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SOHA II Builders Thread - Page 56

post #826 of 1688
Thread Starter 
Do you mean TPL and TPR measured with respect to ground? Or measured with respect to the B+?
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #827 of 1688
Quote:
Originally Posted by runeight View Post
Do you mean TPL and TPR measured with respect to ground? Or measured with respect to the B+?
With respect to TB+L/R.

Chris
post #828 of 1688
Thread Starter 
OK. At least everything is working properly.

These voltages are abnormally far apart because the two tubes that you happen tohave are mismatched in totally different directions. They are acceptable voltages, but it would be better find two tubes that gave you closer to the 19V design point.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #829 of 1688
Alex, Thanks for your diagnosis. I checked the first plate of the tubes (Pin 1) and there are the expected 19 Volts. So it's really only that my tubes are mismatched. I have four of them so I will try the others and stick with the best ones.

Seems I have "luck" with mismatched parts. The 7815 in this SOHA_II delivers 14,8 V, the 7915 -15,3 V.

Chris
post #830 of 1688
Quote:
Originally Posted by runeight View Post
This setup is ok but it offers more opportunties for noise and hum since the amp won't be grounded to a nice big piece of metal.
Thanks Alex, i took apart an old cd drive casing for use as my bottom ground plate

Quite happy with the casework so far but I'm having trouble deciding which wood stain to use (cherry vs. red mahogany)...





post #831 of 1688
Added above some pics of dry fit.. that is all for now until later this week, I'm now off to an easter turkey dinner!
post #832 of 1688
That is some serious example of what can be achieved when you have the tool's and the know how...well done
post #833 of 1688
Thanks onform. The wood case and the top/bottom "lids" must've took about ~8-10 hours to build and finished sanding. Tube holes still need to be cut and still waiting for a few mouser parts (jacks, switch).

I dread the staining part, I'd be really disappointed to screw this up at this point.
post #834 of 1688
Well it already looks damn pretty zk, really looking forward to the end result... I predict awesomeness
post #835 of 1688
was wondering how this amp faired against the woo audio 6se or wa2? I'm thinking of building one after seeing all your beautiful works of art! ahaha
post #836 of 1688
Very nice zkool448, really creative with wood.

I’m also busy with the casework for my balanced SOHA II, but no wood from this side of the ocean.
It’s a 2 boxes solution…. the amp is feeding by 2 oversized transformers, 80VA each.






post #837 of 1688
I spy an e24.

looks really good ferrari, i shudder at the cost! Schaeffer isnt cheap these days.

have you got any idea of what tubes you are going to use in it?
post #838 of 1688
Quote:
Originally Posted by zkool448 View Post
Added above some pics of dry fit..
Really Beautiful.

But I would be a bit concerned about ventilation. I finished my SOHA_II this week and still without any enclosure the heatsink temperature reaches 60 °C (with a few mA below the recommended bias of 100 mA), R3P yet reaches a few degrees more. And now it's spring not summer. Therefore I already changed my enclosure plans and sure will follow Alex' recommendation of a more than 50% open top plate. If I knew before I sure would have bought higher heatsinks (1.5") and accepted a resulting higher enclosure.

Chris
post #839 of 1688
Quote:
Originally Posted by Ferrari View Post
Very nice zkool448, really creative with wood.

I’m also busy with the casework for my balanced SOHA II, but no wood from this side of the ocean.

It's sloooowly taking shape! Nice to see..

I should post some pics of my latest 'II - it's in the case phase but ZK's wood and your metal work makes me a bit embarrassed to show mine.

Darn DIY'rs continually raising the bar...mumble mumble...
post #840 of 1688
Quote:
Originally Posted by adamus View Post
I spy an e24.

looks really good ferrari, i shudder at the cost! Schaeffer isnt cheap these days.

have you got any idea of what tubes you are going to use in it?
Yes, the ε24 circuit is on board.

Since the heater power supply circuit on my amp is modified a bit: based on LM338 (instead of LM337), feeding by an 80VA transformer separately, I’m thinking of trying some current hungry tubes like 6N1P, 6N6P and 6N30P...
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