I recently replaced my sources. On the analogue side a Music Hall Stealth replaced an Audio-Technica LP-1240 and on the digital side an iPad replaced a BlueSound Node, after testing and realizing playing my music library via USB into Chord M Scaler => Quetest sounded better than Airplay through the BlueSound Node. I play Radio Paradise and TuneIn with the iPad for variety.
step up transformer (previous integrated had only MM input)
Hegel V10
phono stage
Apple iPad Pro, 11"
When I first got the Qutest I tested and Airplay => Bluesound => optical => Qutest sounded better than MacBook => USB => Qutest. So I ran the former for a while.
When I added an M Scaler I inserted it into this arrangement: Airplay => Bluesound => optical => M Scaler => double BNC => Qutest.
After having the M Scaler in my system like this for a while I tested MacBook => USB => M Scaler => Qutest, and found it to be major improvement over the former. Hence this iPad, and an AudioSensibility Signature USB to match my loom.
This transformed my system, finally bringing out the potential of the components.
Chord M Scaler
Upscaling digital to digital computer feeding Chord Quetest DAC via dual BNC. Went this route to maximize the Quetest DAC I already had, and to maximize the sound quality of my existing music library on my Apple devices.
Chord Qutest
DAC fed by dual BNC from Chord M Scaler.
Audio Sensibility Signature signal cable loom
Silver interconnects, incl USB; copper speaker cables; Bybee filtered power for pre-amp and mono-blocks.
Pangea Audio Power cable loom
to subs, to Octet power strip for main components and wire world Matrix 2 power strip for accessory components, and to LPS's for M Scaler and Qutest.
Massdrop Drop + THX AAA
headphone amp
Beyerdynamic T1 v3
headphones (not shown)
SBooster BOTW Linear Power Supplies
Linear Power Supplies for Chord Qutest, Chord M Scaler, and Music Hall Stealth
I ordered the Rothwell MCL step up transformer from their web site and they shipped it direct from England, which was easy enough. I like it and would recommend it, though I've not compared it with others. Their website is informative and lists a variety of models for specific voltages etc.
The subs are actually down firing with a passive front. The speaker height is spot on. I’ve played with toe in, and am currently favoring no toe in for wider soundstage and better sound throughout the room.
One other thought; it appears that if you were to switch the subs, you would have the side firing drivers toward the inside. It may be undesirable, but I would try it. The result could be surprisingly good. No harm done and potential benefit.
Lastly, it might be fun to invert the ATC speakers or run them on their sides, perhaps with tweeters outward. This will change the system somewhat and lend variety to experiences. Of course companies will not advise, but this is your system and it's all fun. Take a look at my virtual system and you can see I tend to play around with such things as speaker position in order to get different experiences with soundstage. Such experimentation is informative as to how sound fields are influenced by design.
Nice, tight system; well thought out! Kudos! If your monitors are not at seated ear level, you may wish to play with the baffle slope a bit to tune them in as regards soundstage and center imaging. But it appears that with the stands they are in the zone. I presume you have played with toe in of the monitors. :)
Also in regard to the ATC monitors, consider a method I have used and endorse - in fact, using it now with a set of Wharfedale Opus 2-M2 speakers - which is to double (parallel) speaker cables, running two sets. It is a most efficacious improvement that keeps the character of the sound, but enhances it notably.
Just make absolutely sure all connections are perfectly parallel, no crossing over of terminations at amp or speakers. I triple check such connections and never change gear when tired, because mistakes can be made. Typically I keep on hand both spade and banana terminated speaker cables for that purpose. :)