Hi,
Quick question:
From what I understand, the First Watt clone power amplifiers require a bipolar supply of +/-24. Is there any tolerance for this, what would I need to take into account if I used a 2 x 19v transformer that would give a couple of volts over the recommended supply?
Thanks
Quick question:
From what I understand, the First Watt clone power amplifiers require a bipolar supply of +/-24. Is there any tolerance for this, what would I need to take into account if I used a 2 x 19v transformer that would give a couple of volts over the recommended supply?
Thanks
more expertise than I can chime in but I understand the fets to handle such a scenario just fine.
I have considered getting transformers with 20V secondaries as the diode drop in the rectifier section has me sitting closer to +/-23VDC. I think Zen Mod has suggested such.
I have considered getting transformers with 20V secondaries as the diode drop in the rectifier section has me sitting closer to +/-23VDC. I think Zen Mod has suggested such.
Gary is right. The only possible consequence is reduced class A envelope if you have to reduce Iq due to tempersture constraints. In fact, you’ll have a few watts more off the amp with a 2x19v tranny. Over 30 volts after rectification though, and you will need to worry about the JFETs.
beware also that most of the BOMs include 25v caps. Best sure 30v caps if ending with 25-26V 🙂
I’ve always used 20v secondaries, with no issues. What it ultimately means is higher rails. At this level you don’t have anything to worry about; as you go higher you’d start addressing things like additional heat, dissipation in things like FE jfets, parts ratings, etc. Not to mention the operating points established by the designer.
You’ll never get over 30vdc using a 19vac trafo secondary, even if using active rectification.😉
I know, it was an example. A bit unclear, I see now. But a pity. Magic volts would have been nice!
18Vac, usual FW range of Iq, 25Vdc caps
simple - if Papa is using them, why not; it seems short duration of overvoltage ( say while lazy optobiasing in recent amps is not kicked in**) is not doing any harm (nominal voltage rating is one thing, luckily danger voltage is higher enough)
higher than that, 35Vdc caps
if all that is covering what you means by "derating"
with age, I'm trying to think less
**optobjt nested between gates (think SissySIT), that circ is much slower than really most recent approach, without optos but current mirrors from rails and resistors between gates (think XA252); that one is getting to full Iq in few seconds
simple - if Papa is using them, why not; it seems short duration of overvoltage ( say while lazy optobiasing in recent amps is not kicked in**) is not doing any harm (nominal voltage rating is one thing, luckily danger voltage is higher enough)
higher than that, 35Vdc caps
if all that is covering what you means by "derating"
with age, I'm trying to think less
**optobjt nested between gates (think SissySIT), that circ is much slower than really most recent approach, without optos but current mirrors from rails and resistors between gates (think XA252); that one is getting to full Iq in few seconds