[infinitemonkey]

Thanks for the link, Ziplock.

To save everybody a trip over to the other thread, Jack says:

Quote:

There are two spots in the Fubar you can change the OPAMP, the position U6 is for LPF and the U5 is for DC servo.

Sadly, like the people in the other thread, I have no idea what the ramifications of that statement are and he never follows up.

I gather that the second opamp, the JRC072 is a buffer. Is that right? Is there therefore anything to be gained by rolling it? What sort of replacement would give the best results then?

Thanks in advance to anyone who can help.

 

[infinitemonkey]

Sorry for replying to myself like this, but I found this on the board over at Firestone. It seems to say that there's not much point in changing the 072.

Quote:

Date:2006/3/31 am 11:36:44 Subject: jumpin wrote: I have a fubar II dac and was wanting to know how to adjust the op amps, and what sort of difference to sound it will make. I am sorry to reply late! You may replace the OPA2604 for tuning and please don't care about the TL072.

 

[ziplock]

Quote:

Originally Posted by infinitemonkey /img/forum/go_quote.gif Sorry for replying to myself like this, but I found this on the board over at Firestone. It seems to say that there's not much point in changing the 072.

Hmm, that is interesting. I know the response is straight from FA, but I would like to gather several more opinions before basing decisions on that. I'm stubborn.

Really, why make it socketed if it doesn't matter...

~Zip

 

[Pars]

I don't own this DAC, but a TL072 is just fine for a DC servo, and you should not notice sonic improvements by changing it. I use these in a Gilmore Dynalo for the DC servos and they work much better than the OPA227s that I had originally bought for this purpose. A DC servo works to keep the output at 0 Vdc... i.e., to ensure that you have no DC offset. The OPAs would not work when the offset started to go negative in my application, whereas the TL072s work fine.

If you do change this opamp, I would spend some time with a DMM on the output(s) checking the DC offset to ensure that you haven't made things worse...

 

[ziplock]

Quote:

Originally Posted by Pars /img/forum/go_quote.gif I don't own this DAC, but a TL072 is just fine for a DC servo, and you should not notice sonic improvements by changing it. I use these in a Gilmore Dynalo for the DC servos and they work much better than the OPA227s that I had originally bought for this purpose. A DC servo works to keep the output at 0 Vdc... i.e., to ensure that you have no DC offset. The OPAs would not work when the offset started to go negative in my application, whereas the TL072s work fine. If you do change this opamp, I would spend some time with a DMM on the output(s) checking the DC offset to ensure that you haven't made things worse...

Thanks for the post Pars, good information to know! I appreciate the explanation.

~Zip

 

[infinitemonkey]

Much obliged Pars. That explanation was very helpful.

It jibes with what I found when I switched out the 072 in the Fubar. There was little or no difference, and any change there might have been was towards an increased harshness.

The OPA2107s on the other hand, in both the Fubar and the Cute Beyond, made a noticeable improvement, at least to my ears.

I have some OPA2111s here I may try if I get some time. Is there anybody here who's tried them, or can offer an opionion of what to expect in using them as a replacement for the 2107?

Here's another quote from the board over at Firestone:

Quote:

Can you recommend some nice opamps to try rolling in the Cute Beyond and the Spitfire dac? Thanks, Matt Hi Matt, For my personal, OPA2111 & AD827AQ are good shoots. Regards David Lin

 

[ziplock]

Quote:

Originally Posted by infinitemonkey /img/forum/go_quote.gif Much obliged Pars. That explanation was very helpful. It jibes with what I found when I switched out the 072 in the Fubar. There was little or no difference, and any change there might have been was towards an increased harshness. The OPA2107s on the other hand, in both the Fubar and the Cute Beyond, made a noticeable improvement, at least to my ears. I have some OPA2111s here I may try if I get some time. Is there anybody here who's tried them, or can offer an opionion of what to expect in using them as a replacement for the 2107? Here's another quote from the board over at Firestone:

Good stuff here. I guess it's back to the JRC op amp then. At least there is one less variable to bother with when "tweaking" our Fubars.

 

[mADmAN]

Quote:

Originally Posted by infinitemonkey /img/forum/go_quote.gif Much obliged Pars. That explanation was very helpful. It jibes with what I found when I switched out the 072 in the Fubar. There was little or no difference, and any change there might have been was towards an increased harshness. The OPA2107s on the other hand, in both the Fubar and the Cute Beyond, made a noticeable improvement, at least to my ears. I have some OPA2111s here I may try if I get some time. Is there anybody here who's tried them, or can offer an opionion of what to expect in using them as a replacement for the 2107? Here's another quote from the board over at Firestone:

so u have the 2107s on both the fubar and the beyond....did u replace the JRC thingy on each as well?? or just left them there?

i replaced both the JRC and original opamp in the battery

anyway...ive gotten my fubar back from warranty (Jaben REWLS!!

) . and its burning in now and its working beautifully

i forgot to mention that i once tried swapping the JRC and the opamp in the fubar with those originally from the battery ii (EDIT: found them! theyre OPA2277PA & 0720 JRC 5021G) and it did noticeably change the sound...for the better. cant really describe it...as it was only a temp solution.

 

[infinitemonkey]

Yeah, I replaced the Burr-Brown opamps in both with opa2107s. I'm going to try an opa2111 in the Fubar in the near future, but the 2107s are a nice improvement over stock.

As far as the JRC 072 chips go, my understanding is that they're there more or less to make life easier for the other opamp in terms of DC power. That may not be the best explanation of their role (sadly, my tech knowledge is lacking) but the consensus seems to be that, at best, swapping them out won't bring any sonic improvements and might even makes things worse.

So, it seems that it's only the opa2604 in the Fubar and the opa2227 in the amp that we need to worry about.

 

[infinitemonkey]

I've got an opa2111 in the Fubar now, and I'm fairly happy with it. It seems to have a little more bass and overall low-end detail than the 2107.

I still have a 2107 in the Cute Beyond. I like this combo better than 2107s in both of them. At least that's my current impression.

I'm currently listening with the SR80s and I've turned off all equalization, whereas before I had a couple of decibels of boost in the lowest section of bass. The result, with swapping the chip and turning of the EQ, is that the quantity of bass is about the same, the quality is nicer.

As always, take my opinions with a grain of salt, because for the most part I don't know what I'm talking about. The 2111 is a decent opamp in the Fubar, though, from what I'm hearing.

 

[infinitemonkey]

Me again.

After switching from the SR80s to a pair of K240 Sextetts as my main headphones, I've put an OPA2111 in the Cute Beyond as well as the Fubar. It seems to have a bit more snap than the opa2107.

With the Grados, the 2107's seemed to help take a bit of the edge off. With the AKGs, that isn't necessary, so the switch to the 2111's has given me a bit more detail without costing me anything anywhere else, that I've noticed yet anyway.

 

[infinitemonkey]

And now, in the continuing saga of one monkey and his pile of chips . . .

I took the 2111s out and put the 2107s back in both the amp and DAC. While there's a bit less snap, and the sound is slightly darker, I do notice that there's a better sense of space with the 2107s. It's smoother and a bit airier, if you will.

I'm going to keep these in for a while and see what my complaint about them is.

I'm also going to do a bit of research to see if I can find something to improve the gain a bit to give me a bit more headroom with the 600 ohm AKGs.

 

[ziplock]

Hi there monkey!

Sorry, I haven't been paying attention to this thread lately.

I slapped in a pair of 627s on brown dog adapters and have been very pleased with the results. After reading all of the recommendations, I decided to leave the JRC amp alone. Been running this way for a month or two now. I'll most likely try some others when I have more time to fool around.

I've been preparing to move my family which I am not looking forward to. I really don't like moving...

Zip

 

[infinitemonkey]

Hi Ziplock:

I was wondering if there was space in the case for 627s on browndogs. It's good to know they fit. From what I've read, the 2107s are basically just a poor man's 627. I may have to look into getting a couple of those.

Good luck with the move. It really is an awful job, isn't it? At least when you're done you have a whole new place to fill with junk.

We last moved about eight years ago. We still have boxes we haven't unpacked. I've argued that those could safely be thrown in the dumpster, but my wife doesn't see it that way.

I guess the upside of being a headphones guy is you never have to worry about the acoustics in your new place.

Good luck.

 

[cvince]

I just recieved the OPA2107AP.

I don't know what you guys are saying by it not being a night and day difference.

Immediately I notice that ALMOST ALL of the harshness that was once there is gone!
For most recordings, I can turn the volume up to 12:00 on my Gilmore Lite without ringing in my ears now.

Not to mention.. Transients are so much better with this new opamp.

When listening to Byron Janis' Rachmaninoff Concerto No. 2 with the OPA2604, the upper half of the piano was playing in the extreme right, and the lower half was playing somewhere right from center.

After switching, the opamp, the piano actually sounds like it's in one piece, playing approximately 30-40degrees right from centre of you. My orchestral music ACTUALLY makes sense all of a sudden! Violins don't suddenly creep towards the centre when they are playing lower notes.

I was getting skeptical that source upgrades could make this much difference.

If an opamp upgrade can make this much difference, now I'm REALLY wanting to hear what a very good dac sounds like.