Scalable PSU/regulator GB

[dick van nierop]

I suppose the transformer is 110 V primary?

[dick van nierop]

KRO

You wrote you had some transformers ?
Do you have any spare ones you can miss?
Or do you have a good and cheap address in the south of the Netherlands?

Thanks for answering,
Dick.

[BobEllis]

Dick,

The transformer has two 110V primaries, so you in 220 land can wire them in series, while we choose parallel.

Shipping could be expensive, though. There is no USPS flat rate international box that I've been able to find. THere is one for US domestic use that will hold several. While a couple would fit in the Flate Rate GPM envelope, that doesn't seem like the smartest thing to do if you want it to actually arrive.

[BobEllis]

I was asked in the OPA2134 buy thread if I would consolidate orders for overseas shipments for opamps, PSU boards/kits, etc. and filter boards.

For those who would like to consolidate their orders for opamps, filter boards, heat sinks and psu boards/kits into one package, let me know. I will calculate postage and let you know what total shipping costs will be. There is a risk that it will be higher than a few smaller flat rate envelopes. I will NOT ship transformers in an envelope.

Within the US there is the flat rate box for around $8.50 (check the website), so you might save a little.

I have all paid filter boards wrapped and in envelopes waiting shipping labels/postage. Unless I hear from you by noon EST (GMT-5) Sunday March 26th that you want me to hold your order, I will ship it Monday.

Filter board GB round 2 is open...

[dick van nierop]

Hi Bob,

No, I think you're right.
I'll get the transformers over here.

Thanks,
Dick.

[BobEllis]

I received the prototype boards today. They are on the way to Jens for testing. Minus silkscreen and soldermask they aren't pretty. Full up prototypes would have cost $400+, these only cost $75 for 5.

I'll build up one and verify that it works, but other than sticking my scope on the output, I cannot properly test it.

[rick57]

If you are doing a 3 way, with 2 active filter boards per side, ie 4 boards, how many PSU/ regulator boards are needed?
(Dumb question) if all in one box, just one? ~

And Bob,
you referred to Jens' documentation as more helpful than Don Lancaster’s book (which I have, it’s ok) – can we see this documentation, to start to get our head around it better?

Thanks

[BobEllis]

One PSU can deliver over an amp with the heat sinks available on the WIKI. Four filter boards fully stuffed will draw about 320 mA. With a 15V transformer (-> ~20.4 VDC), and 1 ohm in the CRC, the pass devices will drop about 5V, dissipating 1.5W. The pass devices must have heat sinks over 1W. While they don't need the ones gengis is offering, for ~$.50 more than adequate heat sinks, why not go large?

Many will suggest that you go dual mono, use one PSU per channel, all the way back to two transformers. A compromise would be share a transformer but use separate regulators. There is likely to be little if any communication between channels back through the regulators.

Jens' documentation is on his website www.delta-audio.com look under kits and modules, then active filters. These boards are similar in topology to a pair of active filter twos strung together. There aren't as many jumpers, but it gives you an idea about the basic filter design.

I find Jens' approach to the math more user friendly when you just want to design a filter - especially if your goal falls between Lancaster's recipes. I could never work through Lancaster far enough to come up with a spreadsheet, but was able to with Jens' guide.

See Jens' active filter one for notch and peak EQ.

I'm expanding on the possibilities with the input buffer, adding the Linkwitz transform and all pass sections. I will also discuss Cauer-Elliptic filters and show a couple of design examples. I have a couple of long airport layovers the next few days, I might just get the thing done.

[rick57]

Thanks Bob, active filter One or Two?

(So Jens is Delta Audio)

Cheers

[BobEllis]

filter two for the equal component Sallen Key equations, Filter one for EQ.