audio-talk

Thermionic Idler wrote: ↑Sat Nov 24, 2018 1:12 pm This is quite a nice thing to look at - it's a skeletal top-down view from the CAD model showing how everything is laid out for mirror imaging. The ventilated covers are there to hide the stuff that isn't symmetrical!

Clever. The same, but turned around.

Mike H wrote: ↑Fri Nov 30, 2018 7:15 pm

Thermionic Idler wrote: ↑Sat Nov 24, 2018 1:12 pm This is quite a nice thing to look at - it's a skeletal top-down view from the CAD model showing how everything is laid out for mirror imaging. The ventilated covers are there to hide the stuff that isn't symmetrical!

Clever. The same, but turned around.

Indeed, although confusingly I haven't turned around the output stage - this is so that the valves point the same way on both sides. That'll be fun when it comes to wiring it all up...

I don't know what Rozenblit is going to think of all this when it's finally unveiled on the Transcendent forums...

Thermionic Idler wrote: ↑Sat Dec 01, 2018 11:22 pm I don't know what Rozenblit is going to think of all this when it's finally unveiled on the Transcendent forums...

My money would be on him making no comment at all...

I think you're probably right Ray.

So my plan for today is to wire up the output stage of the one which is orientated the same way as the one in the instructions. Then I'll have a model that I can 'map' onto the reversed one. Let's see how far I get...

Well these things always take three times as long as you think. Today's progress - heater wiring.

I took an executive decision on this one. The photo shows the instructions for how to wire up the EL509 heaters - it uses a heater transformer with 12volt secondaries so the heaters are connected in series in pairs. However, the indicated layout seems to me to create a nice little induction loop around each quad of output valves and their circuitry. Also where I turned it sideways, one of the input cables would be running parallel to the heater wire line nearest the fuses.

In reality, in the context of an output stage that may not be critical, and the input cable runs to an unbalancing transformer, so any induced hum would be cancelled anyway. However, I could see no reason not to follow best practice for heater wiring. Rather handily, Pin 1 is unused on the EL509 so that helped deal with the series connections.

It would have made my life a lot easier if I'd bought two different colours of AWG18! Continuity tester to the rescue...

Pin 1 is unused on the EL509

are you sure about that?



http://www.tubezone.net/pdf/el509.pdf

I think it is EL509S that is being used.

No top cap and an octal base.

https://www.tubesandmore.com/sites/defa ... nsheet.pdf

pre65 wrote: ↑Mon Dec 03, 2018 2:10 pm I think it is EL509S that is being used.

No top cap and an octal base.

Yes, that's what the Transcendent kits use.

Correct, I should have said EL509S. I had one in front of me just to make sure and there was physically no pin 1.

I approve of your method. Neat.

Thicko question - what are the tall black things?

Fuse holders?

Yep, fuse holders. There are LEDs behind each one which go out if a fuse blows - very handy thing as OTLs do blow them on occasion. It was the only Transcendent amp to have that feature.

Where is the fuse located in each o/p valve circuit? I only ask because of having used a fuse in each speaker line, I could hear it and it sounds bad, interestingly even if it's put in a HT supply line, the same, unless there's a supply smoothing capacitor after it to kill the effect. It's something to do with the effect of putting the signal through a thin wire.

Mike H wrote: ↑Tue Dec 04, 2018 11:59 am Where is the fuse located in each o/p valve circuit? I only ask because of having used a fuse in each speaker line, I could hear it and it sounds bad, interestingly even if it's put in a HT supply line, the same, unless there's a supply smoothing capacitor after it to kill the effect. It's something to do with the effect of putting the signal through a thin wire.

They're on the anodes of the positive drive bank, and the cathodes of the negative drive bank, according to the circuit diagram. It's a "totem-pole' output stage quite similar to Futterman, key difference (and the patent) being in the way it's driven. The idea being that if a tube goes bad leading to an unbalanced situation with too much current flowing, the fuse goes pop. And I've had it happen a few times "in the field" with my Son of Beast. They have to be there to stop the speaker going up in smoke every time a tube fails.

It is basically the same output stage as SOB, repeated a few times with a meatier driver stage. So I know it'll sound good (bloody better do with the amount of work and money I've put into this).

Sexy work as always, darling. Utterly shabby.