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stax t8000 clone (well sorta)


kevin gilmore

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In T2 one tube act as lower and the other tube as upper device.  Another way would be to have one tube for each side.

This adapter board changes to single tube per side.
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The T2 way makes the layout a bit more elegant then single tube per side. Else pro/cons - I have no idea… anyone?

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For a cascode stage (SRX, T2) I prefer to use one tube as the lower and one tube as the upper. The reason is that the input tube cathode sits at ground (roughly), whereas the upper tube cathode sits a a positive voltage. Most input tube types specify a maximum filament-to-cathode voltage of 100 volts max. So the potential issue if you use a dual triode tube per side is that either the lower or upper cathode filament-to-cathode voltage will exceed that maximum, leading to shortened tube life. OTOH, if you use one tube for the lower and another tube for the upper and float both filaments, you don't have that issue.

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Still in progress. Board shortened now 160mm x 80mm. Found models of tubes on the internet. The small tubes even have golden pins.

I got the tube models from grabcad.com and the creator of EL34 and small tube (12AX7) is Andrew Whitham, United Kingdom.

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Edited by JoaMat
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I usually work with imperial system in Proteus as I find it pretty convenient. For my 10K Afternoon Run the metric system is way more comfortable.:rolleyes:

 

8 hours ago, mwl168 said:

Can KSA1156 be used in place of the 2SA1486 here?

The voltage cross 2sa1486 is 580 – 590 V. That’s why I chose between stn9360 and 2sa1486. I guess you could use a pair of ksa1156 and split the voltage cross them.

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Milled and drilled right side board today. Same size as the single tube input version. Here single and twin small tube side by side. If lucky Mouser package arrives tomorrow and if Proteus ratsnest works it should play soon. If I haven’t done something stupid…

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Edited by JoaMat
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Replaced the original right board with the dual small tube one.

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First power on without any funny smell, smoke or explosions. But both outputs at positive rail voltage. Back to schematic and after a while I found two mistakes I’ve done. I managed to correct them on the PCB which now looks awful but it plays music all right.

 

small.jpg

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