The JE Labs/ Angela SE 2A3 amplifier, revisited
- Thread starter Redboy
- Start date
That's a lot of premium parts right there...your friend is going to be really happy with this amp!Time to put the lid on this power supply.
I can't imagine (actually, I can imagine all too well) how much that choke cost.
Had I known you guys were gonna be so gaga over that choke, I'da taken some glamour shots of it before I installed the thing!
I hope he likes it. I think he might, whenif he finally gets it.
I may have gone overboard on the parts a bit, but that's okay. I mean, I suppose I could change out the copper-in-oil coupling caps for some Orange Drops or something. Maybe he won't notice. 🤔
Throw a few NTE cement resistors and some clapped out old Sprague can caps in there for good measure.Had I known you guys were gonna be so gaga over that choke, I'da taken some glamour shots of it before I installed the thing!
I hope he likes it. I think he might, whenif he finally gets it.
I may have gone overboard on the parts a bit, but that's okay. I mean, I suppose I could change out the copper-in-oil coupling caps for some Orange Drops or something. Maybe he won't notice. 🤔
I’m not a fan of quoting myself but this question still gnaws at the back of my brain...@paulbottlehead , I keep thinking back to another thread where you and Joseph both mentioned leaky Jensen Cu caps... Should I just swap these out now for something else, to ensure long-term reliability?
I have a feeling I already know your answer.
I grabbed a handful of possible options. Can I get away with a 0.1uf coupling cap or should I stick to the 0.22uf? I'm leaning toward the Kimber Kaps but I am curious about the urushi-treated caps from Feastrex -- they're a 0.1uf
The big glass Potter caps would be a hoot but they’re waaay too big!
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Just go with the K40Y-9 caps, Nate. They’ll last forever and sound pretty darned good, too.
You can use a different value of coupling cap, but you should also adjust the grid leak resistor accordingly. I generally stick to 0.1uF and 249K grid leak, so if I want to use a 0.22uF I would cut the grid leak down to 120K. This process has its limits though, as there is a maximum allowable grid leak resistor and if you make the grid leak resistance too low, you'll load down the preceding stage.
Okay, we're getting a lot closer now but B+ is lower than I'd like, at ~330V even with a GZ34 which doesn't drop that much. Target is 350V.
The current supply is LCLC, with a 390v.d.c transformer > GZ34 > Chicago 8hy choke > (85ohm) > 100uf > 5hy Lundahl (15ohm?) > 100uf
I know y'all are big fans of that second choke, but pulling it would get me closer to my target voltage... though I'm not sure just how much closer. Alternatively, I could "tune" the voltage up with a small value cap just before the choke -- I've seen that referred to as cLCLC -- but I don't know which is the more "elegant" approach.
Anyone care to weigh in?
The current supply is LCLC, with a 390v.d.c transformer > GZ34 > Chicago 8hy choke > (85ohm) > 100uf > 5hy Lundahl (15ohm?) > 100uf
I know y'all are big fans of that second choke, but pulling it would get me closer to my target voltage... though I'm not sure just how much closer. Alternatively, I could "tune" the voltage up with a small value cap just before the choke -- I've seen that referred to as cLCLC -- but I don't know which is the more "elegant" approach.
Anyone care to weigh in?
@forkliftman15 ?
This sounds like his kinda thing...
This sounds like his kinda thing...
That's some high praise.
Abandon the Chicago choke and look for something with lower impedance than 85 ohms. The Hammond catalog has lots of options. Use PSUD to check the current across the choke to be sure you aren't exceeding the ratings, as chokes in choke input filters see lots of AC current.
I'd go cLCLC. You've probably got a little c in your stash that would work. Pulling the second L will leave you with a bit much ripple, me thinks. And it's pretty.
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Whatever you do, don´t pull the Lundahl choke. Get rid of the Chicago choke as Paulbottlehead suggests and put the Lundahl in the first choke position. Lundahls are made to work as choke inputs, and the Lundahl will save you 70 Ohms compared to the Chicago. Put a low DCR Hammond in the second slot.
If I am seeing it correctly your Chicago choke is mounted externally and is part of your ascetic plan.
If so I would go with the small input cap as a first attempt before dumping it.
It's pretty easy to clip lead in and test your voltages on the bench, I would start with 1uf and go up or down from there.
And be sure to use .9999999 alligator clips with silver gold wire for proper sonic benifits...
If so I would go with the small input cap as a first attempt before dumping it.
It's pretty easy to clip lead in and test your voltages on the bench, I would start with 1uf and go up or down from there.
And be sure to use .9999999 alligator clips with silver gold wire for proper sonic benifits...
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