jlow 0 Report post Posted February 2, 2010 Someone came to audition the MJ Headphone Amp, liked it so much that he decided to take it home and never want to return it again. So I made another. This time with tube rectification and running on ac heaters. Sounds just the same. Switchable between normal interconnects and a self made iPod cable connect jlow Share this post Link to post Share on other sites
fonebone 0 Report post Posted February 2, 2010 Thats pretty darn nice. Like the wooden sides. Share this post Link to post Share on other sites
zer061zer0 0 Report post Posted February 2, 2010 Very nice Chassis, tube rolling is always much simpler with tubes exposed. Share this post Link to post Share on other sites
jlow 0 Report post Posted February 3, 2010 Thats pretty darn nice. Like the wooden sides. Thanks. Basically constructed with parts and tubes which i can lay my hands on at home, other than a few resistor values. Notice that the sound is warmer and easier on listing. Primary guess is the tube rectification. My last amp is SS rectified and I just can't help but feel that it is a tad faster and reponsive on those fast notes. But then again, its for personal use so who cares. But need to find a cover for the naked R-core though... jlow Share this post Link to post Share on other sites
jlow 0 Report post Posted February 3, 2010 I have got the EH 6922s and Russian 6N1P and 6H23 (6DJ8) on hand. They all sounded roughly the same. But preferred config is 6H23 on the pre stage and 6N1P on the 2nd stage. As for the rectifier tube using Sovtek 5AR4. Tried 274B the other day but the transformer vibrate a bit, probably due to the higher current draw. Will try that again and listen. tried Vishay 0.47uf coupling caps. Upon listening unsolder them straightaway and threw them away. Now using my favourite Hoveland Musicaps. They are good. Tried Murdorf Gold Oil Caps from Robert and the rest is history. But soldered back the Hovlands as I am using the Murdorfs for other purpose. Very nice Chassis, tube rolling is always much simpler with tubes exposed. Share this post Link to post Share on other sites
zer061zer0 0 Report post Posted February 3, 2010 Very nice, My xiangsheng 708b, a mj clone(thats what i heard) have the hovlands as the input and output, and the mcap supreme at the interstage(not sure of the term). Using mullard 6922 and tungsol 2c51. had a spare pair of amperex 6922. Looking back at the amp now, I felt like an idiot. hahahaaaaaa By the way u have any speaker for sale again? Share this post Link to post Share on other sites
jlow 0 Report post Posted February 4, 2010 Nope lately not shifting house so not selling anything to lighten the load. Lately doing this Speaker Upgrade jlow I have got the EH 6922s and Russian 6N1P and 6H23 (6DJ8) on hand. They all sounded roughly the same. But preferred config is 6H23 on the pre stage and 6N1P on the 2nd stage. As for the rectifier tube using Sovtek 5AR4. Tried 274B the other day but the transformer vibrate a bit, probably due to the higher current draw. Will try that again and listen. tried Vishay 0.47uf coupling caps. Upon listening unsolder them straightaway and threw them away. Now using my favourite Hoveland Musicaps. They are good. Tried Murdorf Gold Oil Caps from Robert and the rest is history. But soldered back the Hovlands as I am using the Murdorfs for other purpose. Share this post Link to post Share on other sites
zer061zer0 0 Report post Posted February 4, 2010 Looks interesting. havent see such a big magnet.. I am looking at getting a pair of speakers, but again I am not in Singapore yet, shifting is tough man. Share this post Link to post Share on other sites
jlow 0 Report post Posted February 10, 2010 The internal, not exactly neat but as long as it works... Looks interesting. havent see such a big magnet.. I am looking at getting a pair of speakers, but again I am not in Singapore yet, shifting is tough man. Share this post Link to post Share on other sites
jlow 0 Report post Posted February 28, 2010 (edited) Ok back to the headphone amp. I took a long time to solder the connecting wire to the iPhone/iPod socket because the pins are so tiny. But it worked. The config is something like this Pin 2 - Gnd Pin 3 - Right Out Pin 4 - Left Out Pin 11 - Gnd, just short to Pin 2 Left and Right out are constant (cannot be controlled by volume pot) at -1 volt rms (believe the usual is -2 volt rms). The amp appeared soft when plugged to iPhone and iPod. When connected to iPod it works fine. When connected to iPhone it shows an error message (something like "You are not plugged in to a supported device.") but works fine. The trick that I found out later is to connect a 68k resistor from pin 21 to ground (short other end of 68K resistor to either Pin 2 or 11) and it should suppress the error message. But if you are too lazy to do that then just live with the error message. This will not blow the iPhone up. I used a 50k volume pot instead of the 100k as recommended. It has some distortion when I crank past 12 o'clock. So out comes the 50k pot and in goes a 100k pot. To make sure that all goes well, I have also bought a pair of input trans from Robert that can step the signal up by 6 times. Let see if this solves the bug for the iPod and iPhone for appearing too soft when plugged in. Adding the input trans is just like adding caps to the iPhone and iPod signal out (if you are familiar with the imod) that did uplift the sonic performance tremendously. But if you are really fussy about what you hear, don't try the unmodded iPhone and iPods, they will disappoint you. The input trans serves it purpose well in this case, and for a change I used trannys instead of caps for this case. Pics Close up, the input trans are housed in an external box so that they can be use for other devices, eg. SS, Chip Amp and others jlow Edited March 1, 2010 by jlow Share this post Link to post Share on other sites
