JE Labs - Simple 45


Senior Member
I realized the other day that I have a lot of the needed parts in my stash, so I thought I would build it and test it out.

I have a quick question about the 20uF cap from 6SL7 cathode to ground. I'm curious if 30uF would work, I suspect it will, but would like to confirm if possible.

If all else fails I'll try it and report!


Most of the time, you can err on the higher side when it comes to caps in a tube amp schematic - 50% to 100% higher capacitance and/or higher voltage rating will not change the equation much, typically. One place in an amplifier where this isn't true is in the power supply, especially if we're talking about the first C in a capacitor input supply. That first cap in a CLC or CRC supply "tunes" the voltage and has a more pronounced effect than in most other positions.

Don't muck with cap values in a loudspeaker crossover either, unless you have a decent idea of what you're doing - that's another place where you'd best stick to "the recipe"! :)


Senior Member
Still collecting parts. I'm also going to be delayed by a few weeks, but for a good reason. I'm switching rooms with my youngest daughter and I'm ending up with a bigger office/lab! I have to build some new cabinetry, shelves, etc. Pull some ethernet, paint her new room (my former office), install new lighting, blah blah.... super excited to have a little bit more space, and this is forcing me to organize some of my components/gear etc. even better, which I will appreciate when it's all done :D


Senior Member
Most of the move work is complete, a bit more organizing, unpacking, and small setup tweaks. I have more room, less closet space, but built a new bookcase for iron, components, etc.


The lab desk, with wiring trough at the rear. I'm making some pop out lids for the trough to keep the wiring concealed. I'm mounting some long power strips in there as well.


The new bookshelf, quickly put together, shelves and sides are ~1" Baltic Birch. This is for strength, mostly for transformers, but also for ease of building. I can get nice 12mm (1/2") Baltic Birch from the lumber yard <5 minutes from my house. So I tend to build a lot with that, doubling up where needed.


Added a shelf for scope, dmm's, and various gear. I will likely add some gear below, still thinking on that one. I also added some office tunes, the most important of the process, clearly.

The monitors in the corner are for a few uses. The first is for one of the large black cases underneath the desks, my main Linux workstation/server. I wanted to have a monitor for it for schematics, videos/tv while building, and of course for reading the Haven! The smaller monitor will be hooked up to the other large case underneath the desks, our NAS/media server. I also wanted to have a monitor available at the desk for work on raspberry pi's when setting up, and the various other similar projects.


Lastly, my day job desk, where I spend the majority of my time in this room.


So hopefully I'll be able to get back to building in the next few weeks. I have all the parts, except for the power transformer now. I scored a few more sets of nice 45's recently, so I hopefully have enough to have a great main pair and some good spares.


Senior Member
Thank you everyone, I'm very pleased with my progress so far. I might do some more work in there this evening. I'm ready to build!


Senior Member
I got a bit more done on the lab desks, some wiring and setup. The last bit of iron I need for the simple 45 build gets delivered this week I believe, and my metal order should be here in a few days hopefully.

For now I'm using Edcor GXSE-8-5k, I also have the 16ohm versions handy. My plan is to listen and tweak with those OPTs, and possibly upgrade to a pair of Electra-Print OPTs after that.

So, depending on when everything gets delivered I should be able to start the build soon. I'm doing a two chassis build, HT and heater supplies in one chassis, and 'signal' components in the other.

I've sketched out some layout ideas, once all the iron is in, I'll confirm spacing and then start the metal work.



Senior Member
Last bits of iron came in, so I thought I would quickly mock up my initial layout ideas. I'm sure I'll re-think and over-think this to death, but for now I think this will work. I'm hoping the ~3/16" aluminum sheet gets delivered soon, so I can get started on the plates.

A few quick pics, ignore the relay sockets for octal sockets, they're simply a placeholder.


The circle connectors are for HT and heaters, I have some 7 pin connectors and could put them all in one umbilical. Perhaps a single umbilical would make it easier to 'tie' the two chassis together for physical earth?

I think I need to sketch this out so I don't lose track.

- B+
- B+ ground/0v
- 6.3v+
- 6.3v ground/0v
- 2.5v+
- 2.5v ground/0v
- physical earth?

Physical earth could also be tied into the braided screen that will be outside the main bundle of wires for the umbilical.

Any thoughts, insights here are greatly appreciated.