[DivineCurrent]

Hey guys, I purchased an Objective 2 + ODAC combo from JDS labs, the limited edition with the RCA input/output option, and I have a little problem with the sound via RCA input. Whenever I connect it to a CD player that doesn't have a volume option for RCA out, I get bad clipping with pretty much any recording. This only happens with the RCA option, not the ODAC. Does anyone else have this problem, or does anyone know how to fix it? Or should I just not use it with CD players or other similar players?

 

[MrEleventy]

You can try clipping a resistor to get a 1x/2.5x gain vs the 2.5x/6x stock.

 

[DivineCurrent]

I don't really want to clip off a resistor cause I need that 6x gain for some of my 600 ohm phones, which actually sounds good from my laptop. I just don't understand why the specs match up correctly with the CD output to the O2 input: I'm using a Nakamichi CDP-2A which has 2.5 V output and according to NwAvGuy's specs, the O2 can handle anything up to 2.8 V without clipping at 2.5x gain. I must be doing something wrong...

 

[DivineCurrent]

well, I plugged the O2 into the preamp output of my receiver, and there's no more clipping so the CD player must have been too much for the O2.

 

[CADCAM]

I believe my NAD has a 2 volt output and I don't have an issue with my O2, I also have 600 ohm Beyers and never need to use the 6X gain. I'm around 12:00 and plenty loud. BTW I do have rear RCA's on the O2.

 

[DivineCurrent]

  I believe my NAD has a 2 volt output and I don't have an issue with my O2, I also have 600 ohm Beyers and never need to use the 6X gain. I'm around 12:00 and plenty loud. BTW I do have rear RCA's on the O2.

Huh, that's strange. I also notice the clipping when I plug a dvd/blu ray player directly into the O2. I'm thinking even the 2.5x gain is making it sound bad, I might have to clip off those resistors to get 1.0/2.5x gain instead.
Oh, and is yours the default 2.5/6x gain?

 

[DivineCurrent]

Ok, I clipped of those resistors, but the clipping is still there. I think I'm just going to use it with my laptop. I'll find a different amp for my CD player. 

 

[CADCAM]

I use my O2 with 2 DVD drives, an Oppo and a Samsung, I also use it with an Onkyo Integra and NAD cd player and have never had clipping issues. My O2 is stock gain and I only use the 2.5X lowest gain setting. I tried the higher gain setting once and did not like it when the 2.5X setting worked so well. I will try the higher gain again and see if I get any clipping with any of my headphones. I believe the higher gain had a higher noise floor and was just to much for me...sounded over-saturated if I recall. 

 

[tomb]

Yep.  This is a well-documented issue with the O2 design.  Specs are one thing, but there many instances where a few tenths of a volt in real-world use can throw the amp into clipping.  This is because the O2 deviates from almost every headphone amplifier design available by placing the volume pot in-between the signal-amplification stage and the output buffer stage.  So, the signal gets amplified before it reaches the volume pot, which is the primary attenuation device in any amplifier.  Every other headphone amp puts the volume pot directly at the input.  Thus, any input signal gets attenuated first - before amplification.  Any clipping that might ever occur would be because the output load itself (headphone or speaker) is too hard to drive for the volume level selected.  In that case, you are still in control and can simply reduce the volume.  In the case of the O2, if the source is too strong for the amp it may clip regardless of volume level selected. 
 
To be fair, there are advantages to placing the pot after the signal amplification stage.  You can get a much higher input impedance reflected to the source, for instance, which can result in a much more linear response and a higher S/N level.  The problem with that kind of design decision is that it depends on every source manufacturer in the world to hold to a standard limit of output voltage level.  The results of deviating from that are what one may call "show stoppers," too - in that the amp clips, which is unacceptable in any audio environment.  JMHO, but designing something that depends on everyone else to adhere to a standard - along with a result of total failure when they don't - is not a good design choice. 

 

[DivineCurrent]

  I use my O2 with 2 DVD drives, an Oppo and a Samsung, I also use it with an Onkyo Integra and NAD cd player and have never had clipping issues. My O2 is stock gain and I only use the 2.5X lowest gain setting. I tried the higher gain setting once and did not like it when the 2.5X setting worked so well. I will try the higher gain again and see if I get any clipping with any of my headphones. I believe the higher gain had a higher noise floor and was just to much for me...sounded over-saturated if I recall. 

Huh, my O2 must have been defective or something... I have sold mine since then, but I would like to get another one soon. Also, mine was the O2+ODAC combo, I don't know if that has something to do with the internal parts being changed maybe contributing to the clipping problem. 

 

[CADCAM]

Was yours a JDS Labs built unit? JDS did an excellent job building mine and I requested rear RCA jacks as well. I didn't need the battery so JDS credited me and installed the RCA's free if I recall correctly. I did order from another builder and had to return the amp...twice...then asked for and received a full refund (minus shipping)

. I have since tried the amp on high gain and it doesn't sound as bad as I thought, actually if I am driving the 600Ohm Senns it's fine but with my other headphones it can get very loud quickly. I just seem to prefer the low gain setting. I am a huge fan of this amp and after purchasing a couple of other amps am even more of a fan now.

 

[DivineCurrent]

  Was yours a JDS Labs built unit? JDS did an excellent job building mine and I requested rear RCA jacks as well. I didn't need the battery so JDS credited me and installed the RCA's free if I recall correctly. I did order from another builder and had to return the amp...twice...then asked for and received a full refund (minus shipping)

. I have since tried the amp on high gain and it doesn't sound as bad as I thought, actually if I am driving the 600Ohm Senns it's fine but with my other headphones it can get very loud quickly. I just seem to prefer the low gain setting. I am a huge fan of this amp and after purchasing a couple of other amps am even more of a fan now.

Yeah it was JDS Labs. I think I'll just go ahead and order a separate O2 and ODAC, for more flexibility. 

 

[CADCAM]

  Yeah it was JDS Labs. I think I'll just go ahead and order a separate O2 and ODAC, for more flexibility. 

I'm not sure exactly how much the combo is from JDS but I just purchased a Beresford Bushmaster MKII here on Head-Fi and it's pretty nice. I have an O2 and the amps sound similar. The nice thing is the Beresford has a internal DAC and a little better desktop presence. It also has 2 toslink and 2 co-ax inputs but no USB so if you are feeding it from a computer it's prob not for you. I don't think I could tell them apart amp wise both clean and articulate. There is plenty of info here and on the web about the Beresford DAC\amp.