I didn’t find a topic for this product, so I figured I’d start one because I would love to read impressions and thoughts from this community.
Topping recently released a discrete design of their A90 headphone amplifier, for which they use 156 (4x39) matched transistors instead of opamps for its gain and output stages.
My Initial Thoughts
Aside from the engineering flex of producing a measurably performant discrete topology, which I applaud, I remain unsure if or how that translates to any experiential improvement to similarly performing IC designs.
Instead, what I find most compelling about this amplifier is that it can produce 6W per channel at a 32 ohm load, and it has a resistor ladder volume control implementation for perfect channel matching and longevity (scratchy volume pots anyone?). The latter is something I personally highly value and is one of the potentially more audibly important vectors that amplifier designs have been under-indexing on while they needless chase different degrees of completely inaudible SINAD performance.
I don’t like the removal of physical switches, and I really wish they had a 3.5mm output instead of that 4.5mm one for IEMs. The remote, while seems functional, doesn’t really look intuitive at all.
All that said, I have been looking to replace my Jot 2 with something that allows me to turn off headphone out and use my IEMS as well as my headphones - so I am very interested in seeing some user reviews.
The 4.4mm is not really just for IEMs, I would say that the majority of people who are going balanced with headphones opt for the 4.4 over an XLR4 lately.
A 6.35mm (1/4") to 3.5mm adapter is something that is very easy to find and is available with a low profile, whereas an XLR4 to 4.4mm, or 4.4mm to XLR4, is not so easy (or cheap) and is usually on the large size.
As for my impressions of the amp, I’ve never owned any of Topping’s products so I am unfamiliar with their sound or build quality from a first-hand experience. The previous version seemed popular enough though.
As others said in their replies, the reduced gain stages along with volume control is interesting. Topping also has an add-on that can increase the number of XLR and RCA inputs, though I’m not what use case that product is supposed to address. Because of the removal of physical switches and the reliance on a remote control, I am inclined to believe that this product is targeted more towards somebody that would have this as part of a home audio system in a living room or den as opposed to a desktop setup.
That was the first thing that came to mind and could potentially be a helpful feature for somebody A/B-ing DACs.
The Ext90 adds 3 additional pairs of XLR and 1 additional pair of RCA inputs to the built-in 1 pair of XLR and 1 pair of RCA connectors. I could see the Ext90 being useful if the use case required more than 1 set of balanced or unbalanced sources, such as an external CD transport, Blu-ray/DVD player, and a standalone music streaming source. This again suggests that a target audience is the home audio system owner.
As an aside, I wonder how much Topping has learned from their Pre90 and applied to the A90 Discrete?
They actually pulled the firmware update v2.0 at the last minute, due to bugs. They just recently released the updated firmware v2.3, which I confirmed works! It also seems to have resolved my issue of resetting when plugging/unplugging to the 6.35mm unbalanced port, instead showing a -5.