iBasso PB-2 Pelican fully balanced portable, DB-2 Dac . . HiFlight recommended op amps page 16. . - Page 5

also a tip for Ron and all you keen opamp rolers; if you havent tried them yet the LME46990 is SUPERB!! has taken the place of AD797 as my favorite opamp cheaper too. 

Something like this qusp ?

Have you tried the newer LME49610 which is a direct replacement to this the LME49600 

The 49610 has 120Mhz BW in low current mode compared to LME49600 110Mhz

and at high C mode it is 200Mhz instead of the LME49600/Buf634 180Mhz 

The one with the crazy spec is LME49990 PSRR 144db CMRR 137db input noise 0.9nV/rootHz THD + N 0.00001%

Never seen anything like that  

Can't seem to find the  LME46990. One thing I get annoyed by National is that they have so many closely spec parts 

I have some of the 49990's and will give them a try in my PB2. I hadn't gotten around to trying them yet. Should also work nicely in the P4. Is that where you are using them?

Quote:

Originally Posted by qusp

also a tip for Ron and all you keen opamp rolers; if you havent tried them yet the LME46990 is SUPERB!! has taken the place of AD797 as my favorite opamp cheaper too.

Quote:

Originally Posted by jamato8 

I wondered about the 32 volts of swing since the battery is 12.6. You can maintain a full 32 volts while using the adapter. So since it is running from the adapter, I would think the better the adapter, the better the sound but 32 volts from a portable and 2.5 watts is more than I though a portable is moving some power. 

Actually, I am pretty sure the battery is 16 volts, but Hiflight can probably confirm this. That would make sense. The charging jack on the back says 16 volts, while the one on the PB1 is only 12.6 volts. So 16 volts seems consistent. Also, the battery is definitely bigger than the PB1's.

Yes, the battery in both the PB2 and P4 is a 16v lithium.  The chargers are identical.  My experience with opamp rolling in the PB2 today has convinced me that there is no non-electrostatic headphone that the PB2 cannot drive with authority.  The PB2 seems to show more sonic differences with different opamps than I have experienced with other amps.  Many of the differences are not subtle. 

Sounds awesome! What about the K1000? I know you posted your rig of the Boomslang and PB1 with the K1000s a while back, and mentioned it lacked some authority in the bass but you loved it because you could take it around. I think I am going to get this amp sometime, it is just a matter of when.

BTW, how do balanced KSC75s sound out of this? If you no longer have a pair, can you mention the improvements to balancing them? I just got a pair and really love them, and am going to really mod them in the future.

Thanks. Just curious, how did you terminate them?

I don't have my KSC75's balanced, but I do have a set of balanced KSC35's with TWag cable and they sound superb, more like multi-hundred dollar phones. The PB2 drives my K1000s much better than the PB1 did. Bass is now very satisfactory. Not much different than my desktop. I must say, though, that I have changed opamps MANY times today searching for what will ultimately become the PB2 Topkit. I am also using the stacked BUF634's in Hi-C mode.

Most of the improvements that I noticed as a result of balancing my KSC35's were related to imaging and stability of soundstage. Tonally, I don't notice a great deal of difference.

I have been too lazy to keep changing gains, as this is accomplished by internal jumpers. Even at high gain which is what the PB2 comes with as default, the channel balance is perfect even at the very low settings necessary with the high gain and KSC35s. I can also turn down the input from my source if I need to as that is easier than changing jumpers. .  BTW, all of my IEMs and smaller phones I terminated with mini-XLR connectors, then made up a Hi-Rose to Mini XLR pigtail that I can use with all of my smaller phones.  For the larger cans, I made up a Hi-Rose to standard XLR 4-pin pigtail.  
 

Quote:

Originally Posted by GeorgeGoodman

Sounds awesome! What about the K1000? I know you posted your rig of the Boomslang and PB1 with the K1000s a while back, and mentioned it lacked some authority in the bass but you loved it because you could take it around. I think I am going to get this amp sometime, it is just a matter of when.

 

BTW, how do balanced KSC75s sound out of this? If you no longer have a pair, can you mention the improvements to balancing them? I just got a pair and really love them, and am going to really mod them in the future.

Quote:

Originally Posted by madwolf 

 

 

Something like this qusp ?

 

Have you tried the newer LME49610 which is a direct replacement to this the LME49600 

The 49610 has 120Mhz BW in low current mode compared to LME49600 110Mhz

and at high C mode it is 200Mhz instead of the LME49600/Buf634 180Mhz 

 

The one with the crazy spec is LME49990 PSRR 144db CMRR 137db input noise 0.9nV/rootHz THD + N 0.00001%

Never seen anything like that  

 

Can't seem to find the  LME46990. One thing I get annoyed by National is that they have so many closely spec parts 

aha I knew I hadnt got that model right it didnt look right.(didnt have enough 9's) its the LME49990 that I meant. I have some I got for 'the wire' project on DIYA and I tried them out in the FiQ just for kicks and whoa!! they are there to stay and i'll have to get some more. I'll try the LME49610TS but in all honesty if you ever go to HiC mode they will oscillate in RF any time your mobile phone rings. 110 is already too much unless the layout and cct are designed for it, needs bandwidth LIMITING, not to be put into HiC mode without bandwidth limiting (~20pf in the feedback loop) IMO and if the leads arent damped and no compensation it wont look good on the scope, so 200mhz is a pointless spec for audio IMO.

kinda like you have, but if you look there is quite a bit of room, so I had in mind a useful amount of heatsinking to take advantage of the better dissipation package, rather than just an adapter. with your setup there you wouldnt be able to get anywhere near the full 250ma current output specified, certainly not at this voltage

right OK well Jamato: 16V is more like it, but where are people getting these output swing (voltage) numbers from? unless there is some sort of charge pump it seems too high to me. of course there is probably something tricky going on i'm unaware of

and yeah you're right national has too many chips that all have almost the same model number, thats why I put that 6 in there because almost all up till now started with 496 or 497, so I guess they really busted out with this one :D

Quote:

Originally Posted by HiFlight 

I don't have my KSC75's balanced, but I do have a set of balanced KSC35's with TWag cable and they sound superb, more like multi-hundred dollar phones.

Ron, I'm always up for a challenge, but is it seriously worth the cost to have a pair of KSC-75s balanced ? I have a pair on the way, but they cost me $39 delivered - I guess its different if you can do this stuff yourself, but for me it would be serious overcapitalisation :)

The Hi-C as provided by iBasso is not the maximum wideband, but rather about halfway between low and high bandwidth.  The does have the effect of lowering the input impedance of the buffer stage and providing better square-wave response of low-signal inputs.  This arguably can result in improvement of low-level detail while the lower impedance allows an increased, albeit farly small, current flow from the LR opamps.. 

When driving my HE-6 to my normal listening level using high gain,  the stacked buffers running Hi-C get only slight warm to the touch.  Although my cellphone is in fairly close proximity to my PB2, I have not experienced any RF interference while using the Hi-C configuration. 

I do have some of the LME49990 opamps that I will try.   The specs do look very good, but I have been somewhat unimpressed by some of the other LME49xxx opamps, so they kind of gotten placed on the back burner. 

I will say that my current configuration is really making my HE-6 sing sweetly!