Looking at the lack of support components, and lack of other components to handle step down from High voltage DC to low voltage DC, I would guess those are DC-DC converters with the label scrubbed off.
What baffles me are the huge (25 W rated?) resistors next to the TO-220 components. The huge copper slab means lots of heat, but surely it is not a resistive dropper!
Thatās a structural add-on or standard on all totaldac products
FWIW Iām pretty sure that that it is a line level transformer.
Itās obviously an SE circuit and it has a balanced output, and there is nothing else on the board likely to provide it. Itās also about the same size as the PCB mounted Jensen units I have sitting in a box.
Assuming itās the Source resistor in a Mosfet follower, Iām sure the resistor is oversized, unless the output is a lot higher than I would expect for a line level device or itās deliberately designed to drive very low impedances.
In the average output stage of a Mosfet amp, itād be sinking a lot of current, but itās also driving 8 Ohms where it wouldnāt be unusual to see 2A and 15V through it.
Could also be a dropper resistor, though they ought to be able to make almost any voltage work with the transistor buffer.
What noise issues are you referring too?
The driver is akin to a buffer amp as all totaldac DACs have a pre-amp function built-in. If using the driver the models with lower voltage output such as the tube based models it can help with any mismatches with a power amp.
Itās not going to make it measure any better, if thatās a Mosfet, and there is no feedback, your unlikely to see better than -70dB before you see 2nd Harmonic distortion, and it could be worse than that.
But itās the wrong measurement to look at.
The only way you do much better than -70dB with any SS device is by adding feedback or going balanced. in a 0 feedback design at low gain levels 2nd Harmonic distortion will rule (tube or SS). adding feedback or making you amplifier balanced just basically removes the 2nd harmonic distortion, and you get the lower 3rd harmonic dominant instead.
Anyone who hasnāt read up on the differences in sound characteristics of the various distortion levels should. Itās basically what determines a lot of the sonic characteristic. Iām simplifying here but definitely worth reading about.
Any good articles you recommend?
Most of the interesting stuff Iāve read has been Nelson Pass in the white papers on the First Watt website.
But those are mostly interesting because he describes his take on the measurements of a design, which gives you some idea what heās looking at/for.
Short version is even harmonics good, odd harmonics bad, ideal interference is a pattern of decaying harmonics 2> 3> 4> 5> 6 ā¦ That comes from I believe BBC research in the 1960ās.
Nelson Pass also looks at the relative phase of the harmonic.
You can get a away with a lot of 2nd harmonic distortion before it sounds ābadā. But 3rd harmonic distortion not so much.
Harmonic content changes with volume, this is especially true of Tubes where distortion rises with volume. So testing an amplifier at say 2V then using it at 200mV the measurement may have no correlation to what your hearing.
And remember music contains many things at many different volumes all at the same time.
But remember you donāt really hear anything more than about 60dBās down (if you hear that much), so itās as much about the behavior of the amplifier, as it is the harmonic distortion directly sounding like something.
Thatās precisely where I was going to point. This is a good read on the general take of H2 from Nelson.
This is a great read on harmonics themselves. I wouldnāt say Good or Bad, but different and that difference can be leveraged to gain or lean towards a desired signature.
https://6moons.com/industryfeatures/distortion/distortion_3.html
As @Polygonhell itās not just the harmonics, itās also the phase and which combinations are used. Itās why the Firstwatt amps all have their own āpersonalityā. Nelson really leverages the theoretical in a good way.
I think in some cases the ideal for me is a combination of 2nd and a dash of 3rd and thatās where the art comes in. One is euphonic in nature the other incisive in nature. As audiophiles we tend to want it all, but physics is not going to allow gains in one without losses somewhere else. So itās the art of compromise.
Thanks, thatās where Iāve been rummaging about the last few months to figure out which of the First Watt amps I wanted to get.
I can appreciate a designer being so transparent around his thought processes, and willing to share it once the time is right. I will readily admit most of the technical stuff is beyond my knowledge, was hoping there were articles that read in a layman manner.
Edit: thanks @dB_Cooper appreciate the supplemental articles!
I got the email too, was a bit disappointed he didnāt post any more detail about the cables. For those prices, they seem very basic at best. Perhaps he posted about them on WBF, he tends to drop information there every now and again,
yah, so the driver does make a pretty damn substantial difference. Changes the entire tonality and presentation of the dac, but manages to keep similar focuses. Its much less colored now. Ill get some better impressions over the next few days and write a propper comparison
The driver is a standalone product and thereās nothing stopping one from putting it between a preamp and and amp from what I understand correct? I know this is in place because the Totaldac leverages the built in pre but Iām not sure if this is to make up for a gap or if it would help non Totaldac implementations like Iām talking about.
Always been curious since M0N mentioned what the box is/does.
I think all it really does looking at the pictures of the internals is provide a large input impedance, greatly drop the output impedance, and provide more current at the output (which is mostly irrelevant), the effect of that would vary based on whatās down stream.
The AIC is the only amp I had issues with impedance on the Pacific (which is probably worse than the totalDAC at least with the tubes I have in mine), so it doesnāt surprise me it was a big change in @Draaly 's system.
Might help with DACās like the Pacific or if you were insane Border Patrol.
Okay, so itās very chain specific what TD is trying to do here for their equopment. It seemed to me that this is āsubstitutingā for some function that a good pre would/could do?
The right active pre probably, I believe the older Total DACās took the output right off the ladder, so there was in effect no output stage (or there was some other reason the output impedance was high) Thatās one less source of noise.
But it relies on the downstream component having a high enough input impedance that you can drive it, too low, it pulls too much current, and you get distortion as it exceeds the current the DAC can provide.
Exceeding that current will occur based on the amplitude of the output signal and Impedances are all frequency dependent, so it can even only affect some frequencies, or just loud passages, which is why you get the weird effects like I did with the Pacific and AIC.
An active pre with high input impedance solves that in much the same way the driver does, the difference being the driver is just the output stage of an active Pre.
Okay, thank you for the explanation. It answers every question I had about it and demystifies this āodd duckā product for me.
The built-in preamp is not a substitute for an actual pre-amp. I connected the First Watt J2 directly to it from the RCA and then from the XLR, and it was not good. It reminded me of the digital pre-amp used in the TT2, all it was doing is putting the output voltage at zero and increasing it to its max output, which when connected with the First Watt it was getting loud but not sounding good at all.
Gave up on that pretty quick, definitely mismatched in this instance, now would the driver help in my situation? No fācking clue, an average pre-amp is more useful
Random post, but I had some cheap brass cones and saucers laying around and decided to put a few under the TD power supplies, then added some brass weights on top. Sound took a noticeable turn for the better ā everything seemed to tighten up and become more cohesive to a degree. Soundstage seemed to improve as well, more in the round. They are power supplies so treating them makes sense, but the outcome with these meager footers and weights was a pleasant surprise
