fubar II dac - op amp rolling
Jun 6, 2007 at 9:06 PM Thread Starter Post #1 of 45
ziplock

ziplock

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Hello All,

I would like suggestions on compatible OP amps for this DAC. I have heard that an 8620 on brown dog adapter is a good choice. What about others? Dual 627s?

I understand that the 2604 is at the output stage. Is the JRC considered a buffer? If so, how would stacking buffers affect the sound? Further, is it a good idea to match both of these or use different amps which cater to the design spec?

I guess I am open to any other mods as well. Anyone know of a PCM2xxx pin compatible DAC that offers hardware mixing?

Thanks!

~Zip
 
Jun 8, 2007 at 9:18 AM Post #5 of 45
-rolling dac chips is most likely not an option

there are endless possibilities about opamp rolling.
ad8620 seems indeed a good choice.
opa2107 or opa2228 if you like a more laid back sound.
ad8066 also gets some glowing reviews about it's very lively sound
lm4562 seems to be a very good opamp too, very neutral

Quote:

there are favourable reports of the BB OPA2107 in use firestone products


It's rather a matter of your ears, not your DAC
wink.gif

Yes, some opamps will require special care, but the ones I mentioned above should all be fine.
 
Jun 11, 2007 at 4:10 PM Post #6 of 45
I just put a opa2107 in my Cute Beyond and I'm happy with the results. It's not a night and day improvement, but it's definitely noticeable. It seems less harsh in the upper mids than the opa2227. The clarity is still there, but some of the edge seems to have gone from the Grados (SR80s).

I have some lm4562s coming in the mail, which I'm planning to put in the Fubar. Can anyone advise me on this? Would it be best to replace both opamps in the Fubar with LM4562s, or go with opa2107/lm4562 in both the Cute and the Fubar. I have two of each chip.

I guess my question kind of revolves on what is the best replacement for the JRC072 that is in both of the DAC and the amp.
 
Jun 11, 2007 at 7:55 PM Post #7 of 45
Quote:

Originally Posted by infinitemonkey /img/forum/go_quote.gif
I just put a opa2107 in my Cute Beyond and I'm happy with the results. It's not a night and day improvement, but it's definitely noticeable. It seems less harsh in the upper mids than the opa2227. The clarity is still there, but some of the edge seems to have gone from the Grados (SR80s).


ive had the same result with my Cute Battery II when paired with the 2107 as well. but i replaced BOTH the 2227 and the JRC thingy with the 2107. Whats the JRC thingy for anyway? the 2107 managed to noticeably tame the highs on my DT990. where before it was bright, now it has a slightly darker and laid back sound sig with tamed highs. i like it
biggrin.gif


ive never had a chance to try and change the opamps in my Fubar though...had to send the thing off for warranty before i could get my hands on a couple more 2107s...but ill be getting it back this week
biggrin.gif
 
Jun 12, 2007 at 2:15 AM Post #8 of 45
I put an opa2107 in the Fubar to replace the opa2604 and the incremental improvement continues. Again, it's certainly not a night and day thing, at least not to my ears, but the sound is somehow sweeter, if that makes sense. The highs are still detailed, but not as harsh.

When the LM4562s show up, I'll swap them for the JRC072s and let you know if I can notice any difference.
 
Jun 12, 2007 at 9:56 PM Post #9 of 45
Well, the lm4562 came and went in the Cute Beyond. To me, it reduced the warmth without adding anything in terms of clarity or detail. That was as a replacement for the JRC072, paired with the OPA2107. So I'm back to the 072 and the 2107 in the amp.

I'll try the 4562 in the DAC later and let you know how it goes.
 
Jun 13, 2007 at 1:10 AM Post #10 of 45
Me again.

After a couple of hours of farting around, pulling chips in and out and trying real hard not to bend the pins, the combination I came up with for the Fubar II that I like the most is the LM4562 in place of the JRC072 and the opa2107 in place of the opa2604.

I tried using LM4562s in place of both at first, but it brought back some of the harshness of the original chips. The 2107 really is a good fit, to my ears at least. I'm not sure how much difference the LM4562 made compared to the original JRC072. It was too many changes in too short a time.

My feeling is that the best way to go would be to start with opa2107s in place of the orginal Burr-Browns. I'm sure how much is gained by replacing the other op-amps.

Some input from people with real knowledge would definitely be welcomed here.
 
Jun 15, 2007 at 11:08 PM Post #11 of 45
Quote:

Originally Posted by mADmAN /img/forum/go_quote.gif
Whats the JRC thingy for anyway?


That is a very good question, I wish I knew myself. I thought it was a dc current buffer to help "smooth" out the sound. I could be completely wrong though. Would anyone care to chime in on this subject?

BTW, thanks for all the replies everyone. I still haven't made up my mind on the op amps. I think I'm just going to buy a large selection of them and spend a few evenings swapping them in and out. I'll sell the excess when I find a pair that suits me.

~Zip
 
Jun 15, 2007 at 11:22 PM Post #12 of 45
please remember - this could get expensive very quickly
I just ordered opamps for 60$, to see which one fits best in my soon-to-be-built pimeta. and I still have to order some lm6172 and ad8620, maybe I even try two opa637 (a 3 channel config with 637/627 is more expansive than 60$... at least here in europe). and then there are those little known chips which I also want to try out. and then I maybe have to reorder, if I want to upgrade my cdps with some new chip I began to like...

but yeah, there's a saying here on the forum about wallets
evil_smiley.gif
 
Jun 24, 2007 at 1:02 PM Post #14 of 45
DUAL 627s in FUBAR is AMAZING, definitely a NIGHT and DAY thing.

Especially the bass.

DO IT!



I'm gradually getting the courage to change the op amp in my little country, but have no idea if it's there for sonic purposes or not!
 
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