[Lohb]

Quick mention to PB2 opamp rollers..not sure any you tried OPA1622...pretty amazing little chip for the price..it is the high current version of OPA1612 and 1612 was the replacement for LME49990 as far as I read.
If you liked LME49990, then give this little chip a try ! Am using 2 in series in a small barebones ES9038Q2M DAC/amp (not Khadas in signature below)...transparency,layering,dynamics,micro-detail,common mode noise suppression..it's all in there.
Specifically designed for driving headphones.

 

[DBaldock9]

Quick mention to PB2 opamp rollers..not sure any you tried OPA1622...pretty amazing little chip for the price..it is the high current version of OPA1612 and 1612 was the replacement for LME49990 as far as I read.
If you liked LME49990, then give this little chip a try ! Am using 2 in series in a small ES9038Q2M DAC/amp...transparency,layering,dynamics,micro-detail,common mode noise suppression..it's all in there. Specifically designed for driving headphones.

With such a high current output capability (~145mA), are you using them in your PB2 with the pass-through headers in the Buffer sockets?
I wish there was a single channel version of the OPA1622, which could be used in the buffer locations.
Since there isn't, I guess adapters could be built, to plug one of dual channel op-amp into two side-by-side sockets.

 

[Lohb]

With such a high current output capability (~145mA), are you using them in your PB2 with the pass-through headers in the Buffer sockets?
I wish there was a single channel version of the OPA1622, which could be used in the buffer locations.
Since there isn't, I guess adapters could be built, to plug one of dual channel op-amp into two side-by-side sockets.

No longer have PB2, just a pretty great rolling chip heads-up.
OPA1611 is single, but 1/3 current output of 1622.

 

[DBaldock9]

No longer have PB2, just a pretty great rolling chip heads-up.
OPA1611 is single, but 1/3 current output.

There is the LME49600, with ~250mA of output current, which is only available in a TO-263-5 surface mount package.
I did a quick search, but haven't found a TO-263-5 to DIP-8 adapter - to make it easy to use in the PB2, and other amps with DIP-8 sockets.

 

[Lohb]

Right. Google images maybe churn something up....

OPA1622 coming quite close to the new gen. THXAAA stuff on the 2 measurement fronts below.
Seems to be a chip that steps into discrete chip performance territory.

 

[plutonim]

I did a quick search, but haven't found a TO-263-5 to DIP-8 adapter - to make it easy to use in the PB2, and other amps with DIP-8 sockets.

https://www.ebay.com/itm/1PCS-LME49600TS-LME49600-ON-DIP-ADPTER-REPLACE-BUF634/322879211538

 

[Lohb]

So the LME49600 is just a buffer like Buf634p in the provided PB2 chips, and not an opamp, and it would go behind the opamps in the PB2 Dip-8 board ?

 

[DBaldock9]

So the LME49600 is just a buffer like Buf634p in the provided PB2 chips, and not an opamp, and it would go behind the opamps in the PB2 Dip-8 board ?

Well, it's a very high current op-amp, which could drive hard-to-drive loads - and could probably be used in either the op-amp or buffer sockets.
But, due to the offset of that LME49600 adapter, it may be hard to install as an op-amp, since there's not much space between the back of the op-amp sockets and the jumpers / battery.

 

[HiFlight]

There is the LME49600, with ~250mA of output current, which is only available in a TO-263-5 surface mount package.
I did a quick search, but haven't found a TO-263-5 to DIP-8 adapter - to make it easy to use in the PB2, and other amps with DIP-8 sockets.

When I was still producing the PB2 Topkits, I developed a custom LME49600 plug and play buffer module which I felt was a significant improvement over the stock buffers. I finally stopped making them after shipping a number of sets as they were very labor-intensive to build.

 

[DBaldock9]

Since all of my current Balanced loads are Earbuds and Earphones, rather than any hard to drive Headphones - I've gone ahead and replaced the 6-pin Hirose Balanced Output connector with a 2.5mm TRRS jack (that fits into the same hole).
.

 

[Lohb]

When I was still producing the PB2 Topkits, I developed a custom LME49600 plug and play buffer module which I felt was a significant improvement over the stock buffers. I finally stopped making them after shipping a number of sets as they were very labor-intensive to build.

Would you rank LME49600's sound characteristics close to mid-tier discrete chips ..and any downsides to it you found ?

 

[Lohb]

Wish iBasso would bring out an improved PB2 for the chip rolling fanatics, the PB3 is discontinued but still avail. from a few online retailers...so it just did not do well obviously.

 

[HiFlight]

Would you rank LME49600's sound characteristics close to mid-tier discrete chips ..and any downsides to it you found ?

Based solely on SQ, the LME49600 is right up there with the best, however I believe production has ceased and it is increasingly difficult to find existing stock. As there are no adapters available to convert this case style to DIP8, using it in the PB2 will be strictly a DIY endeavor.

 

[HiFlight]

Wish iBasso would bring out an improved PB2 for the chip rolling fanatics, the PB3 is discontinued but still avail. from a few online retailers...so it just did not do well obviously.

While the PB3 is an excellent sounding amp, it is not a candidate for opamp rolling due to the case dimensions ...it is simply too thin.

 

[HiFlight]

Since all of my current Balanced loads are Earbuds and Earphones, rather than any hard to drive Headphones - I've gone ahead and replaced the 6-pin Hirose Balanced Output connector with a 2.5mm TRRS jack (that fits into the same hole).
.

Great idea and well implemented!