[makasin]

I was thinking of putting some sort of switch that you could disconnect the outputs from the jack (like when you turn it on or off) and I am wondering how I should go about doing it? Should I attach a dummy load to the amp in the standby setting? like a 2W 600ohm? Or should it go to nothing.

 

[heatmizer]

how about something like an e12 time delay and use a switch to power the e12 circuit you then get time delay on outputs, dc offset protection and manual control of outputs

 

[makasin]

Well I dont have the time or the money for such an endeaver. Will this method work?

 

[FallenAngel]

It probably will, just don't short the output or make the load WAY too small. 600Ohm 2W is overkill, go for 1/4watt 300Ohm like the HD650

 

[amb]

The SOHA doesn't need any dummy loading. You can just let it float when the switch is in the "off" position. If you must load it, something like a 1K ohm 1/4W resistor is enough.

 

[makasin]

ah ok sounds good thank you!

 

[makasin]

I have another question:
I am putting the transformer in the enclosure. How far away should it be from the board and what can I use to shield it?

 

[makasin]

Also, where would I go about connecting a power LED?
The LED terminal under the tube is blocked by the tube so its unusable.

 

[amb]

Quote:

Originally Posted by makasin /img/forum/go_quote.gif I am putting the transformer in the enclosure. How far away should it be from the board and what can I use to shield it?

If you're using a small toroid, I'd suggest no closer than 3" away from the amp board if possible. Distance is your friend when it comes to transformer and audio circuitry. As for shielding, it's not a trivial matter and I invite you to read the recent posts in the β22 amp thread at headwize.

Quote:

Also, where would I go about connecting a power LED? The LED terminal under the tube is blocked by the tube so its unusable.

Anywhere across the +/-15V rails that the opamp runs off of, with a 10K ohm current limit resistor (actual value may need to be varied depending on your choice of LED).

 

[tomb]

Quote:

Originally Posted by makasin /img/forum/go_quote.gif Also, where would I go about connecting a power LED? The LED terminal under the tube is blocked by the tube so its unusable.

Not sure you realize that the LED is installed from the bottom - you push a 3mm, T1 LED through the hole in the board and bend over the leads into the pads from the bottom of the board. If needed, you can parallel another LED with wires soldered to the tube LED leads/pads, and pulled up through to the top through one of the many mounting holes on the side. This is assuming you're using a Hammond case - the holes on the side are not blocked by the slots. If it's not a Hammond case where the board rests in the slots, you'd probably have plenty of room to bring the leads up and around the front of the board.

These pads come off of the 12.6V heater circuit, which should be a better choice than the +or- 12V opamp power rails and their virtual ground (or the Steinchen-proposed +or- 15V power rails). Those should be left alone, IMHO.

Quote:

Originally Posted by makasin I have another question: I am putting the transformer in the enclosure. How far away should it be from the board and what can I use to shield it?

My preference is to put the xfmr in a Jameco walwart enclosure, and use a 3 or 4 wire DIN or double 2.1/2.5mm DC-style sockets. Batman used this method for his original P2P SOHA (although he just left his direct-wired), and Amb did the same for his CKKIII. Any issue with hum from the xfmr goes away completely and a toroid is not even needed. The SOHA board also fits perfectly into a Hammond 1455N1201 case, which is only ~4" x 4.7" x 2" high. If you already have the bigger Hammond case, you can push the board to the front or back and save the extra room for Steinchen's new buffers.

If I recall, you used one of the TRIAD flat packs anyway. In that case, you may not be able to use a case big enough to increase to a non-hum distance within the same enclosure. One of those flat packs fits very easily into the Jameco enclosure, though (what I use) - as does the toroid.