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Old 30th May 2011, 04:31 PM   #1
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Default Resistors for a Chip Amp

Hi Guys,

I'm a new member as of to-day! What a great resource the group is!

I've joined the thousands who can't be wrong and am building a Chip Amp using PCBs from Brian Bell. I didn't buy completed kits as I didn't see any point in having components that I could buy in the UK flown across the Atlantic. That decision is causing me some problems as I hadn't realised to what extent Brian had downsized the boards. I now can't find a source for quality resistors that are small eneough to fit the 5mm lead spacing. Could any members tell me what make of resistor Brian supplies in his kits and a UK or European supply source for them? I don't want to have to stand larger resistors up on end as it looks bad and results in longer leads than need be.

Apologies if this has been answered before but a search found nothing.

Thanks guys.
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Old 31st May 2011, 09:06 PM   #2
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What if you contact Brian and nicely plead with him to send you the resistors? Postage for an envelope with them in it shouldn't be too pricey compared to the aggravation of hunting some down and still having to drive there or pay shipping locally.

You do realize that you don't have to use 0.5W resistors, yes? 1/4W would work fine too, except of course they can't replace the 2 x 2.7 Ohm on the output.

Hmm, it seems that a domain squatter has acquired (or I was redirected to it because the domain name expired), Brian's personal 'site with the amp gallery pictures so the wrong site loads at the URL briangt.com... I'd link it but there is no point since it doesn't go where it should.

Last edited by !; 31st May 2011 at 09:09 PM.
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Old 31st May 2011, 10:35 PM   #3
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Buy a development kit of quarter watt 1% resistors off ebay from a UK supplier. Stand them up on end, lots of miniaturized radios were built that way in the past, the extra bit of lead will make no difference at audio frequencies. Handsome is as handsome does.

you'll get 1000 delivered for 10, and you'll have the surplus to start off your junk-box (laboratory stores).

w
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Old 31st May 2011, 10:57 PM   #4
jemraid is offline jemraid  United Kingdom
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Hello Levi,

I've just ordered a load of bits to make Brian's LM1875 kit, I got the boards from him and ordered the bits from Cricklewood Electronics Cricklewood Electronics - CCTV. CCTV Equipment. CCTV Systems. Digital CCTV Cameras good company because they do sell one offs of lots of things you don't have to buy 10 of everything, like some of the large companies.

e.g. They sell 1/4 Watt 1% resistors 10 for 50p.

Rgds - Jim
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Old 31st May 2011, 11:06 PM   #5
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Old 1st June 2011, 12:22 AM   #6
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Default Just do it this way...

mount normal resistor vertically, I've used 1/2 watt resistors...
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Old 1st June 2011, 12:25 AM   #7
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Quote:
Originally Posted by wakibaki View Post
Buy a development kit of quarter watt 1% resistors off ebay from a UK supplier. Stand them up on end, lots of miniaturized radios were built that way in the past, the extra bit of lead will make no difference at audio frequencies. Handsome is as handsome does.

you'll get 1000 delivered for 10, and you'll have the surplus to start off your junk-box (laboratory stores).

w
Previously I was implying that since 1/4W resistors tend to be smaller than 1/2W, the OP might find some 1/4W short enough that they don't need to be tombstoned (up on end), or if they are a tight fit, a tiny bit of bending at the ends might still allow them to sit horizontal on the board even if a little nub of each lead remains.

I have also built things with vertical resistors and they sounded ok, but the theory and hype is that not doing it makes for a shorter signal path and less little *antennas* to pick up radio waves within the feedback loop, not only by decreasing the lead length but keeping it closer to the ground plane (assuming, since I don't remember for sure, that his kit PCB has a ground plane on the back...).

Last edited by !; 1st June 2011 at 12:41 AM.
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Old 1st June 2011, 01:00 PM   #8
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These will fit fine, I used them in my p2p LM3886 http://docs-asia.electrocomponents.c...6b80382001.pdf I got mine at RS australia, but it doesn't look like they have them at RS UK unfortunately.

however these (assuming that the values are the same as in my LM3886 which I based on Brians Schematic) might fit the bill
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Old 1st June 2011, 02:45 PM   #9
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I just got the bits for my LM1875 build, what I will do is solder the chip in place and then bend the legs to accommodate the FB resistor, with the shortest leads I can get with both of them and then bend them down to the ground plane.

Jim
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Old 1st June 2011, 02:51 PM   #10
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When you over bend resistor leads you stress the end cap where the actual connection is made and some resistors will become noisy as a result. The miniature Panasonic metal film resistors will fit.
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