DAC DIRECT IN TO AMPLIFIER OR TO PREAMPLIFIER

After acquiring a preamp primarily for analog attenuation, I've become convinced that a separate high-quality active preamp can significantly enhance sound reproduction and elevate the overall listening experience in almost every aspect. The key lies in the preamp's ability to establish good 'synergy,' including impedance matching, not only with the DAC but also with the amplifier. The specific elements contributing to this 'synergy' might be challenging to define, but you'll know when you find the right one.

The Aesthetix Calypso receives rave reviews as a remarkable piece of equipment. However, it appears that no one has mentioned a potential issue related to its impedance matching with your amplifier. Although the average output impedance (OI) is rated at 300 and 600 ohms for SE and XLR line outputs, JA (Sterophile) pointed out that both SE and XLR OI can rise to 3150 and 3900 ohms at 20Hz. This necessitates an amplifier with at least a 40k input impedance to avoid bass sounding lean.

My experience goes back so many years it might not be useful in discussing modern equipment. Many years ago I ran an old Phillips CD with variable output directly into my amp. I thought it sounded pretty good. Then purchased a Conrad Johnson PV9a preamp and added it to the system. It was a noticeable improvement to me. 

Separately, I found this Bascomb King interview on the subject interesting. 

https://youtu.be/HHl8F9amyY4?si=HhNsdbI1xXADABk9

@lanx0003 

Although the average output impedance (OI) is rated at 300 and 600 ohms for SE and XLR line outputs, JA (Sterophile) pointed out that both SE and XLR OI can rise to 3150 and 3900 ohms at 20Hz. This necessitates an amplifier with at least a 40k input impedance to avoid bass sounding lean.

The case of output impedance rising in the lower frequencies was not unusual amongst tubed preamplifiers.  I believe it was related to the size of the coupling caps used.

With almost any tubed amplifier, and with most SS amplifiers, the rising output impedance wasn't a problem but there are some SS amps like my SMc modified monoblocks that have input impedance of only 10K ohms, or some of the earlier Pass Labs amps that had input impedances of 20K or 22K ohms, where a high'ish output impedance from a tubed preamplifier might roll off the bass early.  The rule of thumb was to have an input impedance of at least 10x the output impedance, but I have always preferred to see at least 20x.

@mitch2 I believe it was related to the size of the coupling caps used.

I concur. After conducting some research, we could apply the general guideline of a 3dB cut-off frequency at 2Hz to calculate the desired load input impedance (RL) in ohms using the formula RL = 0.5 / (π * f * C), where f is the cut-off frequency (2Hz in this case) and C is the capacitance in Farads.  For a better understanding of why 2Hz is suggested, you can refer to [https://www.v-cap.com/coupling-capacitor-calculator.php].

The Aesthetix Calypso Standard (Saturn) series employs 2uF output coupling capacitors. Therefore, the desired RL is calculated as RL = 0.5 / (3.1416 * 2 * (2x10^-6)) = 40k ohms. This calculation aligns with JA’s measurements in the lab.

Now, if the load input impedance at the amplifier doesn’t match the desired 40k ohms, one possible solution is to replace or upgrade the 2uF caps with the 4uF Dynamicaps used in the Signature series. This would reduce the desired RL to 20k ohms, resulting in benefits such as improved bass extension, resolution, dynamics, and reduced grain. According to the manufacturer’s website, the existing Saturn units can be factory upgraded to Signature specification. Alternatively, you could consider purchasing the Signature edition. In the used market, the Signature edition typically costs around $3,800, compared to the sub $2,500 price tag for the standard version.

I know a lot of folks do not care for this guy or his musings, but he has a point if you are digital only. https://youtu.be/81RQLo0tLHE?si=t9BKS9t34O0bESV2

Dealer OCD Mike peddles a 22k Playback Designs DAC that voids all preamps apparently on most of his videos. This video is no surprise. It is very doubtful that the dude's dac does endless miracles with every amp on earth..

It is not that much a mystery that amp manufacturers will design a pristine sounding  poweramp and pretty much try to lock you into a pristine sounding $$$$ preamp they specifically designed for it (atleast in the high end). All the DACs and the preamps from other manufacturers can sound less optimal thereafter with that poweramp (Not always though and there are enough exceptions, of course)..