J-Mo Mk II headphone amplifier - Page 11 - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems

Headphone Systems Everything to do with Headphones

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th May 2013, 06:46 AM   #101
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
I was not aware mosfets could sound so clean.... I am wondering how a Zen should sound like

PS: Would you care to sketch the circuit you wrote about so I can visualize it properly ?
__________________
RC
  Reply With Quote
Old 27th May 2013, 10:46 AM   #102
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 103
Real quick and dirty, just to prove it works.

If you are clever, I'm pretty sure you can get rid of the bias network entirely.
Attached Images
File Type: png buffer.png (82.8 KB, 319 views)
__________________
RJM Audio (phonoclone.com / G+)

Last edited by rjm; 27th May 2013 at 10:54 AM.
  Reply With Quote
Old 27th May 2013, 04:46 PM   #103
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
__________________
RC
  Reply With Quote
Old 28th May 2013, 01:37 AM   #104
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 103
Unfortunately I can't take credit for this particular bit of cleverness. It turns out this circuit is already known.
Attached Images
File Type: png buffer 03.png (82.7 KB, 302 views)
__________________
RJM Audio (phonoclone.com / G+)
  Reply With Quote
Old 28th May 2013, 01:50 AM   #105
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Blog Entries: 103
original version redrawn to match the new circuit
Attached Images
File Type: png buffer mod.png (21.5 KB, 290 views)
__________________
RJM Audio (phonoclone.com / G+)
  Reply With Quote
Old 28th May 2013, 12:22 PM   #106
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Nice...
__________________
RC
  Reply With Quote
Old 18th November 2013, 10:49 PM   #107
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
I've just built up one of these using a kit from RJM (also built a sapphire) - thanks Richard!

Sounds great, although I need to go back and tweak the circuit for the 2n5486 that I had as I'm running out of adjustment on the trimmer. Anyway the thing is running a little underbiased but it sounds very good indeed. Big sound with very solid bass. I'm listening to some steely dan as I type this and the bass is absolutely rock solid on the k701s. I'm impressed!!

The sapphire is an excellent HPA too - either circuit is well worth building!

Fran
  Reply With Quote
Old 19th November 2013, 01:21 PM   #108
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
after including the kmultiplier before the psu shunts, sound became really amazing...

Where can I find the sapphire circuit ?
__________________
RC
  Reply With Quote
Old 19th November 2013, 10:14 PM   #109
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
RJM Audio Sapphire Desktop Headphone Amplifier


Tell me more about the kmultiplier - is that extra capacitance?

Excuse my ignorance!

Fran
  Reply With Quote
Old 19th November 2013, 10:42 PM   #110
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
Some numbers for mine:

V+ is 16V fed by a salas shunt. Bias at 5.5V (which stays steady once you do a final adjustment at working temp) and I changed R3 from 1.5k to 2.2k which allowed me to bring the bias up (I think my 2n5486 were a shade on the low side). Temp on the metal tab of the IRF510 is 45degC - which is ~25 above ambient. I'm more worried about the temp on the shunt heatsink which is sitting at 53degC now - and this will probably rise a bit more when the lid is on the box.

Its a joyous amp to listen too - really sucks you in a keeps you coming back, zero fatigue. Very powerful bass which just is grippy as hell - listening to some steely dan last night and the drums were just so tight, the ring from them was fantastic. Lovely treatment of vocals too - I'm listening to Terri Hendrix singing "The Dark" from the tribute to Guy Clark album and her vocals are lovely - warm, but detailed and no over-emphasis of sibilance. I'm really impressed with it!

Overall, I'd say the Sapphire is the cleaner more neutral amp and indeed it sounds great too, but I am developing a bit of a sweetness for the J-Mo!! I suppose the other thing is that the Sapphire is more of a universal amp in that it will take all impedances. However, you could do like I jsut have (inspired by the pic RJM posted in the Sapphire thread) and build both into the one chassis - that way you can use either!!



I'm listening to CDs, on a shigaclone, fed into a EUVL 9022 dac powered by LiFePO4 batteries and a JG filter/buffer powered by salas shunts and then to the J-Mo and then K701s.

Thanks Richard for the kits and advice along the way. Its a lovely amp!!

Fran
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
My Aleph 5 MK II Power Amplifier Agus Widarto Pass Labs 17 14th October 2010 08:06 PM
Classic Aragon (2004, 2004 MK II, 4004, 4004 MK II ) problems, experience and repairs MagicMarksy Solid State 1 22nd May 2010 04:36 PM
HLLY MK III 3 Vacuum Tube Headphone Amplifier Pre Amp hllyelec Vendor's Bazaar 2 19th July 2009 06:54 AM
7W HLLY MK-II Mini Vacuum Tube Amplifier New Product hllyelec Vendor's Bazaar 3 12th July 2009 01:36 PM
Carver mk II modified audio amplifier RichP714 Swap Meet 41 11th February 2009 04:52 AM


New To Site? Need Help?

All times are GMT. The time now is 03:10 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2