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Old 13th December 2003, 03:32 PM   #1
Morse is offline Morse  United States
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Default Can I use 22 or 26ga wire here?

Hi everyone and thanks in advance for your help and suggestions!

I'm in the process of building a 2 channel TDA2030 portable amp, and have two issues to resolve before proceeding. First off, it's my understanding that lead lengths from the filter caps must be kept short; to facilitate this, I laid out the chassis so that the filter caps and FR diodes I used are between the 2 chips (which use the chassis floor as a heat sink).

How small of a wire gauge can I use for the power leads to the TDA2030's and how small a wire gauge can I use from the chips to the speaker terminals? Usually on my valve amps I use some pretty beefy stuff, but here the dimensions and fragility of the chip leads are working against me.

Can I use 22ga solid core wire? 26 ga solid core wire? Or would there be either an audible degradation or a problem with excessive current through a 2 to 4 cm length?

Now, the second question. Testing the PS last night and this morning indicates +/-18.2 to 18.6VDC whereas the TDA2030 lists Vmax at +/-18V. Is that too much overvoltage or is there some "slop" in solid state devices like this? On valves, I wouldn't give a second thought to being over Vmax by rather more than this.....

Sorry for the dumb questions.....but I usually use valves with an internal bus without worrying about lead length and this is a BIG departure from past practice.

Thanks again and all the best,
Morse
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Old 14th December 2003, 05:52 AM   #2
ofb is offline ofb
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hey morse, i don't know an aspen from a pole in the ground but if i post my inexperienced opinion then maybe that'll aggravate our more learned into answering you.

1. go ahead and try the 22 ga. i don't think you'll find it too beefy if you use a good iron and a light touch. try to get some aligator clips in there as heatsinks. you should be careful but i think maybe you're letting yourself get too intimidated by how small the stuff looks. on my first amp i did a SMS AD8620 adaptor like sijosae's third example and i got away with that fine.

http://www.headphoneamp.co.kr/bbs/vi...desc=asc&no=52

2. good question. i'm having a conversation about this elsewhere re the lm3875. eeehaah has been running his out at the edge with just a shutdown issue at high volume. sounds like national does have a little slop past the published max.

i don't crank my music, so i'm about to try the same in order to use a tranny i have on hand. i plan on using generous heatsinks and crossing my fingers. check your TDA2030 datasheet to see what it has for a protection circuit to ensure you won't damage anything if you decide to try it.

probably a thing to think about is how stable is your house supply? if your power company isn't too great on that, they may bump you into the red more than you like.
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Old 14th December 2003, 01:26 PM   #3
Morse is offline Morse  United States
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Thanks OFB;

My GOD, that link has pics of some incredible soldering work!! It makes me feel like a dinosaur, comparing my usual valve stuff to that.....

Hmmm, I did try 22ga wire with 26ga for the signal carrying leads, so you're right, it can be done. Unfortunately my first effort was a flop (15VDC on the output leads - DOH!). Fortunately I only paid $1.85 each on the TDA's (and I only risked on of 'em on my first try) so we'll see what happens on attempt number 2 (there was a REAL error on my part - I'd omitted the resistor from pin 2 to ground - BIG DOH!!!).

First time I've made a mistake like that in a LONG time......so I was overdue for a foulup.

You're absolutely right about power company fluctuations. Perhaps I will pull out a LM4766 and try it instead, since it's got more "overhead" on it's Vmax and there's no point in toasting chips; this is a "project on the cheap" using a PS trafo I had on hand, etc. Here the AC mains have hit a routine low of 113VAC and a routine high of 128VAC. For my good valve gear I run it through a DIY power filter w/ autotransformer and adjust it in 6 volt increments to be as close to 115VAC as possible. Would that I could afford an automatically regulated AC power supply....

Thanks again for the input. I'll keep everyone posted on how it goes.
All the best,
Morse
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Old 14th December 2003, 01:39 PM   #4
ronc is offline ronc  United States
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Default ^ Why i.......

use batteries.
ron
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Old 14th December 2003, 06:19 PM   #5
Morse is offline Morse  United States
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Hi Ron;

I'd love to use batteries in the future, but for this particular application, AC mains are (unfortunately) called for.

That said, how many amp hours would you recommend for a gel cell that's appropriate for running a 20wpc gainclone and efficient fullrangers? Or could I just use 6V lantern batteries in series and get enough life out of 'em that recharging is not really necessary? Just use and toss....

Thanks in advance for any information!
All the best,
Morse
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Old 14th December 2003, 06:32 PM   #6
ronc is offline ronc  United States
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I have gone to 12V 7.2 amp/hr gel cells(5 total, 1 for the pre) and i leave the amp on 24/7.I have a charging system comprised of relays, timer and 1.5 amp trickle chargers that is a plug in and forget system. except when the power goes out and i have to reset the timer.I set the charging cycle from 2AM to 5AM, it charges every night.
ron
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Old 14th December 2003, 07:20 PM   #7
ofb is offline ofb
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Quote:
My GOD, that link has pics of some incredible soldering work!!
yeah, sijosae does some great fun. click around the links there. stuff like a headamp in a hollowed out 9v batt; just clip it to another 9v and away you go. wish i could read korean.
http://www.headphoneamp.co.kr/bbs/zb...id=diy_sijosae

sijosae is a very nice chap who sometimes posts to headwise. iirc he teaches electronics and a lot of these projects are teaching aids to demonstrate the circuits.

Quote:
Or could I just use 6V lantern batteries...
imho, do as ron suggests. he's well through the learning curve and between web reading and my experience rigging non-audio battery stuff in the past, lantern batts are a bit of a waste of time and wasteful generally.

i'm only going with trans because i want to play with that first (this is a new hobby, dig?) and i've got out-of-date misgivings about having a trickle charger running big cells while i sleep. but truth is we've been using the stuff in emergency lights and computer apu's for decades without trouble. very likely i'll follow ron after i do a few tranny psu's.

here's a few links to get you thinking. in my cowtown the local lighting outfits tend to gouge for emergency light batteries unless you know someone behind the counter. dig around your area and see if you have better luck.

http://www.batterymart.com/battery.mv?p=SLA-12V7-F2
http://www.batterymart.com/battery.mv?p=ACC-12BC0500D-1
http://www.batterymart.com/battery.mv?p=ACC-BATMAT
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Old 15th December 2003, 04:03 AM   #8
Morse is offline Morse  United States
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Hi Ron;

Thanks for the information on battery powering my projects. After this afternoon's fiasco (long story), I'm pretty well decided to follow your lead, at least for my solid state projects after this one. On this one, I will make it work if for no other reason than sheer obstinance!

Hi OFB;

WOW! Thanks for the links! Between you and Ron, you've made believers of me on the viability of battery power on this.....

Thanks again guys and all the best!
Morse
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Old 19th December 2003, 05:56 PM   #9
ronc is offline ronc  United States
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Default "he's well through the learning curve"

And what a lumpy curve it was!
ron
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