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Active filter board GB

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quickshift

Member
Joined 2005
It looks we are almost at the magic 100 filter boards and very close to 100 PSU boards :)

I think we should leave the group buy open for maybe another week to try to make it to 100 boards of each type before ordering.

I don't mind getting extra boards to make it up to 100 and 100, I'll just hang onto them because I'm sure someone will want some after the buy is closed.

How does that sound?
 
rob3262

rob3262

Member
Joined 2005
Re: suitable PS

Sorry Rob, the board is set up to require a split supply.
Click to expand...

If they are old linear pwr supplies you can open the bricks and re-use the transformers. :smash:

If they are SMPS then you're SOL. :D
Click to expand...

Thanks Bob & Troy

OK, filter requires split supply. I popped open a brick, switch mode :mad:

But the PS looks sophisticated, there's gotta be some use for it. So I did a quick search and found myself over at Rod Elliots ESP site, where he has posted Project 43.

I wasn't thinking of going the voltage divider route, but it's real simple to implement. The Dual Op amp supply would be easy enough, just a touch added complexity to the project.

What say the community - Divider network is sufficient, or the fiter requires better regulation? Regarding Rod's Op Amp buffered supply, would current limits be adequate for 2-3 filter boards (24v 1.7A input)? I have a half dozen of these bricks and wouldn't mind using them for something other than occupying space...

- Rob
 

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BobEllis

BobEllis

Member
Joined 2003
The bricks would be up to it, but the virtual ground might not. The ground opamp may need a booster (another dual opamp or emitter follower stage). Sure, not a lot of current SHOULD flow to ground and the rails should have balanced currents, but if something goes funny, you could toast everything.

I'm just a little leery of virtual grounds for a high quality application with no real reason. PSU 2.2 can be built (including transformer) for around $50...
 
M

music2diy4

Member
Joined 2008
Thanks Bob,

Board cost is very reasonable.:D

I wish I had run across this group buy last April. I had put together an active 24 dB 2 way Linkwitz crossover with a notchfilter on the upper end, but due to time constraints and ignorance of this project availability, I ended up making do with some Rat Shack perf boards. - oh well.
 
rob3262

rob3262

Member
Joined 2005

I'm just a little leery of virtual grounds for a high quality application with no real reason. PSU 2.2 can be built (including transformer) for around $50...
Click to expand...

Agreed, no need to.. I'm in for 3 pcb's
At 100 pieces or so it is ~$5. Add a bit for shipping to the organizer and final shipping packing material costs.
Click to expand...

All the more reason. They're practically being given away :D

I suppose I should get some extra PSU 2.2 for the front end boards of the Jens Rasmussen Leach clone group buy ?

From the Leach clone group buy -
Originally posted by BobEllisYep it's frustrating having to wait for parts. It seems OnSemi only runs them once or twice a year. Back when I was trying to kit the PSU 2.2 it was really hard to find MJE1503x at any price.
Click to expand...

Bob, would there possible be parts availablity issues for PSU components? Substitutions maybe?

Thanks & regards,
Rob
 
BobEllis

BobEllis

Member
Joined 2003
Generally there is no problem getting the parts - they were chosen for general availability. Everything can be ordered from Mouser and Digikey. I think some of the parts may have been "obsoleted" - read: RoHS compliant substitutes are available.

EDIT: Don't sweat the parts substitutions. For the resistors and caps anthing that will fit should work. For lower voltages any of the BC5xx group would be fine, you could even go to the old standby MPSA42/92 if you are willing to give up a little bit of performance and remember to turn them 180 degrees from the silkscreen orientation. MPSA or other higher voltage transistors are required if you are trying to go much over 30V. /Edit

In the course of the group buys, Mouser was out of stock on the BC546/556 just after I started the buy, and I had to buy 10,000 of each. Then there was a dry spell of MJE1503x - probably there was some large commercial use keeping the distriutor market empty. I haven't noticed much of a shortage of them since, although the MJL4281 now seems a little scarce.

I've built a 65V regulator on PSU 2.2 boards, but haven't had the time to try it with either my Leach amps or A75s.
 
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