A less used approach

[SuppersReady]

I looking for a bit more detail on external PSUs for power amps. It was raised in this thread,

http://www.diyaudio.com/forums/showthread.php?s=&threadid=3493&perpage=15&highlight=remote%20AND%20power%20AND%20supply&pagenumber=1

but the thread then drifted off topic. GRollins and Fred Dieckmann both mentioned using extra capacitance in the amp enclosure.

Does this extra capacitance need to be a significant percentage of the overall capacitance? My aim is to use 26000uF caps in a C-C-L-C-C on each rail, where L=2-3mH. Could I simply move the last cap to the seperate enclosure? (I have the caps already, and am looking for a UK outlet for the chokes)

My other option would be to get an amount of smaller caps - 1000uF or thereabouts - and use those in addition to the existing caps.

All help will be gratefully accepted!!! Please!!!

Cheers

Paul

 

[tiroth]

Probaby half or more should be close by the amp. Reason: you need enough C by the rectifiers to absorb the spike (otherwise EMI probs and ohmic losses), but after that you ideally want to lower the impedance of the supply, which means keep the capacitance close to the circuit.

 

[SuppersReady]

What spike?

 

[eLarson]

The spikes he refers to ride on the voltage
rail and are due to the rectification of the
AC mains.

A nice article about power supplies can be
found here:

http://www.tnt-audio.com/clinica/ssps1_e.html

It may go a long way toward answering
your questions.

Best,
Erik

 

[Nelson Pass]

Ideally we keep the transformers and first bank of
caps a few feet away, and then have another bank
of caps locally at the circuit. (This for Monos only...)

This also provides a nice opportunity to insert and R or
L to make a pi filter and take out some ripple.

 

[SuppersReady]

eLarson,

Thanks for that link, just downloaded and printed. I'll read that asap.

Nelson,

Do I take it that the chokes or resistors are in the transformer box or the amp box?

Everybody,

Thanks for your input.

Cheers

Paul

-------------------
Every step is one step closer to the prize.

 

[eLarson]

If the goal is to get the power feed to the
amplifier box as clean as possible, I reckon I'd
put the bulk of the caps (with the choke
between the banks to make a pi filter) in the
PS box.

In the amplifier box I suppose I would put a
good sized cap (2200 or so) near the front end
circuitry, then one near each output device for
some "localized power delivery." (Honestly I'm
not sure how much that would really help, I've
never tried it with anything other than a
lineamp. YMMV)

Another thing to keep in mind is how to deliver
the power from the PS box to the amp box.
Allied with that concern is how to ground
everything. Keep the grounds for the lower
current front end circuits separate from those
for the output stage. I'm thinking the main
ground should be back at the PS box and the
others should connect to that one way or
another.

You may end up with an umbilical that looks
almost like an undersea cable by the time
everything is said and done!

Good luck with it,
Erik

 

[SuppersReady]

YMMV?

 

[nemestra]

YMMV

Your Milage May Vary

James

 

[SuppersReady]

Many thanks!!

Paul

 

[SuppersReady]

Suitable?

Following on from the original question of this thread, I have found a local (well, it's in the UK at least) source. http://www.audiocom-uk.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=A&Product_Code=AirCoreCU1.4

Would these be suitable for the PSU described earlier? The resistance seems higher than some of the American sourced chokes of similar guage. The transformer (one per channel) will be a 500VA device (ILP, I believe)

Cheers

Paul

 

[SuppersReady]

Oops!

Or you could try this.

www.audiocom-uk.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=A&Product_Code=AirCoreCU1.4

Better luck this time

Paul

 

[uli]

Re: Oops!

Or you could try this.

www.audiocom-uk.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=A&Product_Code=AirCoreCU1.4

Better luck this time

Paul

Hi Pauil,
IMHO these are Xover inductors!
I wouldn´t use them in a high DC-Current Powersupply!
You may take a look at www.rs-components.com

C-R-C-C is what I use 3 times 22mF with a 0R22/25W Resistor
for Aleph2 -kind amps.

Uli

 

[SuppersReady]

IMHO these are Xover inductors!

So are the inductors from Zalytron as I understand, yet I have seen these recommended regularly on this forum for PSU use. Hence my interest in these parts.

Have checked wire guage since, they don't seem much of a bargain anymore. Are there any more realistic UK sources out there? Net searches don't seem to produce many useable results.

Paul

 

[SuppersReady]

I've never used inductors in my PSUs before hence my caution in selecting them. This inductor appears to give a good balance of price/DCR/wire guage. Shipping shouldn't be too bad from Europe.

?http://www.intertechnik.de/cgi-local/shop4/shop4_erg.pl?0&&Elektronikbauteile&&Spulen&&Rollenkernspulen&&none&&29

Article number:1340266

My question: Will these inductors be up the task if used in the PSU outlined at the beginning of this thread?

Help on this will be greatly appreciated!

Cheers

Paul

 

[uli]

DC-current

Hi Paul,
normally those inductors (especially with some metallic core)
are NOT intended for use with heavy DC-current flowing thru
that device. But exactly this are you doing in a PSU. You can
build them on your own ore look for Switch mode PSU
inductors. www.hammondmfg.com/195.htm is a source for what you´re looking for...

Uli

 

[jan.didden]

less used

Hi Paul,

You may have already decided how to do it, but for a C-L-C I would put all C after the L in the amp box. That way you have short wires to the load so the caps can source the best they can. The cabling between the amp and supply becomes part of the L, which will make the influence of the cable very small. The spikes and other junk filtered out by the L will actually appear across the L, so you want to keep that out of the amp box. Lastly, the first C will be close to the rectifiers so rectifier noise will be less likely to propagate throughout the system.

Jan Didden

 

[Nelson Pass]

It seems to me that putting some of the 2nd "C"
in the psu box will have at least one benefit, which
is that interupting the circuit won't generate a big
spike.

pass/ - getting sleepy after many posts, glasses of wine,
lounge music CD's

 

[SuppersReady]

Thanks everybody,

Finally ordered the inductors after emailing wuffwaff who has used the same type without problems reported. Chose the Intertechnik luftspullen, 3.3mH. The DCR is high but since I'm using a 30-0-30 trafo I can lose a volt or two anyway.

Jan and NP, food for thought. Positioning of the caps re:spikes was not something I was aware of. Reading back through threads, some people argue for a small capacitance before choke followed by larger capacitance. This suggests that C-L-C-------C-C would offer the 'best' compromise.

Any thoughts?

Cheers

Paul