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Post by nickyboyo on Jan 22, 2009 8:01:26 GMT
Perfect timing Alex  i am just populating the amp board, and i am wondering why the 2SA1930 and 2SC5171 heatsinks have to be orientated the other way? |
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Post by Deleted on Jan 22, 2009 8:38:48 GMT
nick
The 2SA1930 and 2SC5171 have a different pin out to the BD139 and BD140. You need to turn them around in the PCB. The heatsinking will work a little better if the heatsinks are also orientated with the devices.
When looking at the front of the 2SA1930/2SC5171, the pins are
base, collector, emitter, from left to right.
When looking at the front of the BD139/BD140 , the pins are
emitter, collector,base from left to right.
Alex
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Post by st on Feb 28, 2009 19:42:15 GMT
Replacing the Input capacitors with 4.7uF Polypropylene capacitors. has there been any further development on the best caps to use in this location? I have seen different members use different types and values of capacitor in this location and it sound like they have a major affect on the characteristics of the amp. I'm looking for a high quality replacement, preferably which can be sourced in the uk. Thanks |
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Post by Deleted on Feb 28, 2009 21:46:23 GMT
Replacing the Input capacitors with 4.7uF Polypropylene capacitors. has there been any further development on the best caps to use in this location? I have seen different members use different types and values of capacitor in this location and it sound like they have a major affect on the characteristics of the amp. I'm looking for a high quality replacement, preferably which can be sourced in the uk. Thanks st Check the attached link (reply 8)for what I did with my own and Miguel's HA . They are 4.7uF polypropylene capacitors as used in speajker crossover networks. Although mine came from Jayca, they should also be available in the U.K. See also the Tweaks thread. Alex rockgrotto.proboards39.com/index.cgi?board=chitchat&action=display&thread=3622&page=1 |
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Post by st on Feb 28, 2009 22:01:52 GMT
hi! alex?
any reason you chose 4.7uF? is a smaller value not better in this location so long as the corner frequency is not too high - can you explain why you didn't get a smaller value?
I'm open to suggestions here but really just want to get the best suitable cap on the board at the start as small UK parts orders are pretty expensive.
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Post by Deleted on Feb 28, 2009 23:57:10 GMT
hi! alex? any reason you chose 4.7uF? is a smaller value not better in this location so long as the corner frequency is not too high - can you explain why you didn't get a smaller value? I'm open to suggestions here but really just want to get the best suitable cap on the board at the start as small UK parts orders are pretty expensive. st Several members have reported a subjective improvement by going to 4.7uF instead of the more likely 2.2uF at this location. However, 2.2uF polyprop will do quite well. Certainly better than a 2.2uF or 4.7uF Wima MKT. Incidentally, where electrolytics are used at that location, current thinking is to use 10 times the original capacitance value. Not only gives better linearity, but helps to preserve some of the source's low impedance attributes. (so I am told !) I will send you an email shortly. Alex |
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Post by st on Mar 1, 2009 17:39:59 GMT
thanks sandyk - 4.7uF polypropylenes it is then!
While we're on the subject of caps, any reason why you chose to use 100uF power rail caps on the main board? Why did you not choose larger values?
Also do you have a recommended brand for these?
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Spirit
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Post by Spirit on Mar 9, 2009 6:21:38 GMT
Mains Wiring...  If you look at the connections of the DPDT switch from outside (in front of) the case... Would the connections be?: primary winding 1 || primary winding 2 ------------------------------------------ Neutral || Active |
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Post by Deleted on Mar 9, 2009 6:54:43 GMT
spirit
For increased safety reasons,I terminated the Blue (Neutral) mains wire from the I.EC. socket on the left tag in the centre of the switch. The Brown (active) from the I.E.C socket is terminated on the right tag in the centre of the switch.
The Blue wire from the transformer primary winding is then terminated on the left tag at the top of the switch. The Brown wire from the transformer primary winding is then terminated on the right tag at the top of the switch. All switch wires have short lengths of heatshrink tubing slid on to them, and pushed well back along the wires before they are terminated (to prevent premature shrinking). After soldering the wires to the switch, the tubing is then slided over the soldered joints. The unused terminals of the toggle switch also have heatshrink tubing slipped over them.A hot soldering iron in close proximity, can then be used to shrink the tubing for a tight fit (carefully!) in the absence of a heatshrink gun or heat blower on low temperature. A larger piece of heatshrink tubing may then be cut to size, and slid over the toggle switch from the front, although this is not strictly necessary. The same procedure can then be used to ensure that it is a tight fit over the switch and terminated leads before mounting the switch to the front panel.
Alex
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robertkd
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Post by robertkd on Mar 9, 2009 8:31:00 GMT
gee Alex a soldering iron, rough ;D As for the switch, if you wire supply to center tags i.e. common then when the switch is off the unused contacts have power, I usually put input to the out side pair top or bottom (bottom tags for up is on) and transformer to center tags, that way when switched off there is no unexpected mains on the unused tags  Also Jaycar sell a "hot air" gas powered device which for $20ish isn't to too shabby  ouch it $40_ and Jaycar don't have them  www.altronics.com.au/index.asp?area=item&id=T2480Phil looking good Robert |
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Post by Deleted on Mar 9, 2009 8:49:30 GMT
gee Alex a soldering iron, rough ;D As for the switch, if you wire supply to center tags i.e. common then when the switch is off the unused contacts have power, I usually put input to the out side pair top or bottom (bottom tags for up is on) and transformer to center tags, that way when switched off there is no unexpected mains on the unused tags Also Jaycar sell a "hot air" gas powered device which for $20ish isn't to too shabby Phil looking good Robert Robert Yes, I forgot to add that there is also heatshrink tubing over the bottom unused tags,as well as a cover over the whole lot. This can be seen in the photo too.This can be seen more clearly in the photo of Miguel's HA at : rockgrotto.proboards39.com/index.cgi?board=chitchat&action=display&thread=3729&page=8Thanks for the reminder. ;D As many of these guys are putting together their first electronic kit, they are highly unlikely to have items such as PCB drills and Heatshrink blowers. BTW,I normally use a DSE Heatshrink blower,which has 2 heat settings. Alex P.S. Re the dig about shrinking the tubing with a soldering iron, I did state in the absence of a heatshrink blower, recognising that most 1st time constructors are unlikely to have one.. Incidentally, the majority of Silcon Chip projects that I checked, show the transformer primary connected to the top tags of the power switch. ? ? ? ? Which post are you referring to ? mmmm sorry |
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Post by jeffc on Mar 9, 2009 10:58:27 GMT
If in Oz, Bunnings had 1800W XU1 heats guns with 2 settings for $15 before Xmas which I couldn't go past for this very purpose. Need to keep a reasonable distance though even on the low setting.
cheers..jeffc
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robertkd
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Post by robertkd on Mar 9, 2009 11:07:33 GMT
Jeff, what your saying is with this device it's a fine line between shrinking the tubing and having a molten blob |
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Post by rossman on Mar 9, 2009 11:39:39 GMT
I tend to nick the other halfs hairdryer for heatshrinking   |
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robertkd
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Post by robertkd on Mar 9, 2009 11:50:28 GMT
indeed and I agree paint strippers and even hair driers work, however I feel I should at least state the obvious both of these devices, the paint stripper especially can heat a large area to some very high temperatures, just be aware of the potential for disaster nor am I saying the gas hot air device is any better it too can wield havoc  Robert |
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robertkd
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Post by robertkd on Mar 9, 2009 13:15:48 GMT
Well I thought the picture was Phil's rig but seems not  well not yet, but his working on it Incidentally I managed to loan a lindos test set tonight and measured distortion at 0.0006% into 22R both channels  mmm how to improve Robert |
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Post by PinkFloyd on Mar 9, 2009 13:33:14 GMT
hi! alex? any reason you chose 4.7uF? is a smaller value not better in this location so long as the corner frequency is not too high - can you explain why you didn't get a smaller value? I'm open to suggestions here but really just want to get the best suitable cap on the board at the start as small UK parts orders are pretty expensive. st Several members have reported a subjective improvement by going to 4.7uF instead of the more likely 2.2uF at this location. However, 2.2uF polyprop will do quite well. Certainly better than a 2.2uF or 4.7uF Wima MKT. Incidentally, where electrolytics are used at that location, current thinking is to use 10 times the original capacitance value. Not only gives better linearity, but helps to preserve some of the source's low impedance attributes. (so I am told !) I will send you an email shortly. Alex I can vouchfor Black Gate 10uF Non Polars in this position. I don't normally "do" Black Gate but in this application they are the best I have yet tried (had 10uF film caps in position before)..... Honestly, they are the dog's nads in the SCHA and nice and compact too.... do you really want two extremely large portions of polyprop taking up valuable real estate in your amp? ;D |
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Post by st on Mar 9, 2009 18:43:06 GMT
probably not mike but I can't source any !!! unless you can help?
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leo
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Post by leo on Mar 9, 2009 19:49:25 GMT
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Post by st on Mar 9, 2009 19:53:50 GMT
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Post by rossman on Mar 9, 2009 20:01:18 GMT
That'swhere I was looking but hadn't got as far as the stock page  |
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Post by leo on Mar 9, 2009 20:16:29 GMT
Thats not much good then is it  Only others to try is Michael percy or Partsconnexion |
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Post by Deleted on Mar 9, 2009 21:59:27 GMT
Well I thought the picture was Phil's rig but seems not well not yet, but his working on it Incidentally I managed to loan a lindos test set tonight and measured distortion at 0.0006% into 22R both channels mmm how to improve Robert Robert Great results. ;D Unfortunately, some people think very good figures like that, and great SQ, are mutually exclusive ! Perhaps if you had been able to use noise nulling techniques,as suggested by Douglas Self, the figures may have been even better ? Alex |
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robertkd
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Post by robertkd on Mar 10, 2009 2:44:49 GMT
Well I thought the picture was Phil's rig but seems not well not yet, but his working on it Incidentally I managed to loan a lindos test set tonight and measured distortion at 0.0006% into 22R both channels mmm how to improve Robert Robert Great results. ;D Unfortunately, some people think very good figures like that, and great SQ, are mutually exclusive ! Perhaps if you had been able to use noise nulling techniques,as suggested by Douglas Self, the figures may have been even better ? Alex Well I need to make some adapter type cables that was using both channels as a balanced amplifier (differential amp) which means each channel will individually would be better again. meh low noise and distortion does it for me I'll try and do some more measurements, who said I haven't modded the amp more ;D |
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Post by rossman on Mar 13, 2009 12:45:15 GMT
The bipolar input capacitors should be replaced by higher quality film type capacitors. The Wima 4.7uF MKS2-XL capacitors are a good choice , as they have 5mm lead spacing. Polypropylene capacitors will give slightly better results again, but are physically awkward to implement because of their bulk. (See Reply#8) What is the minimum capacitance allowable for the input caps, I have a couple of 2.2uF polypropylenes to hand, would these be OK here until I can get something else? PS oops Oh bugger I do apologise Robert |
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mmm how to improve 
