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A Very Compact Hybrid Amp - Page 12

post #166 of 2203
2/6/09 at 2:15am
Thread Starter 
Quote:
Originally Posted by holland View Post
I couldn't resist. My hat's in the ring too.

20mA before falling out of class A? What are the clipping points into low-Z?
The buffers can get to about 2V of the rails so 20Vpp. For low Z phones they will be limited by the current sourcing capacity of the PS. This is because the rail splitter is just like the buffers and it can do everything that the buffers can do.
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post #167 of 2203
2/6/09 at 2:42am
alittle more searching

553-WAU24-1000

AC/AC Adapters 120 to 24VAC 1.0A Wall Plug-Ins
They have 2.1mm ends unregulated but not stocked.. nvmd
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post #168 of 2203
2/6/09 at 2:56am
Quote:
Originally Posted by keyid View Post
But theres no end plugs.
http://www.mouser.com/catalog/637/1948.pdf
there is two tabs for the power wire. Im thinking of permanently attaching the adapter to the amp.
Argh,

you're right - the previous (more expensive) ones I looked at had the 2.5mm plugs...

This is what we need:

http://cgi.ebay.com/BRAND-NEW-24V-1A...3A1%7C294%3A50

Maybe they are more ubiquitous, there are a billion on Fleabay... so this may not be so big a deal
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post #169 of 2203
2/6/09 at 4:05am
^ That one is DC. You need AC.
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post #170 of 2203
2/6/09 at 8:52am

Glad this came up, wanted to mention fuses w/this

OK a few things to think about here:
  • What does the amp draw? forsakenrider can measure the draw with higher-draw heated tube, easy way is to pull the fuse & use DMM able to measure up to 2A across its leads. Want initial peak draw & continuous draw readings. W/12.6V/300ma heated tube mine drew about 0.7A.
  • Plug diameter - I ordered a couple PCB mounted A/C jacks from Mouser & got lucky one matched my adapter... If a RadioShack/The Source/Etc is around you could go there to find a matching plug & solder it in. It's A/C so polarity doesn't matter.
  • Fuse rating - Thinking the draw w/max heater could be darn near 1A so picked a 1.5A sloblo. This was because I shorted my adapter, opened it up & found a 2A fuse in this 1A adapter. Probably should test/try to lower the fuse rating to 1.25A & perhaps not sloblo to assure it goes before any in your A/C adapter does. This only when you short something by mistake OR bad build error like wrong orientation on PS diodes.

I just scanned ebay & picked up a pair for like $30 shipped... Then I found this 0.8A one at home & used it. But if I move up to higher draw heated tube I'll use one of my 1A 24VAC ones (the one that now has an external fuse that I installed Best to stick with 1A min I think.

One note searching ebay for 24VAC adapter gets a few & always gets the Surveillance type ones that have no cord... You could add your own w/plug that works for your PCB mounted jack.... Or go to RS, etc & get plug that matches & solder/heatshrink onto the adapter you find...
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post #171 of 2203
2/6/09 at 10:01am
Is it possible to figure out a BOM with a SMPS from the least number of vendors to decrease shipping? (Or alternatively would Glassjar audio be able to put something together?) Or would we need 2 rounds of prototypers first?
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post #172 of 2203
2/6/09 at 11:41am
Quote:
Originally Posted by m0b1liz3 View Post
Is it possible to figure out a BOM with a SMPS from the least number of vendors to decrease shipping?
I have had a look at the BoM and it lists two suppliers, Mouser and Digikey.
You should be able to get away without ordering from Digikey however.

The L1H choke looks like it is available from Mouser, Part No 542-70F336-RC 70F336AI-RC

The L2H choke and LM2595 Reg can be ordered locally through RS Components.
L2H Part No 617-1316 Wurth Elektronik | Passives | EMC, RFI and Surge Protection | Inductor Through Hole | Inductors: Suppression
LM2595 Part No 533-3664P National Semiconductor | Semiconductors | Power Supply and Control | Variable Switching Regulators | Adjustable Voltage Switching Regulators
RS do not have these in Australia but list a 6-8 working day delivery time and if you can pick up locally then there is no delivery charge, if not there delivery charge should be a lot cheaper than Digikeys international shipping.

The 24V AC 1amp power supply is available locally from Altronics, Part No M9379. This has a cable but no plug, but they have those as well.

This should just leave the Tubes and socket(apart form the board of course).
Most Tube vendors also sell sockets. Parts ConneXion & vacuumtubes.net both have cheap shipping options from memory but there are plenty more Tube suppliers to try and most are happy to quote you on shipping if you ask.

Hopefully runeight or cfcubed can confirm the linked parts are correct, if not confirm for yourself.
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post #173 of 2203
2/6/09 at 11:45am
Quote:
Originally Posted by wiatrob View Post
507-XR-2440LED
Should work. It looks like it's the only one (that's not 'medical grade' - that's optional for the power cord crew!
Yes, those Amseco adapters are the type w/o a wire (see here for pics). But no biggie just add one & pick a plug that matches the PCB jack(s?) you order (order a couple? Goto RS & peruse their plug collection?)

$11 USD is a darn good price I think for a 24VAC 1A+ adapter esp if combined w/the rest of your order (maybe we should spec a couple in BoM)...
Going > 1A (or > 24VA ) is OK just means overly large adapter size.

> Is it possible to figure out a BOM with a SMPS...

Think jaycar(?) has a straight lead LM2595 you could just bend leads to fit.... Yes, perhaps when production PCBs are around runeight or someone could pursue bundling options (at least enough to build this w/one Mouser order).

> Edit: Thanks Forte for more sources! Hopefully runeight or cfcubed can confirm the linked parts are correct,

Those parts look fine to me... We are looking for 2uH -> 4uH, 800ma min rated L1H and 220uH toroid 800ma min rated L2H that fits. Later I'll post closeup pics of top 1/2 & bottom 1/2 of completed PCB so you can see there is a fair amount of clearance for them...
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post #174 of 2203
2/6/09 at 11:54am
Still working through the Mouser side of the BoM and want to check a couple of things.

The D1L & D1R Amp diodes list 610-1N5305 followed by the comment
Quote:
1.8ma 1N5304 or 2.2ma 1N5306 low cost alts?
Has it been confirmed yet if these will work?

Also noticed most of the caps are rated at 85 degrees. Would it be worth finding 105 degree rated caps, especially for those near the 24V & LM2595 regs?
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post #175 of 2203
2/6/09 at 11:58am
Thread Starter 
We originally thought that those diodes would work, but I meant to take that option out of the BoM. Please use the one specified.
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post #176 of 2203
2/6/09 at 11:59am
Quote:
Originally Posted by Forte View Post
The D1L & D1R Amp diodes list 610-1N5305 followed by the comment
Has it been confirmed yet if these will work?
I've got to go now... They will work (using 1.8ma myself), but it's only $5 extra to use the right ones as runeight just said I got burned using non-BoM BCs, so best if you follow BoM / runeight speced parts...

Quote:
Originally Posted by Forte View Post
Also noticed most of the caps are rated at 85 degrees. Would it be worth finding 105 degree rated caps, especially for those near the 24V & LM2595 regs?
Anything > 85c might be too big. We are quite tight on space here (both diameter & height in some cases), best to stick to BoM parts if possible... Or same type, value, rating & size...
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post #177 of 2203
2/6/09 at 12:00pm
Thread Starter 
Oh, the caps. I don't think that 105d caps are necessary. And they probably won't fit. But, you can always use them if you can squeeze them in.
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post #178 of 2203
2/6/09 at 1:14pm
Thread Starter 
Boards have shipped to those interested. There are two left if anyone wants one. If not, some of the current proto group have asked for more than one.

Let me know soon . . .
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post #179 of 2203
2/6/09 at 4:16pm
Quote:
Originally Posted by runeight View Post
Boards have shipped to those interested. ...

Thanks Runeight! Looking forward to this one...
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post #180 of 2203
2/6/09 at 8:52pm
Quote:
Originally Posted by runeight View Post
Boards have shipped to those interested. There are two left if anyone wants one. <snip>
Sure you want to wait till the next batch

Here's top-half & bottom-half pics I was threatening to post... New BoM changes maybe 6-8 resistors & uses smaller diameter C5P & C10P caps.





Little purple annotations are clues to which TO92s go where, but runeight's BoM + silkscreen PDF are what you'll want to have handy.
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