5E3 in Vjr Head Cab

[Rocketrob]

This is only my second scratch build so I thought it would be a good idea to post the progress so some more experienced builders could look over my shoulder as I go along. Pull me out of the quicksand if I get too deep please.

I made the chassis myself. Hammond transformers: 272DX for PT and 1608 for OT. Custom Orange Drop 418 series caps and carbon comp resistors. Pretty much straight forward 5E3 circuit with only a few value changes planned. Also using a 120v pilot light instead of the usual 6.3v type. Feel free to jump in; comments welcomed. Rob

[cminor9]

That looks a lot like the layout I used for the 5E3 head I built a year ago.

I don't see a square hole where the AC goes in on the back panel, instead I see a round hole where it looks like you'll put in a strain relief bushing for the power cord. One thing to consider: use an IEC plug for the mains instead. I never regretted doing that on mine.

I changed out most of the carbon comp resistors in my 5E3 head with metal film resistors (initially was 100% CC.) The only change I noticed was less hiss. I left in all the 220k and 100k CC resistors, where they supposedly matter (mainly the plate resistors). The amp *really* hissed with all CCs. Even if you replaced only the cathode resistors with metal film, I'd bet you'd notice less hiss.

Can't speak for the 120v pilot light, so long as it works who cares?

Just to compare notes, one year later I am modding my 5E3. Why? I don't need the touted interactive volume controls; I just leave the unused volume at about 2 O'clock. I also don't need the second channel. Never use it. I am going to use that extra triode to provide a different pre-amp voicing which I can switch on and off. I am also going to replace the unused channel's pot with a resistor.

I'd recommend building as stock as you can, then tweak as needed. I ended up undoing a lot of mods I built into the original build. But definitely replace the first two coupling caps with something like .02 mfd instead of the .1. With the .1 caps, it's just too dark and muddy with humbuckers. If you play yours with buckers and it's too dark, that's the fix.

Have fun!

[txstrat]

That looks professional. Would you mind sharing your technique of making the chassis with us?

[Rocketrob]

Hey, thanks for the replies.

Cminor9,
You know, I wanted to put an IEC socket in there but didn't think there would be enough room with the recto socket so close. I have another chassis like this one that is going to be a 5E5 I think, so maybe I'll try to fit it in on that one.

Well, I have the carbon comps so they're going in for now; but may be I will try the metal films on the cathodes. I have those values on hand.

For sure am going to put in the .02 caps in the PA and see how it sounds from there.

Txstrat,
The chassis was punched on a CNC machine so it all lines up great. I made a Lite IIb on the same size chassis too.

I could make a bunch of these if there is enough interest.

More pics comming soon.

Rob

[Rocketrob]

A little more progress made. The OT and output jacks are wired up as well as a switch for impedance selection. Antique Electronic Supply sells a rotary switch for the Hammond 1600 series for this. It took me a while to figure it out; but i think I got it. The 1608 has 5 wires on the output side. Time will tell...

The input jacks are in too; kind of a PITA even doing the wiring outside of the chassis. Maybe I shouldn't work on it late at night

I'll have more pics tomorrow; I forgot to bring the camera to download the pics. Rob

[Rocketrob]

Two more pics to show what else I've done so far.

I've got the board populated so that will be going in next. I'm still wavering on the choice of coupling caps for V1. My first choice would be .047 for the bright chanel and .022 for the normal channel; I could try the two different values and then change if I don't like one or the other. Any ideas? Rob

[cminor9]

For the bright channel you'd want the smaller value cap. .02 is great for a bright channel. Put it this way: whatever you use the .02 on will be the de facto bright channel.

[Rocketrob]

Fired up last night. Check my voltages.

Well, finally got this one running last night and I have some numbers that I would like to have checked by builders here.

AC line in: 121V

No tubes:
PT HV: 677
5V: 5.5
6.3V: 6.8

With Recto Only:
pin 8: 454
B+1: 454
B+2: 454
B+3: 442

With all Tubes Installed:
All Heaters: 6.6
B+1: 369
B+2: 328
B+3: 243

V1
pin 1: 104
pin 2: 0
pin 3: 1.90
pin 6: 111
pin 7: 0
pin 8: 1.90

V2
pin 1: 147
pin 2: 0
pin 3: 1.40
pin 6: 190
pin 7: 2.92
pin 8: 46.3

V3
pin 3: 366
pin 4: 327
pin 5: 0
pin 8: 18.28

V4
pin 3: 365
pin 4: 327
pin 5: 0
pin 8: 18.28

V5
pin 8: 369

A few bugs appeared as I finished the fire up procedure; Some low frequency hum and a major buzz in the bright channel that I tracked to an input jack that was not closing when there was nothing plugged in. It was too late to hear what it really sounds like. Maybe today. I've got some detective work to do now. More pics to follow too. Rob

[Rocketrob]

Here are a few more pics of this 5E3 head. I changed a couple of things since the pictures were taken; now using elevated heaters and connected the PT center tap directly to the negative side of the first filter cap, then they all go to ground. This arrangement seems much quieter.(Thanks Bruce!) I started with a .047 cap for the normal channel and a .022 cap for the bright channel. This seemed a little too bright so I left the .047 in and changed the .022 to a .1 cap for further testing. The .1 cap sounds great with a tele or strat and the .047 works for HB pups. I've been playing it through a weber clone of a jensen a 12125F, I think, (can't remember the exact model #), and an old EV SRO 12". It might be the Hammond 1608 OT and its wide frequency range that makes the amp sound brighter than expected; not sure though. It does sound pretty good and surprisingly loud, especially with the EV speaker. Rob.

[Rocketrob]

more changes and cab done

well, the beat goes on as they say...The more I played this the more i noticed the bottom end was too much. Strange ghost notes and such, so I took the advice of many builders here and changed the coupling caps again. This time I changed the caps at V2 pins 6 & 8 to .047, and changed the bright channel coupling cap at V1 to .022 and the normal channel cap to .047. Voila! Mo betta sounds.

Also got the panel done for the front of the cab. Here is how it looks now. Rob.

[tubeswell]

Wow that's a nice looking amp Rob

[black_labb]

looks nice. really looks good in the cabinet.

[Rocketrob]

Hey, thanks for the nice comments. I've really enjoyed the designing aspect of building this amp. I bought the valve junior head for the purpose of learning more about tube amps because it's such a simple circuit. So i took that one apart and built a tweed princeton (with SS recto) in it, then I built a 18 watt lite IIb to fit the same cab, and finally, the 5E3 here. Interchangeable chassis for the same cab; kinda wierd, I know. Now I'm looking at a 5F4 circuit, but I think I'll have to stretch the chassis a few inches to fit the bigger iron, choke, and extra PA tube. Time to make a new cab I guess. The circuit board in the 5F4 is the same length as this whole chassis! Rob

[Rocketrob]

Sound Clip Done

Here's a little bit of blues noodling over a backing track. Just a little hair to the tone, mostly clean. I really like the touch sensitvity of the 5E3 circuit.

Recorded with a Shure Beta 57 about 8" from the speaker (EV SRO 12). Using my home built tele style on the neck pickup (Fralin blues special). This amp is great fun. Rob.

[mandi]

hi i am new in this page and i decide to make a 5e3 amp please give the chassis layout to make the holes