# Building my own balanced to unbalanced cables **URL:** \ **Category:** QA40x\ **Created:** [April 12, 2024, 4:19pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351 "2024-04-12T16:19:30Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![ScottRichardson](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/scottrichardson/32/1423_2.png) [@ScottRichardson](https://forum.quantasylum.com/u/ScottRichardson)\ **Post date:** [April 12, 2024, 4:19pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/1 "2024-04-12T16:19:30Z")
I just pulled the trigger today and ordered a QA403. However, connecting cables will be an issue for me because I work almost exclusively on vintage tube preamps and amps with unbalanced inputs and outputs (plus speaker connections). The QA403 manual has some details about interfacing with various balanced connectors like XLR, but not much about connecting to unbalanced inputs and outputs. I would like to make my own cables to connect the QA403 to unbalanced inputs/outputs and think the configuration in the attached drawing would work. Note: the shield on the BNC jacks on the QA403 would not be connected. Please let me know if this looks good or if there are concerns or advice. Thanks. ![Bal to Unbal](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/2X/2/2baffaf513276341adfc4afc8707e64be2de486b.jpeg) ---
**Author:** ![VAR](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/var/32/959_2.png) [@VAR](https://forum.quantasylum.com/u/VAR)\ **Post date:** [April 12, 2024, 8:04pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/2 "2024-04-12T20:04:06Z")
No need to make your own unbalanced cables for testing preamps where you have RCA jacks, just use a bnc to rca adapter. Your diagram looks correct though. If you have not watched it, search for a video I did on Youtube on using the QA402/3- just search for “Using the QuantAsylum QA40x Audio Analyzer”- it may have some useful info since you are just getting started ---
**Author:** ![ScottRichardson](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/scottrichardson/32/1423_2.png) [@ScottRichardson](https://forum.quantasylum.com/u/ScottRichardson)\ **Post date:** [April 12, 2024, 8:30pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/3 "2024-04-12T20:30:21Z")
So I don’t need to connect anything to the center pin of the “-” BNC socket? The shield of the “+” BNC socket can be used as the ground or “-” connection therefore the shield of the shielded cable connects to the “+” BNC socket via the BNC to RCA adapter? ---
**Author:** ![restorer-john](https://avatars.discourse-cdn.com/v4/letter/r/b5a626/32.png) [@restorer-john](https://forum.quantasylum.com/u/restorer-john)\ **Post date:** [April 13, 2024, 12:16am UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/4 "2024-04-13T00:16:57Z")
@ScottRichardson If you want to use the differential inputs on the QA (and benefit from the common mode cancellation), your wiring diagram is 100% correct. @VAR 's suggestion to just use bnc-rca adaptors doesn’t do that with SE sources. If you are simply using SE input and output, RCA-BNC adaptors are fine and a single cable per channel. ---
**Author:** ![ScottRichardson](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/scottrichardson/32/1423_2.png) [@ScottRichardson](https://forum.quantasylum.com/u/ScottRichardson)\ **Post date:** [April 13, 2024, 1:03am UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/5 "2024-04-13T01:03:45Z")
Thanks to VAR and restorer-john. You made my life a lot easier! Also, VAR-- I enjoyed your video on YouTube. Thanks for taking the time to make it. ---
**Author:** ![VAR](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/var/32/959_2.png) [@VAR](https://forum.quantasylum.com/u/VAR)\ **Post date:** [April 13, 2024, 1:30am UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/6 "2024-04-13T01:30:12Z")
@ScottRichardson- Glad you liked the video- I am debating on doing another on right now. Maybe I was not clear in that I was assuming you would be doing mainly Unbalanced (SE) testing. I may not have been clear about this as @restorer-john pointed out. ---
**Author:** ![ScottRichardson](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/scottrichardson/32/1423_2.png) [@ScottRichardson](https://forum.quantasylum.com/u/ScottRichardson)\ **Post date:** [April 13, 2024, 3:12am UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/7 "2024-04-13T03:12:19Z")
Yes, I will be doing exclusively unbalanced testing except for the speaker outputs of amps and if I test output transformers, crossovers, etc. However, all preamp connections and amp input connections will be unbalanced. ---
**Author:** ![Claudio](https://avatars.discourse-cdn.com/v4/letter/c/7cd45c/32.png) [@Claudio](https://forum.quantasylum.com/u/Claudio)\ **Post date:** [April 13, 2024, 4:36am UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/8 "2024-04-13T04:36:53Z")
Hi @ScottRichardson. At this link [https://hifisonix.com/wp-content/uploads/2021/09/Measurement-with-the-QA401.pdf](https://hifisonix.com/wp-content/uploads/2021/09/Measurement-with-the-QA401.pdf) you can find very useful information to be able to reduce the noise induced in the QA and DUT connection. I hope it can be useful to you as you start to utlilize the QA403. I, at the time, applying the described rules, found benefit in measurements (reduction of induced ambient electrical noise). ---
**Author:** ![ScottRichardson](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/scottrichardson/32/1423_2.png) [@ScottRichardson](https://forum.quantasylum.com/u/ScottRichardson)\ **Post date:** [April 13, 2024, 10:18am UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/9 "2024-04-13T10:18:20Z")
Claudio- Excellent! Clear and well-written. That will be extremely helpful in setting everything up. Thanks! ---
**Author:** ![HawkerAMpT](https://avatars.discourse-cdn.com/v4/letter/h/ac8455/32.png) [@HawkerAMpT](https://forum.quantasylum.com/u/HawkerAMpT)\ **Post date:** [April 15, 2024, 2:12pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/10 "2024-04-15T14:12:41Z")
I went round and round with this. A lot of people think the QA ground should be shorted to the DUT (device under test) shield etc. They are wrong. The lowest noise, and most signal rejection I got was running the QA - center BNC to the shield of the DUT plug and the QA center + to the DUT + pin. The QA “ground” is just a shield over the cable but does not connect or short to anything on the device side. I had an Ebay vendor make me the cable for 1/4" that works perfectly. I’m sure they can do it in RCA if you wish. > **[6.35mm mono 1/4" to 2x BNC Male Cable 1~16' For​ Quant Asylum QA40x audio...](https://www.ebay.com/itm/285664070945?var=587677493418)** > > Find many great new & used options and get the best deals for 6.35mm mono 1/4" to 2x BNC Male Cable 1~16' For​ Quant Asylum QA40x audio tester at the best online prices at eBay! Free shipping for many products! ---
**Author:** ![VAR](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/var/32/959_2.png) [@VAR](https://forum.quantasylum.com/u/VAR)\ **Post date:** [April 15, 2024, 4:28pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/11 "2024-04-15T16:28:01Z")
You might ask him to do a similar thing with XLR cables- with both male and female connectors… ---
**Author:** ![HawkerAMpT](https://avatars.discourse-cdn.com/v4/letter/h/ac8455/32.png) [@HawkerAMpT](https://forum.quantasylum.com/u/HawkerAMpT)\ **Post date:** [April 15, 2024, 5:16pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/12 "2024-04-15T17:16:36Z")
I’ve bought quite a bit from this Ebay dealer. They have some great parts cheap especially their knock off of the Pomona BNC to 1/4" adapter. I have multiple times requested a slight modification of an existing cable. They sometimes ask for a drawing to be clear but every time they did it with no problems. So if you want it with XLR or RCA or whatever just ask. Quality is pretty good. They use really thick good RG-174 and Canare wire. The jacks are o.k. quality, but not fantastic mostly Neutrik’s china version. My only complaint is sometimes the strain relief is not adequate and I added extra heat shrink. ---
**Author:** ![yegolebi](https://avatars.discourse-cdn.com/v4/letter/y/5f8ce5/32.png) [@yegolebi](https://forum.quantasylum.com/u/yegolebi)\ **Post date:** [April 15, 2024, 8:06pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/13 "2024-04-15T20:06:06Z")
look also here: [Balanced cable for SE measurements - QuantAsylum Forum](https://forum.quantasylum.com/t/balanced-cable-for-se-measurements/1348) > [@ScottRichardson](#): > > I would like to make my own cables to connect the QA403 to unbalanced inputs/outputs For QA403 output → DUT input you need standart RCA cable + BNC to RCA adapter. Just leave the ‘-’ output open. ---
**Author:** ![ScottRichardson](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/scottrichardson/32/1423_2.png) [@ScottRichardson](https://forum.quantasylum.com/u/ScottRichardson)\ **Post date:** [April 15, 2024, 10:55pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/14 "2024-04-15T22:55:48Z")
I sent a message to the cable seller on ebay about making a version with an RCA plug on the end instead of the 1/4" plug. ---
**Author:** ![ScottRichardson](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/scottrichardson/32/1423_2.png) [@ScottRichardson](https://forum.quantasylum.com/u/ScottRichardson)\ **Post date:** [April 16, 2024, 4:54am UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/15 "2024-04-16T04:54:02Z")
He already offers an RCA version: [1Pair RCA Phono to 2x BNC Male Cable 1~16FT For​ Quant Asylum QA40x audio tester | eBay](https://www.ebay.com/itm/285665693325) ---
**Author:** ![ScottRichardson](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/scottrichardson/32/1423_2.png) [@ScottRichardson](https://forum.quantasylum.com/u/ScottRichardson)\ **Post date:** [April 16, 2024, 12:59pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/16 "2024-04-16T12:59:50Z")
Here’s a question that I haven’t found addressed: Is the wire gauge important in connecting the dummy load to the QA403? I have some fairly thin BNC/coax cables that I can use unless something beefy is needed. ---
**Author:** ![Claudio](https://avatars.discourse-cdn.com/v4/letter/c/7cd45c/32.png) [@Claudio](https://forum.quantasylum.com/u/Claudio)\ **Post date:** [April 16, 2024, 2:28pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/17 "2024-04-16T14:28:43Z")
Hi @ScottRichardson. I connect my dummy load to the QA403 with BNC terminated RG316 cables. They have never given me any problems. I don’t know if that’s what you wanted to know. ---
**Author:** ![VAR](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/var/32/959_2.png) [@VAR](https://forum.quantasylum.com/u/VAR)\ **Post date:** [April 16, 2024, 2:37pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/18 "2024-04-16T14:37:31Z")
I ended up making my own BNC cables using 12gauge wire into the BNC adapter (center terminal connected ownly, not the ground) that connect from my dummy load. It seems to work better for me, though I am not sure it makes a ton of difference… Kinda a pain to make them. ---
**Author:** ![handsome](https://avatars.discourse-cdn.com/v4/letter/h/53a042/32.png) [@handsome](https://forum.quantasylum.com/u/handsome)\ **Post date:** [April 16, 2024, 3:48pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/19 "2024-04-16T15:48:44Z")
Cable from amplifier to dummy load (low impedance) carries all the currents, cable to QA device (high impedance) has minimal current ---
**Author:** ![ScottRichardson](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/scottrichardson/32/1423_2.png) [@ScottRichardson](https://forum.quantasylum.com/u/ScottRichardson)\ **Post date:** [April 16, 2024, 4:19pm UTC](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351/20 "2024-04-16T16:19:03Z")
I have some Canare LV61S (75-ohm shielded video cable) with BNC connectors. Do you think that will be okay? [Next page](https://forum.quantasylum.com/t/building-my-own-balanced-to-unbalanced-cables/1351.md?page=2)