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dave_m HeadWizer Joined: Jul. 1, 2006 |  Message [#240] posted on: 01-12-2007 05:12 AM CST (US).   |  | 
You are thinking along the right lines. I looked it up.. RFI and EMI are names for the same thing (see Wikipedia). I think then that transformers don't emmit any EMI, they just have a magnetic field that leaks out.
What's the rush? You still need to order the parts to build? That will take a couple of days. The longer you have to wait, the better it's going to sound I'll have the transformer in the same case, I don't like external PSUs much. Make sure you earth your case properly if you do the same! [Edited by dave_m on 01-12-2007 at 05:19 AM.] |
| seaside Member Joined: Aug. 16, 2005 | Message [#241] posted on: 01-12-2007 02:21 PM CST (US). | | amb, thanks for your kind answers. Right after I asked those questions, I took my time and went over this thread from the page 1. I found some answers are already there. But it is very kind of you answering me one by one, not saying "read the F'in thread". Thanks again. One more question, regarding C37, C38.... is it possible to use 470uF right there instead of 220uF? Thanks a lot. |
amb Headphone Council Joined: Apr. 1, 2004 | Message [#242] posted on: 01-12-2007 02:38 PM CST (US). | |
Yes, as long as it fits. However, unlike other things in life, bigger is not necessarily better here.  |
Ferrari HeadWizer Joined: Apr. 29, 2006 | Message [#243] posted on: 01-13-2007 06:30 AM CST (US). | | Just finish the build of my CK2III with 2SC2238/2SA968 as output devices  .One small remark: I use the schematic as depicted in post #92 and see that R49 is present on both left and right channel (2x). I think that R49 on the right channel corresponds to R39 on the PCB/part list. Don't know if it's already changed yet (after post #92)? |
gewa HeadWizer Joined: Sep. 22, 2006 | Message [#244] posted on: 01-13-2007 06:50 AM CST (US). | | Is it an idea to also start a "CK2III building thread" as we did for the SOHA? Regards |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#245] posted on: 01-13-2007 08:28 AM CST (US). | |
Yes, I mentioned this error in a previous post. Here are the correct schematic diagrams that will appear on the CK2III website: Left channel Right channel Power supply
We can just continue in this thread. Attachment: C2508.png,C2509.png,C2510.png |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#246] posted on: 01-13-2007 08:42 AM CST (US). | | One other thing, the BOM I posted in Post #186 was missing two capacitors, C20 and C21. These are just 0.1uF radial X7R multilayer ceramic caps with 0.100" or 0.200" pitch, such as Mouser 80-C320C104K5R). You can also use film caps for these (e.g., Mouser 581-BF074D0104J, the same as what's in the BOM for C25-C32). Sorry about the omission. I just fixed Post #186 to make it right. |
| Ferrari HeadWizer Joined: Apr. 29, 2006 | Message [#247] posted on: 01-13-2007 09:00 AM CST (US). | |
Thanks for the correct schematic diagrams. After approx. 2 hours burn in, I try to listen to some music with this little amp, the fisrt impression is very positive... no hiss or hum at all! (listening to Hotel California - The Eagle when typing this, sounds good ). |
| dBel84 HeadWize Fanatic Joined: May 5, 2006 | Message [#248] posted on: 01-13-2007 09:12 AM CST (US). | | where's the eye candy?  ..dB |
runeight Headphone Council Joined: Mar. 8, 2002 | Message [#249] posted on: 01-13-2007 11:02 AM CST (US). | | Ferrari, did you build with C8, C9, C17, C18?? I posted a while back that it should be ok to leave these caps out. They will make the amp a little slower and are only needed if there is oscillation in the output stage. |
| Ferrari HeadWizer Joined: Apr. 29, 2006 | Message [#250] posted on: 01-13-2007 11:28 AM CST (US). | | runeight, I build the amp without C8, C9, C17, C18. With the 2SC2238/2SA968 as output devices, I notice no oscillation. @dBel84, pics will follow soon! |
| Dave_M HeadWizer Joined: Jul. 1, 2006 | Message [#251] posted on: 01-13-2007 11:35 AM CST (US). | | Is it ok to leave out C5, C6, C14, C15? Bad idea? |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#252] posted on: 01-13-2007 11:58 AM CST (US). | | You can leave them out, although they tune the high freq response of the amp. I think it's better to have them if it's not impossible for you to find them. Also, C8, C9, C17, C18 don't have a terribly big impact on the amp so if you build it with them, don't sweat it. |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#253] posted on: 01-13-2007 12:00 AM CST (US). | | Ferrari, with the different output transistors are you able to dial the output bias to 30mA? And how much higher can you go? |
| Ferrari HeadWizer Joined: Apr. 29, 2006 | Message [#254] posted on: 01-13-2007 03:24 PM CST (US). | |
Yes, it was able to dial the output bias to around 30mA. I adjusted the voltages across R23 and R47 at 15mV, a bit more than recommended (14mV). I use clip-on heatsinks for the output transistors, they does get warm but not hot  .I think that if the output transistors are well heatsinked, it should be possible to pump the output bias to 40-50mA. Since I have to swap the 2SC2238/2SA968 180 degrees due to the reverse pin-out, mounting these transistors on a large heatsink (or on the side pannel of the HiFi-2000 enclosure) is not possible. |
| jrossel Member Joined: Oct. 30, 2006 | Message [#255] posted on: 01-13-2007 07:30 PM CST (US). | |
I think this cap part number needs a slight adjustment. 100nF 63V MKT should be 581-BF014D0104J not 581-BF074D0104J the case size is smaller than the 07 size. Looking at the catalog I have a question: I just wonder what is the difference between the BF and BQ series? They have the same specifications and performance characteristics. Does anyone know? Thanks for pointing out that we need 10 and not 8 of these caps. Jeff |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#256] posted on: 01-13-2007 09:30 PM CST (US). | |
Ah, good catch. The BF01x is half as thick as the BF07x. They both have 0.200" pitch, so I should change the recommendation to 581-BF014D0104J.
Looks like the BF is not lead-free while the BQ is. The latter is thus RoHS compliant, but I don't think it matters much to us. |
| Ferrari HeadWizer Joined: Apr. 29, 2006 | Message [#257] posted on: 01-14-2007 11:31 AM CST (US). | | In thread #210 there was a note about connecting the transformer to the CK2III amp, that we have to be sure that the two secondaries are wired to the amp in proper phase. I understand that we have 2 secondaries of 15V (~18V when unloaded) and 2 leads for each secondary. The 2 leads of each secondary will be connected to one connector (J3 or J4) on the PCB. But how can we know whether the secondaries are wired to the amp in proper phase or not  ? My amp works but I'm not sure about the phase. |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#258] posted on: 01-14-2007 12:15 PM CST (US). | | Haven't looked at the thread, but the secondaries don't need to be in phase for this power supply. They are operating totally independently and phasing them actually doesn't make any sense. Just don't connect them together to try to make a single center tapped secondary as this will likely damage something. Use the two secondaries as though they are actually two separate transformers. [Edited by runeight on 01-14-2007 at 12:20 PM.] |
| Ferrari HeadWizer Joined: Apr. 29, 2006 | Message [#259] posted on: 01-14-2007 02:04 PM CST (US). | |
I indeed connected the secondaries to my CK2III this way. Thanks for clearify it! |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#260] posted on: 01-14-2007 02:36 PM CST (US). | | So, Ferrari, how does it sound after a few days of breaking it in? |
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