by Kevin OBrien on January 3, 2022


With so many new high end reference cans on the horizon or already shipping for 2022, how are we going to test and evaluate them all properly? I have it figured out, pick up a headphone amplifier that is as versatile as is it is good looking. I'm talking about an amplifier that can be right at home with a pair of Audeze LCD-XC and still power HiFiMAN Susvara well enough to make them sing. Hmmm? That's not an easy task for any amp now that you mention it.

If you're out of Poland and your name is Ferrum Audio, you don't have anything to worry about because this is exactly what you've been busy coming up with for the past two years. But honestly, how can one amp possibly fit all these flagship headphone models under one roof?  I am calling BS. Well I'll be damned, it turns out you can do just that. If you have flexibility with gain settings along with multiple connection options, from inputs to outputs, you're all set. That's where Ferrum comes in again.

Ferrum started out of a need from its parent company, HEM, to come up with a headphone-specific line-up of audio gear that could compete with the 'high end' gear but keep the prices closer to reality. HEM makes Mytek gear for the 2-channel world. HEM makes Ferrum gear for the headphone world. Problem solved.

Here comes Ferrum OOR mated to Ferrum HYPSOS to save the day. This pairing can power any headphone currently on the market (electrostats excluded obviously) with ease and do it with versatility in mind. The OOR + HYPSOS Stack is how versatility will be measured going forward. I know, that's a bold statement. Read on and see what we mean...

Let's begin by talking a bit about OOR. There is a single set of RCA and XLR inputs and outputs on the rear panel along with the volume control bypass switch and the power input connections. One power input is specifically designed to be used with HYPSOS and is called 'Ferrum Link'. The other power input is a 2.5mm x 5.5mm female DC barrel connector (use this if you want to try a YFS LPS with your OOR). You can use OOR as a stand-alone preamp if you so desire by implementing the outputs on the rear panel. OOR can bypass its volume control as well if you already have that covered elsewhere (like in your DAC). Working your way around OOR, there's a set of headphone outputs, one balanced 4-pin and one 1/4" (6.3 mm) single-ended, located on the front panel. Input (RCA, Stand-By, XLR) and gain selection (Low, Standard, High) are handled on the front panel as well. This is one handy and versatile amplifier.

HYPSOS is Ferrum's answer to multi-rail linear power supplies. This particular power supply is a linear / switching 'hybrid' design of sorts. It's not a linear or a switcher. Interesting. It definitely mates well with OOR and that is its ultimate purpose but it can be used to power all sorts of HiFi devices. HYPSOS comes pre-programmed from the factory with a multitude of device settings (Voltage and Current output settings). Select your device from the menu on the front panel OLED display, and you're ready to go. The front panel shows your device output voltage, current, and power output in Watts. Very cool! HYPSOS can output 5V up to 30V at a max of 6 Amps of current output ( 80 Watts max output -> W= (V x i) ). We must say, that all sounds pretty slick.

So anyway, how does it sound? It sounds great! The Ferrum Stack looks and feels like it should be clinical when judging a book by its cover. It's a solid state amp after all. As it turns out, OOR sounds more like a good tube amp than a solid state amp. This sounds crazy but it's true. We were able to test with our Audeze LCD-5 and HiFiMAN Susvara. These are two of the most difficult loads to drive on the market currently. The Ferrum Stack made quick work of the Susvara in 'high gain' mode. The Ferrum Stack made the LCD-5 sound incredible in 'standard gain' mode. There was never any hint of harshness or brightness at all but the presentation was ultra-detailed and bass was tight. Everything was spot on. WOW! Impressive. We have to hand it to Ferrum here. 

Keep in mind the Ferrum Stack is fully balanced, even when using the single-ended inputs. The Stack converts all incoming signals to balanced, if they are not already, and then does its thing. OOR outputs 8 Watts into 60 Ohms via the XLR inputs and outputs 2 Watts into 60 Ohms via the RCA inputs. Not bad at all for a little 10 pound stack of gear with a 8.5"W x 8"D x 4.5"H footprint. This is impressive. If you're on a budget, you can purchase OOR by itself and then partner it up with HYPSOS later on. This is a smart way to go financially if money is tight. After all, this hobby isn't cheap. We tested OOR on its own and it does sound good but it doesn't 'wow us' like it does when mated to HYPSOS. If you can swing it, pick up the entire stack at once. You will be rewarded. We were SO impressed with OOR, we became dealers. YFS is an authorized Ferrum Audio dealer.

US Distribution for Ferrum Audio (VANA Ltd.) is out of NYC which is nice and convenient. It gets old sending money overseas when placing orders. The standard factory warranty is 2 years from date of purchase and defects are handled in NYC. What's not to love?

Thank you for spending your time with us and reading our review. Contact us for pricing and availability. Let us know if you have any questions or concerns.

Until next time..