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The Opamp thread
Mar 6, 2019 at 7:12 AM Post #6,451 of 7,383
Any changes in performance? What are you trying to figure out by doing the acetone soak? I thought acetone was for stripping some plastic away so ceramic would need something alot stronger
 
Mar 6, 2019 at 7:35 AM Post #6,453 of 7,383
Spektykles said:
Obviously stripping away "fake" marking if there is any. It sounds a bit different to my ANZ and one of them has a thump when powered on.
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Well i work with ceramics, its tough stuff, most acids wont do much, but Hydrogen Flouride might do the trick, but i think that would eat the metal too, it will be pretty difficult to open up. the circuitry is microscopic so not sure how you could without completely damaging it then you wouldnt be able to see whats in it, maybe using a ceramic diamond file in theory you could file the edges until you get to the division and chip/crack it off
 
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Mar 6, 2019 at 5:36 PM Post #6,455 of 7,383
If you go to ad.com and read their documentation you'll notice that "SQ" is conisdered their flagship line number on all amps they sell, by the way Single will always sound better than dual because of direct passage +% output is bypassed which brings higher latency. About the military grade AD did make a ton of those types of all models for extremely cold areas where transformers would sit out in 0 degree tempatures, but I dont know about 797 if they did not?
 
Mar 7, 2019 at 12:48 AM Post #6,456 of 7,383
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Yup, AD never made an "SQ" version for AD797, instead they put a bunch of number as model #.
Then What is the thing I received? NE5534 remarked?
 
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Mar 8, 2019 at 8:17 AM Post #6,458 of 7,383
Folks, I'm looking for single channel op-amp to replace OPA551 in Pmillet's NuHybrid amp.
Operating V: 24V
Unity gain stable
Powerful enough for planars

I have tested few myself but in terms of SQ OPA827 wins with the OPA551 but the latter outputs more cuurent.
If there only was single channel version of AD8397
 
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Mar 8, 2019 at 10:33 AM Post #6,461 of 7,383
Of course I can, but only if it really improves something like THD, noise...anything. But in this case you will get no improvement at all, you might just cause issues.

I assume you were reading Pete's comment from his website: "You can substitute your favorite opamp or buffer for the OPA551. It needs to support a 24V power supply, and be unity gain stable. Other than that it's up to you". Given the fact that you need to drive planars, you really need those fully 200mA from this very good output buffer OPA551. However, if someone here can provide a replacement suggestion in this scenario, just take care to any possible oscillations, so an oscilloscope might be helpful. Of course, the output RC filter could be adjusted to stop the oscillations, if really needed.

Here's the schematic: http://www.pmillett.com/nuhybrid.html
Here's OPA551 datasheet: http://www.ti.com/lit/ds/symlink/opa551.pdf.

Like Pete said, you could probably try some workarounds with the BUF634, but he already stated that lowerst harmonics, in given schematic, are achieved with OPA551 and not with BUF634. Please, have in mind that you're trying to swap a 200mA opamp!

In NuHybrid, if you really want to increase its performance or change sound flavor in any way, you might try to swap the tube, but not the output stage opamp. This my personal opinion, after swapping several opamps in many amplifiers and DACs. At this moment I have about 100 opamps in my self, from 5532 to MUSES01/02 and Burson SS V5/V6.
 
Mar 8, 2019 at 10:55 AM Post #6,462 of 7,383
raoultrifan said:
Of course I can, but only if it really improves something like THD, noise...anything. But in this case you will get no improvement at all, you might just cause issues.

I assume you were reading Pete's comment from his website: "You can substitute your favorite opamp or buffer for the OPA551. It needs to support a 24V power supply, and be unity gain stable. Other than that it's up to you". Given the fact that you need to drive planars, you really need those fully 200mA from this very good output buffer OPA551. However, if someone here can provide a replacement suggestion in this scenario, just take care to any possible oscillations, so an oscilloscope might be helpful. Of course, the output RC filter could be adjusted to stop the oscillations, if really needed.

Here's the schematic: http://www.pmillett.com/nuhybrid.html
Here's OPA551 datasheet: http://www.ti.com/lit/ds/symlink/opa551.pdf.

Like Pete said, you could probably try some workarounds with the BUF634, but he already stated that lowerst harmonics, in given schematic, are achieved with OPA551 and not with BUF634. Please, have in mind that you're trying to swap a 200mA opamp!

In NuHybrid, if you really want to increase its performance or change sound flavor in any way, you might try to swap the tube, but not the output stage opamp. This my personal opinion, after swapping several opamps in many amplifiers and DACs. At this moment I have about 100 opamps in my self, from 5532 to MUSES01/02 and Burson SS V5/V6.
Click to expand...

Thanks for your reply.

I cannot swap the tube as this is unique and one of its kind. Simply there is nothing to replace it with :)
I believe Pete Millett when puting this amplifier together had cost and part avaibility as 2 most important factors. Hence my believe that there has to be something better, altough I find it good sounding as it is. Just the way I am, if the IC is is the socket it means it could be upgraded:D
 
Mar 8, 2019 at 11:27 AM Post #6,463 of 7,383
There is something, a solid-state opamp (DIY), but it's big in size. It would be something solid-sate, but not sure it will oscillate or not, so a scope is still needed: https://www.soundskulptor.com/en/proddetail.php?prod=SK99. Given the powerful BD139/BD140 you will have no issues with driving planars.

If you really want to be frugal on this, maybe you'd like to email Pete and nicely ask him if really worth spending the money on those SS opamps. I mean, specs are great, I would probably no hesitate to try them out, but still...36 EUR + shipping for 2 opamps, so it could get over 50 EUR in the end.
 
Mar 8, 2019 at 11:41 AM Post #6,464 of 7,383
raoultrifan said:
There is something, a solid-state opamp (DIY), but it's big in size. It would be something solid-sate, but not sure it will oscillate or not, so a scope is still needed: https://www.soundskulptor.com/en/proddetail.php?prod=SK99. Given the powerful BD139/BD140 you will have no issues with driving planars.

If you really want to be frugal on this, maybe you'd like to email Pete and nicely ask him if really worth spending the money on those SS opamps. I mean, specs are great, I would probably no hesitate to try them out, but still...36 EUR + shipping for 2 opamps, so it could get over 50 EUR in the end.
Click to expand...

I tried to engage with Pete and others on the build thread but without much success and feedback. Don't really want to email himself as he reads the thread.

Thanks for suggesion with the SS opamp, I'll try that. Also I'm considering converting the AD8397 dual channel to single channel.
 
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