I notice the Paypal receipt says I have authorised a payment to Arrow and the funds will be transferred when Arrow processes the payment - maybe the accountants at Arrow will realise no profit is showing in that transaction and it will not be processed - who knows!! Then free FEDEX delivery on top of that, I get free FedEx delivery at Mouser and Digikey when my order is over $60.00 AUD ($50.00 USD).
Wait and see what happens with the deal.
Wait and see what happens with the deal.
Built but not tested. Sure glad I have a stash of KSA1381's! The Arrow solution is very practical, so I don't think you guys need to worry. I am using the big 220uF 50v Nichicon Muse on the output and not using any of the input of output bypass filmcaps. My personal opinion is that when things are this dense, SMT would have been easier/cleaner. Lots of vertically mounted resistors make for a very dense forest of components. This is one dense amp!
Attachments
Last edited:
Well, color me embarrassed for missing the P-type. I was going on memory. I happen to have 8 each of the KSC2690A and the KSA1220A, which I ordered a while back for a different project. Sadly not enough to share with the class. Looks like the P-type KSA1220A will ship in June from the manufacturer to Mouser. I believe that the 160V devices will in principle work as good substitutes for the 300V devices in the BOM, once they become available.
Vince,
Thank you for putting together the BOM and finding than alternative source for the KSA1381’s.
It reminds me of an old Radio Shack radio control receiver that I assembled for a little r/c airplane back in the late 70s. Since there is one SMD cap that snuck its way onto the board, might as well go all the way and replace the other resistors with 1206 SMDs. Does the hole spacing lend itself to some careful soldering of such devices?
We originally had an all SMD board but people seem to prefer the TH one. So I stopped bothering g to ask JP to make a SMD update on V2. You might be able to for 1206 where the parts are standing up but it’s not ideal. What was nice for SMD version was that all the SMD were on the underside so there is total clearance.
Received confirmation from Arrow Electronics that my huge $3.33 order for the KSA1381 transistors has shipped by FedEx totally free of charge from the US to Oz, Members should add Arrow to the Mouser and Digikey supplier list as their webpages for ordering are very similar, pricing is much the same and every order, no matter what the total is seems to ship no charge by FedEx any where in the world. Now I call that service, but have no idea at all how either Arrow or FedEx make any money on the deal.
I just had a chance to test out the Melbourne for functionality and they work well. So the layout is good. I used a +/-24v Darlington BJT cap multiplier by Prasi. and measured 41mA bias current. With no matching of input pairs and using 15k 1% vs specified 14k9 for R104 and 15k 1% for R106, I got 21mV DC offset on one channel and 30mV DC offset on the other channel (not too bad). I am using a 220uF 50v Muse output coupler so that's not an issue. The 41mA current produces about 1w of dissipation in each of the two output transistors (DN2540 and KSA1381) - warm but not hot. Output noise as measured by Fluke 101 is 100uV rms. The output responds to input as verified on an O-scope. I did not have a chance to install it on the M2X amp yet as the PSU is sort of in disarray on the amp at present.
You can be sure that this preamp will work if assembled properly using the BOM shopping cart that Vunce made.
Use the top-board stuffing diagram or you will never know where to put the resistors based on the silk screen markings alone.
When building these, always a good idea to test it outside of the M2X with a simple dual rail supply to make sure the bias current flow is correct before installing in the amp. Even a +/-15v supply test is better than nothing.
Photo of bias current test showing 0.339v across 8.2ohms = 41mA (use the provided test points for alligator clips):
You can be sure that this preamp will work if assembled properly using the BOM shopping cart that Vunce made.
Use the top-board stuffing diagram or you will never know where to put the resistors based on the silk screen markings alone.
When building these, always a good idea to test it outside of the M2X with a simple dual rail supply to make sure the bias current flow is correct before installing in the amp. Even a +/-15v supply test is better than nothing.
Photo of bias current test showing 0.339v across 8.2ohms = 41mA (use the provided test points for alligator clips):
Attachments
Last edited:
Hi Gary,
The part is a Fischer Elektronik SK95-25 that RS Components carries.
I do not know the cross reference part number for a heatsink that Mouser carries. Looks as if you can use the aluminum finned TO-220 sinks that X is using. Check his posted pics of the built Melbourne.
Regards,
Vunce
The part is a Fischer Elektronik SK95-25 that RS Components carries.
I do not know the cross reference part number for a heatsink that Mouser carries. Looks as if you can use the aluminum finned TO-220 sinks that X is using. Check his posted pics of the built Melbourne.
Regards,
Vunce
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.