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Post by Deleted on Jul 31, 2012 10:45:49 GMT
Hi All Taking a break from the busy schedule that life throws up from time to time to confirm Jon’s comments on Alex’s superb amps. I still feel sooo lucky every time I switch on and listen. Yes Jon So details and smooth and natural without a hint of listener fatigue. A very special pair of amps indeed. Stick with it guys I’ll be joining you later when time allows. Take care
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pagan
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Post by pagan on Jul 31, 2012 11:37:11 GMT
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Post by Deleted on Jul 31, 2012 15:26:20 GMT
Hi Shaun, nice to see you'r still enjoying the music So that's X2 Regards, Alan
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Post by Deleted on Aug 2, 2012 18:47:15 GMT
Just an update on my slow progress to the finish line with my SandyK 15W model. First pic, amp fronts-piece in the plain wood just the fixings to go on the back and it'll get a coat of varnish. Second pic, fixings are in place and she hangs good, just needs the three or so coats of varnish. First coat applied still wet looks great........patience just a little patience and this project will be put to bed.
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Post by Deleted on Aug 3, 2012 17:24:30 GMT
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jonclancy
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Post by jonclancy on Aug 3, 2012 19:50:49 GMT
Hi Jon Thanks for the kind words. Are you able to measure the value of small inductors such as used in the Zobel network ? Recently a friend of Geoff's tested an amplifier from Geoff that used my recycled modules and was surprised that the square wave response didn't go a little higher. This was despite decreasing the Zobel network components from the original 6.8uH and 150nF to 4.7uH (approx.) and 100nF. .... Simply halving the number of turns will give more like 2.3uH Hi Alex, I can measure the inductors some time next week. Actually, I did source some eBay enamelled wire on a part reel that is a smaller gauge than I was originally using. There is probably a calculator out there that would allow me to plug in the gauge, air core etc and give me the number of turns to aim for. Ah, found one: www.diyaudioandvideo.com/Calculator/Inductor/It uses inches and mH, but we can work with that!! Cheers Jon
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jonclancy
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Post by jonclancy on Aug 3, 2012 19:53:12 GMT
BTW, that amp is PROPER DIY!
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Post by Deleted on Aug 4, 2012 1:03:09 GMT
MY PRIDE AND JOY
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Post by Deleted on Aug 4, 2012 13:20:22 GMT
Alan, I like the sinewave idea and beautifully finished, BTW how did you acheive the horizontal dark line across the middle? To all, I was thinking of building my own enclosures but cheating with the heatsinks, for which I've been having problems finding. Are these sensibly priced? Taking into account I'll need four and total postage comes to $48 (I asked).
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Post by Deleted on Aug 4, 2012 16:51:01 GMT
Hi Chris, I pondered for ages as to what I could do with the front always like wood so when a bit of skip wood said to me, " hey Alan take me home and put me to good use", I knew just what would suit it. The dark strip is European Walnut the skip wood is a hard wood it could be sapele or one of the Shorea family probably Meranti it has a lovely grain structure. The finish is clear poly however I'm not happy with what I've done as the surface has hundreds of tiny pin holes however I intend to flat it down a bit and then apply a coating of paste wax polish and buff up to a high gloss that should kill the holes. Ah! the sine wave............yes I really like that it's a screen shot of a section of the wave form in Audacity of Norah Jones number "Turn Me On" thought that was quite appropriate, it works for me. MGLW says, " I should be so lucky". The art work is burned into the wood then filled with super glue.
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layums
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Post by layums on Aug 6, 2012 20:28:55 GMT
Nice work, I'm new here, learning the ropes through mikes kits. You had fun with the rivet gun ;-) I hope to reach that level sometime soon.
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Post by gommer on Aug 6, 2012 21:09:13 GMT
Heatsinks are always terribly expensive for some reason. So $29 per piece seems very reasonable to me.
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Post by Deleted on Aug 6, 2012 21:56:12 GMT
Heatsinks are always terribly expensive for some reason. So $29 per piece seems very reasonable to me. Altronics in Australia has the original types at $25 each for 4+ , but P and P from Australia would most likely be quite expensive due to their weight. Alex
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jonclancy
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Post by jonclancy on Aug 6, 2012 22:02:46 GMT
Hi Jon Thanks for the kind words. Are you able to measure the value of small inductors such as used in the Zobel network ? Recently a friend of Geoff's tested an amplifier from Geoff that used my recycled modules and was surprised that the square wave response didn't go a little higher. This was despite decreasing the Zobel network components from the original 6.8uH and 150nF to 4.7uH (approx.) and 100nF. .... Simply halving the number of turns will give more like 2.3uH Hi Alex, I can measure the inductors some time next week. Actually, I did source some eBay enamelled wire on a part reel that is a smaller gauge than I was originally using. There is probably a calculator out there that would allow me to plug in the gauge, air core etc and give me the number of turns to aim for. Ah, found one: www.diyaudioandvideo.com/Calculator/Inductor/It uses inches and mH, but we can work with that!! Cheers Jon OK, in reply to myself, here goes!! First, convert units. www.unitconversion.org/inductance/microhenry-to-millihenry-conversion.html3.3uH is 0.0033mH - got to make that right or it all goes to pot! My part reel of Marshalls Enamelled Copper Wire (2 Oz) is 22 SWG. This converts to 21 AWG as per the table I found here: www.extremeelectronics.co.uk/index.php?page=wireguageThis is for use in the inductor calculator only. BTW, 21 AWG has a diameter of 0.0285 inches, and should wind around 13.8 turns per CM. My gash calcs below are in the ballpark. The inductor bobbins we're using have an external diameter of 13mm and a height of 9.5mm. As 22 SWG wire has a diameter of 0.711mm, so I assume we're going to get around 13 turns per layer - wound by hand as tightly together as we can. Google Says: 13 millimetres = 0.511811024 inches 9.5 millimetres = 0.374015748 inches Chuck that lot into the calculator and you get... ... ... ... Inductor Calculator Inductance 0 mH DC Resistance 0.03 Ohms Wire Gauge 21 AWG Wire Diameter 28.5 mils (1 mil = .001 in) Coil Length 0.37 in Coil Inner Diameter 0.51 in Coil Outer Diameter 0.63 in Average Turn Diameter 0.53 in Wire Length 2.62 feet Copper Weight 0.01 pounds Turns 19 Levels 1.45 Turns/Level 13.12 Sound about right? We'll see tomorrow when I wind one up and stick it on the LCR meter. Stay tuned!!! Jon
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jonclancy
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Post by jonclancy on Aug 6, 2012 22:04:16 GMT
I suppose I could have hunted for a metric calculator, but where's the fun in that?
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Post by Deleted on Aug 6, 2012 22:38:13 GMT
Hi Jon I took a stab at 16 1/2 turns of 1mm wire on that former being just over 3.0uH , so I wound up a couple. I will see how they go when I can get motivated. Kind Regards Alex
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jonclancy
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Post by jonclancy on Aug 7, 2012 21:22:24 GMT
Hi Jon I took a stab at 16 1/2 turns of 1mm wire on that former being just over 3.0uH , so I wound up a couple. I will see how they go when I can get motivated. Kind Regards Alex Hi Alex, I have completed one inductor that measures around 3.1-3.4uH, depending on which way the wind is blowing. That was with nearly two layers of wire = 21 turns and then a couple of turns taken off. So 19 turns is pretty accurate if you use the wire I do. I'll try another in the next day or two to see how near I get to a matched pair!!! Just to remind everyone, you will need to plug your wire gauge into the calculator to get an accurate estimate of winds, or just do a couple more and unwind them as you measure. Does waste a bit of wire though. Cheers Jon
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Post by Deleted on Aug 7, 2012 22:02:27 GMT
Hi Jon I am using 1.0mm enamelled wire from a Jaycar reel, and 16 1/2 turns is almost 2 complete layers on these formers. The original said 25 1/2 turns of 1.0mm wire on these formers for 6.8uH, so it is very surprising that the inductance with around 19T should measure less than half of that.Perhaps the accuracy of your meter is not so good at these very low values ? Kind Regards Alex
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jonclancy
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Post by jonclancy on Aug 8, 2012 22:12:33 GMT
Hi Alex,
I don't really know as I have not used my LCR that much. The 19 or so turns is similar to that predicted by the calculator, though.
The calc says you would need around 18 turns, and for the original it says 24 turns. These are all in the ball-park. But it is surprising, I agree.
Cheers
Jon
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Post by Deleted on Aug 8, 2012 22:44:40 GMT
Hi Jon BTW, the SC (Jaycar) HA specified 21T of .62mm wire on the same former for 4.7uH The 15W Class A specified 24.5T of .8mm for 6.8uH The SC 20W Class A specifies 25.5T of 1mm for 6.8uH I am suggesting that a few less turns of 1mm wire may be more appropiate, as these days more and more speakers dip down to 4 ohms, and more people listen to wider bandwith (high res.) material these days. Regards Alex
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Post by Deleted on Aug 10, 2012 8:42:50 GMT
Matching face plate almost ready to bolt onto the Preamp just several more coats of varnish to lay and the jobs done. Second coat applied this afternoon.................tomorrow flat it down a little and coat again.
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Post by Deleted on Aug 10, 2012 9:03:04 GMT
That looks stunning !
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Post by gommer on Aug 10, 2012 10:22:12 GMT
About the inductor winding, are you guys talking air core inductors?
Just asking, as i have experience with ferrite core inductor building and any calculator has at least a 30-50% error compared to the final result. Tuning is done by changing the air-gap (and with a very accurate +€20k-LCR-meter).
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Post by Deleted on Aug 10, 2012 10:43:19 GMT
About the inductor winding, are you guys talking air core inductors? Just asking, as i have experience with ferrite core inductor building and any calculator has at least a 30-50% error compared to the final result. Tuning is done by changing the air-gap (and with a very accurate +€20k-LCR-meter). Hi Marc They are air cored. Attached is a photo of one of the existing PCBs. Compared with the magazine's photo , I have probably well under the 4.7uH that I aimed for in these PCBs. I doubt that the wire I used was 1.0mm either, although it came from one of the original kits.It looks more like .8mm ? Douglas Self has also gone down from around 6uH to 2.3uH without problems, according to his books.Although my speakers are a nominal 8 ohms, some of the guys may have closer to 4 ohms, hence me trying to retain more HF response into loads like that. Kind Regards Alex Attachments:
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Crispy
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Post by Crispy on Aug 10, 2012 16:19:57 GMT
Matching face plate almost ready to bolt onto the Preamp just several more coats of varnish to lay and the jobs done. Second coat applied this afternoon.................tomorrow flat it down a little and coat again. That's a fantastic job Alan. It's great to see you managed to get the square word calligraphy incorporated onto the front panel as well.
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