Lehmann Linear DIY or how to clone a purebred German with a good result

It all started with the fact that, like on the Beyerdynamic DT880 600ohm (!) Wiretap of my ears, I stuck them in some kind of thoroughbred tube amp and realized that I couldn’t live with my old man (also tube).

Spoiler final result:

By the way, the old amp is also self-soldered (completely) from a DIY set of two interesting guys - one is Dutch (apparently, the designer), and the second American (apparently, sales person ) - GARAGE 1217 - Project Horizon:

By the way, back in 2013, it was bought for fabulous for DIY (on a 6N23P lamp) - $ 250!

But the monster who pushed me to the idea that you need to change something in the life of Home Audio (top left):

In general, the headphones were immediately sold and instead bought at auction DT1770, but that’s another story ...

Searches in the network, digging up forums like diyaudio.com, head-fi.org and the same HBR, led me to LEHMANN LINEAR or rather to its cloned copy. The original, by the way, is no less than 60-70 thousand rubles on the Yandex Market (for what?).

The analysis showed that Ali has several offices that have put a theme on the stream with copying the pedigree and proven products of the old world. Variants weight from full DIY with separate PCB, components and cases to the assembled amp.

On Ali, there are only 3-4 manufacturers of these clones of the SENGTERBELLE, HI IC type, the rest of the pictures strongly resemble the resale of the first ones. I decided to dwell on the manufacturer ZERO ZONE, since these guys offer the so-called Hi version - supposedly from good components like VISHAY, ON and so on. Plus they sell the already wired board and free shipping. It is important to note that I immediately dug in the direction of the order separately to get rid of the delivery of the transformer, which can be bought in Russia of excellent quality. A transformer from China - this is immediately hit on the cost of delivery in the region of 2-3 thousand because of the weight in kilo more, and the declared characteristics from the category "but this is not accurate" ...
Plus, good feedback on other products was about ZERO ZONE.

So were ordered:

  1. Soldered card itself LEM-COPY - 4500r. free shipping,
  2. The case, the benefit with the case, the Chinese have already put the connection terminal 220V, the necessary blades for connecting trance and silicone legs - 2500r. free shipping,
  3. Linear I / O terminals 4pcs - 200r. for all free shipping,
  4. TOREL transformer in ChipDip - 1100r free shipping.
  5. Cable, solder, tool - priceless.

The board itself:

And a box from under it, packed into 4-5 layers of a pimple!

I read the Chinese press while unpacking the case

At first, the landing dimensions of the terminals did not fit, extended with a drill and a Dremel by 1 mm in radius.


A bit touched from the inside with a drill when expanding

The second joint, which was warned on the forums when ordering from different suppliers: the mounting holes did not fit, I had to drill

Then there was a problem with the muzzle - the holes for the TRS terminals for headphones on the aluminum muzzle did not coincide with the board, and by 1-2mm. I solved the problem with a slight warming and raising the terminals in one direction, which is why they went up a little, but they clearly climbed into their windows

Then the transformer went twice as much power (60VA), which, as ordered, climbed into the place of the standard (30VA). Somewhere on the forum they wrote that the "Chinese" 30VA is not enough for a high impedance load, and they put 40-50VA, well, I decided not to skimp and put an honest Russian 60 (VA) (and did not lose).

I had to rewrite the hole for the mounting bolt and go for the bolt and nut in Leroy.

In the photo, the random M-3 bolt was subsequently replaced with the M-5 with a normal lockout.

Solder / crimp blades to connect to power terminal

Good wires were found in the bins with a double screen, which later was planted on the ground of the board, which I think had a good effect on noise immunity due to the dense wiring with a transformer. Without the land did not check.

Soldered to the board

Here is a general view of the assembled product.

For comparison, the original amp and its transformer

Then there was a tambourine dancing when turned on, there was no power from the trance - it turned out the Chinese did not put a fuse, and it was possible to find it at 11 pm on Saturday only in a multimeter, from where it was successfully dissected and inserted together with a 10 amp beetle (approximately).

Surprisingly, the assembly of the body itself and the muzzle was just perfect! very beautiful hexagon bolts, looks nice!

Despite the fact that DT1770 is still awaiting shipment from Munich, and my relatives DT880 have already left the new owner, we managed to test the sound on some computer SENNHEISER HD180 found in the office.

My conclusion is definitely worth the effort of time and rubles. The sound is clear, silence in the channels at any volume. From a good, in my opinion, multibit DAC plays very fascinating and clear even with these ears.

For my part, I can recommend for purchase / assembly.

UPD 02/17/2019
Below, the RMAA measurements are made on the line input of the integrated sound card Lenovo M93 - High Definition (HD) Audio, Realtek ALC662, I can not check how accurate the measurements are:

Frequency response

Noise level

Dynamic range

Harmonic distortion + noise (-3 dB)

Intermodulation distortion

Interpenetration of stereo channels

Intermodulation distortion (variable frequency)

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