Weber 5E3 Build and Questions

[andrewRneumann]

I've tried every combination of normal, bright, inputs 1 and 2, plus jumping the channels together and interactive volume settings.

I assume this means you made sure you used the bright channel, high input, and had the unused channel volume set to 0. Keep using two 12AX7's.

I'm not sure anything is wrong with your amp either. I don't own a 5E3, but the one that I played had less overdrive available than I expected.

Have you checked these resistances?

There are definitely ways to hijack the preamp circuit so that it overdrives earlier. If you want to go down that road, we can start throwing out ideas. But for now I will just assume you are looking for a true 5E3.

 

[NTC]

What is the output transformer impedance ratio? If I am informed correctly, a 5E3 has an OT with a 8K:8 ohm ratio and a black panel Deluxe has a 6600:8 ohm ratio. The latter will have a cleaner response.

For what it is worth, mine is very loud by 3 on the volume control and just starts to overdrive after that, not getting much louder. I think my volume pots are not the right taper...

 

[King Fan]

I agree the 5E3 has a weird volume response curve, and gets plenty loud. And we don’t have much “how loud is it?“ data yet. But I seem to be stuck in the camp thinking something isn’t right with the voltages. IF this is the stock Weber PT, and I see the red HT leads on the rectifier, we should be getting 340VAC there? If I’m thinking straight this would yield B+ about 100V higher than the 320 plate voltage the OP reports…. Maybe I’m overlooking something.

@Dortoh5968 , your team seems eager to help but also for more info. Feel free and let us know if we’re asking for stuff you’re not sure about.

 

[D'tar]

Everyone seems to think there's possibly something wrong with your build. What I got from your original post is that it's too loud.

Your plate voltage is low, which explains the seemingly low bias. That doesn't necessarily indicate problem. Did you use the lower voltage secondary? You don't really want more voltage if it's too loud already.

I keep thinking in line with this^^^^.

I dont know your speaker but an efficient speaker can get obnoxiously loud real quick.

I do however recommend a full voltage chart just to ensure there are no compounding issues to complicate things.

 

[Dortoh5968]

I will post a voltage chart later today. That nasty 4 letter word, work, is in the way at the moment.

 

[Dortoh5968]

Okay here is what I came up with. The wall voltage when I made these measurements was 117.4 a few hour later it was over 118.5 which gave me different readings when I checked again, but when I made these it was 117.4

I also checked all the resistors for there true values, but mainly to make sure I didn't screw up. While I was at it I did the D'tar input resistance test which turned out just like the chart.

I included the specs for the transformers. I'm using the 120 input on the power transformer.

 

[King Fan]

Good for you; nicely done. Love the details: “True resistor values in green.” So your B+ is 361 and your plate voltage is 356, not 320? This makes more sense. I’m gonna let my smart friends look at the rest of the voltages, like those screen volts.

But now your plate-to-cathode voltage is 356 - 19 = 337. And if I’m punching the buttons right, that’s 12W dissipation, not 10. Not totally typical, but very possible.

So let’s talk loudness. What are the knob settings where you “can’t stay in the same room?” What is the loudest amp you use otherwise? What are your other / reference amps that get good and dirty?

 

[D'tar]

Nice post of plenty o info! So, 6k6 is more deluxe reverb OT. Not a huge difference IMO but does clean things up a bit. Your voltages look pretty good, and 117 at the wall... nice. I have to use a bucking trans to get there from 123vac. Back to the speaker eh? And of course the wonderful volume interaction!

 

[Dortoh5968]

Nice post of plenty o info! So, 6k6 is more deluxe reverb OT. Not a huge difference IMO but does clean things up a bit. Your voltages look pretty good, and 117 at the wall... nice. I have to use a bucking trans to get there from 123vac. Back to the speaker eh? And of course the wonderful volume interaction!

Just looked again on Weber's site and that output transformer is actually 25 watts and as you said 6600ohm. I checked out some Hammond transformers for a 5e3 and there 8500 primary and 15 watts.

 

[Dortoh5968]

Good for you; nicely done. Love the details: “True resistor values in green.” So your B+ is 361 and your plate voltage is 356, not 320? This makes more sense. I’m gonna let my smart friends look at the rest of the voltages, like those screen volts.

But now your plate-to-cathode voltage is 356 - 19 = 337. And if I’m punching the buttons right, that’s 12W dissipation, not 10. Not totally typical, but very possible.

So let’s talk loudness. What are the knob settings where you “can’t stay in the same room?” What is the loudest amp you use otherwise? What are your other / reference amps that get good and dirty?

Well as I have seen others complaining about, the volume on the bright channel does nothing for the first 20% than comes on. By 35% it's louder than I really want to hear at home.
As for as it breaking up maybe I was expecting too much, but it isn't anything like the demos I've watched.
As far as reference amps I've got a reissue Twin Reverb that I've had more almost 30 years that can be crazy loud (not to mention way too heavy for me now days) and is pretty much always clean, and a couple of Bugera's that can get pretty dirty.

 

[Dortoh5968]

Since I haven't done this yet I wanted to thank all you guys for your help and info. This is my first build, and I really haven't done any serious electronics work in 43 years so I'm learning a lot. I'm wanting to build another one, maybe a 18 watt Marshall clone, but I don't really have any place to put it.
I did put all the graphics on the front last night since I had it out of the cabinet.

 

[NTC]

Just looked again on Weber's site and that output transformer is actually 25 watts and as you said 6600ohm. I checked out some Hammond transformers for a 5e3 and there 8500 primary and 15 watts.

6600 will give you lower distortion - cleaner. On the other hand, that Hammond is MUCH smaller than a Deluxe ot should be physically. It is more suited to a Harvard or Vibrolux. That said, it seems like it does get used a lot in a 5E3.

 

[D'tar]

6600 will give you lower distortion - cleaner. On the other hand, that Hammond is MUCH smaller than a Deluxe ot should be physically. It is more suited to a Harvard or Vibrolux. That said, it seems like it does get used a lot in a 5E3.

Indeed, used quite a bit by builders that make a lot of 5e3 type circuits. So much so, that I used a 6k6 in my 5e3. The not knowing drove me into a classic tone 8k8r. I didn't record before and after but IMO, the difference isn't night and day, just different. There's soooo much small details such as this and the proper speaker that tender true 5e3 experience. Lots of kits are "in the style of" 5e3 as lots of people are underwhelmed by the copies they end up with. Likely 85% of us with 5e3 circuits never plugged into an original.

 

[Dortoh5968]

I installed a pre phase inverter master volume today. I put it in the external speaker jack hole that I'll never use anyway. I can't say that it did a lot, but it does just enough that I can get some dirt and much more of a difference with the interactive volume controls. I'm a much happier camper now.

I do have one question for those in the know. When I first finished it and did the initial testing I had 320 plate voltage. The testing I did yesterday I came up with 356 volts on the plates. I also had higher voltage on pins 1 and 6 of V1. I couldn't figure out how I could have come up with such a difference then it dawned on me. I did the initial testing with a 12ay7 in V1 and in a quest for more breakup I changed it to a 12ax7 while I was playing it. Am I correct in think that is what gave me the higher voltage readings?

I think it's completely finished now...... at least until I change something else.

 

[andrewRneumann]

I installed a pre phase inverter master volume today. I put it in the external speaker jack hole that I'll never use anyway. I can't say that it did a lot, but it does just enough that I can get some dirt and much more of a difference with the interactive volume controls. I'm a much happier camper now.

I do have one question for those in the know. When I first finished it and did the initial testing I had 320 plate voltage. The testing I did yesterday I came up with 356 volts on the plates. I also had higher voltage on pins 1 and 6 of V1. I couldn't figure out how I could have come up with such a difference then it dawned on me. I did the initial testing with a 12ay7 in V1 and in a quest for more breakup I changed it to a 12ax7 while I was playing it. Am I correct in think that is what gave me the higher voltage readings?

I think it's completely finished now...... at least until I change something else. View attachment 995685

Yeah, I think your analysis on voltage changes is accurate assuming your wall voltage didn't change. The 12AY7 is probably drawing a little more current than the 12AX7. You could measure the voltage across the plate resistors to see if that is the case.

Nice work. It's good to be done and just appreciate a work of art for what it is.

 

[NTC]

Beautiful cab on that one...

 

[Dortoh5968]

It's been a few weeks, but just incase anyone is interested I discovered the real reason my voltages changed so drastically from my first tests till when I tested again to post here. When I did the first bias calculations and voltage measurements I was following Uncle Doug's video. He stressed to have it plugged into a current limiter. I tried it both ways the other day after changing the output transformer to one closer to an original 5E3. The plate voltages varied by 42 volts depending on if I was using the 200 watt light bulb current limiter or not. It changed all the voltages enough to change the bias from 9.81 to 12.88.