of the 12AX7 double triode.

The 12ax7 is two tubes in one envelope. The two sides of the triode Pins 1,2, and 3. Are the plate, grid, cathode. Respectively pins 6,7, 8 are plate, grid cathode.

Treat pin 8 the same as pin 3. Put a bypass cap on it.

Lol...I'm gonna say the opposite here....yes make the NFB switchable, as the amp is too hairy when it's cranked. No NFB at lower volume is where I like it best.
A 25uf cap on the second 1.5K makes the amp too bright, but each their own. If you feel you need more treble it's trail and error to get it right. Of course you could make that switchable to

[charisjapan]

Originally Posted by hackworth1

No switch. Don't need a NFB switch. Omit the 22k resistor that connects to the speaker output jack tip. That's the NFB connection. You're left with a 1.5K cathode resistor just like the one on the other side of the 12AX7 double triode.

The 12ax7 is two tubes in one envelope. The two sides of the triode Pins 1,2, and 3. Are the plate, grid, cathode. Respectively pins 6,7, 8 are plate, grid cathode.

Treat pin 8 the same as pin 3. Put a bypass cap on it.

Hackworth,

Thanks for the clarification!

But I was right that the (much lauded, but sometimes decried) NFB switch is one that allows you to bypass (cut out) the 22K from the circuit, or put it back in ... Yay! Got that now.

I understand what you mean to ground both cathodes of the double triode V1 using the same 'cap piggybacking the resistor' method. Makes sense.

If I wanted to, I could do both, right? You're just saying that it's not really necessary.

There's a glimmer of understanding rising in the East!

charisjapan

[keithb7]

Charis you mention bigger iron for more cleans. That got me thinking about a recent experiment I did. Ripping apart a Hammond organ I now have many vintage 12AU7 tubes. I tried one in my 5F2A. Much cleaner. You gotta work your pick hand hard to get some medium crunch. Unsure but it seems to me it also delivers a little less volume. Maybe its easier to change a tube depending how much dirt or gain, you want?

My thoughts on how a NFB switch works, is no, it does not allow you to remove the 22k resistor. It stays there all the time. You are just cutting off and blocking the signal coming off the speaker jack, that was headed to the 22k resistor. So nothing goes in. The 22k resistor controls how much signal goes through, back into the circuit. I thought that was how I wired mine up. I also thought you could put a variable resistor on a knob, a pot, to have a variable amount of NFB. This pot, replacing the fixed 22k resistor. I'm still learning too, so maybe I'm out to lunch. An expert could surely correct me, pls do!