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  1. NelsonVandal

    A very DIY portable alu box

    Since the price of Hammond J1201 has become shockingly expensive at ELFA, I've desided to fight capitalism and make my own box. It's not as pretty or sturdy, but it does the job. Since the aluminium is thinner it's very lightweight. The heatsink on the LM317 is also DIY as you can see. I use...
  2. NelsonVandal

    Active passive ground?

    I've been fiddling some more with ground since I'm not satisfied with the active ground channel in my discrete amp. I don't know if it's because of a lowish output impedance or stability issues, and there are so many options tailoring the sound it's driving me crazy. Since I'm no EE I need some...
  3. NelsonVandal

    Bad, Bad ALPS RK097

    This inevitable little lump has annoyed me far to often. The difference between channels can be as much as 20 % at half volume, and that's where the volume mostly is. 20 % is very audible. ... but I've found a cure for it. Set the volume at half and add a resistor on the louder channel from...
  4. NelsonVandal

    To TzeYang or anyone... LTSpice transistors

    There are many models out there to be found with different specs. The results are roughly the same. Why not have a LTSpcie-model-thread. Do you know how to add them to LTSpice? .MODEL BC550 NPN(IS=2.24183E-14 Vceo=45 mfg=Fairchild Icrating=100m NF=0.996496 ISE=1.90217E-14 NE=2 BF=228.4...
  5. NelsonVandal

    Portable JISBOS with gain

    I've had my stripboard portable JISBOS for a while, modding it back and forth. From 3 ch JISBOS to 2 ch passive ground to 3 ch with opamp ground etc. I'm sorry I cut the board and removed the ground channel. The sound has been good all the time though, but it was best with JISBOS in all 3 ch. I...
  6. NelsonVandal

    Help me with this discrete amp

    I've been looking for an all discrete portable headphone amp, preferably all bipolar. Because of portability it has to either operate at low voltage (9V) in class A or AB using AAA's, or operate at higer voltage (18V) in class AB using 2x9V batteries. I know almost nothing about electronics, but...
  7. NelsonVandal

    AD797 now sounds like it should

    EDIT: This thread has become a bit longer than expected. In short. I implemented AD797 in a bad way and found the sound to be colored. Now it's better implemented and it sounds very neutral, and it has become my favourite opamp. Very smooth and unfatiguing, maybe there's a lack of...
  8. NelsonVandal

    AD823 failed its last chance

    I've always thougt AD823 sounds horrendous, and I've only listened to it for a couple of minutes at a time, before my ears start to bleed. Then I read the rave reviews of the Voyager and Solo, and I thought I should give them some more burning in. I think they have about 100 hours now. I've used...
  9. NelsonVandal

    Cheapish AD797 and OPA627 on Ebay, fakes?

    Do you think the cheapish AD797's and OPA627's are fakes, or just bought in large batches and so can be sold cheaper? They're delivered from Hong Kong.
  10. NelsonVandal

    LME49713, could be a killer opamp

    http://www.national.com/pf/LM/LME49713.html#Datasheet A current feedback, super spec'd opamp from National. They call it an audio opamp! "Easily drives 150 Ohm loads". High bias current of course. I guess one has to use caps or a DC-servo. Anyone tried it or thinking of trying it? I'm very...
  11. NelsonVandal

    Re: disturbing trend

    It seems that everybody's reading that thread. I think we all agree that portable amps sound worse than home amps, maybe that's why we like to talk about them - they're not good enough, and we tend to hope that every new amp that comes around will be the saviour, and all they really are is...
  12. NelsonVandal

    Portable JISBOS buffer-amp

    I finally boxed my JISBOS amp. It's gone through some changes. At first it was 3 ch active ground, but because of massive current draw and some stability problems, it's now 2 ch with TLE2426 as virtual ground. The sound was better with active ground, better mid frequenzies and better center...
  13. NelsonVandal

    Pocket LISAIII clones

    Just finished my LISAIII clones. One almost a LISAIII with AD744's and AD829. What differs is resistor values. I lowered them to something like suggested by W Jung in his article. I hoped there would be lower noise, but I think it's the AD744's that's noisy. I couldn't fit all the OS-CON's so I...
  14. NelsonVandal

    AD8099

    And you thought AD8397 was cranky. This chip is as stable as a teenage girl with borderline personality disorder. I managed to get the DC-offset down to - 50 mV, but the offset was drifting a bit and it seemed very sensitive to interference. I only have one chip left, but I connected it to my...
  15. NelsonVandal

    When braiding - do I need a shield?

    I've always used a proper shield (connected to one end) for my signal cables, but is it necessary to use a shield with a 3- or 4-strand braid?
  16. NelsonVandal

    Please help! "No company - no order"

    I've tried to order from Farnell Sweden "if you don't have a company - you can't order from us" . It's the same with RSonline. Now I've tried to order from Newark USA, and I must have a "carrier account", which i don't (why should I). Please help me, where can I order the stuff I want...
  17. NelsonVandal

    Do nice sounding stuff need burn in?

    There are definately audio products that sound fabulous right out of the box or right after being soldered. I've never experienced that those "nice sounding" amps change their qualities/tonality and going nasty and then again good while "burning in". I don't own any of those great products now...
  18. NelsonVandal

    Transistor rolling

    I just finished making new buffers for my amp. The only difference is I used BD137/38 instead of BC327/37 as output transistors. The difference in sound is astonishing. How can a single component make this difference? No wonder different opamps sound so very different. The BD's sound so...
  19. NelsonVandal

    Transistors, help to find matching pairs

    I've recently bought BC327-25/337-25 and BD137G/138G. It's impossible to match them, even though the corresponing pairs are from the same manufacturer (the BC's are Philips and the BD's are ON). For example the Hfe for the BC337's are about 310 +/- 10 and the BC327's 390 +/- 10. Is there a...
  20. NelsonVandal

    Most radical Xtra X1 mod

    Posted in DIY-section. http://www.head-fi.org/forums/showthread.php?t=240891 1. opamp removed and bypassed 2. small caps from output to ground (low pass filter) removed 3. output resistors removed 4. changed output transistors to BD137/138 5. active ground channel, LMH6654, added 6...
  21. NelsonVandal

    Pseudo balanced, buffers only amp

    I finally got around to build this one. 4 Sijosae buffers (the first ones with emitter resistors on the input), power supply with TLE2426 and opamp (PINT-like). Due to Hfe's far from each other in BC337/27 there's about 20 - 25 mV DC offset. I've done this to not have to use opamps for audio...
  22. NelsonVandal

    Xtra X1 mod

    I've always found this amp a bit on the dark side. It improved a great deal after the removal of the opamp, but still a bit dark and unclear. So now I've removed the small 47 nF capacitors going from output to ground. I can't see why they're there. At the same time I removed the 22 Ohm output...
  23. NelsonVandal

    MURDER by an opamp

    Once again I bypassed the input opamp in Xenos OHA-REP. The input amp is a LM4562 and the buffers are once again the original LMH6642's. This is a revelation. Input opamp's are killing sound quility. I did the same some time ago using AD746 (also one time AD8620) as input and LMH6654's as output...
  24. NelsonVandal

    Xenos OHA-REP with LM4562/LMH6654

    Just switched OPA2134 for LM4562 and 2xLMH6642 for 2xLMH6654 from National. I was really going to try AD8620 after Andrea's recommendations, but it's delayed from Analog. I'm going to let it burn-in for a while now. My first impression is that the congested Xenos-sound seems to be gone. The...
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