Build This Tube Amp With A Screwdriver

[Lavane]

That certainly looks much nicer than a cage. The only advantage of a cage is that it also eliminates the possibility that someone will touch the hot tubes.

I was more worried about grand kids touching high voltage bits on the board. I like to be able to see the tubes. I bought one that was intermittently shorting and ad able to shut it down quickly. I did put a cage on my ST-35 though, it's just too ugly without one. Plus it's the two exposed PCB's and the bias board I added. I would like to find a shop with a CNC machine and
have some slots cut in the sides of the cage. I don't like that the output rubes are so close to the sides thst aren't ventilated.

 

[Rockyhill]

I was more worried about grand kids touching high voltage bits on the board. I like to be able to see the tubes. I bought one that was intermittently shorting and ad able to shut it down quickly. I did put a cage on my ST-35 though, it's just too ugly without one. Plus it's the two exposed PCB's and the bias board I added. I would like to find a shop with a CNC machine and
have some slots cut in the sides of the cage. I don't like that the output rubes are so close to the sides that aren't ventilated.

Say what? I love the look of mine! I have a cage but don't use it.

I like the idea of putting slots in the side panels, both for ventilation and visibility. I wonder if Kevin sells paint...

 

[Lavane]

Say what? I love the look of mine! I have a cage but don't use it.

I like the idea of putting slots in the side panels, both for ventilation and visibility. I wonder if Kevin sells paint...

A CNC machine probably wouldn't make a mess of the paint. I've seen them operate. It would be nice if he sold rattle cans of the paint used though.
There was just too many places to get shocked if a kid touched the thing without a cage. I wish there were covers made for the M-125 mono blocks PCB's.

 

[Lavane]

I thought @FlaCharlie 's Simplissimo amp was an interesting idea.
I checked my parts bins and I had the tubes, along with the caps and resistors needed. So I decided to built this amp like he did without using any solder. The difference between his and mine is I'm using an aluminum plate I have and mount everything on the under side of it and wrap that plate in wood. I found some tube sockets with screw terminals on the bottom made to attach to a chassis. I have most of the parts collected, just waiting for the power supply and OPT's to arrive. The SMPS will be mounted underneath on the aluminum plate with thermal grease between it and the chassis. I'll drill a few holes around it for ventilation and maybe add a 12V whisper fan since the 12V tap isn't needed for anything else.
I'll start a thread on this build when the rest of the parts arrive.
I did have another thought. What about building a parallel single ended version using this design? I have the tubes for it.
That is if the power supply can produce enough current.

 

[FlaCharlie]

I did have another thought. What about building a parallel single ended version using this design? I have the tubes for it.
That is if the power supply can produce enough current.

Although these SMPS units claim they can supply 600mA I think that they need to be de-rated considerably. When I was breadboarding this design I tried using a smaller / less expensive version that claims to be able to supply 300mA (also 300v). The amp only draws a bit over 170mA. The smaller one worked but got really hot.

So I don't know if the larger one would supply 340mA or not. To be fair, I don't have them mounted on heatsinks so if you did that perhaps it would be OK?

The other issue with PSE is that the primary impedance of the output transformer needs to be cut in half I don't know how available or expensive a 1.75k OT might be.

I do have a PSE design breadboarded using the same SMPS but total current draw is only ~139 mA. The tubes I'm using want to see a 10k load in SE so I'm using a 5k OT by the same manufacturer as the one used in this amp.

 

[Lavane]

Although these SMPS units claim they can supply 600mA I think that they need to be de-rated considerably. When I was breadboarding this design I tried using a smaller / less expensive version that claims to be able to supply 300mA (also 300v). The amp only draws a bit over 170mA. The smaller one worked but got really hot.

So I don't know if the larger one would supply 340mA or not. To be fair, I don't have them mounted on heatsinks so if you did that perhaps it would be OK?

The other issue with PSE is that the primary impedance of the output transformer needs to be cut in half I don't know how available or expensive a 1.75k OT might be.

I do have a PSE design breadboarded using the same SMPS but total current draw is only ~139 mA. The tubes I'm using want to see a 10k load in SE so I'm using a 5k OT by the same manufacturer as the one used in this amp.

Thanks for chiming in. I'll stick with the original SE design then.
I really don't want to have to order another set of OPT's.
I was just thinking king if that PS would acually handle two extra power tubes. I agree these SMPS specs stretch there limits some.
I wouldn't want to run one that hard. Even if I had it heat sinked.
I'm on the left coast, so it shouldn't take that long to get the PS and OPT's.

 

[kward]

Very clever. Nice Work!

Though the title reminds me of this old Jefferson Starship song, which I didn't like.

Same. Love Mickey Thomas' voice, didn't love him singing that particular song. For those who know Mickey's background, here's a subtitle for this thread: "Fooled around and built...an amp!"