audio-talk

I have had high Voltage on the secondary side of something, that is 'floating', due to inter-winding capacitance maybe, but was a long time ago so can't remember the details. I mean relative to mains earth. Ideally you want to connect the secondary side ground to mains earth, and have some sort of ...

When mounting the large boards to a chassis or copper sheet, what size of nylon support pillars should be used? I've been using 6mm and they work but just feels like there's tension between the transistors (which screw flat to the copper) & the board (which is held off by the 4 pillars). Would 5...

Problem solved. I realised the 2 boards I want happy with were the first board I built, and I'd never built a PCB before that. Sure enough there were some joints I was less than happy with. Reworked those and all is well. I've now built 24 of these boards (16 large, 4 small) and I'd like to think I'...

No actually even targeting 2.5v it's slow to rise, just less noticeable. After about 10 minutes it gets to 2.44v. Temperature of both D44H11 & LD1085P are stable (around 44 & 54 deg C respectively, bolted to a 3mm copper sheet). To be honest I could live with it, but I don't like things not ...

It would be interesting to measure the signal voltage (if any) across that resistor. I agree. I'm going to build it without 0v references first, then add them in with perhaps 100R inline. I can experiment with what difference it makes being in vs not, also which connection to the 0v reference sound...

The circuit is complete without that 0v reference wire though. The bottom of the LTP returns current to the bottom of the 2nd LC. Without the ground wire the cucumber would work perfectly, but would not have a 0v reference. I don't think that matters as the valves are linked by transformers and I'm ...

Ok I've built all my boards for the new amp (4 small, 8 large) and am testing them now. All good, but one board takes forever to reach the value. The others are all perhaps 20 seconds, but this one I timed (patiently) and recorded the values over a lengthy period. Aiming for 5v, after about 5 minute...

OK - having finished Geoffs amp (small buzz still to track down, but otherwise ...) it's time to move on to my own build of this amp. Initial 3D designs attached. Changes will include; DC heater boards for all valves including the 45s, so 12 DC boards total and 6 toroidals (thanks Andrew) - no LCRC ...

It's a generally easy way of avoiding ground loops. If you have two bits of kit both referenced to true earth you may get ground loops if signal connections are not thought through. In the case above it goes a little further to provide a little more isolation. I suspect it's not quite that simple t...

I struggle to understand the reasoning behind putting a resistor in the ground connection. Could someone enlighten me? The circuit... TX - LCLC - PP TX - VALVE PAIR - LTP - BACK THROUGH LCLC ... is self contained and galvanically isolated. A connection to star ground (and thence to safety earth) giv...

Ok fair point

Maybe consider an anode choke? Lundahl 1667-05mA would give 800H ish!

How did you decide on 68k grid stoppers Steve ?

Well done sir. I'd like to have a beginners go at working out what frequency the curve on your scope shows, in the hope the more experienced folk will put me right and I'll learn from it. Your time dial is set to 2ms (2nd picture), so each small block represents 2ms. The curve is approx 3.5 blocks b...