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amb  Headphone Council Joined: Apr. 1, 2004 |  Message [#160] posted on: 12-17-2006 07:55 PM CST (US).   |  | 
Hi tomb, if you bias the output transistors to 30mA, then you don't need heatsinks. Each output transistor will dissipate 0.45W which will make them pretty warm, but should still be ok without heatsinks. If you set the idle current any higher, though, then they should be heatsinked. As for how big a heatsink to use, it depends on how high you set the bias. For this amp I don't see a need to go much above 30mA, though. The slots on the side of the Hammond cases do not provide a good heatsink surface. So if you want to heatsink the transistors, use real heatsinks or use a case where you could bolt the transistors to a flat case wall (with appropriate TO-126/TO-225/TO-220 insulators, of course). |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#161] posted on: 12-20-2006 12:03 AM CST (US). | | This is just to remind those of you who had posted in the Marketplace Interest check thread... The PCB group-buy is now in progress. If you haven't already done so, I need you to send me a PM to confirm the number of boards you want, and your paypal email address. Details are in this post. Thanks! The first message in that thread contains a list of names and the status of the group buy. [Edited by amb on 12-20-2006 at 12:04 AM.] |
| jrossel Member Joined: Oct. 30, 2006 | Message [#162] posted on: 12-20-2006 10:13 AM CST (US). | | If people are interested I am willing to put together a BOM kit for this amp. I have put one together for the B22 and it saves people close to 7.00 per board, not to mention shipping savings. I will make it up with Vishay Dale resistors and provide a choice for caps (Muse and Panasonic FC) if possible. Please feel free to PM me if you are interested. I will sum up the kit price tonight. Check here--> http://www.geoci...l/CKK3_kit.html Jeff [Edited by jrossel on 12-21-2006 at 02:48 AM.] |
runeight Headphone Council Joined: Mar. 8, 2002 | Message [#163] posted on: 12-20-2006 03:48 PM CST (US). | | Although I've already collected parts for this amp from the early stages of the redesign, this seems like a good idea to me. If I were starting from zero I would buy the package from you. |
raromachine HeadWize Fanatic Joined: Apr. 15, 2005 | Message [#164] posted on: 12-21-2006 03:31 AM CST (US). | |
Definately a good idea if you're willing to ship internationally |
| jrossel Member Joined: Oct. 30, 2006 | Message [#165] posted on: 12-21-2006 10:36 AM CST (US). | |
Sure I can do this. Jeff [Edited by jrossel on 12-21-2006 at 10:38 AM.] |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#166] posted on: 12-26-2006 09:50 PM CST (US). | | ETA of production boards is about 10 days. Please see this post for group buy status and info. This is updated daily. |
| vnguyen3459 Member Joined: Dec. 28, 2006 | Message [#167] posted on: 12-29-2006 11:10 AM CST (US). | | What is the best way to reduce the voltage gain to about 4.6? Would changing R12 and R13 to 820 be okay? Do I need new value for R17, R18, & R19 for the idle current circuit? |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#168] posted on: 12-29-2006 09:49 PM CST (US). | |
Changing R12/R13 to 820Ω will drop the gain to about 4.1 according to simulation. The idle current circuit should not be impacted. However, I did not explore the effect of this change on phase and square wave response. |
seroxatmad Member Joined: Nov. 13, 2005 | Message [#169] posted on: 12-30-2006 11:54 PM CST (US). | | Hi Are the spice files etc available to all? Regards John |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#170] posted on: 12-31-2006 12:10 AM CST (US). | | Which ones would you like? I have B2Spice files and amb has PSpice files. Although I can't speak for his willingness to let you have them. OTOH, the circuit is extraordinarily simple. Why not just find the models and do it yourself? OTOH, if you're using a demo version of PSpice you won't be able to sim the circuit because you will exceed the Q device limit set into the demo. You can try LTSpice if you don't mind fiddling with its awkward UI. |
| seroxatmad Member Joined: Nov. 13, 2005 | Message [#171] posted on: 12-31-2006 01:44 AM CST (US). | | Hi At the moment i can only afford Ki-Cad PCB prog which is free! At the moment i am not working due to ill health, hence lack of money (but plenty free time) hence getting back into my audio/electronics interest.(last time i made a JLH headphone amp was at college and using graph paper... Regards and thanks again. John PS. What is latest rev's of CD and PCB etc. The CD is not really linked to later on in the posts. PPS I have tried exporting netlist as spice (via the option) but when i import into SWCAD III it says models missings... [Edited by seroxatmad on 12-31-2006 at 03:08 AM.] |
| yhmzzz Member Joined: Sep. 8, 2002 | Message [#172] posted on: 12-31-2006 03:54 AM CST (US). | | I'm planning to build a pre amp using CK III. Do I need any modification for driving power amps? PS. I'm also preparing beta22.(as a pre amplifier) |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#173] posted on: 12-31-2006 06:09 AM CST (US). | |
No, both amps should serve well as preamps. |
| yhmzzz Member Joined: Sep. 8, 2002 | Message [#174] posted on: 12-31-2006 10:54 AM CST (US). | | Thank you very much. I think so.  I'll order beta,sigma,CK boards soon. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#175] posted on: 01-02-2007 01:30 AM CST (US). | | Please see the Final reminder about the group-buy of this PCB. Thanks for your attention. [Edited by amb on 01-02-2007 at 01:31 AM.] |
| seroxatmad Member Joined: Nov. 13, 2005 | Message [#176] posted on: 01-02-2007 05:57 AM CST (US). | | Hi all What sort of input pot would you recommend for the project? I'm in the UK and not even 100% sure about sourcing all the transistors at the moment - but getting excited waiting for my paypal email... Can you confirm the PCB size again and a link to the latest schematic diagram if possible. Regards John |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#177] posted on: 01-02-2007 06:45 AM CST (US). | |
A popular one to use is the 50KΩ Alps RK27 stereo audio pot.
4.7250" (120mm) x 4.200" (107mm) Schematic: http://headwize.com/uploads/C2298.gif |
| seroxatmad Member Joined: Nov. 13, 2005 | Message [#178] posted on: 01-02-2007 01:48 PM CST (US). | | Hi again... Has anyone used WELWYN resistors or have any sonic experiences of them? Its the range RC55C-2K37DI. I was after some Vishy ones but not easy to find here in the UK. Also anyone from the UK building the headamp? Im after sourcing of the input fets transistors. I quickly produced this in AutoCAD but would like advice on wether the transformer will be to close or should be in a separate case. Regards and thanks John P.S My e-mail notify doesn't seem to be working. [Edited by seroxatmad on 01-03-2007 at 01:56 AM.] Attachment: C2461.pdf |
| Dave_M HeadWizer Joined: Jul. 1, 2006 | Message [#179] posted on: 01-03-2007 03:59 PM CST (US). | | In UK you can order nearly all parts from Farnell. AMB should be selling a pair of JFETs with the board, otherwise there should be an alternative at farnell. Generic metal film resistors are fine. I get my resistors and other small items from Rapid.
[Edited by Dave_M on 01-03-2007 at 04:01 PM.] |
| 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. |
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