The SE outputs add a little sumthin sumthin to the output. Just a touch of extra “hello”. “Kathy’s Waltz” from Dave Brubeck has a bit of extra spring in its step with the snares and upper-middle piano register.
Listening on @dBel84 modified Hifiman HE560v4 on Schiit Modius/Magnius stack.
No matter balanced or SE, it’s wonderful. 🥰
Just doing balanced in right now.
Oh wait, just remembered I have others to test!
Listening on @dBel84 modified Hifiman HE560v4 on Schiit Modius/Magnius stack.
No matter balanced or SE, it’s wonderful. 🥰
Just doing balanced in right now.
Oh wait, just remembered I have others to test!
The other three have problems among themselves at varying degrees. Mainly distortions and slight gain differences between channels. My first subject spoiled me! But I know how they can sound. So I’ll put on my tiny soldering iron tip and touch up the components.
Issues aside, I really like the way they sound. The SE output still has a teeny, tiny bump. But I dig it. Won’t be enough for me to complain.
Issues aside, I really like the way they sound. The SE output still has a teeny, tiny bump. But I dig it. Won’t be enough for me to complain.
The SE output is the beautiful intrinsic sound of the OPA1656 as driver. My favorite opamp. The OPA1637 does the balanced drive and probably less current capability. Touching up the gain setting resistors with a hot iron tip to reflow the precision 0.5% resistors may help. Be careful not to set gain too high. Generally, 6dB is perfect for general purpose preamp. 14dB is good for low gain (circa 15dB) amps. 20dB is for buffer output stages circa 0dB amps. If you use 14dB on a standard 29dB amp, you might hit clip real easily.
I picked these mainly for their buffering. The gain is a bonus. So I’ll put them at unity until I need something more. They’re being used with an Aleph P preamp stage which has a gain adjustment itself, so sounds like I need to be careful. All flowing into an Aleph J amp.
Loving it so far. Just need to work out a couple of kinks!
Loving it so far. Just need to work out a couple of kinks!
After touching up the gain resistors as suggested, as well as all the components for that matter, most of the imbalances were resolved. A couple of them weren’t completely fixed, but I was able to compensate for them with a single switch flip to bump the gain slightly as needed. Not totally ideal, but okay for my purposes. I’m satisfied with that given my first super small SMD project. 
I did end up replacing one of the SE opamps. Whether it was a rotten solder job or component damage, we may never know. That one turned out to be my rock start buffer and I’m going to save it for a special project.
I’m calling this project a win!
I did end up replacing one of the SE opamps. Whether it was a rotten solder job or component damage, we may never know. That one turned out to be my rock start buffer and I’m going to save it for a special project.
I’m calling this project a win!
After a look at the resistors as suggested, it appears there is some variance that would explain the gain differences that I'm seeing -- just as you described it. I'm not sure if it's a soldering problem or an out-of-tolerance resistor. I can certainly give them another pass, as well as remove the ones that are fairly well out of bounds, and see if there are any solder issues near the pads. Thanks for the suggestion! I was worried I didn't purchase the suggested 0.5% resistors. But I checked my parts order and I did get the right ones.
The top and bottom resistors highlighted in orange are the default resistors with all switches out. On my buffers #3 and #4, there's definitely a problem as shown in these results. Certainly why the left side has slightly higher gain than the right on both the balanced and single-ended circuits. Also on buffers #3 and #4, one side of the high-gain circuit is significantly off from the other. It was said that his circuit probably won't be used often due to the possibility of clipping the input downstream. So maybe not as important to fix those two. But why not if I'm in there anyway, right?
The top and bottom resistors highlighted in orange are the default resistors with all switches out. On my buffers #3 and #4, there's definitely a problem as shown in these results. Certainly why the left side has slightly higher gain than the right on both the balanced and single-ended circuits. Also on buffers #3 and #4, one side of the high-gain circuit is significantly off from the other. It was said that his circuit probably won't be used often due to the possibility of clipping the input downstream. So maybe not as important to fix those two. But why not if I'm in there anyway, right?