About this page
The NV73 was the first product from The Don Classics, a UK name in build-it-yourself studio gear. It is a 500 series microphone preamp modeled on the Neve 1073, sold from this address as a kit and also offered as a finished module.
TunedRoom now owns the thedonclassics.com address, so older links to the NV73 arrive on this page. We are an independent publication with no connection to the maker. We did not make this kit, we do not sell it, and we cannot provide parts, manuals or build support. The background is on our page about The Don Classics DIY audio kits.
Where the NV73 is sold now
During 2025 this address forwarded to Quantum J Audio (opens in a new tab), a UK shop that now sells an NV73 and an NV73EQ. Its NV73 is offered as a full kit or a built unit, and the page credits the design to Don Classics and has its own documents tab.
That shop is the place to ask about buying, documents and support. TunedRoom has no connection with it. The rest of this page records what the maker published about the kit sold from this address, with the year of each archived copy.
What the NV73 was
The Neve 1073 is a console module from 1970 that pairs a Class A, transformer coupled microphone preamp with a three band equalizer. The preamp half on its own is one of the most copied circuits in recording.
The Don Classics built the NV73 around that preamp. By the maker's account the goal was an authentic copy: three full gain stages, as in the original, and the same kinds of polystyrene, tantalum and electrolytic capacitors. The founder designed it for their own freelance work before selling it to other engineers.
How the circuit builds up its gain
A microphone puts out a very small signal, and a preamp exists to raise it to the level the rest of the chain works at. The 1073 design does not do that with one amplifier. It spreads the work across separate stages and brings more of them into the path as the gain switch is turned up, so no single stage is pushed hard to reach the top settings.
An input transformer sits in front of those stages and an output transformer sits behind them. Each one adds some gain and some character of its own. That combination of stages and transformers is what people mean when they talk about the sound of the design, and it is the part a simplified copy tends to trim.
The maker listed three full gain stages, like the original, as a requirement. The kit list shows a main board, a converter board and separate input and output boards.
Published specifications
These figures come from the maker's specification page for the assembled NV73, as archived in 2016.
| Item | Published figure |
|---|---|
| Microphone gain | 0 dB to +65 dB in 5 dB steps, around 71 dB with the Lo Z switch pressed |
| Input impedance | Around 1,200 ohms, or 300 ohms with Lo Z pressed |
| Maximum output | Above +26 dBu into 600 ohms |
| Output impedance | Around 50 ohms |
| Frequency response | +0 dB, -0.5 dB from 20 Hz to 20 kHz |
| Inputs and output | Transformer balanced |
| Power | Plus and minus 16 volts from the rack, converted to a single 24 volt rail inside the module |
| Current draw | 125 mA at most |
The front panel also had a 0 dB line setting, an output level control that sat at unity when fully clockwise, a polarity switch and a 48 volt phantom power switch. The 300 ohm setting was offered for older ribbon microphones.
What came in the kit
The kit page, as archived in 2019, lists the main circuit board, a 16 volt to 24 volt converter board, separate input and output boards, the front panel and bracket, a heatsink for the 2N3055 transistor, the push switches and their caps, the output level control, all 13 polystyrene capacitors and the mounting hardware.
The list does not include the transformers. The maker's overview page said the other parts came from three further orders with carts prepared in advance, one of them for the knobs.
One build note from the maker's own questions page is worth keeping: each preamp uses a pair of 6.81k resistors that must be matched to each other. For a stereo pair you match two per preamp, not all four together.
Prices
In archived copies from 2022 to November 2024 the NV73 kit was listed at £149, or £248 with the EQ add-on, with worldwide shipping included. A 2016 copy lists a fully assembled NV73 at £550.
The NV73EQ add-on
The NV73EQ was a second kit, listed at £129, that added the equalizer stage and turned the NV73 into a full preamp and EQ. The maker's listing carried the words dual slot.
It was not a standalone equalizer. As in the original design, the EQ sits between the preamp's input amplifiers and its output amplifiers, so it needs the NV73 to work. Its kit held two circuit boards, a front panel, three control pots, 13 polystyrene capacitors and hardware.
The 19 inch versions
Later the maker moved the same idea into a 1U rack. The 2NV-Rack, listed at £169, held two modules and had its own power supply. The 2NV73, at £225, was a preamp and EQ with a line input and a guitar input, up to 80 dB of gain and a switch between 1,200 and 300 ohm input impedance. The 2NV73+ and 2NV66+, at £259 each, added a switchable high shelf frequency.
Audio samples
The original site hosted blind comparison recordings of the preamp. Those files are not hosted here.
A microphone always needs a preamp somewhere in the chain, even in a simple home setup. Our guide to connecting a mic to speakers explains where that gain comes from when you are not using studio hardware. A record player needs the same kind of help from a phono stage, which we cover in connecting a turntable to speakers and in our list of turntables with a built-in phono preamp.
The maker's other kits have their own pages here: the 250EQ and the U76a compressor.
Common questions
Is the NV73 still available?
Not from TunedRoom. Quantum J Audio, a separate UK shop, now sells an NV73 as a full kit or a built unit.
Did the NV73 need a 500 series rack?
Yes. It was a 500 series module and took its power from the rack. The later 2NV versions were made for the maker's own 19 inch rack instead.
Could the NV73EQ be used on its own?
No. By the maker's account it needed the NV73, because the EQ sits between the preamp's input and output amplifiers.
How much gain did the NV73 have?
The published figure for the microphone input is 0 dB to +65 dB in 5 dB steps, and around 71 dB with the Lo Z switch pressed.
More in this category