TotalDAC's d1-driver gives us a hint. In their catalogue, discrete R2R modules couple direct to variable DAC outputs for the shortest signal path. That omits a traditional output buffer. However, designer Vincent Brient learnt that in many systems, adding a high-current active 'line driver' improves the sound. On his website he explains that "the strength of active preamps is their output stage more than volume control. The active stage helps to drive the power amp." Given this, why not build an active stage into his volume-controlled DACs to eliminate an extra box? Because to the client, sometimes direct does sound better. Denafrips DACs couple their FPGA-switched resistor ladders to the outputs without an extra current buffer too. It's why you don't use their XLR/RCA simultaneously or else one loads down the other. Without built-in volume control, all Denafrips converters expect a preamplifier with its own output stage; or that of an integrated. Omitting their own output stage avoids double trouble.
EX-P7
The upshot is this. Even if we had only one source to not need a preamp's switching facility; and even if that source had its own volume control – still a preamp can improve our sound unless the source had its own truly wicked output buffer. And this didn't yet consider our volume control implementation. Is it digital or analog? Is it a pot with wipers or a switched resistor matrix? Though we may prefer otherwise, it all has a sonic influence. In the name of purity, high-end preamps have done away with tone controls, balance controls, loops for 'black boxes' and more. In the same name of purity, volume-controlled DACs may eliminate traditional output stages. At times purity simply lacks cojones to come off like an androgynous angel. It doesn't party. It may lack certain get-down qualities we associate with optimal drive. That includes dynamics, pressure and tone density. Now we're ready to inspect the EX-P27. We're prepared to consider that its add-on of more in the signal path than DAC-direct could just have very real benefits.
At Guangzhou hifi show 2021 in all black livery.
Using his ears, John Darko of darko.audio already concluded this to be true for himself. His preamp of choice is a PS Audio BHK Signature. Shopping on purist specs, theories and ideals alone is far more likely to consign the analog preamplifier to the heap of discarded legacy notions. "The 21st century has moved on." It's why our ears must remain the final arbiter. It's why dedicated preamplifiers keep on selling in active or passive flavors, with tubes or transistors, with volume control executed on boutique attenuator chips or multi-tapped autoformers. For all of them, there's still a market. Others swear by digital volume like Leedh's. They prefer going direct. Yet others like COS Engineering package a DAC, phono stage, streamer, headphone amp and analog preamp all into one chassis.
Live and let live.
Living with the P27 means "a new motherboard for a fuller midrange with now three aluminium-encapsulated toroidal power transformers for the display, volume control and gain/buffer stages. This essentially equates to dual mono in one chassis. The remote can enable the new HT bypass on XLR and RCA to defeat the P27's volume control for integration with an AV system's pre/pro." What hasn't changed is the 8-10mm thick chassis. The volume control remains an MCU-controlled relay-based resistor ladder with 95 linear steps. Bandwidth remains 0-300kHz -3dB but THD+N has improved to 0.002%, S/NR to better than 100dB A-weighted and channel separation to above 106dB. i/o impedance remains at 50k/75Ω and max output voltage is still 16Vrms. Power consumption is 80 watts tops, weight 15kg so up 2kg and dimensions are 43x12x33cm WxHxD. Here is the PowerPoint owner's manual.
Combing the evidence, over the P7 the PX27 adds features for more inputs plus home-theater bypass. Then Ivan took a redesign opportunity to tweak his original circuit for still higher performance. The price for these improvements is an extra $900. The P7 remains in the portfolio. If you don't run a combined HT/2.0 system, you won't need the bypass feature. But the P27's improved PCB and beefier more segregated power supply still pull. Without a P7 for comparison, I can't say how many extra miles that clocks, how much farther a P27 will take your sound. That requires pure imagination where yours is as good as mine. I'll tell you about actual A/Bs against three challengers:
♦ a single-ended icOn 4Pro SE autoformer passive from Pál Nagy in the UK
♦ a single-ended Vinnie Rossi L2 direct-coupled DHT linestage with bypassed tubes from the US
♦ a fully balanced Wyred4Sound STP Level II also from the US as a transistor preamp without voltage gain because I'd not use it above 63 on its dial. It's only at 64 where E.J. Sarmento's circuit kicks in voltage gain. Below that it operates as a passive with active i/o buffers for constant Ω.
They'd all drive Ivan's flagship monos to explain tube bypass. The Elrog ER50's direct-coupled bandwidth in the Vinnie Rossi is 900kHz for no low-pass effect from usual output transformers. Into our 2.5MHz Kinki monos, that combo embeds strange 'intermodulation' tube noise. It's not hum at the speaker drivers but a metallic grit inside the sound. As soon as the tubes bypass, that disappears so is my default mode when using these amps. Unlike the EX-M1 integrated which looks very similar, the P27 disassociates its power function from the big control knob to instead relocate it right behind the front baffle. Holding that belly button for 5 seconds triggers standby. Pressing it shortly toggles through the output modes.
