add dt770 bluetooth mod page

input/blog/2021/2021_09_05_dt770_xlr_mod.md

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+title: Blog
+post: BeyerDynamic DT770 Mini-XLR Mod
+description: For easier use with a Bluetooth Rx
+date: 2021-09-04
+parent: projects
+---
+
+In 2011 I bought my first set of headphones, the [BeyerDynamic DT-770 Pro (250 Ohm)](https://europe.beyerdynamic.com/dt-770-pro.html).
+Even though I now own them for 10 years, they still hold up absolutely great!
+Of course I had to replace the ear pads and the top-strap cushion after a while, because they degrade with age and sweat and sunlight.
+But thanks to the very professional service of BeyerDynamic, you can get _all_ [replacement parts](https://www.beyerdynamic.de/service/ersatzteile) for a reasonable price.
+
+I'm definitely not an audiophile, I don't use fancy expensive equipment to power these headphones.
+But they are more than good enough for my requirements / my ears, and I can wholeheartedly recommend them!
+
+Especially being stuck at home with Corona the last year, I started using my headphones with a small Bluetooth receiver attached to them.
+This worked surprisingly well, even though I own the 250 Ohm version of the DT-770.
+The only hassle was carrying around the long and heavy cable.
+
+Because of this, I decided to add a Mini-XLR connector and make the cable detachable.
+
+<!--%
+lightgallery([
+    [ "img/dt770_xlr_6.jpg", "Close-up of the connector with plug" ],
+    [ "img/dt770_xlr_7.jpg", "Total top-down view" ],
+    [ "img/dt770_xlr_8.jpg", "3D printed Bluetooth Receiver mount" ],
+    [ "img/dt770_xlr_9.jpg", "Original cable with newly fitted Mini XLR connector" ],
+])
+%-->
+
+I decided to use a 4-pin connector.
+This way, each speaker can be connected to its own positive and negative pins, without connecting the two negative poles inside the headphones.
+This way, a balanced connection can be used to drive both speakers completely separately, as long as the amplifier supports it.
+But this is only a future option, for now I have used normal Stereo cable and a 3-pin connector for the other end, so still unbalanced.
+
+Here is a list of the materials I bought for this little project:
+
+<!--%
+tableHelper([ "align-right", "align-last-right", "align-right monospaced"],
+    [ "Part", "Description", "Cost" ], [
+        [ "xlr-male", ("Mini XLR 4-pin Panel Mount Male", "https://www.ebay.de/itm/402639518058?var=672917202885"), "2.08€" ],
+        [ "xlr-female", ("Mini XLR 4-pin Metal Shell Female", "https://www.ebay.de/itm/402639518058?var=672917202949"), "2.61€" ],
+        [ "trs-male", ("3.5mm TRS Male", "https://www.reichelt.de/de/de/klinkenstecker-3-5-mm-stereo-3-pol-ksskg-35-p9585.html"), "0.40€" ],
+        [ "cable", ("Microphone Cable 2x0.1mm² Shielded", "https://www.reichelt.de/mikrofonleitung-2-x-0-10-mm-rund-10-m-ml-209-10-p13307.html"), "7.99€" ],
+        [ "", "Sum", "13.08€" ]
+    ]
+)
+%-->
+
+To fit the male panel mount connector to the headphone shell, the original cable hole has to be enlarged.
+I simply drew the estimated dimensions on the case and used a dremel to remove excess material until the connector fit just so.
+Make sure to move the hole as far to the outer side of the case as possible, away from the speaker.
+
+Even before attempting this, I was worried about the lack of space behind the speaker membrane.
+And in fact even the small Mini XLR connector was a bit too long. I had to leave a nut on the outside to reduce the length inside the case.
+
+There is also not enough room to properly fix the connector with a nut on the inside.
+I decided to use epoxy resin, which seems to work fine.
+
+<!--%
+lightgallery([
+    [ "img/dt770_xlr_1.jpg", "Original cabling of the speakers" ],
+    [ "img/dt770_xlr_2.jpg", "Original cable hole" ],
+    [ "img/dt770_xlr_3.jpg", "Estimate of the required cut-out" ],
+    [ "img/dt770_xlr_4.jpg", "Connector fitted and right speaker soldered on" ],
+    [ "img/dt770_xlr_5.jpg", "Left speaker soldered on as well" ],
+])
+%-->
+
+This is a very common modification and others all over the internet have already done it before me.
+Here are some of them I found and used for inspiration.
+
+ * [DT770 Pro Detachable Cable Mod with Custom 4-pin Mini-XLR to 3.5mm Cable](https://www.reddit.com/r/DIYAudioCables/comments/ki76cv/dt770_pro_detachable_cable_mod_with_custom_4pin/)
+ * [The (hopefully) ultimate guide to a mini XLR detacheable cable mod for the Beyerdynamic DT 990 PRO](https://www.reddit.com/r/headphones/comments/gdbuk2/the_hopefully_ultimate_guide_to_a_mini_xlr/)
+ * [Beyerdynamic Balanced Removable 4 Pin Mini XLR Mod ](http://www.diyaudioblog.com/2015/05/beyerdynamic-balanced-removable-4-pin.html)
+ * [Modded my DT 770 pros to detachable mini xlr](https://www.reddit.com/r/headphones/comments/k9z4fu/modded_my_dt_770_pros_to_detachable_mini_xlr_and/)
+
+To properly hold the Bluetooth receiver and not have it dangle around, I designed a simple 3D printed piece to mount it to the top cushion.
+You can find it [in my 3D print Git repo](https://git.xythobuz.de/thomas/3d-print-designs/src/branch/master/dt770) or [on Thingiverse](https://www.thingiverse.com/thing:4949404).