About this page
The U76a is a build-it-yourself compressor first sold by The Don Classics, a UK name in 500 series studio kits. It is a FET compressor modeled on revision A of the 1176, the early version the maker called the blue face.
TunedRoom now owns the thedonclassics.com address, so older links to the U76a 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 U76a stands now
During 2025 this address forwarded to Quantum J Audio (opens in a new tab), a UK shop that now sells an NV73 preamp and a 250 EQ. It lists a u76a blue face FET compressor too, with no price and no way to order when we checked in October 2026.
That shop is the place to ask. 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 U76a was
The 1176 is a studio compressor first sold in 1967. It uses a field effect transistor to turn the level down, which lets it react extremely quickly, and it has been in constant use on vocals, drums and bass ever since. The first revisions are known for their blue striped front panels.
The Don Classics built the U76a on the revision A circuit and fitted it into a 500 series module. The maker's site said builders could work from its own schematic or from the original 1176 schematic.
What revision A means
The 1176 was changed many times over its production life, and the versions are known by letter. Revisions A and B are the earliest and carry the blue striped panel. Revision C arrived in 1970 with lower noise circuitry and the black panel most people picture when the compressor is mentioned.
Builders and buyers care about the letter because the revisions do not sound the same. The early ones are often described as the more colored members of the family, which helps explain why a kit maker might choose revision A to copy and say so on the product page.
Price
In archived copies from 2023 to November 2024 the U76a kit was listed at £149 including worldwide delivery.
What came in the kit
The kit page, as archived in 2019, lists:
- The main circuit board
- A 16 volt to 30 volt converter board
- A control amplifier board and a meter board
- The front panel and bracket
- A heatsink, standoffs and screws
- Push switches and their black caps
- Screws and nuts for the transformers and the meter
The list does not include the transformers or the meter. The maker's overview page said the other parts came from two further orders with carts prepared in advance.
A 500 series rack supplies plus and minus 16 volts. The converter board's label shows this circuit running at 30.
Setting it up after the build
An 1176 circuit is not finished when the last joint is soldered. It has to be calibrated, which includes biasing the transistor that does the gain reduction and zeroing the meter so that it reads correctly. A multimeter and a steady test tone belong on the bench next to the soldering iron.
The maker published a build manual for the kit. Its advice for a build that did not work was to look over the work again, read the manual and check the support thread on a builders' forum.
Reading the controls
The front panel of an 1176 trips people up in one respect. The attack and release knobs run in the opposite direction to most compressors, so turning them clockwise makes the compressor faster, not slower.
The attack is also far quicker than on most designs. Even its slowest setting is under a thousandth of a second, which is why the 1176 is reached for when a peak has to be caught before it gets through.
Linking two for stereo
The maker's questions page covered this directly. To link two units for stereo, the FETs have to be matched between the two units, four matched FETs in total. With that done, the stereo link on the rack sets whether both channels react together to a combined signal or each channel reacts on its own.
What a compressor like this does
A compressor turns loud moments down so the quiet ones can be turned up, which makes a performance sit at a steadier level.
On an 1176 style unit there is no threshold control. You turn up the input to push the signal into compression and use the output to set the final level. Buttons choose how firmly it clamps down, with ratios of 4, 8, 12 and 20 to 1, and two knobs set how fast it grabs a peak and how fast it lets go.
Home equipment uses the same idea under friendlier names. The night mode or volume leveling setting on a TV or soundbar is a compressor that keeps explosions down and speech up. Our guide to making TV dialogue easier to hear explains when that setting helps, and there is more in our TV and soundbar guides.
The maker's other kits have their own pages here: the NV73 preamp and the 250EQ.
Common questions
Is the U76a still sold?
Not by TunedRoom. Quantum J Audio, a separate UK shop, lists a u76a blue face compressor, with no price and no way to order when we checked in October 2026.
What did the kit cost?
The listed price was £149 including worldwide delivery.
Could two be linked for stereo?
Yes, by the maker's account. The FETs had to be matched between the two units, four matched FETs in total, and the rack's stereo link was used to join them.
What rack did it need?
A 500 series rack. The kit included a converter board labeled 16 volts to 30 volts.
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