MJ Mini Tube Board

[digi01 0]

those are all manufacture OEM case,for audio diy used.

[huangyong 0]

wah.. a bit expensive for the price..

but the size is a bit too big for the purpose..

may i know how big is the PCB?

what is the material used? stainless steel? or aluminium?

Edited August 25, 2004 by huangyong

[digi01 0]

Yes,a littel expensive.but top grade

 

the case size is 240x380x130mm,the thickness of the front board is 4mm,all aluminium.

Edited August 25, 2004 by digi01

[huangyong 0]

the case size is 240x380x130mm,4mm face board,all aluminium.

yeh,i know the dimension of the case. But how big is the PCB and the space needed for the MJ amp?

[digi01 0]

the main PCB board size is 134mm x 120mm,psu board size is 134mm x 47mm.including the transformer and AC socket,VOL pot rooms.I think the minimum size of case is 160mm x 180mm,height 100mm(tube inside building).

Edited August 25, 2004 by digi01

[digi01 0]

a US diyer have finished it.url:http://www6.head-fi.org/forums/showthread.php?t=87661

 

FAQ:

 

- Is this amp based on the ordinary EarMax or the EarMax Pro?

Yes,it is besed on EarMax Pro.

 

- What exactly did you mean when you said optimised?

The optimized Morgan Jones amplifiers (with and without feedback) can output more than 3 times the current of the original into a 32-ohm load.These modifications resulted in better performance into both 300-ohm and 32-ohm loads.

 

- Can it power both low & high impedance headphones?

Sure:-)the amp can drive my HD495(32ohm) and AKG141M(600ohm) never so good.

 

- Any other relevant information provided would be greatly appreciated (like cost etc).

the amp cost around 120USD,based on parts.

 

BTW,the design is based nearly 100% of the informations of headwize and diy workshop forums. My contribution is transfering it to protel project and making the pcb.

 

 

digi

Edited October 8, 2004 by digi01

[bpribadi 0]

Thanks for the usefull information!

[ckng 0]

Sorry to dig up an old thread but I just came across this and found it interesting. How much does just the MJ PCB alone cost vs the whole kit?

 

Regards

CK

[skyskraper 0]

maybe the best way to get an answer is to email digi001?

[neutralzz 0]

yup email or get him on msn, very friendly guy

[neutralzz 0]

btw when you build an OTL amp like this the sound quality is probably 80% dependent on the tubes.. input and output and toobs can cost more than the kit itself

[ckng 0]

Thanks guys, I'll contact digi01 by email.

 

Regards

CK

[huangyong 0]

ckng, if you get a board from him, pls get a transformer from him too.. i still have his board with me and the project stucked simply because cant find suitable transfomer..

[ckng 0]

huangyong, thanks for the tip. You mean a 220:220 + 6.3V or 220:220 + 19V transformer isn't readily available? Is the 220:18 + 18:220 you mentioned earlier thread feasible? Shipping a heavy item like a transformer is going to cost

 

I was just looking and reading about Earmax/Earmax Pro vs the Morgan-Jones and there appear to be something missing in the M-J version. How did the Earmax people get everything into such a small enclosure? The original power adaptor is a 19VAC one, which powers the 3 filaments in series. But how the Earmax/Earmax Pro derive get the 220VDC with the apparent lack of another transformer is the interesting bit.

 

Anyone has one of these babies and don't mind posting photos of its internals?

 

Regards

CK

Edited December 6, 2005 by ckng

[huangyong 0]

hi ck, yes the 220:18 -> 18:220 is theorectically OK. but here only digi01 tried before, i dare not..hehe...