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runeight  Headphone Council Joined: Mar. 8, 2002 |  Message [#180] posted on: 01-04-2007 09:14 AM CST (US).   |  |  Strange Mouser behavior on the BC550/560CTA. Batman has pointed out to me that Mouser is now back to normal on the CTAs, making them available in small quantities. We may never know what is going on, but maybe now would be a good time to order a bag of these. |
tomb Headphone Council Joined: Mar. 1, 2006 | Message [#181] posted on: 01-04-2007 09:44 AM CST (US). | | What about BC546 instead of BC550? I can get BC560 and BC546 at B&D Enterprises (www.bdent.com), but not BC550. Spec sheet for BC560 says complement to BC546. (They have almost all of the other output trannies that Steinchen likes - in addiiton to the BD139/140). |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#182] posted on: 01-04-2007 09:57 AM CST (US). | | I don't think that B&D is correct. The BC546 is complement to BC556. The bias points in the amp are set for the 550/560 (as best can be done with sim models). They don't have BC550/560 in an designation, such as BC550B? |
| tomb Headphone Council Joined: Mar. 1, 2006 | Message [#183] posted on: 01-04-2007 10:01 AM CST (US). | | EDIT: The BC560 they have is BC560C. The spec sheet actually lists a number of trannies in that series, but I didn't see an explicit distinction between complements - one-to-another. 'Course, I don't read trannie spec sheets every day.  EDIT2: OK, it does look like they list trannies in series. So, I guess the BC546 is not the complement. Sorry - just looking for a substitute because BDent carried one, but not the other. [Edited by tomb on 01-04-2007 at 07:00 PM.] |
amb Headphone Council Joined: Apr. 1, 2004 | Message [#184] posted on: 01-05-2007 12:22 AM CST (US). | | Mouser lists the BC560C as "stock available" rather than the usual "In stock", and the footnote says that they're to be shipped from a separate warehouse than their usual one, and there is a 10 day lead-time. I'm not sure how reliable that lead-time is, sometimes it could be quite bogus. At any rate, I have secured enough of the BC550C and BC560Cs such that no one building this amp (or the β22) need to worry about it. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#185] posted on: 01-05-2007 01:02 AM CST (US). | | Good news! Production boards have arrived... Top side: Bottom side: I got busy tonight and built one to test. Works great! It's not cased up yet so I didn't run anything extensive, but the circuit is well behaved, with no turn-on or turn off pop. DC offset is within ~0.7mV, I biased the output stage to 30mA, let it warm up, re-adjusted the bias several times and then gave it a listen. I don't like using audiophile language to describe it, but suffice to say that it sounds very good. The PCB group buy will end in about 1 hour as I write this, and I will start sending out Paypal bills to those on the list shortly after.
I am also working on a website for this amp similar to my other project sites. Hopefully by the time you all receive your boards the site will be ready. [Edited by amb on 01-05-2007 at 01:15 AM.] Attachment: C2478.jpg,C2479.jpg,C2480.jpg |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#186] posted on: 01-05-2007 01:23 AM CST (US). | | FYI, this is my BOM for your reference, it uses Mouser for all parts except the input JFETs, BC550C/560C transistors and the Amveco transformer. All parts are a perfect-fit on the PCB. Ti's Cavalli-Kan Kumisa III BOM Mouser: Qty Description Mouser part # Digikey Qty Description Digikey part # AMB audio shop Qty Description Other (from my stash): [Edited by amb on 01-13-2007 at 09:31 PM.] |
| meat Member Joined: Feb. 17, 2003 | Message [#187] posted on: 01-05-2007 10:26 AM CST (US). | | You have been very busy AMB with the B22, O22, O11 and now this! Thanks for all of the work you have put into these amplifiers! Now I just have to decide which one(s) to build. |
| dBel84 HeadWize Fanatic Joined: May 5, 2006 | Message [#188] posted on: 01-05-2007 11:05 AM CST (US). | | That looks really neat Ti , looking forward to the realworld measurements..dB |
| jrossel Member Joined: Oct. 30, 2006 | Message [#189] posted on: 01-05-2007 03:04 PM CST (US). | | That is fast building Ti! Looks great. For those of you who are building this up and need parts, I have put together the kit I mentioned a while back. You can see the BOM (essentially Ti's BOM) here: http://geocities.com/jeffrossel/ detailing parts along with the cost. Send me a PM if you have questions or would like to order. |
Ferrari HeadWizer Joined: Apr. 29, 2006 | Message [#190] posted on: 01-05-2007 05:36 PM CST (US). | | I have some Toshiba transistors 2SC2238/2SA968 on hand and I'm planning to use these devices instead of BD139/BD140 on the CK2III. I'm aware of the reversed pin-out, so I have to swap these devices 180 degrees on the PCB (comparing to BD139/BD140). Is there any other aspect I have to pay attention to? Ti, very good news... the board looks great |
.| tomb Headphone Council Joined: Mar. 1, 2006 | Message [#191] posted on: 01-05-2007 06:47 PM CST (US). | | Ditto on the board, Amb. I can't answer your specific question, Ferarri, but one of Steinchen's earlier posts challenged us all to a transistor shootout. I believe he expects that some of his favorite output transistors will work very well here (in place of the BD139/140), but I'm not sure anyone knows for sure yet. FWIW, B&D Enterprises (www.bdent.com)has several of Steinchen's favorites: In addition, they have the BD139/140. As far as I can tell, they don't have any of the others he's mentioned, unfortunately. They also have the 2SK170BL/2SJ74BL, but I imagine many will order the last two from Amb. I can testify to B&D's good service (Amb's, too!). You can find Steinchen's reviews on the same output transistors for the Millett DB's here: www.diamondstar.de/dDB_partslist.html (scroll down to "Note 2: output transistors") At any rate, Ferrari - the ones you mention are Steinchen's most favorite, I think. I have been unable to find them in the US. [Edited by tomb on 01-05-2007 at 06:50 PM.] |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#192] posted on: 01-05-2007 07:02 PM CST (US). | | I think that Steinchen's idea of a O/P transistor shootout is a good one. Most of those transistors will probably work. There is a fairly large range in the bias adjustment, but in some cases the range may be slightly shifted for particular devices. While I'm here, however, I want to thank amb for making these boards available and for putting the CK2III on his list of supported products. When I asked him about making boards for and supporting the redesigned Kumisa III a few months back he was in the middle of the b22/s22 work. Even though he didn't have much extra time, he still took on this amp too. So, amb it's been great working with you to make the CK2III available. And thanks to Benny for the concept, dBel84, awpagan, and Dave_M for the collaboration to work out the kinks in the original design. Perhaps we can do it again. I hope you all like this amp. [Edited by runeight on 01-05-2007 at 07:05 PM.] |
| heady HeadWizer Joined: Jun. 15, 2004 | Message [#193] posted on: 01-05-2007 07:16 PM CST (US). | | Thanks to all who made this project possible. Will be looking forward to the arrival of my board. Will I be out of place to suggest to those who have completed building this amp to post their opinion of the sound vs the beta22 sound? After reading the post re: NFB, I am curious. |
seroxatmad Member Joined: Nov. 13, 2005 | Message [#194] posted on: 01-05-2007 07:21 PM CST (US). | | Hi all Typical i ordered 2 PCB's and 2 lots of fets (as poor sourcing here in UK). My so called friend now not after a headamp - dont want to mess a busy Ti around asking for only 1 (plus piad for 2 now) so will be probably be offered on ebay!. Anyway...can i ask what is the difference bewteen bd139-10 amd bd139-16 etc? Regards John P.S Did anyone look at my earlier pic of a case layout i done. |
| awpagan HeadWizer Joined: Jan. 6, 2005 | Message [#195] posted on: 01-05-2007 07:36 PM CST (US). | | gain range of transistor bc139/140 10, 16 25 40 similar to bc550's A, B, or C's if you can find 139/140's in 25's or even 40 better |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#196] posted on: 01-05-2007 07:41 PM CST (US). | |
The suffix is the Hfe class. BD139-6 has the lowest Hfe (40-100), -10 is midrange (63-160) and -16 is the highest (100-250). Note that the ranges overlap. Generally we prefer to have high Hfe to reduce the base current drive requirements.
Yes, the only comment I have is to swap the positions of your IEC and the RCA input jacks so that the input wiring doesn't come straight into the path of the transformer. In fact, you should move the transformer as far away from the low-level signals as possible. This means orienting the board so that the PSU input side of the board faces rear so that the amp portion of the board is further to the front of the case, and run your input wires along the opposite sidewall away from the transformer. Even though my BOM shows an IEC with a built-in fuse and no switch, I think I will change to one that also has a switch, so that I won't have to run AC power wires to the front panel. |
| Dave_M HeadWizer Joined: Jul. 1, 2006 | Message [#197] posted on: 01-06-2007 05:18 AM CST (US). | | Glad to hear the amp works ok with no troubles. I was wondering how much control the servo has, what is the output voltage of the opamp? Did you try to match BJTs? I'm trying to find alternative JFET input transistors. For P-channel there is 2N5462 and not much else. Is this one ok to use? Not sure on the specs, is there anything to look out for? Datasheet:www.fairchildsemi.com/ds/2N%2F2N5462.pdf [Edited by Dave_M on 01-06-2007 at 05:20 AM.] |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#198] posted on: 01-06-2007 05:28 AM CST (US). | |
My input JFETs were selected from groups that were Idss matched to within 0.5mA, but none of my other transistors were matched. The servo opamp's output voltage was roughly 60mV in both channels. I think there is plenty of control range to keep the offset at bay.
You're on your own there... since there are not many JFETs out there specified by the manufacturer as complementary, and using arbitrary devices will probably yield poor results. Ideally you'll want high Gm devices with low noise. |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#199] posted on: 01-06-2007 10:36 AM CST (US). | | Dave_M, the equivalent, but not necessarily complementary, n-channel devices are 2n5457-2n5459. If you pick an equivalent pair, 2n5457/2n5460 you might get decent results. If you match them you might get good results. Their Vgsoff are in the same ballpark, although the Toshiba jfets have a stated wide variability. And their Idss are also in the same ballpark. But the transconductance of the fairchild jfets is quite a bit smaller. You'll just have to experiment. Also, the pinouts are not the same. You'll have to take care to insert the fairchild fets in the right arrangement. No guarantees though. You will be on your own. |
| Dave_M HeadWizer Joined: Jul. 1, 2006 | Message [#200] posted on: 01-06-2007 05:24 PM CST (US). | | Correct me if I'm wrong... Gm = Transconductance = Forward Transfer Conductance
I will probably try matching a 2n5457/2n5460 combination or similar. But if all else fails will it be ok to just install BJTs without changing resistor values like the input resistor? [Edited by Dave_M on 01-06-2007 at 05:26 PM.] |
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