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seroxatmad Member Joined: Nov. 13, 2005 |  Message [#280] posted on: 01-17-2007 05:16 PM CST (US).   |  |  My Boards arrived 8 days after posting...thanks amb...only 8 days to get to the UK so on sorting components out to order. Anyone else from UK with theres? Years ago when tesing designs and building JLH desings i killed a few headphones so would recommend buying some really cheap ones for inital testing. I have no scope to test mine when its built but does anyone recommend a cheap PC type osc scope addon i often see advertised? Other than that a visit to my local college/university may be required. Regards john |
amb  Headphone Council Joined: Apr. 1, 2004 | Message [#281] posted on: 01-17-2007 11:24 PM CST (US). | |
If your aim is to use the scope to look for high frequency oscillations, then the cheap PC scopes (that are based on sound cards) are useless. They don't show much of anything over 20KHz. A good PC scope (with an extra adapter, and with specs good enough for real work) would be just about as expensive as a good standalone scope, except without the handy and easy-to-use knobs. See this thread: http://headwize....fnum=3&tid=6579 If you use all the recommended parts and install the 220pF caps at the output stage, and check the DC offset, then there should be little chance of damaging your headphones. |
| jrossel Member Joined: Oct. 30, 2006 | Message [#282] posted on: 01-18-2007 01:08 AM CST (US). | |
Try the 581-BQ014D0104J they are available in individual quantity and lead free to boot! JR |
| awpagan HeadWizer Joined: Jan. 6, 2005 | Message [#283] posted on: 01-18-2007 02:53 AM CST (US). | | pcb's arrived today, thanks amb as for a pc scope check this out allan |
| awpagan HeadWizer Joined: Jan. 6, 2005 | Message [#284] posted on: 01-18-2007 03:06 AM CST (US). | | As for the snubber cap's are they really necessary on fast diodes? and/or are they different value cap?
ps I do know, s74's no have. |
| awpagan HeadWizer Joined: Jan. 6, 2005 | Message [#285] posted on: 01-18-2007 03:07 AM CST (US). | |
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| amb Headphone Council Joined: Apr. 1, 2004 | Message [#286] posted on: 01-18-2007 04:06 AM CST (US). | |
That site's DNS isn't resolving for me at the moment, but I've looked at BitScope in the past. It's pretty cool, but for the price, and if you must have only one scope, I'd buy a good used standalone analog scope instead. Analog scopes and digital scopes are each good for different things, and I have both (actually, one analog and two digital ones). If you search for bitscope and other related terms on www.head-fi.org, you'll find some good discussions on these topics.
This is a controvertial issue, and I don't have an easy answer. But, my own habit is to use smaller snubber caps (in the 100pF to 330pF range) on fast recovery diodes such as MUR820, and 0.01uF to 0.1uF on standard rectifiers like 1N400x. [Edited by amb on 01-18-2007 at 04:08 AM.] |
Steinchen HeadWizer Joined: Oct. 12, 2005 | Message [#287] posted on: 01-18-2007 05:46 AM CST (US). | |
there is no need for ultrafast diodes when rectifying snail slow 50 or 60Hz mains, this isn't a high efficiency switching psu. You rather want a diode that doesn't "snap" with reversing voltage (additionaly maybe low reverse leakage current). Thus plain schottky barrier diodes (e.g. 11DQ06...11DQ10, MBR1100, 31DQ06...31DQ09, MBR160...MBR360, 50SQ60...50SQ100, MBR1060) or soft recovery diodes (e.g. HFA08TB60, RHRP860) are preferable. As for the snubbers: calculating them is rather complicated, you need C + RC snubbers instead of a plain C snubber to eliminate the ringing and you need to know a lot of parameters (inductance of the transformer, junction capacitance of the diodes, ...) |
| awpagan HeadWizer Joined: Jan. 6, 2005 | Message [#288] posted on: 01-18-2007 06:11 AM CST (US). | | Always preferred analogue scopes but just unavailable to me at present  althought the 100mhz digital on a pc. havn't been to Head-fi for a while, may look it up. As for the snubbers on fast diodes
allan
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alfie Member Joined: Jul. 12, 2006 | Message [#289] posted on: 01-18-2007 07:21 AM CST (US). | | About the bipolar electrolytics: I cannot find them here. No chance, but buy expansive ones online. So, are they really exchangeable by the 1µF 63V polyesters without any consequences? What do you people think about a balanced CKIII? |
n_maher HeadWize Fanatic Joined: Dec. 15, 2004 | Message [#290] posted on: 01-18-2007 07:28 AM CST (US). | | There's actually what looks like a good deal on a 100MHz Tektronix scope (and signal generator too) on Head-Fi right now. Ask the owner and you'll find that it comes with 2 10x probes and an additional 1x probe. Look for a thread by "raduray" in the FS forums. I'd pick the package up if the beta22 hadn't just put my wallet through some serious pain! |
| jarpatus Member Joined: Aug. 3, 2005 | Message [#291] posted on: 01-18-2007 11:39 AM CST (US). | |
Thanks for you reply runeight! I added heatsinks to regulators and no problem with them anymore I hope. Tuned trimpots for 14mV and output transistors do still get burning hot - can't put finger on them longer than second (I remember old thumb rule for computer CPU's, if you can't keep finger on CPU for 3 seconds it's too hot)... Well let's see what happens - I have few spare transistors left. Sound quality seems to be excellent. I do not have my DAC since I took PSU from it but even when connected to my sound card it seems very good. About hose 10uF bipolar caps... they were only thing available, did not find any small ones Best regards, |
Ferrari HeadWizer Joined: Apr. 29, 2006 | Message [#292] posted on: 01-18-2007 01:53 PM CST (US). | | Jari, Try to find some clip-on heatsinks for the output transistors, it helps a lot. I use these clip-on heatsinks on my CK2III and it was able to adjust the voltages across R23 and R47 at 20mV  (~42,5 mA). The heatsinks does get warm but not burning hot. I can put my fingers on them as long as I want.
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| seroxatmad Member Joined: Nov. 13, 2005 | Message [#293] posted on: 01-18-2007 04:05 PM CST (US). | | Hi Ferrari Its looking good. I notice you have used a 1uF Poly and not a 10uF Bipolar cap for C19,C22 etc. I was after a little bit advise as im about to order my parts. I think sound quality wise, that is the best option as the 1uF cap is probably better quality than a 10uF bipolar. Its just a pity the 2 resistors have to be of a different make i.e not vishay as all the others are. Regards John [Edited by seroxatmad on 01-18-2007 at 04:07 PM.] |
| Garlicknots Member Joined: N/A | Message [#294] posted on: 01-18-2007 07:03 PM CST (US). | | Just as a heads up, if you open up any old computers you have you might find those clip on heat sinks. I found 6 in a ~1999 era compaq. YMMV, of course. |
| Ferrari HeadWizer Joined: Apr. 29, 2006 | Message [#295] posted on: 01-19-2007 03:14 AM CST (US). | | These clip-on heatsinks are also available at Conrad, I got mine from there. Regarding the voltages adjustment across the output resistors R23 and R47, I notice that the voltages across these resistors are very sensitive to the environment (room temperature, the amp testing on table or cased up). The voltage can drift 2-3 mV easily and resulting in a higher output current, things to keep in mind. [Edited by Ferrari on 01-19-2007 at 10:06 AM.] |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#296] posted on: 01-19-2007 03:19 AM CST (US). | |
Yes, and since BJTs have positive tempco, the current will increase as it warms up. So, while you're adjusting the bias, you might want to set it a bit lower than your target, so that when the board is cased up, it will settle closer to where you want it to be. Some quiescent current drift is no concern, as long as the transistors don't get too hot. |
| awpagan HeadWizer Joined: Jan. 6, 2005 | Message [#297] posted on: 01-19-2007 03:26 AM CST (US). | | and the pcb should have earth connected |
raromachine HeadWize Fanatic Joined: Apr. 15, 2005 | Message [#298] posted on: 01-19-2007 05:12 AM CST (US). | | It's far from complete, so it doesn't really count but I like it  Also - I found amongst my stash 4x 3300uf Nichicon caps. I know that bigger isn't necessarily better, but it is free-er
Attachment: C2557.JPG |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#299] posted on: 01-19-2007 05:14 AM CST (US). | |
It's fine as long as it fits properly. |
| raromachine HeadWize Fanatic Joined: Apr. 15, 2005 | Message [#300] posted on: 01-19-2007 05:31 AM CST (US). | |  Attachment: C2558.JPG |
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