5e3 Fat switch mod.

[fakuverymuch]

First solder a 100K resistor in series between the negative Cathode bypass cap lead (the far right one by the preamp section C3) and ground. Now solder a wire to the connection between C3 and the 100K resistor. This wire goes to the center terminal of the soon-to-be "fat" switch. Wire one of the outer terminals of this switch to a nearby ground connection (input jack would be great).

When this switch is open, C3 sees 100K between the cap and common ground and therefore C3 does not effect the gain of the circuit. When the switch is closed, C3 sees this ground connection through the switch and the gain of the circuit goes
way up.

Has anyone here tried this mod? It was recommended to me by Rob Hull from Tube Depot.
Any thoughts you may have are appreciated.

[fezz parka]

One thing a 5e3 doesn't need is a fat switch.

[Phil_tre]

Originally Posted by fezz parka

One thing a 5e3 doesn't need is a fat switch.

+1

[Badside]

Yeah, fat is probably not the right term, this is more of a gain boost switch, except it works by limiting gain when off, so "on" is the stock sound.

You could put another smaller cap (say .68uF) straight from the cathode to ground (would not go through the existing cap or that 100k resistor) on top of doing the switch as described. In "off" mode, you'd get more of a high-mid emphasis (tighter, less fuzzy gain), in "on" mode you'd get the stock (fat) sound.

[muchxs]

That's an anti- fat switch.

Resistor in series with the cap takes the cap out. The unbypassed cathode resistor is thin sounding compared to the bypassed resistor.

Switching the 100k out restores the amp to its stock condition. Hey, ho! Sounds "fat" compared to the modded version.

Pick a sound you like and hardwire it. Buy a Boogie if you want to diddle with switches and knobs.

[JohnnyCrash]

Go for it. You might like it in the OFF position, and in the ON position it goes back to stock sounds. Badside also gives you another cap/tonal option with this kind of switch.

[LeroyBlues]

The only switch you need on a 5e3 is the on/off. Well, maybe the standby too.

[fakuverymuch]

Thanks for the input folks.
Now I see...it's really a less gain switch. I think some of you have got it right. The amp doesn't need any more switches. I am always adding bells and whistles to my gear, only to find out later that I hardly ever use them. I never learn.
When I actually used to play gigs I had FX that where almost never used. Just strait into the amp and touch controlled seems to be the best.
I wish I could get a no fat switch for my wife's derriere.

[stingray_65]

Hey,

Try this, you need a center off SPDT switch, a .68uf 50V axial cap, a 2uf 50v axial and a 10uf axial cap. You can get all this stuff from your local Radio Shack.

Yeah! I said Radio Shack! LOL! .The .68 you can get off the fleabay for a couple buck. this whole mod costs about $10.

Any how This is my favorite mod for Tweeds in particular, but I add this circuit to nearly every amp I build.

The cathode bypass cap (25uf 25V on your 5E3) not only effects the gain in the pre-amp, it also sets the frequency response. Remember those early amps weren't designed by rock and roll engineers, they were lifted straight out of text books as general purpose audio amplifiers. Not bad ones either.

Any how they tended to lean toward the high fidelity side of things. The 25uf value passes a pretty wide audio spectrum. A lot wider than the frequency response of a musical instrument speaker and a WHOLE lot wider than a guitars frequency spectrum.

Combine that wide band pass with a higher gain, and it sounds REAL good with a single coil pickup, especially the tele's with their lip stick covered neck pup and steel surrounded brass backed bridge pups.

I can't tell you how many times I've seen on other forums people looking to mod their tweed for a LesPaul or their Strat with a hot Humbucker. They get real dark and muddy.

So lets look at another design, from across the pond, that kicks ass with a LesPaul. It is almost a joke where Marshall got his inspiration for his designs. A Fender Tweed as we all know. One of the minor design changes that evolved was to lower the cathode bypass capacitor value to .68uf.

Now the pre-amps band pass is much narrower, closer to the speakers abilities to reproduce, closer to the frequency range of a guitar, and much less GAIN. Now play your LesPaul in that and the humbuckers wider frequency response is narrowed and emphasizes it's punchy mid-range, It's hotter output is tamed a bit by the pre-amps lower gain.

I attached a modified 5E3 layout that is real simple and easy to follow.

If you have a 4 input amp, you can remove the #2 low input jack and mount the switch there to try it out, if it doesn't work for you, just change it back.

How the circuit works is when you run capacitors in parallel, their uf values add up.
A .68 is mounted to the board in place of the 25uf25V cap. depending on the cap, .68's can be either polarized or non polarized, so be aware if there is a polarity and orient it just like the 25uf.
Next mount the switch. A wire will go from the center post of the switch to terminal (eyelet or turret) that has a wire going to pin 3 of V1.
Now you want to mount a 2uf cap (this WILL BE polarized, the + goes to the switch) to either post on the switch and the other side to the ground on the input.
Mount the 10uf cap the same way on the other post. I use a 10 instead of a 25, they are smaller and easier to mount and STILL pass way more band width than necessary,but a 25 will work just as well too.
Here is where the stuff happens. The switch is a center off, so when the switch is in the middle, just the .68uf cap is in circuit and gives a Marshally Bright kind of sound.
Flip the switch, and the 10uf cap value is added to the .68 and you get that great Tweed sound.
Flipped the other way and its a middle of the road kind of setting that REALLY shines on hot wound single coils.

The 5E3 is one of the greatest sounding amps (IMHO) but is some what limited to guitars that sound good played through them.

This mod adds LOTS of versatility, especially if you have more than 1 guitar.

You can also still jumper your inputs from lo 1 to hi 2.

Ray

[Telenut62]

+1 cool

[fakuverymuch]

Holy crap Sting Ray....
Now this sounds a lot more interesting than the other mod. IN fact more interesting than most of the 5e3 mods I have seen on the net. I have the switch, just have to locate the caps. I think I may very well give this one a shot.

[Telenut62]

Does this mod suffer much from popping when the caps are first engaged?

[Fatknuckle]

I have done similar mods on 18-watters with the 0.68 and 25uf caps, using DPDT push/pull switches on a 500k tone pot. That doesn't require another hole in the chassis or sacrificing an input. There is not as much pop as there is always a cap engaged on either setting. I have heard some talk of putting a resistor across the switch to eliminate the "pop", but I am not sure how that would work. I am interested in this setup as well.

[stingray_65]

Originally Posted by Telenut62

Does this mod suffer much from popping when the caps are first engaged?

I've never noticed any pop ever, and I am VERY critical of my builds.

Ray

[stingray_65]

Originally Posted by fakuverymuch

Holy crap Sting Ray....
Now this sounds a lot more interesting than the other mod. IN fact more interesting than most of the 5e3 mods I have seen on the net. I have the switch, just have to locate the caps. I think I may very well give this one a shot.

I really love the tweeds. There aren't many mods tho that you can make to them without loosing the "tweediness".

It's such a simple circuit, its a lot like a baseball bat. You start changing things too much on a tweed circuit and it stops being a baseball bat and starts to be more like a golf club, or what ever.

This mod is more for versatility without having to "tone sculpt" a lot of coupling caps and what not, and it does it pretty well. (IMHO)

Ray

[JohnnyCrash]

I have a 1uF I can switch on via a pot pull-switch (located on the Bright channel's Volume pot). Takes up no extra room on the front or rear panel. More gain and more Marshally type of midrange when on. When off it's stock 5E3. I also have a VVR pot (with a power switch) as the Power ON switch.

The only extra hole I had to drill on the chassis was a switch for SS (which also adds larger filter caps) or 5Y3 rectifier (stock) on the bottom of the chassis.

[stingray_65]

Originally Posted by Fatknuckle

I have done similar mods on 18-watters with the 0.68 and 25uf caps, using DPDT push/pull switches on a 500k tone pot. That doesn't require another hole in the chassis or sacrificing an input. There is not as much pop as there is always a cap engaged on either setting. I have heard some talk of putting a resistor across the switch to eliminate the "pop", but I am not sure how that would work. I am interested in this setup as well.

IF you wanted to add a shunting resistor to eliminate POP. you would need 2 500k resistors. even 1/8W would work.

Simply land both at the center post of the switch and the other end of each to the outer posts.

The idea is that the capacitors will be already "trickle charged" before they are engaged.

Ray

[fluid69]

Thats really insightful ray

"If you want rules, read the IRS tax code. If you want to build guitars, make some sawdust." -Colt W. Knight

[Fatknuckle]

Thought I had heard something similar, but with 1-meg resistors. Would that be adverse?

[Badside]

Originally Posted by Fatknuckle

Thought I had heard something similar, but with 1-meg resistors. Would that be adverse?

As long as it's high enough to effectively take the cap out of the loop (anything at least 10 times higher than Rk would do) without leaving the cap hanging (which would make it pop when you switch it back in)