Morgan Jones headphone amp

[Edwin 0]

A few of the fellow sgheadf'ers been asking me to do a short review on the MJ amp that digi01 had helped me built. So here goes...

 

I'm currently using the MJ with an Amperex 6922 as input and a couple of Siemens E88CC as outputs. One thing to mention about tube amps is that they do really benefit from a warming up period. I would switch on the amp 15 minutes beforehand, to allow the tubes to warm up nicely before passing any signals through them.

 

Also, the tubes used is very important. Did tried to roll a few tubes on the MJ, realised that different tubes do produce different sonic signature.

 

The stepped attenuator that digi01 had sourced from diyzone feels good. Was expecting something much stiffer when turning but this wasn't the case. It feels like a normal volume pot just that it has steps on it.

 

I had tried to use the ATH-900LTD and Grado SR60 to listen to any hissing or hum across the whole volume range and pleasantly none was detected.

 

The MJ amp really brings out the details in my music. Previously, my 900LTD has the much publicized recessed mids problem, but when paired with the MJ, the mids are more pronounced. The bass department is tighter and has more force. The highs are well tamed like for most tube amps. The soundstage has also increased in both size and depth. I think AT's A series headphones do benefit from a good amp, against the common norm.

 

One thing I would like to bring out is that when pairing the SR60 with the MJ, I do experience some distortion in some of the music that I play, more prominently in the instrumental category. Kenny G's sax sounds like it going to burst the drivers anytime. I guess the SR60 has reached its max in resolving the signals.

 

digi01 has done a nice job putting the MJ amp together. The casing feels solid with no creaks or rattles. The built-in IEC plug is a added bonus, allowing the use of aftermarket power cables.

 

Think I will end my review here. Still need to let the MJ burn in for a period of time before I can conclude on the final sonic signature.

Edited April 4, 2006 by Edwin

[Edwin 0]

Back view of the MJ

[Edwin 0]

The TT and PSU board

[Edwin 0]

The heart of the MJ

[Spunky 0]

Nice! Where did u get the case?

[Edwin 0]

Nice! Where did u get the case?

Thanks for the compliment. The case was sourced by digi01 from China.

[neutralzz 0]

very nice how much did yours cost you? i had one mj from him too but a more compact design.

 

there's generally no hum unless you use a very high sensitivity earphone.

 

but after my exams i m going to take the transformer out and re-house it.. to maximize isolation your amp would be rather perfect if you had requested the psu to be in a similar separate box

 

i quite like the sound of this amp when coupled with a high impedance headphone. thats when the sound's very warm and magical. if you use a portable media player you can actually tweak the equalizer of the player to some higher bass setting.. and you get this very interesting "wet bass" that i had experienced. doesnt boom, it slams but sounds.. er. WET. very interesting. as a hifi person loss of bass control is terrible, but in this case control doesnt seem to be lost, just a decay difference.. i would describe juicy and fat sounding, especially when the double bass twangs on Forgiven/not forgotten blues by ray brown

 

with low Z headphones, doesnt sound as good, and as you've described, slight tendency to distort.

 

from my experience it sounds v good with a beyer, and with the type of highs it pushes for, would make the senn hd600/650s a good match as well

 

after quitting headfi, this is the only amp that i've been keeping.. very uncommon sound and musical in its own way, took digi01 abt 3 days to finish it via point to point, something special, and i cant bear to sell it either

[neutralzz 0]

*update

 

i just took the transformer out of the box, and re-wrapped it in 3m aluminium sheets and dumped it into a cardboard box :X kinda budget but tried to achieve maximal isolation

 

i even used an interconnect cable and rca plugs as a power line when the IEC plug wasnt enough (3 connections max)

 

and the difference is heaven and earth.

 

its so much sonically superior right now that when i first tested the amp with a cheap pair of earphones.. the senns mx 400s.. i was hooked.. hearing imaging and details and the precision.

[stocker 0]

Hi, I'm also using a DIY tube headphone amp based on the MJ design, however, I'm using the output from my preamp to drive the WCF pair of 5687s (instead of 6922). I'm using a Beyer 990, which is 250ohms and it absolutely rocks (like what you experienced). But for low Z cans, like Grados, you will probably get better results if you include some kind of negative feedback, I don't think it's the cans fault. The 6922s does not have enough drive for the low Z, thus some amount of negative feedback would aid considerably. And if you make one which is adjustable, then your amp can run many type of Z cans by tweaking the feedback!

Edited June 22, 2006 by stocker

[stocker 0]

Just to add on, you can possibly eliminate the hum by using DC powered heaters/filaments and I cant tell from your picts if you have done that.

 

Found another thread with DC heaters and feedback on thos board:

http://www.sgheadphones.net/index.php?show...c=493

Edited June 22, 2006 by stocker