The Amp Garage

That's a clearer explanation of what I was worried about. If the bias is a tap, not a separate winding then the whole bias generation rectifier/filter/is pulled down by the zener setup. The bias voltage is shifted. I - think - what I wrote is consistent with that, at least from the perspective of to...

I ... think... that moving only the PT high voltage center tap was the right thing to do for everything except possibly the bias. How is your bias voltage generated? Is the output stage cathode biased? Is it fixed bias? If fixed bias, does the bias voltage come from a tap on the high voltage winding...

I'm having some trouble visualizing exactly how you have it hooked up. Can you post even a quickie, crude sketch so I don't mis-visualize it? If I'm visualizing correctly, the MOSFET reducer installed in the ground-to-PT/CT should have no effect on the circuit at all - as long as you tie nothing but...

Got it, replied.

I believe it's the best practice, yes. Star grounding is not the only way to get a hum-free setup. It's just the only way that is known to work ahead of building and trying. I like the term I heard here - "constellation grounding". This is a handier way to wire grounds with very, very, very nearly t...

Yep, PCB grounding scheme is the most likely culprit. It may be the PCB combined with how your connections to chassis ground is done. I can't figure it out from the diagrams either (no part designators shown), but one possible issue might be grounding the tremolo depth pot (and in fact the whole tre...

Don't forget to drain those filter caps! Even better, permanently install a 220K 3W resistor across the first filter cap to always drain whenever the amp is off. + 1 on the drain-down resistor. The life you save could be your own. I like to put an LED in series with the 220k to have a glowing indic...

pdf64 wrote: ↑Mon Apr 01, 2024 5:32 pm Just to confirm and clarify, the CT of the high voltage winding should be directly connected to the negative of the first filter (reservoir) cap, rather than to a lug at the star ground?

Yes.

Good planning! Running extra ground wire is the bane of star grounding. And good thinking - ideal versus real world is always a consideration. If it were me, I would feel free to bundle the ground wires neatly as they head back to the star ground point, with two exceptions. I would route the PT cent...

Haven't been able to find the answer online. The PT has a 125V and 120V primaries. Does the attached schematic show the 125V (BLUE) connected to the switch, or is the 120V (Brown) connected, or are both connected? If some one could explain the reasoning behind the 125V primary when the US power sup...

I just use it because I think it looks nice. But apparently lacing is longer lasting than nylon zip ties, and less prone to cutting into the wires' jackets than zip ties. These are not likely to be reasons to use lacing in home-built gear, though. In industry, zip ties have the huge economic advanta...

@ Magnatron: Sorry for the flurry from bepone. It can get confusing when people get off into bickering over minutae. That little back and forth didn't help you much, I think.

Did you get anything useful to answer your question?

just a note for you because youre spending too much words for nothing i wound maybe several hundreds pts in my life and projected another several hundred .. And as a note for you, you are wasting your time and words too. You''re back to the argument that "well, I've seen this, and therefore, that's...

R.G. it is almost impossible to wind differently heater winding halves, how did you manage to make that? :mrgreen: if you want centre tap, it will be exactly on the centre bepone, it's an easy mistake to make. I've both done it on my earliest winds, and seen other beginners do it when they're learn...

ok for the lifted heaters.. but with humdinger pot you can see that hum is depending of the heater construction in the tubes and for all the preamp, mixed tubes is variable.. you can see where is minimum on the turn That is, you're re-stating what I said: hum comes from lots of places, and you can ...