Has anyone here built a flat board amp design center?

[mort]

What I mean is, components laid out on a flat piece of wood, for easy access and manipulation. I've seen similar things in HVAC classes to use as working displays of how AC circuits work, but I've never seen one of a tube amp circuit.

I'm thinking of building one and I was curious to see some photos of others, if they are around. I'm not sure what to google in order to get those kinds of results.


I'm starting mine off with a pair of transformers from an old Hammond organ and whatever I have lying around.

H-A0-22111-1 PT
A0-20935-4 OT

(is there a schematic available for these? Can't seem to find one)

It used a pair of 6v6's and a 5u4G. The idea is to simply start by putting together a B+ supply, and then going from there, testing various methods and experimenting with new ones perhaps. This sort of open ended project would be a great vehicle for me to go through the various sections of amplification, bit by tedious bit, and learn by doing and experimentation. It would also be nice to have a nice wide open area in which to separate the sections so that it's easier to visualize what's going on and where, and how they relate to each other. It's all to easy for me to get "horse blinders" on when working on amps. If I can see it all laid out in front of me in sections, it would make it easier for me to compartmentalize. Plus, it'll keep my hands from being idle.

Anyway, anyone know of any pics of this sort of thing?

[jazbo8]

The Tubelab.

DummyLoad's breadboard.

My own tubelab knockoff.

Jaz

[mort]

The Tubelab.

DummyLoad's breadboard.

My own tubelab knockoff.



Jaz

Nice. I like those tube sockets with the screw terminal bases. I'll have to check the local surplus store for some of those.

[eschertron]

Not a breadboard exactly, but I have started my amp-building with a test bed made from an old silvertone organ chassis. some of the parts are visible in the picture, others - like the PT section - are not, they being mounted on their own rig (currently a short length of 2x4, so I guess that sorta counts as a breadboard ). I do like the concept of mounting the components on terminal strips for quick exchange and redesign. The experiments I started late last year resulted in the design shown in the second pic, a nominally 1W amp with a 12AT7 for the power tube.




...I just had to show some very low-skilled and low-budget counterexamples after Jaz's links!

[Enzo]

The octal sockets with the screw terminals around the base are "relay sockets" and were made for octal based relays to plug into. But they work for tubes too.


Mouser Part #: 528-464

And I like these things, tube sockets mounted on a piece of board with a two or three rows of turret posts. They come in both 9-pin and octal with one two or three sockets on a board. I'd link a picture, but their format won't work here.

Terminal Board - 2 x 8 Pin Socket | Antique Electronic Supply

Terminal Board - 3 x 9 Pin Socket | Antique Electronic Supply

[mort]

Ahh... I thought I knew those sockets from somewhere. I run into them sometimes in the HVAC field. The octal relays are known as "ice cube" relays in the field, due to the fact that they are square and have clear plastic encasing them. Alot of the sockets I run into for them don't have the convenient screw lugs on the base, nor a convenient test point at the socket, forcing the troubleshooter to find other places in the circuit to test operation.

[Enzo]

The sockets do come in other base styles, but I chose the one with screws. They also come in standard 11-pin format as well, for all you guys with 11-pin tubes...

Oh wait, I see the second image is of the 11-pin. I tried to delete it but I guess I didn;t

[jazbo8]

The octal sockets are made for relays, they are like a buck each...

Jaz

[mort]

Thanks for the term "breadboard" guys. I did not know the term or really what they were. All sizes and shapes, and some of them are cheap too!


I was wondering, is it possible to have a small plastic meter display as a bias gauge? I saw some dc current gauges for a couple bucks each, but the ranges wouldn't work for fine readings of mA. Would an amp still play like normal with correctly ranged meters in place?

[Enzo]

The problem is that your idle current is low, but much larger currents flow when the tube is in use. Take that into consideration. If you wanted meters, I'd prefer to see you stick with the 1 ohm resistor with a volt meter across it. Otherwise you are relying on the meter itself to maintain the tube circuit. A resistor will be a lot more reliable and stable.l

[mort]

OK thanks. Just picked up several extra 1 ohm resistors today, as well as some 8-pin octal relay sockets.

I'm looking at various breadboards now, on ebay. Are the cheap chinese ones sturdy enough for the kind of voltages I'll be putting through them? If yes, then for a couple bucks each I'll grab a whole stack of 'em.

[jazbo8]

Are you talking about the white breadboards with tiny pin holes on them? If so, they are not safe to use with tube circuits as they are not rated to handle the HV. If that's not you mean, could you please post some pictures/links?

Jaz

[Enzo]

Nothing wrong with going literal. You can lay a pine plank on the table, drive some nails into it, and solder parts to the nails. One of the photos earlier in this thread showed a board with an array of fahnestock clips. They work. In the 1950s when I was learning, fahnestock clips were everywhere. You can screw the clips to the board in any pattern you like.

[km6xz]

To make tube projects even easier, find a Lambda 50 or 71 tube regulated lab power supply. They have continuously variable B+ 0-500, C- 0-50, 5v and 6.3 a 0-200 screen supply using small variacs for the screen and anode voltages. They are not very big and fit on the bench easily. They weigh about 50lbs and have continuous metering of B+ and switchable metering between bias and screen voltage and current.
I have one back home in storage and did not bring it here because it is 117 VAC only.

[defaced]

I prototype with wood (poplar specifically) and copper plated nails. This allows me to prove out the layout and the circuit at the same time. I don't have any pictures of it, but I also have an old chassis with sockets/OT/PT mounted on it that I use for prototyping as well.

This is an image of the prototype and final build of a build based on the lead channel of the SLO preamp: