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Melbourne Daughterboard for M2X
Melbourne Daughterboard for M2X
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Old 9th March 2019, 08:49 PM   #171
gary s is offline gary s  Australia
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Join Date: Nov 2002
Location: Australia
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.
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Old 10th March 2019, 03:49 PM   #172
xrk971 is online now xrk971  United States
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Join Date: Oct 2012
Location: Metro DC area
Melbourne Daughterboard for M2X
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):
Melbourne Daughterboard for M2X-mel-build-testing-04-jpg
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File Type: jpg Mel-build-testing-04.jpg (282.3 KB, 158 views)
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Last edited by xrk971; 10th March 2019 at 04:14 PM.
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Old 10th March 2019, 04:09 PM   #173
xrk971 is online now xrk971  United States
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Join Date: Oct 2012
Location: Metro DC area
Melbourne Daughterboard for M2X
GB Status Update:
Quote:
witchie (4) boards - Canada = PAID
spind (2) boards - Canada = PAID
Russellc (4) boards -USA = PAID
batty (4) boards - Australia = PAID
TungstenAudio (4) boards - USA = PAID
zman01 (2) - USA = PAID
dBel84 (2) boards - USA = PAID
BigE (4) TH boards -Canada = PAID
wcwc (2) boards - USA = PAID
BRN (2) boards - USA = PAID
jwjarch (4) boards - USA = PAID
poseidonsvoice (2) boards - USA = PAID
tomservo (4) boards - USA = PAID
mordikai (4) boards- USA =PAID
asanden (4) boards - NL = PAID
Vunce (4) boards - USA = PAID
vvs07 (4) boards - USA = PAID
BEYoung (4) boards - USA = PAID
Roundtoit (4) boards - USA = PAID
TboneAK (4) boards - USA = PAID
Meanie (4) boards - Singapore = PAID
silasmellor (4) boards - DEN = PAID
Kokanee (4) boards - CAN = PAID
jims (2) boards - USA = PAID
davidjt (2) boards - UK = PAID
aljordan (4) boards - USA = PAID
Kokanee (4) boards - CAN = PAID
KevinHeem (4) boards - USA = PAID
Windwardmt (4) boards - USA = PAID
I will start sending shipments out tomorrow.
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Old 10th March 2019, 11:13 PM   #174
gary s is offline gary s  Australia
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Join Date: Nov 2002
Location: Australia
Hi X and Vunce, one small point on the Mouser cart that you have compiled - the 2 small heatsinks on the output transistors is not shown.
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Old 10th March 2019, 11:26 PM   #175
Vunce is offline Vunce  United States
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Join Date: Jan 2014
Location: LI, NY
Melbourne Daughterboard for M2X
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
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Old 11th March 2019, 12:06 AM   #176
gary s is offline gary s  Australia
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Thanks Vunce, any small TO220 heatsink should be OK there as long as it fits in with all the other components.
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Old 11th March 2019, 12:09 AM   #177
Vunce is offline Vunce  United States
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Join Date: Jan 2014
Location: LI, NY
Melbourne Daughterboard for M2X
Yup
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Old 14th March 2019, 07:46 PM   #178
xrk971 is online now xrk971  United States
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Join Date: Oct 2012
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Melbourne Daughterboard for M2X
I sent out the orders that did not have to be combined with another GB today.

Quote:
twitchie (4) boards - Canada = SENT
spind (2) boards - Canada = SENT
Russellc (4) boards -USA = SENT
batty (4) boards - Australia = SENT
TungstenAudio (4) boards - USA = SENT
zman01 (2) - USA = PAID
dBel84 (2) boards - USA = SENT
BigE (4) TH boards -Canada = SENT
wcwc (2) boards - USA = SENT
BRN (2) boards - USA = SENT
jwjarch (4) boards - USA = SENT
poseidonsvoice (2) boards - USA = SENT
tomservo (4) boards - USA = SENT
mordikai (4) boards- USA =SENT
asanden (4) boards - NL = SENT
Vunce (4) boards - USA = SENT
vvs07 (4) boards - USA = SENT
BEYoung (4) boards - USA = SENT
Roundtoit (4) boards - USA = PAID
TboneAK (4) boards - USA = SENT
Meanie (4) boards - Singapore = PAID
silasmellor (4) boards - DEN = SENT
Kokanee (4) boards - CAN = PAID
jims (2) boards - USA = SENT
davidjt (2) boards - UK = SENT
aljordan (4) boards - USA = SENT
Kokanee (4) boards - CAN = PAID
KevinHeem (4) boards - USA = SENT
Windwardmt (4) boards - USA = SENT
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XRKaudio https://www.etsy.com/shop/XRKAudio
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Old 14th March 2019, 07:58 PM   #179
davidjt is offline davidjt
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Join Date: Nov 2015
Melbourne Daughterboard for M2X
Thanks for all the effort - much appreciated.
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Old 18th March 2019, 02:45 PM   #180
poseidonsvoice is offline poseidonsvoice  United States
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Join Date: Jul 2004
Location: North Carolina
Melbourne Daughterboard for M2X
XRK!

Got the boards! Thanks a million!

Best,
Anand.
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