200mV DC offset? There is not chance that properly soldered parts would give you such big offset. Even if transistors are completely different. You did something wrong and you must check connections again. Parts can't be so bad. The highest offset that I saw once, was with combination of...

I would not remove 10k resistors because ALPS pot has always the same resistance but not on OPAMP side. It has always 50k on source side. On OPAMP side there is variation between 50 kOhm and 0 kOhm. So if I remove 10k resistor, when volume is close to maximum, I will get 50k resistance to ground...

Quote:   Any output source has DC offset, unless it has capacitor in series that block DC component. Feedback loop is not here because that involves more components and problems with ringing and oscillating if feedback loop is not made in proper way. Furthermore, if there was feedback...

Quote: Excellent. And 10 mV DC offset becomes 40-80 mV offset on output. I doubt that all people walk with multimeter in pocket and can always check if DAC has DC offset or not.   Stay with input capacitors. MCap are excellent. Old ERO (big blue box) are very good. Losses are close...

Quote: +/- 15 V power supply. 500 mA current.   You can use +/-12 V supply but output transistors will operate "closer to B class". (Now they are in high AB class).

Quote:   Try to find good external DAC/AMP and forget fancy Xonar/Blaster/etc gadgets. PC cards have good analog output section but problem is if PSU in your computer makes EMC noises or not. If it does, your XONAR will behave worse than hand made DAC/AMP soldered with left hand, on rusty...

Quote: Everything is better than Grado? I do not agree with you, at all. You should try Grado headphones on good (strong) amplifier. Grado headphones have tight and very strong low end when they are properly amplified. And miles away from mellow Senheisers. Also mids are not shy. Mids...

Quote:   Output RCA are volume controlled because everything goes through volume pot.

Quote: Whatever you do, try polystyrene as opamp coupling (10nF 63V). In combination with OPA2604 and Grado SR225 deep bass really kicks butt. Almost like sub woofer. With OPA2107 bass is higher but more wide, and I prefer this combination for watching movies.

Quote: It is strange...  With pots I am able to tune offset down to 1 mV. Probably transistors are from different series. How good is sound from the amplifier? Do you hear something unusual?  

Quote:   You should try lowering voltages with trimpot. The lower the input voltages are - the lower DC offset will be. So try lowering your input voltages to +/-15V or even lower (around 14.5V). Try lowering down both voltages. But that you will be able to do only if you have two...

If you want change capacitors, avoid WIMA FKP2 at all costs. It is high quality capacitor but it is not made for audio. Especially near OPAMP... Every polystyrene (even 50 years old) kicks its ass.   Only capacitor that is good for signal circuit is Wima MKP10. That capacitor behaves almost...

Quote: I like PRPs too. They are excellent.

Quote: Supply caps won't blow unless there is overvoltage or wrong polarity. Even in that case it will take a minute or two. You can put them AFTER transformer that has 1kVA power and they will be ok.   Diodes will blow when current through them is greater than specified. That means...

Quote: Try Cambridge DAC Magic or Audiotrack Dr DAC.  

Quote:   If you want to replace toroidal transformer with bigger (80VA) you should change 230V fuse to 0.63 A or 1 A. Cold start (inrush current) will be higher because bigger toroidal transformer (higher magnetization current when powering up the amplifier) and everything else (after...

Quote: Nice review man!   It seems that LC loves high current headphones from 32 to 64 Ohms. Grado works good too.   95% agree about opamps. I can't say nothing about OPA627 because I think that don't have genuine TI. Agree about OPA2604. It shines with Grado too.   It has to...

Quote: Sure!  That is the reason why I bought it!      

Quote: Nobody... My name is Nobody.  :)      

Quote:   The answer is subjective.   In real world there is no equipment that will give you 4x better results if you compare two things that are working right. Let's say that amplifier A has noise level that is around  -80 dB, then amplifier B (4xbetter) should have -320 dB... Which...

Quote: Still 2.5x less.

Quote: No. But costs 4 times less.  

Quote: I wouldn't bother myself with voltage right out of regulators. I would give more attention to DC offset. Point is not in achieving equally voltages between negative and positive rail. Transistors have their own characteristic so if you want to pull out best from your setup then you...

Quote:  Right value depends on frequency range that you want in your opamp. Stock capacitor is 100pF. Input impedance is variable and starts from 10k (when your volume pot is to max) and ends with 60k (when your pot is to min).   With 100pF you will have:   volume to max - 10k...

Quote:             These two. Resistors before opamp.  With 470uF capacitors they make RC filter that isolates opamp circuit. RC is used for noise and ripple suppression.