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Melbourne Daughterboard for M2X

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Founder of XSA-Labs
Joined 2012
Paid Member
This is a GB for the Melbourne daughterboard (DB) for the Mark Johnson (Pass) M2X amplifier. It will follow the standard M2X hole pattern for electrical connections and have an additional pin for GND. This is needed because this DB can be configured to have gain rather than a 0dB buffer. More info on this board can be found in this thread, and also here in the Melbourne HPA thread.

Edit Mar. 2, 2019: 3D live render here in 3D pdf
https://www.diyaudio.com/forums/att...bourne-daughterboard-m2x-melbournetht_00b-pdf


734405d1549477964-aksa-lender-pass-hybrid-m2-alph-m2-amp-melbourne-th-v2-top-1-png


734406d1549477964-aksa-lender-pass-hybrid-m2-alph-m2-amp-melbourne-th-v2-top-2-png


734407d1549477964-aksa-lender-pass-hybrid-m2-alph-m2-amp-melbourne-th-v2-bot-3-png


Basically it is an Aksa-Lender preamp but redesigned for dual rails of +/-24v with a built in CRCRC filter to clean up the supplies a bit. Also has an upgraded mu-follower output stage for lower distortion in order to drive the 600ohm impedance Edcor transformer. It can be DC coupled, but probably best to leave the C2 AC-coupling cap (on the M2X) in place to avoid saturation of the Edcor.

The board measures 70mm x 35mm x 1.6mm with single thickness copper and ENIG finish in blue.

The Melbourne can also be used as an excellent standalone preamp or even as a headphone amplifier. Indeed, I have used it for both and it works great on all accounts. Currently, it is driving my MOAMOFO:
732435d1548767426-build-mofo-3865e04f-88ef-4973-96a5-047e5a663eb8-jpeg


Here it is HPA:
720693d1544279377-melbourne-class-headphone-amp-pre-amp-melbourne-standalone-preamp-hpa-02-jpg


Note that above photos shown with v1 of the board which had incorrect M2X pinout holes, now fixed on v2.

Prices will probably be about $20/pair depending on how much interest there is. Shipping in US is $5 and $10 to Canada, and $15 everywhere else.

Please add your name to the list below with qnty desired and country shipping to.

I want to thank JPS64 for doing such a fantastic job on the layout!

Cheers,
X

Top silkscreen, schematic, and parts list below.

EDIT Feb 11, 2019: Motherboard for stand-alone Melbourne as preamp or HPA in progress.
735683d1549901793-melbourne-daughterboard-m2x-mel-mb-3d-render-01-png


Edit Mar. 8, 2019: Mouser shopping cart for BOM here.

Please note that the parts list below has a few errors (the schematic is correct):
1. R114 should be 0.1% tolerance metal thin film
2. R116 should be 0.1% tolerance metal thin film
3. C116 should be NP0/C0G 100v
 

Attachments

  • MELBOURNE-THT_PBA-TOP_002b.pdf
    25.8 KB · Views: 368
  • MELBOURNE-THT_SCH_002b.pdf
    23.8 KB · Views: 435
  • Melbourne-THv2-Parts-List.txt
    1.9 KB · Views: 280
Last edited:
twitchie (4) boards - Canada
spind (4) boards - Canada
Russellc (4) boards -USA
batty (4) boards - Australia
TungstenAudio (4) boards - USA
zman01 (2) - USA
dBel84 (2) boards - USA
BigE (4) boards
wcwc (2) boards - USA
BRN (2) boards - USA
jwjarch (4) boards - USA
 
Founder of XSA-Labs
Joined 2012
Paid Member
Hi Folks,
I am glad I clarified whether or not you all wanted 2 or 4 pieces!

JPS64 is working on a full-featured motherboard (MB) for this Melbourne DB so that we will have a stereo pair of DB’s fitted with 4 selectable inputs, a volume pot, and a built in linear power supply using a Talema 25w potted PCB mounted toroidal trafo, with a dual rail cap multiplier. It will be usable as either a Preamp or as a Headphone Amp (HPA). Will give more details soon. But it would make the DB’s very versatile and one can change the gain or the application as Preamp or HPA by making a new relatively cost-effective DB. Knowing this may or may not change your desired number of DB’s.

Basically a neat integrated version of my preamp on a plank as seen below. :)

720432d1544167446-jumas-easy-peasy-capacitance-multiplier-mb-th-verify-build-04-standalone-pre-jpg
 
Last edited:
JPS64 is working on a full-featured motherboard (MB) for this Melbourne DB so that we will have a stereo pair of DB’s fitted with 4 selectable inputs, a volume pot, and a built in linear power supply using a Talema 25w potted PCB mounted toroidal trafo, with a dual rail cap multiplier. It will be usable as either a Preamp or as a Headphone Amp (HPA). Will give more details soon. But it would make the DB’s very versatile and one can change the gain or the application as Preamp or HPA by making a new relatively cost-effective DB. Knowing this may or may not change your desires number of DB’s.

Now, wouldn't that be cool? Bring it on! :)
 
twitchie (4) boards - Canada
spind (4) boards - Canada
Russellc (4) boards -USA
batty (4) boards - Australia
TungstenAudio (4) boards - USA
zman01 (2) - USA
dBel84 (2) boards - USA
BigE (4) boards
wcwc (2) boards - USA
BRN (2) boards - USA
jwjarch (4) boards - USA
poseidonsvoice (2) boards - USA
tomservo (4) boards - USA
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.