Hi all
Well I have just ordered my James 6123SH output TXs from sandy my intended build is a 5842-2A3 but I'm stuck for the PSU I have a Mains TX of 270-0-270 volts @200ma plus a Hammond choke 10H @200ma 82ohms or I have two 10H 200ma @160ohmes can anyone come up with the best Psu for my intended 2A3 amp see schematic
all thoughts welcome on this
thanks
Hi Colin-given your "bits" i would be tempted to use the single choke in the "normal" way and then split the power supply to L & R channels and use the other two chokes (one for each channel) if you understand what i mean.
Best to play with PSU designer (much easier if you can work out the current draw in ma and insert that into the model.)
The only thing necessary for the triumph of evil is for good men to do nothing.
A number oif choices come to mind, choke input with SS rects would give 240v, and cap input would be in the order of 360v, so the obvious would be choke input, with a smallish first cap to boost the voltage up. Or you could use a valve rect to increase the voltage drop and use cap input.
The currenr draw per amp is something like 45ma per side, so you could go with TX, valve rect, cap (say 20uf), then 200ma choke, then a 47uf cap, then split to the two 100ma chokes, each with a 100uf cap following.
But you would need to simulate in PSD to get the nicest looking response.
As always "best" is a problem, but the above is what I would do.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
Hi Philip
I hadn’t though of splitting the psu with choke to L/R channels due the to chokes ohms I think I will lose to many volt I don’t think you can model a split psu in PSU designer can you with two 2a3/ @60mA plus Two 5842 @10mA total current of 140mA
You can Colin, kind of. You insert a current tap where the split between channels would be and give half the total current to each tap. But I'm never completely sure what's really happening as you aren't modelling one of the chokes and caps, they're just represented by a current tap. This is why Nick et al bang on about breadboarding stuff so you can hear what it actually sounds like, and can then change things around to see if there's any difference, and if so is it better or worse or just different.
That's the beauty of 'tuning' the voltage with the first (small) cap before the first choke. The bits you have a perfect for an excellent PSU - go with Nick's suggestion. For rectifier, use GZ34, though you could use others a GZ34 would be perfect. You have a 5volt winding for a rectifier?
Erm, how are you lighting up your 2A3s? Hammond heater trafos? If so, mount them underneath the top late as close to the 2A3s as fits. Keeping the leads short stops hum. In my 2A3 SE amps I just haven't needed a humbucker pot across the 2A3 heaters with the hammonds close to the valves.
And .... sorry to be a pedant.
I really like 417s - they are so neat! But some people get them to produce all sorts of high frequency instability. Keep leads short on the components you solder direct to the valve socket. You may need a grid stopper (1k) on the grid. Tie all the internal conections marked to each other on the socket too (Grid=pin 4,5,7 & . This often helps.
Hi
Nick/Simon/Andrew
Thanks for the ideas when I say best PSU
I sort of meant quiet but with a view on better later on in the build
Yes 2a3 heater Trans the mains TX, I have is this one the B+ is 270-0-0270 but I'm unsure which way round the connection to the valve rec is on the b+ side can anyone confirm on this rec heater is pin 18/19
thanks
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Well, 60ma through 160R is only 10v, you have about 50 to burn, so if you use a rect with a drop of 30v at 140ma that leaves you another 10 or so to loose in the first choke, sa as Andrew said, a gz34 would fit right in.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
colin.hepburn wrote:I'm unsure which way round the connection to the valve rec is on the b+ side
what i meant by this is to which pin on the TX is the top of the B+ winding or does this matter to the rec valve plus should the 2a3 be ran at 60mA or less what would be the better current to run it at see 2a3 schematic top post
. This often helps. 
plus should the 2a3 be ran at 60mA or less what would be the better current to run it at see 2a3 schematic top post