Bass frequencies matter too

So the EE in me has some questions.. What are you trying to show?

Transformers are inherently bad at square waves, because they aren't designed to work with square waves, especially low frequency squares that have 50% duty, like the ones you are showing the pic.. You're going to get a hot, magnetic core doing that stuff. Some folks will argue that it's a valid test because "square waves are nothing but overlapping sine waves" or some such. Mathematically, that's how they're modeled, but realistically, the density of sine model is too great for practical use. You'll never have real square waves in audio no matter how dense the music. You're better off showing complex measurements like intermodulation/IP3.

secondly, those traces look more like uncompensated probes, rather than ringing/overshoot. Looks like you're using alligator clips.. Have you calibrated/compensated them? I'm not sure it's possible with that scope though.. But I've seen very, very highly paid design engineers troubleshoot issues with overshoot over transmission lines only to find out that their 'scope probes weren't calibrated to the 'scope. Just sayin'.

Third, are you comparing unloaded transformers? are you matching loads to the source impedance and/or ratio?  Are you using flat loads like resistors, or variable impedances?  Are you using the same load between devices, or matching the load specifically to each device?  Are both of these using the same output tube configuration? 

Fourth, maybe the ADL designers decided that they'd take some low end overshoot (which is not what is shown in the trace) in return for high end extension.. Zobels/snubbers are narrowband tuned circuits, and while they might help a range of frequencies, they can hurt others. Frequently with wideband transformers, you're matching for a more narrow range of bandwidth than you'd like, but you're also doing so as a tradeoff to not roll off your high end with a parasitic zobel.

I'd love to learn more about what you're doing and I hope my questions and comments don't offend. I just don't understand the picture..

Hi Svart,

These photos were more of hype to put on Facebook for some of my engineer friends. To be honest, I'm quite a newb at building gear, although I have been playing music professionally for 30 years.

To cut to the chase, our studio has owned this ADL 600 for several years and my colleagues and I never have liked it. It's harsh in the top end, mushy in the lows, and it never made sense to us what was going on with it. Tube swapping didn't really help much. It's odd because the designers are reputable guys, but the preamp just doesn't sound so great - for whatever reason.

I only recently have been getting into learning the oscilloscope, and I need to learn much more about how to properly measure specific devices. I attempted to measure from the same points in the circuits with the same settings. Measurement leads were calibrated, although I did break a cord the other day and needed to use an unloaded cable between the function generator and the preamps. I agree that this is the cause of the slight overshoot/ringing.

(I admit again - I don't know a whole lot about the subject and hope to learn more.)

Whats up with that ADL?? I always thought it was "dark" and super dense sounding. Tight and Dense. Maybe its me. The vibe on this piece has emotional problems. Just my 2cents. If your box is more transparent and has some Tube Mojo, I would pay the price you asked....