Thor, an all discrete Lateral FET Headphone Amplifier.

[Snaffe]

Originally Posted by Neutrality

Thor AB MKII updated with 78L09/79L09 regulators for the DC servo.

The board is now done and ready for manufacturing.

First a big thankyou to you for posting your build and also do. to all the peop that keeps diyaudio.com running.

If you have not bought your Beyerdynamic yet you should listen to the 990 before going for the 880.

I actually prefer the 990 overall than the 880 for casual listening (and I am not alone)+(I also have 3 Stax phones to give you an indication of the quality level I am going out from)

http://www.4sound.dk/shop/hovedtelefoner/beyerdynamic/dt-990-pro-250-ohm.html

And its more than 800 Danish Dollars cheaper than the 880 (approx 135 USD)
You can listen to it at Aage (4sound) store but bring your own music and equipment, cause aages is not the best.
If you are looking for a phone for Ipad/Iphone give the DT1380 ad listen too.
http://www.4sound.dk/shop/hovedtelefoner/beyerdynamic/dt-1350.html

Even if it is 80 Ohm it gives a good sound level cause of its high efficiency.
Maybe that comes from the powerfull magnets used ?
My son prefers the DT1350 to the 990 for use in his recording/mixing sessions, also why you can wear them for ours w/o problems, so if you are young and not like me only can hear max 14-15 kHz tops that can (may) be the phone for you.

[Neutrality]

I have been looking at getting the DT 880 PRO, the price is lower than DT 880 Premium and the headband is of a considerably higher quality than the Premium headband.

[Snaffe]

Originally Posted by Neutrality

I have been looking at getting the DT 880 PRO, the price is lower than DT 880 Premium and the headband is of a considerably higher quality than the Premium headband.

Yes i notished that phone also, have to listen to it and bringing the 990 (250 ohm)with me so I can compare them, also trying to persuade Aage to take The Tesla T1 home so I could hear it.
But until now w/o luck.
Talking about headband, for me the 990 and the Stax SR-202 fits my head much better than the SR-507 so a fit test on top of the listening test is mandatory for me.

Btw have you considered to offer paired transistors together with the PCB cause hate to buy maybe 100pcs to get only the few needed for the Thor ?

[Neutrality]

Originally Posted by Snaffe

Btw have you considered to offer paired transistors together with the PCB cause hate to buy maybe 100pcs to get only the few needed for the Thor ?

Well, I do have some input JFET's left(bought 50 each of SK246/SJ103) but they aren't that closely matched, I could maybe match each pair within 1mA IDSS and each N and P channel pair within 1mA IDSS. Matching within 1mA IDSS should be more than close enough. But it is time consuming and I'm a little lazy

Would probably have to charge $20 USD for a complete set of matched JFET's for 2 Thor Amp Boards, not exactly cheap. Ebay is cheaper.

I also have more than enough of KSC3503 and KSA1381 BJT transistors left and they require no matching.

I don't have any 2SK1056/2SJ162 Lateral FET's left.

[Snaffe]

Originally Posted by Neutrality

Well, I do have some input JFET's left(bought 50 each of SK246/SJ103) but they aren't that closely matched, I could maybe match each pair within 1mA IDSS and each N and P channel pair within 1mA IDSS. Matching within 1mA IDSS should be more than close enough. But it is time consuming and I'm a little lazy

Would probably have to charge $20 USD for a complete set of matched JFET's for 2 Thor Amp Boards, not exactly cheap. Ebay is cheaper.

I also have more than enough of KSC3503 and KSA1381 BJT transistors left and they require no matching.

I don't have any 2SK1056/2SJ162 Lateral FET's left.

I will try to pm you so we can talk

[Neutrality]

I have ordered MKII of my amp board PCB's and they are on their way to me. I have also ordered MKII of my No Thump PCB's, they should be shipped sometime this week or earlier next week.

I'm almost ready to buy a pair of Beyerdynamic DT 880 PRO 250 Ohm headphones, maybe I'll have them next weekend for testing on V1 of my amp. Should give a good idea of the performance on MKII, since the designs are almost 100% identical and with the same performance.

So besides upgrading all my boards to MKII I'm also changing the volume pot in my amp. I had a little bit of background noise(NOT 50 or 100 Hz from mains) when turning my 50K pot above 10 O'clock, going down to 10K would hopefully reduce that. Also, you still get all kinds of crappy sounds from your PC when connecting the amp directly to the PC. Getting a decent USB DAC(Cambridge Audio DacMagic 100 most likely) should also improve the noise levels.

[Neutrality]

This thread has been quiet for a while but expect to see a few updates this month.

I have been preparing for my exams the last 7 weeks so I haven't had much time for this project. However, this Wednesday I passed my exams with top marks, which means that I am now an Electronics Technician, Yay for me.

Anyway, since I now have Amp Board MKII and No Thump Board MKII PCB's in my hands I can move along with mounting and testing of those PCB's. I don't expect any issues since the MKII PCB's are basically the same designs with a few tweaks and fixes as well as small layout changes.

I expect to be finished with those 2 MKII boards before the end of this month with the Supply Board MKII finished sometime next month.

[Telstar]

keep up the good job

[Nisbeth]

Congrats on the exam, looking forward to seeing the updates to this project in due time.

/U.

[Neutrality]

Originally Posted by Neutrality

This thread has been quiet for a while but expect to see a few updates this month.

I have been preparing for my exams the last 7 weeks so I haven't had much time for this project. However, this Wednesday I passed my exams with top marks, which means that I am now an Electronics Technician, Yay for me.

Anyway, since I now have Amp Board MKII and No Thump Board MKII PCB's in my hands I can move along with mounting and testing of those PCB's. I don't expect any issues since the MKII PCB's are basically the same designs with a few tweaks and fixes as well as small layout changes.

I expect to be finished with those 2 MKII boards before the end of this month with the Supply Board MKII finished sometime next month.

I have finally upgraded my Thor headamp with MKII Amplifier Boards and MKII No Thump Boards.

Increased supply rails to +/-15VDC, reduced bias to around 120 mA pr output FET.

My amp is now significantly cooler running than before, mostly because I'm using the same transformer as before so I only have to drop a few volts across the regulators instead of around 5 volts with +/-12 VDC supplies. Total quiescent current of the amp is also reduced from 200mA to 160mA and that also helps with the heat.

The sound? No difference at all compared to V1 which is what I expected.

Only things left somewhere in the future when I get around to it, is an upgrade of my Supply Board to MKII and substituting the 50K Alps RK27 volume pot with a 10K version of the same.