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Walt:

You obviously missed the whole point of this device. If you read the whole data sheet you would see it is nothing like a common differential Op Amp. It is specifically designed to get the maximum benefit when converting from a balanced to unbalanced line where even a precision differential Op Amp cannot compete when doing the conversion because of even extremely small differences in input impedance. Here are a few extracts that should help explain if you do not want to delve into the whole data sheet. When doing a conversion from balanced to unbalanced, the goal is not to create a "toaster" with high dissipation, but rather to retain the CMRR of the balanced line when doing the conversion while not stressing the output stage of the output balanced line.

Thanks for finding them, but the THAT1200 is incompatible with the existing design, so cannot be tested directly from what I see in the datasheet.

The IC's I am testing are the TI OPA132, OPA134 and LME49710's. The discrete units are Sparkos Labs 3601, Staccato OSH-S so far. The SX52B is a dual discrete that looks interesting, but not compatible with the single units.

The SX52B's would work with either the Douk A5 or FOSI V3 Mono amps.

[quote="tomp"]Walt:

You obviously missed the whole point of this device. If you read the whole data sheet you would see it is nothing like a common differential Op Amp. It is specifically designed to get the maximum benefit when converting from a balanced to unbalanced line where even a precision differential Op Amp cannot compete when doing the conversion because of even extremely small differences in input impedance. Here are a few extracts that should help explain if you do not want to delve into the whole data sheet. When doing a conversion from balanced to unbalanced, the goal is not to create a "toaster" with high dissipation, but rather to retain the CMRR of the balanced line when doing the conversion while not stressing the output stage of the output balanced line.

I didn't miss the point. My point was that the more crap you put in the critical signal path playback quality deteriorates accordingly. Personal experience -- not theory.

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Walt

The BUD chassis arrived yesterday and the drilling and cutting has started.

It is 3.5U size for plenty of space to work inside and have height for the discrete opamp heatsinks.

Walt:
First, let me say that I am not denigrating the work you have done on your system. As you know, in the past in this forum I have suggested that people listen to what you have done as an example of an alternate way to get good sound. What I take issue with is your statement that adding “more crap” to the system deteriorates the sound. I think you need to realize that there are people in the audio world that are much smarter than either of us and have gobs more experience than both of us combined. They have come up with solutions that add components but greatly improve the sound. The key is to do it right and not add crap like a lot of the audiophile bling, but things with genuine merit.

The enlightened audiophile realizes that there is no one way, but only the way that works for him/her. It is interesting to see the emoji you selected of butting your head against a wall as an example of how you have achieved benefits in sound. If you continue to go down one path, you are bound to run into walls in the process. If you have a problem that your hammer does not fix, the answer may not be to use a special military spec gold plated hammer, but perhaps try another tool. As always, it depends on what you are looking for. In my case it is to get the sound in my room the closest to what I hear when attending the many Philadelphia Orchestra, Lansdowne Symphony, Warrington Symphony and other live venues in my area on a regular basis. Is that what everyone wants? No, but it works for me.

So, I would respectfully suggest you be more tolerant of approaches that may differ from yours. You might not have to keep beating your head against a wall and in the process have more fun.

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Walt

One way to improve IC opamp sound is to bias the output stage with a current source to the negative power supply. This will put it into Class A output stage operation. Don't forget the heatsink!

This has been around since the '70s, but not discussed much. I even believe Walt Jung wrote about it.

To me the advancement, if there is one, for discrete opamps is Class A bias and heatsinks to dissipate the extra heat.

Now back to the project and see what happens when balanced output is converted to single ended the correct way, and not half done!

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Walt

An improvement over his resistor pull down biasing is to use a current source. James Borgiono showed one method. TI makes the NS LM334 an adjustable current source as well.

The chassis is getting drilled and cut for connectors and AC power access.