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iBasso P3 Opamp Rolling Thread *Let the rolling begin!

post #1 of 122
Thread Starter 
I copied this thread title from the "Full-size Amps" forum, as it probably more correctly belongs here. Thanks to Lucifix for beginning this thread, which undoubtedly will grow to some great length!

I spent considerable time tonite running thru part of my opamp supply, namely the ones that I thought would most likely show promise in the P3. I was comparing each to the D3 as many folks really like the presentation of that amp.

Phones used were my JVC DX-1000s and recabled RS1s.
Source was iRiver H140 line out.
P3 gain was set to 10 (high) as I wanted to check max driving ability.
Music was high bitrate MP3 both vocal and classical. Sorry, no rock tonite!

I will list the different combinations with a few comments I made as I ran thru the changes.

I found that, indeed, the P3 has great potential and is capable of matching the sound quality and soundstage of the D3.

I also should mention that a number of different combinations sounded very similar, and it would probably take better ears than mine to detect the very subtle differences, if any.

To cut to the chase, I will first list my top 2 favorites.
1. LME49720 in LR, iBasso buffers, and THS4032 in ground.
This combination just sounds really right, soundstage, tonal
accuracy...it has it all. Probably not real great on battery
life, but, hey...that's what AC adapters are for, right??

2. ADA4841-2 in LR, iBasso buffers, ADA4841-2 in ground.
This is about an exact replication of the D3. So far, it is as
close as I have been able to come. I doubt I could reliably
tell the difference. Battery life should be excellent.

Additional combinations, in no specific ranking, are as follows:

OPA2111 LR, bypassed buffers, ADA4841-2 ground: large soundstage, a bit bright.

ADA4841-2 in both LR & ground...bypassed buffers
A little brighter than the D3, lively & detailed. Expect very long battery life.

THS4032 LR, buffers bypassed, OPA2134 ground...dynamic and punchy..probably very good rock combo.

OPA2134 LR, buffers bypassed, THS4032 ground...better balanced than above.

AD746 LR, bypassed buffers, ADA4841-2 ground...nice soundstage, highs a bit recessed.

ADA4841-2 LR, bypassed buffers, LMH6643 ground...rather narrow soundstage that is back aways from the listener. Similar to that heard with crossfeed.

LT1028 LR (x2) sibilant with anything I tried with them.

Good ground opamps:

The THS4032 is very low noise, and can output a lot of current and is stable at a gain of 1, which makes it an ideal ground opamp. It lives up to its specs, IMO.
AD8599, neutral, nice balance.
AD8066 wide soundstage, detailed bass.
OPA2134..nice allaround performer.
LMH6643...works very well with ADA4841 & AD8066
Generally speaking, the iBasso buffers add some body and warmth as well as more output current. I did try the BUF634, a very much-used buffer, but preferred the sound of the iBasso-supplied buffers in most cases.

I tried several combinations using the AD8599 and OPA2134 in LR, in addition to using them in the ground channel socket. They both sound quite similar and work well, sounding very well-mannered with all types of music, especially with buffers and the THS4032 in the ground channel.


I think that the P3 is capable of driving any dynamic phones that currently on the market, as I never even began to approach the limits of the P3 output while running the tests.

I have more combinations to try, but I was reaching the point where everything was beginning to sound alike, so I knew it was time to hang it up for the evening, and just listen.

I will keep the LME49720/buffer/THS4032 combo in my P3 for awhile and see how it wears on me for several days.

All of the above comments are my opinions only. YMMV!!!!
post #2 of 122
Thanks for the information HiFlight, it's really good information for people who don't know what the different opamps will do. It's funny how you say these are only your opinions, but I think that most people who are just starting out (like me) will read them like they were the gospel truth. Looking forward to more impressions/ information, and thanks again.
post #3 of 122
Sorry for the duplication of posts, I've decided to move the P3 hissing issue to the opamp rolling thread because it is more relevant to opamps.

Quote:
Originally Posted by HiFlight View Post
Quote:
Originally Posted by lucifix View Post
Ok I was running the Heron in its stock opamp configuration with the Transister Buffer being used, and encountered a serious problem and was wondering if any other P3 owners experience the same problem.


I have the P3 in low gain setting, and had my UM2's on with no music playing.

Adjusting the volume pot within the range of the first two dots as shown in the diagram where the red arrow indicates the range of volume pot adjustment, I heard lots of unwanted noise.

I will try to describe it to the best of my ability but have included a direct-download link to the .WMA file which I have tried to record the sound with success by attaching my voice recoreder input to the output of the Heron.

http://rapidshare.com/files/152895478/DS300076.WMA

What I heard was a shrill whistling sound that was never before heard in my Viper. This sound was very persistent and there was lots of white noise also, and only untill I move the volume pot past the second dot, where it would be pitch black and then noisy again, with lots of white noise.

Whilst recording I first turned on the unit with music playing and turned it to the second dot, where I then stopped playing music and turned the knob back down again.

Please let me know if anyone else has been experiencing this and if I should return this to iBasso.

Btw, I have given the P3 a good 24 hour burn in period with the buffers as I thought the problem will go away after that.

Thanks.
I have tried to duplicate this with my Heron and UM2s but I get normal sound, albeit at extremely low volume position due to the extremely sensitive UM2s. Your recording sounds like it has some 60hz hum in it. Running on batteries, there should be none. I would first try unplugging the DC adapter, if you are using it. Then try a different source using different interconnect cables.

If the problem persists, try changing the LR opamp and putting in the bypass buffers.

If problem persists, back to Dr iBasso for them to fix.

That sound is usually due to an opamp artifact, but can be mimiced by cables, etc.

FWIW, my Heron is running the LTC6241HV, iBasso-supplied transistor buffers, and an OPA2134 opamp in the ground channel.

Good luck, and post your results of the above trials.

HiFlight
I swapped the opamp combination to the LMH6655MA LR with the 6241HV 3/4 with transistor buffers and the whistling sound is gone.

This isolates the problem and I think it is caused by the AD797's.

HiFlight, do you have similar whistling and hissing sounds with dual AD797's? (in its stock configuration)
I may have to get iBasso to send replacement opamps

The most amazing thing about swapping opamps is how much difference it can make! When I tried again with the 6655 and 6241's, it was totally pitch black, even quieter than my stock viper which was considered relatively silent with absolutely no hissing at the first four notches of volume.

Furthermore, with this combination it just made my music come alive with every singer coming forward.

I read on the Viper opamp rolling thread that you had lots of praise for the 6655's, in your opinion, how do they sound in the Heron?

This opamp rolling thread is really interesting and I can't wait to order more samples to fill the empty browndogs. Oh and just for fun, I even created a little opamp farm L@@K

post #4 of 122
Thread Starter 
[QUOTE=HiFlight;4849223]

........................snip....................

To cut to the chase, I will first list my top 2 favorites.
1. LME49720 in LR, iBasso buffers, and THS4032 in ground.
This combination just sounds really right, soundstage, tonal
accuracy...it has it all. Probably not real great on battery
life, but, hey...that's what AC adapters are for, right??

2. ADA4841-2 in LR, iBasso buffers, ADA4841-2 in ground.
This is about an exact replication of the D3. So far, it is as
close as I have been able to come. I doubt I could reliably
tell the difference. Battery life should be excellent.
............................................snip.. .................................


Upon further listening with Yuin OK2 buds as well as my various phones, I find I am not real pleased with the LME49720...
It sounds very good with topnotch phones and source, but is very intolerant of lesser recordings and average phones.

I would, as a result of todays listening, suggests the dual ADA4841s with buffers.

I will next be trying dual THS4032s with bypassed buffers and AD8397 with bypassed buffers. They should both do well in the P3.

The LME49720 is an opamp that has superb specs, but one that I have found doesn't always live up to the promise. It seems very picky as to circuit, source, and selection of phones.

I will pass on more impressions as I have time to wade thru my opamps...

I did try others that I did not post results for, as they didn't show any improvement over the OEM installed opamps.
post #5 of 122
I have tried the 49720 over and over and even in my LD Micro tube amp but it and the 4572 just don't sound musical after a while. To me they are plastic sounding. So many choices and so much soldering to do. :^)
post #6 of 122
Thread Starter 
Quote:
Originally Posted by jamato8 View Post
I have tried the 49720 over and over and even in my LD Micro tube amp but it and the 4572 just don't sound musical after a while. To me they are plastic sounding. So many choices and so much soldering to do. :^)

John...
That has been my experience also, many like the 49720, but many times I have found it unstable. This time I thought it would work, but with anything less than top line components and source, it doesn't sound very good. It is one opamp that I am ready to give up on. Too bad I have quite a few of them.

Ron
post #7 of 122
Thread Starter 
I tried 2 more opamp combinations, both of which sounded very good. First: LR AD8397, bypassed buffers, THS4032 in ground. Very dynamic sound with excellent detail. Treble a bit on the bright side so this would suit darker phones such as the Sennheisers.

Second combination, which I like even better with my phones and personal musical preferences is:

LR: ADA4841-2, iBasso buffers, OPA2134 in ground. Sound is nicely detail and soundstage is further back than the AD8397 combination. This is a very natural sounding combination for IEMs.
and also works very well with my RS1s.

FWIW, I still have not been able to match the expansive soundstage and openness of the D3.
post #8 of 122
HiFlight,

Was just wondering if you have similar whistling and hissing sounds with dual AD797's in the P3? (in its stock configuration)
post #9 of 122
Thread Starter 
Quote:
Originally Posted by lucifix View Post
HiFlight,

Was just wondering if you have similar whistling and hissing sounds with dual AD797's in the P3? (in its stock configuration)
IIRC, I had some sonic artifacts that caused me to no longer consider the AD797s for the P3, but I don't recall exactly what they were. When I get a chance, I will retry them and see what happens. They are usually a really good choice for LR in most amps. They are Analogs answer to the OPA627.

Sometimes, for a variety of circuit-related reasons, an opamp just doesn't work out in practice the way the data sheets would indicate that they should. The ears are better guides than any test equipment!
post #10 of 122
Thread Starter 
Finally after a lot of time spent comparing the P3 to the D3 and trying to get the soundstage, imaging and tonal accuracy of the Heron to match that of the Python, I think I happened across a combination that is probably about as close to the same as is possible to get, considering circuit differences, etc.

The setup is: AD8066 in LR, buffers bypassed with iBassos supplied dummy opamps, and an LMH6643 in the ground channel. Gain is set to 10. (Jumpers set to opposing sides of the 2 sets of connectors)

The sound of this P3 configuration presents an effortlessly wide soundstage, and is well-balanced across the audio spectrum. Instruments sound real, not like they have been recorded. Vocals are especially pleasing.

Try it, you'll like it!!
post #11 of 122
Thread Starter 
After further testing and trials, I have yet to find a better sounding P3 combination than that mentioned in the previous post. AD8066/LMH6643!
post #12 of 122
Quote:
Originally Posted by HiFlight View Post
After further testing and trials, I have yet to find a better sounding P3 combination than that mentioned in the previous post. AD8066/LMH6643!
Ron,

After reading the specs of the 6643 on the company's website at LMH6643 - Low Power, 130MHz, 75mA Rail-to-Rail Output Amplifiers
there are so many variants that I do not know which one to get.

Is the 6643 you use LMH6643MA, or LMH6643MAX?

Its confusing! Same thing goes for the AD8066
post #13 of 122
Quote:
Originally Posted by HiFlight View Post
After further testing and trials, I have yet to find a better sounding P3 combination than that mentioned in the previous post. AD8066/LMH6643!
I have tried the exact configuration with good result, thank you for the recommendation. With recommended dummy opamps, P3 can even drive AKG K601 reasonably well without current output of transistor buffers. This combination really benefit from burn-in as initial impression was not really good. I will let it break in for at least 100 hours and see how it go.

I purchased AD8066ARZ (dual/SOIC8) and LMH6643MA (dual/SOIC8) from local Farnell store. I suppose alphabets after part numbers of opamps denote only working temperature, packaging and other parameters which should not affect sound quality. The basic parameters of opamps with same part number should remain the same.

I notice one channel is slightly louder than the other channel. Wonder whether the slight imbalance is caused by overheating when trying to clear solder short between pins with 23W soldering iron. I though dual opamp should have better balance than individual single opamps. After restored back to stock opamp configuration (single AD797 x2 in L/R, dummy x2 in buffer and dual LM6172 x1 in 3/4) and burned in for short period, the imbalance still exist thus I suppose it has nothing to do with opamp rolling.

Does single opamp usually provide better specification and performance than equavalent dual opamp ? Will there be any improvement if I switch a dual LMH6643 with a pair of single LMH6642 and dual AD8066 with a pair of single AD8065 ? Beauty of P3 design is it allows dual or single packaging with the same SOIC-to-DIP adapter (always one opamp unit on a adapter).
post #14 of 122
Thread Starter 
I have not noticed differences between the dual and single versions of the same opamp.

It is possible but not likely that the imbalance was caused by overheating. That will usually kill an opamp rather than affect its sound. You might make sure it is seated completely and that the pins all make good contact. You might try cleaning the pins and re-installing.
post #15 of 122
Am currently using ADA-4841-2/THS4032. Bass is very strong, although overall it's pretty balanced. is there a combination that's tailored toward IEMs?
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