Any DIY stuff in your system?

Back in the day, DIY was not unusual- whether from a kit or scratch built. Today, different story. 

Still, wondering how many folks incorporate some DIY in their gear.

I will start- 

I have DIY equipment

Bottlehead headphone amplifiers (I've built 2 of those) - these were kits; my first Bottlehead (Crack) is far from stock these days

Interconnects- all from scratch- cables have been DH Labs and Klotz and connectors have been Vampire, Neutrik and Rean- must admit I've built clones of the Rega Couple (Klotz AC-110 and Neutrik Profi)

Power cords- from scratch-  Belden and Supra, with Wattgate connectors

I have also modified tuners- first, a Dynaco and more recently, a Magnum Dynalab (which I eventually returned to stock) 

Now I'm contemplating building a small ultra high efficiency speaker (98 dB or better)

Building something yourself self that doesn't blow up, spark or smoke, or cause a fire, and actually sounds good, is very satisfying.
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I have somewhat-DIY subs. Speaker/cross-over designer Danny Richie of GR Research collaborated with Brian Ding of Rythmik in the design of an OB/Dipole subwoofer. The Rythmik Direct Servo Feedback A370 plate amp is mated with either two or three 8" or 12" GR Research servo-controlled woofers that have been optimized for open baffle use. Those components are obtained from either Danny or Brian, and the woofers are installed in a DIY OB "frame" of either "W" or "H" structure. Plans for the frames are available on the GR Research website, and can be fairly easily made (or have built by a cabinet maker), as well as being available as a flat pack by a couple of people. I got lucky and found a guy selling a pair of W-frames made by ED before they went out of business.

If a dipole sub sounds familiar, it's because the Finnish company Gradient offered such a sub, made and marketed specifically for use with the QUAD ESL63 in the 80's and 90's (check your old TAS' for a review of it). Gradient built their H-frame with the same footprint as the Quad, being designed and intended to be used as a base for the Quad. The GR Research OB sub is quite a bit more sophisticated, and a much-higher performing one. 

The woofers are installed, in the case of a 2-woofer sub, with the drivers facing in opposite directions, wired in opposing polarity. The open baffle operation results in a null at each side of the frame, as in any dipole. This causes increasing roll-off as frequency descends, with which to compensate for Brian designed and installs into the amp a shelving circuit.

The sound of the OB Sub is very different from any and all other subs. The servo-controlled woofers, combined with the lack of a resonant sealed or ported enclosure, results in a very "nimble", start-and-stop-on-a-dime sound quality. The sub doesn't make it's presence overtly known, instead making the speaker it is used with appear to have gained an octave or more of extension at the bottom. It doesn't have the thick, heavy, slightly-behind-the-loudspeakers sound of non-OB subs, even very good ones. I know you guys with really good subs (including Rythmik's "regular" ones) think yours are "quick", but you won't after hearing the OB/Dipole Sub! Just ask anyone who heard it at RMAF (either in free-standing form, or as part of the GR Research Super-V loudspeaker), where it was voted Best Bass at the Show many years running.

While being a great sub for any application, the OB/Dipole is, for obvious reasons, particularly good for use with any and all dipole loudspeakers. If you remember, the SPL decrease with distance differs between a dipole and a non-dipole loudspeaker, and the same is true with subs. If you mate a dipole speaker with a non-dipole sub, the balance between the two will differ according to location and listening distance---not good. With a dipole sub, the balance between it and a dipole loudspeaker remains constant, regardless of where the speaker/sub and the listener(s) is/are located. The balance between the two will also be affected by their differing room-loading characteristics. Speaking of loading, the Dipole sub doesn't load the room with bass the way a non-dipole sub does, that loading resulting in the room boom familiar to subwoofer dislikers. But, then, what of the OB/Dipole sub for use with a non-dipole loudspeaker? True, the balance with listening distance will differ, but with most non-dipole loudspeakers that is far less of a problem than the speaker's inherent shortcomings. Okay, I'm a dipole lover!  

A pair of First Watt F5 clone mono amps. Wonderful.

Fine silver power cords and speaker cables from scratch. DIY balanced ICs using Connex/DH Labs BL-Ag bulk cable.

Much of the rest of it is DIY modified.

Modified Atma-Sphere MP-1 preamp with LDR volume control, VSE Superregulators, all-film power supplies & high-gain hybrid phono section.

Modified Pass XP-25 phono with ClarityCap MR coupling caps and TX2575 load resistors.

Modified Merlin VSM with ClarityCap/Duelund crossover, Duelund silver wire, and modified BBAM with ClarityCap MR, teflon bypass caps, TX2575 resistors, and bespoke Hynes power supply.

Modified Velodyne DD-15 with fast recovery rectifiers, silver wire, and cabinet resonance treatments.

DIY AC balanced power using Signal DU-5 transformer.

DIY can lead to satisfaction in surprising ways.

I have a DIY'ish VPI Classic "2.7" TT.  The plinth is the basic Classic 1/2 variant.  However, I switched out the standard Classic tonearm and base for the Classic 3 (stainless steel) version.  I had to drill out the top plate using a VPI supplied template and steel cutting drill bit.

I also switched out the standard Classic 600 rpm motor for the 300 rpm version used on the Classic 3.  While fiddling with the motor I also replaced the stock cap.  As a result, turn-on/off thump has ben eliminated.

So, I have a Classic "2.7" variant.  Some VPI boosters have suggested that I switch out the stainless steel wand for the 3-D printed upgrade.  It's on my bucket list of things I may want to do.