Does anyone know where i can get an Mj earmax clone pcb???? - Head-Fi: Covering Headphones, Earphones and Portable Audio

onform · #1 (**permalink**) 05-03-2008, 05:23 PM

I want to build this kit and was wondering if anyone had any boards for sale??? or knows where i can get one..ideally with instructions/parts list but not essential.

Anyone else looking to build the clone of this great headphone amp?

Any help would be greatly appreciated..thanks

dBel84 · #2 (**permalink**) 05-03-2008, 05:32 PM

You should look at the tweaked version of the circuit = CJ , I have not built it but I would accept that the changes made were an improvement over the original.

I don't know about pcb's, however this amp should be fairly staright forward to build PTP ( assuming you have experience working with high voltages and tubes? ) ..dB

edit ..... just noticed that you already have the earmax pro ! why not build an amp that uses a different topology?

onform · #3 (**permalink**) 05-03-2008, 05:37 PM

Quote:

Originally Posted by dBel84

I don't know about pcb's, however this amp should be fairly staright forward to build PTP ( assuming you have experience working with high voltages and tubes? ) ..dB

This will be my first project so i would ideally get hold of a board.

Uncle Erik · #4 (**permalink**) 05-03-2008, 06:05 PM

You might want to ask around at Headwize. I think some members there had PCBs made up at one time. There might be some extras still floating around.

Going point-to-point isn't that much more difficult. It's not as easy as stuffing a board, but how hard is it to loop wire/lead through a hole, squeeze it with pliers, then apply solder? It's a little more involved, but you can absolutely do it. Think of all those people who started out years ago building ST-70s and their own radio gear. They did it and so can you.

nikongod · #5 (**permalink**) 05-03-2008, 06:17 PM

there was a smallish group buy for the boards a LONG while back. i dunno if any are still unbuilt.

for whatever its worth, when i consider the difficulties with casework to accommodate a rigidly fixed PCB and associated mounting hardware, building PTP may turn out easier overall.

indikator · #6 (**permalink**) 05-04-2008, 03:37 PM

a newbie question,

why is it danger working with tubes and high voltage?
isn't it disconnected from wall socket when we build it?

AndrewFischer · #7 (**permalink**) 05-04-2008, 04:13 PM

Quote:

Originally Posted by indikator

a newbie question,

why is it danger working with tubes and high voltage?
isn't it disconnected from wall socket when we build it?

It isn't when you are using it.

If you make an error you could have +400V or more on a volume knob, headphone jack or other exposed component.

If it doesn't work, you may need to troubleshoot it with the power on. Also dangerous if you don't know what you are doing or make a mistake.

By dangerous I mean potentially fatal.

tomb · #8 (**permalink**) 05-04-2008, 04:19 PM

Quote:

Originally Posted by indikator

a newbie question,

why is it danger working with tubes and high voltage?
isn't it disconnected from wall socket when we build it?

Andrew is correct, but it's dangerous when disconnected, too. That same high voltage is often stored for long periods in the capacitors. If one of those is accidentally discharged, it could be enough to throw you to the floor - or worse.

onform · #9 (**permalink**) 05-04-2008, 08:00 PM

Thanks guys.. I am gonna consider p2p then i can have the layout as i want it. and put the ps in a different enclosure.. has anyone had experience with building this amp??

indikator · #10 (**permalink**) 05-04-2008, 09:03 PM

gulp...
you guys freak me out already...
how about sitting on bed, I don't get shock by my computer that way

and then, is it true that a balanced amp is two stereo amp?
can we build this amp balanced?
just imagine it,
earmax + HD650 = sinergy
balanced + HD650 = improvement
=> balanced earmax = heaven like.....

vvs_75 said he did build this amp, why not invite him to this thread?

Todd R · #11 (**permalink**) 05-04-2008, 09:18 PM

I built one several years ago and if I remember correctly I got a board from Chu Moy of Headwize.

ericj · #12 (**permalink**) 05-04-2008, 09:43 PM

I don't think Chu has ever sold boards.

digi01 - the guy behind the poor-quality and buggy soha boards - used to sell an MJ amp board on headwize, though. maybe he still has some, but qty1 shipping from china could be annoying.

Todd R · #13 (**permalink**) 05-04-2008, 10:34 PM

Quote:

Originally Posted by ericj

I don't think Chu has ever sold boards.

digi01 - the guy behind the poor-quality and buggy soha boards - used to sell an MJ amp board on headwize, though. maybe he still has some, but qty1 shipping from china could be annoying.

digi01,
That's the name, not Chu. My mistake.
My board was fine.

nikongod · #14 (**permalink**) 05-05-2008, 12:01 AM

Quote:

Originally Posted by indikator

and then, is it true that a balanced amp is two stereo amp?
can we build this amp balanced?
just imagine it,
earmax + HD650 = sinergy
balanced + HD650 = improvement
=> balanced earmax = heaven like.....

2 separate MJ's will probably have too much gain, build them with a long-tail phase splitter as the input stage, and the same output stage.

this will also allow a "bridged" output from a single ended source.

i would jsut build it single ended, its well documented, and works well for the hd-600/650

vvs_75 · #15 (**permalink**) 05-06-2008, 12:18 AM

I built this one:
Building a "Bottlehead" Cavalli-Jones Headphone Amplifier

I would say that this one not difficult to build even for a first project.
The instructions have everything you need to finish it, just do what it tells you and you will be fine.
The case work/parts placing will take about 60% of total work.

PSU in this amp very convenient. It have separate switch for the tubes filament supply. So during long listening the tubes could be always on and ready, and you can just use second switch for the main supply. Feed back also helps. I could adjust it and drive my 600 ohm DT 990 with ease.

I used Hammond case and redesigned the parts layout a bit for more convenient wiring.
The MJ is a very musical good sounding amp. My tubes are current production EH 6922 gold pins cryo. I liked the amp so much that I sold my Earmax Pro. Even though almost all my parts are boutique if you go with the standard parts listed in the BOM you will be pleased with the sound.

I am now recasing it. Here are pics of the old case.

Note: If you going to build the amp place RCA inputs as close to the volume control as possible. ( I placed the RCA jacks on my second case on the side very close to VC, just few inches from it.) That is one of the reasons I am recasing it. My old amp had a transform. hum at max volume. You will never listen at that volume and at regular level the hum was not present but I am perfectionist by nature and could not stand the fact.