Another PSU question.....

[hobgob_inc]

Hey all.

I'm quite sure i need to re think my PSU a bit. What I'm running at the moment was supposed to be temporary but I'm just loving tweaking so can't be bothered changing anything.
Currently i'm running both the Cgs power supply boards hanging off one 1.3A "wall wart" supply. I'm powering-
Cgs VCOx2
Cgs Steiner VCF
EFM ADSR/LFO
home made splitters
Cgs Sub oscillator
Cgs Wave multiplier
EFM dual VCA
Cgs Dc Mixer
Cgs Gate sequencer
Cgs Burst Generator
Cgs psycho lfo

I have been to scared to try my cgs tube VCA on top of all this due to its large current draw. Would anyone know roughly how much current these modules draw and where i could find a suitable transformer, as i can't seem to find what i need...

Also, I had an idea that you are supposed to have a power supply which can supply twice the current that you actually need, to allow for transient current etc. Can anyone confirm this??

Thanks heaps, Luke

[hobgob_inc]

Ok i admit that was a shitty question.....

I think i'm just gunna aim to get a 2-2.5 amp torroid. Should be enough. Can anyone advise if i should use several smaller transformers and PSU circuits or just go for the one big tranny?

Cheers,

Luke

[andrewF]

Do you mean the CGS27 tube VCA? indeed the tube heater for that sucks 300mA, about as much as 8 regular modules. The newer CGS65 tube VCA is much less thirsty (~13mA), no need to worry

I have all kinds of power supplies running, 1A transformers with CGS14 PSU and 3A transformers driving three 1A CGS PSUs. really the CGS14 PSUs are close to max at 800mA - and if going to such lengths, best to attach the regulators to big heavy heatsinks off the board (tho as close as u can to keep the wires short).

What is best avoided is trying to build say a 3A or 5A PSU, look around the net and you will see very few people do it cos it is a PITA.....and when it blows it BLOWS! (this is from experience)

Looking at your list of modules and assuming the new tube VCA, 1.3A PSU should be fine.

[hobgob_inc]

Hey Andrew

Thanks for coming to my aid..... Yeah i am talking about cgs27 tube which is why i've been a bit scared thus far. All the modules listed are running great on the 1.3A transformer, so i'm thinking i'll try a 2-2.5A tranny with both the cgs PSU boards hanging off it and this should hopefully give me a enough for the tube.

This is the impression i was under in terms of sticking to lower amp supplies and having a couple of them...but sorry what is a PITA???

Thanks a lot.

Luke

[andrewF]

PITA - pain in the arse

you're in geek territory now

If you get a new transformer and it has a 5, 6 or 6.3V connection, you could hook this up directly to the tube heater. No need to convert it to DC, caps, regulators or anything.
Many tube hifi amps have 6.3V AC heating the tubes (mine does) so long as the wires are twisted together and don't get too close to other components there should be no audible hum.
Most tubes require 6.3V AC or DC, but Eric Barbour has said you can use 5V with no problems.

That being said it is quite simple to whip up a little 5V DC PSU with a diode, 7805 and a couple of caps.

[hobgob_inc]

Yeah i was going to just use a 7805 with a 100n....

Could you explain the way you were referring too?


Luke

[andrewF]

maybe have a look at this page
6CM5 tube amp
You can see on the schematic the 6.3 v heater connections are coming straight off the transformer.
Just under the schematic is a diagram on how to connect the heater wiring (the right/wrong pix)

btw this is an excellent tube amp and the output transformers are available from Altronics (oz company) for ~$12 each, much cheaper than $150 for regular old Hammonds.

[hobgob_inc]

hey andrew. yeah thats all good i was mainly referring to how to wire the decoupling caps and diode after the regulator. I think its pretty obvious though anyway.
Speaking to an engineer friend he said that the caps wouldn't really be necessary at all, but i think i'll chuck some in anyway.

Thanks