5E3 too clean, no distortion

[Alex R]

Try lowering the value of the first stage cathode bypass capacitor.
Standard is 25uf.
On most Fender amps, especially the lower powered ones, that value simply lets too much of the bass frequencies through.
Start by using a 15uf & then a 10uf, or even a 4.7uf.
Use which one sounds best.

yep or if you only want an o/d sound maybe as low as 0.68uF. Farty overdrive is often the result of too much bass feeding through. The 25uF bypass on the first stage wasn't meant to produce the best overdrive sound.

[barfoden]

The 470 ohm screen resistors seperate the two 6v6 screen from each other which can be a good thing, but they also limit the screen from drawing too much current..
I am not sure they are needed in a 5e3 deluxe running with period correct voltages (360Vp/320Vs) which allready have a lot or resistance in the +b supply line (a large 5k screen dropping resistor), and if you were to fit them I would chose a lower value, a 220 ohm will probably be enough and transparent.
A deluxe reverb definately needs these as they have very little resistance in the supply line with a 4Hy, 150 ohm choke.. The output transformer in the deluxe has more resistance between the pins and hence the plate voltage is similar to the screen voltage which is not a good situation.

THe problem gets even worse with old vintage deluxe reverb amps from the 60's. They will tend to run a little hotter than the 415V plate of the schematic, and you really have to bias them cold in order to prevent the screens from burning up under heavy playing.

An amp tech saw a lot of older twin reverb with toasted 470 ohm screen resistor.. He upped the wattage to at least 3W and used 1K resistors in stead. This proved to be stable for his costumers, that reported that the amp was a little more responsive. You get a little less max output with the 1K screen resistors in the twin reverb but if the amp is vintage and running with higher voltages than the schematic values, a little more resistance on the screens is not a bad idea..

The 6v6gt and 6l6GC are beam tubes and draw less screen current than the european pentodes such as a EL84 and EL34. High voltage marshall with just a choke between plate and screen really need those high wattage 1K screen resistors when voltages are high about 450V plate.

[zbones]

interesting thread, was there any solution to this?

[6v6Pin1]

I had this exact same problem. My 5e3 sounded good, but it was totally clean, like a BF. I installed the Paul C mod, and now the amp has lots of breakup. It's like a totally different amp. I doubt it was the mod that made such a big change. I think I had a bad resistor (they all tested fine after I removed them) or solder joint in there.

[robrob]

Don't know the outcome but here's a "Lead" voice mod for one 5E3 channel that will tighten up and modernize the overdrive tone:

https://robrobinette.com/5e3_Modific...m#Lead_Channel

[Justin Thomas]

totally clean, like a BF...

I've only met one amp in my whole life of ANY kind that did that: an old Lectrolab that had no cathode bypass caps and a wrong preamp tube in it. Haven't met a Fender that can't crunch yet, though my Champion 600 (new issue) came close. Then again, I don't think a Super Twin is that loud, either. >:O

Any Fender that's clean on "10" (or "12") I call broken. I vote for a bad solder joint, too.

Dustin

[g1]

Don't know the outcome but here's a "Lead" voice mod for one 5E3 channel that will tighten up and modernize the overdrive tone:

We're all about the schematics here Rob (hint hint )

[Dave H]

...I installed the Paul C mod, and now the amp has lots of breakup. It's like a totally different amp. I doubt it was the mod that made such a big change.

It could be the Paul C mod. If it has the 1M and 2M2 resistors it sets the bias of the cathodyne too hot so it clips before the 6V6s, meaning you hear PI clipping but don't have full power. It's a bit like having a pre-set post PI MV.

[6v6Pin1]

It could be the Paul C mod. If it has the 1M and 2M2 resistors it sets the bias of the cathodyne too hot so it clips before the 6V6s, meaning you hear PI clipping but don't have full power. It's a bit like having a pre-set post PI MV.

Yes, the cathode now has 56k, the 2M2 feeds B+ into the grid, and the 1M is a ?voltage divider? on the grid. Do you prefer different values for that mod?

I haven't played any other 5e3 so I don't have a frame of reference. Which stage is responsible for distortion in a stock 5e3? Does the PI distort?

[Dave H]

Yes, the cathode now has 56k, the 2M2 feeds B+ into the grid, and the 1M is a ?voltage divider? on the grid. Do you prefer different values for that mod?

I replaced the 2M2 with 3M9 but it sounded exactly like the stock circuit so I returned it to stock.

I haven't played any other 5e3 so I don't have a frame of reference. Which stage is responsible for distortion in a stock 5e3? Does the PI distort?

I think the PI distorts first if you have the Paul C mod (with 1M and 2M2 resistors) but for the stock circuit it will be the output stage so it will only distort at high volume which is fine for a gig but usually too loud for home use. As Justin said above if it doesn't distort on '12' with a Strat or Tele it's broken but it won't distort at low volume.

[Enzo]

I wish when people talk about things like modifying amp, they would at least put up a link to whatever the circuit is they are discussing. I have no idea what the Paul C mod is, and while I am sure I could do some research and find it, I shouldn't have to. people wanting advice ought to put up the background.

[Chuck H]

The Paul C mod is what some call a "fixed bias" alteration to a cathodyne PI. I'm not so sure that's accurate, but here you go.

[Dave H]

Sorry Enzo, this is the circuit I used. The 1k5 is from the original cathode biased circuit. I was too lazy to remove it.

[6v6Pin1]

The schematic that Chuck H posted is the one I used that gave me lots more breakup. To reduce the signal, it looks like I could increase the 2M2 or decrease the 1M? What would be the difference between those two approaches?

[Chuck H]

You shouldn't use those resistors for signal attenuation. They set the bias for the PI. Altering their ratio will change more than signal level and likely bias the PI incorrectly.

It would help to know where the extra clipping is happening. Is the PI bias skewed such that it's being clipped more or is the new PI configuration putting out more swing so that you are getting more power tube clipping.?.