Another SSS #002 build thread (Ryan/Erwin)

[ThePanda]

Sounds good. I believe adding the caps to UF4007 actually does more harm than good wrt reducing switching noise.

You mean using UF4007 are not a good idea?

[martin manning]

No, using caps with UF4007 is not recommended.

[GAStan]

No, using caps with UF4007 is not recommended.

Hmmm, looks like I need to revisit my SSS for this and the caps mentioned earlier. Thanks Tim and Martin for bringing this up.

GREAT looking build so far Tim, I enjoyed catching up.

[timrobertson100]

Watching the incredible captaincoconut #5 build thread motivates me to get back to this.

I'm using teflon for the first time, as I've always admired the Amp Nation builds. 22AWG/600V for the preamp and grid signals and 20AWG/600V for B+ line and screen, then cloth 18AWG for the heaters - please say if that sounds wrong.
Also, I advise not to buy Mouse AlphaWire 5855 and 5856 as it comes in funky colours - red is more like pink

I'm planning on mounting a daughter board for elevating the heaters just north of the PT, where I've got those sharpy dots - the heater run can then go straight up and down to the last tube socket. Seem reasonable, please?

[GAStan]

Looking good, however the 500ohm/5w resistors are very close to the Grid1 terminals on your power tubes. Those two points combine to make the highest voltage potential in the amp; Bias- to B+. That's putting a LOT of faith in the resistor coating to insulate against. If it were mine I would carefully bend the leads to get a bit more air gap between these two items.

[timrobertson100]

Looking good, however the 500ohm/5w resistors are very close to the Grid1 terminals on your power tubes. Those two points combine to make the highest voltage potential in the amp; Bias- to B+. That's putting a LOT of faith in the resistor coating to insulate against. If it were mine I would carefully bend the leads to get a bit more air gap between these two items.

Thanks Glenn. That's not something I've every really thought about but it makes total sense - thanks for raising it.

The camera angle made them look pretty close - here is another picture which shows the gap clearer. In your opinion are they still an issue please?

[GAStan]

You're right, it was the camera angle.

IMO that's fine, no closer than the socket terminals.

Great looking build so far!

[captaincoconut]

Looking great so far!

[Richard1001]

picture sss build.jpg

Looking good, however the 500ohm/5w resistors are very close to the Grid1 terminals on your power tubes. Those two points combine to make the highest voltage potential in the amp; Bias- to B+. That's putting a LOT of faith in the resistor coating to insulate against. If it were mine I would carefully bend the leads to get a bit more air gap between these two items.

Thanks Glenn. That's not something I've every really thought about but it makes total sense - thanks for raising it.

The camera angle made them look pretty close - here is another picture which shows the gap clearer. In your opinion are they still an issue please?

The way the 470k resistors are wired, the amp will surely wake up your neighbours when you fire it up. The control grid should not be connected to the heater supply.

[pottedplant]

picture sss build.jpg

Looking good, however the 500ohm/5w resistors are very close to the Grid1 terminals on your power tubes. Those two points combine to make the highest voltage potential in the amp; Bias- to B+. That's putting a LOT of faith in the resistor coating to insulate against. If it were mine I would carefully bend the leads to get a bit more air gap between these two items.

Thanks Glenn. That's not something I've every really thought about but it makes total sense - thanks for raising it.

The camera angle made them look pretty close - here is another picture which shows the gap clearer. In your opinion are they still an issue please?

The way the 470k resistors are wired, the amp will surely wake up your neighbours when you fire it up. The control grid should not be connected to the heater supply.

I assumed he was just going to snip them later and pull the excess straight out, but yeah that would be wild lol

[timrobertson100]

The way the 470k resistors are wired, the amp will surely wake up your neighbours when you fire it up. The control grid should not be connected to the heater supply.

Thanks Richard, appreciate the note of concern. PottedPlant is right, those are just dry fitted, not soldered yet.
I paused to deliberate on what was the best wire colour scheme from what I had and the funky (ugly) Alpha teflon colours, plus checking I was using the right gauges (22AWG from grids, 20 for the higher current stuff)

[Richard1001]

Ah yes, that makes sense.

[timrobertson100]

When using Martin's bipolar supply, am I correct in understanding this involves changing the Ryan/Erwin layout with:

1. Changing the 220k cathode resistors to 100k
2. Using a 75k, 24k 10k-pot divider network for the bias range

I don't have a 75k or 24k, but I think 68k, 22k and 10k-pot should give similar range.

Does this sound about right, please?

[martin manning]

When using Martin's bipolar supply, am I correct in understanding this involves changing the Ryan/Erwin layout with:

1. Changing the 220k cathode resistors to 100k
2. Using a 75k, 24k 10k-variable divider network for the bias range

Yes on the 100k replacing 220k. I have 75k and 27k with 10k pot, but your tubes may need something different to center the range. 82k in place 0f 75k would be close.

[timrobertson100]

Yes on the 100k replacing 220k. I have 75k and 27k with 10k pot, but your tubes may need something different to center the range. 82k in place 0f 75k would be close.

Thank you