This post is part of the Focal Arche “episodic” review, that begins here.
Amplifier Modes & Frequency Response
One of the more interesting aspects of the Focal Arche is the option for different settings on the amplifier. These include a conventional “voltage” output mode, a “hybrid” mode (presumably biased more towards a current-output topology - Focal aren’t specific here), as well as specific options for all of Focal’s current “audiophile” line-up of headphones.
Focal simply describe these as being optimized for their various headphone offerings, currently covering the Elear, Elegia, Clear, Stellia and Utopia (the Arche has user-updatable firmware, so presumably if Focal release more headphones in the future they can be added to the list of selectable models).
When I first got my hands on the Arche, a couple of months ago, I was most interested to see what differences there are between these settings and whether they were audible or not - but didn’t have the time to do a proper evaluation of the differences. My initial take away was that you could hear a difference … i f you really paid attention , but that I didn’t have an obvious preference for one mode or setting over another.
Now that I have the Arche back in my hands for more extended evaluation, I decided not only to do more comparative listening, but also to measure the frequency response with the amplifier in different modes and with different headphones. You can read about my measurement rig and practices here.
Voltage vs. Hybrid vs. Focal Preset Modes w/ Focal Headphones
The goal here was simply to first listen to a couple of Focal’s headphones in each of the Arche’s different modes and try to characterize any differences I heard. Then, after listening, measure the frequency responses in each mode and see if there was any delta and/or if such correlated to what I was hearing.
Utopia
For the Utopia, audible differences were not highly tonal in nature. Low-frequency replay had more impact and slam in “hybrid” mode and more still using the “Utopia” preset, the highest frequencies seemed smoother and both treble and mid-range were slightly less emphasized vs. either “voltage” mode or when I drive the Utopia from other well-matched amplifiers. There was also a sense of improved speed (on what is already a very fast headphone), perhaps a hint more micro-dynamic subtlety, a feeling that the presentation was slightly more balanced and the overall sense of tonal “richness” or “weight” that the Arche seems to exhibit in general.
As far as the actual frequency response comparisons go, while they bear out a slight increase in bass level from “voltage” to “hybrid” and then “hybrid” to “Utopia” modes, they are fundamentally identical across the rest of the frequency spectrum. The change in bass-level is small, but should technically audible, and it’s impossible for me to say if this is responsible for what I perceived when listening or not … though my listening impression wasn’t of “more” bass, just more “impact” to what was there … even if the overall “feel” of the headphone wound up seeming more balanced.
Stellia
Audible and measured behavior here can be described in exactly the same terms as for the Utopia. The same, apparent, audible changes exist, and the differences in frequency response across the three different modes offered by Arche were essentially identical.
Voltage vs. Hybrid Modes w/ Non-Focal Headphones
Having seen essentially identical changes in frequency response for the two Focal headphones across different operating modes, I was interested to see if the same effect was apparent with other headphones. For these I just used the “voltage” and “hybrid” amplifier settings.
Rosson Audio RAD-0
Since the Focal headphones are low and medium impedance designs, I wanted to include both another headphone of lower-impedance as well as use a different driver technology. I settled on the Rosson Audio RAD-0 for this purpose.
Sound, overall, was excellent (I’ll cover that in more detail in a subsequent “episode”) here … but switching from “voltage” drive to “hybrid”, other than a sense of better low-end grip or drive-authority with energetic bass lines I didn’t not perceive any difference at all here. No tonal changes I could detect, nor any other apparent difference beyond Arche’s seemingly-innate “richness” (apparent in any mode).
Measurements show no difference at all. So other than, perhaps, the low-impedance nature of the RAD-0 fitting better with the available current in “hybrid” mode (which is speculation on my part), there’s nothing in the numbers here that suggest there should be a difference. I was expecting there to be a slight up-tick in bass level here, in hybrid mode (based on what I’d seen with the two Focal headphones) but that did not occur.
Sennheiser HD800S
To add a high-impedance headphone to the mix, I chose the Sennheiser HD800S. This might be one of my favorite solid-state pairings for the HD800S, where the already-mentioned-to-death “richness” of the Arche really plays well with the typically somewhat lean and brighter signature of the Sennheiser headphone. The end result, in either “voltage” or “hybrid” modes was thoroughly engaging, but was not audibly different in any other way.
Amplifier Modes & Frequency Response - Summary
While there are subtle, but measurable, frequency response differences among the settings for Focal headphones, this isn’t really reflected with non-Focal headphones. Similar, the differences in overall sound are more apparent in the “model specific” modes here and are less, or not apparent with some other headphones (this may change with others).
Other performance metrics, such as distortion, available power, and so on may show bigger differences when it comes to measurements.
And for now, if I was using the Arche as my day to day amplifier, I would choose to run it using the appropriate model preset if using Focal headphones, in “hybrid” mode for low-impedance non-Focal cans and “voltage” mode for higher impedance headphones.
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See the updates to First Impressions of the Focal Arche for links to other parts of this review.