I'm working on multiple builds, amp, pre, etc., and I am trying to make the circuits as compact as possible. One problem I'm running into is once the device is sufficiently small the connectors tend to dominate the footprint; this makes large RCA, XLR and Speakon headers appear very clunky. SMA connectors and cables (even better MMCX) are very attractive just based on the much more appropriate size scale. So, is there some tradeoff in using compact RF connections for audio interconnects?
is this internal or external to the amplifiers? Internally mcx or even MMCX (if you are delicate) works well. Externally I personally prefer SMA as they are more beatings proof.
Of course you can get stereo down a 5 pin DIN and those IMO are a very suitable connector for audio.
Of course you can get stereo down a 5 pin DIN and those IMO are a very suitable connector for audio.
Good to know, and thank you for pointing out a few of the subtleties. I'm speaking externally so I'll keep the frailty issue in mind. I just wanted to make sure there wasn't some 'gotcha' to do with audio frequencies or some other weird reason. They will likely be less than six inch cables going from preamp to amp, so they should be mostly out of harm's way...in theory.
BTW, I checked out the DIN connectors but they don't have the small footprint that I'm looking for. LEMO has the nice middle ground for size and I almost went that route. But the realization I could spend a tenth of the money and shrink the footprint by half again with SMA is a powerful one lol-
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The only gotcha if you are buying premade cables is that you need to check the specs as a lot of RF cables have a steel core. Doesn't bother me, but for those with audiophilia nervosa...
If you are making your own they do need some practice. When younger I messed with SMAs on semirigid cables. Terminating semi-rigid seemed so easy when the space qual techs were doing it. Turns out I am too ham fisted to cut everything correctly and the H&S official terminating kit is expensive.
If you are making your own they do need some practice. When younger I messed with SMAs on semirigid cables. Terminating semi-rigid seemed so easy when the space qual techs were doing it. Turns out I am too ham fisted to cut everything correctly and the H&S official terminating kit is expensive.
I'll probably go the premade route. At the lengths I'm working with they are pretty affordable and I can upgrade to the good stuff, if necessary, for not too much money.
I use the REAN mini xlr range from Neutrik for all my interconnections now. The are small, cheap, well made and come in 3,4, 5 pin connectors and sockets. I havent seen
any premade ones. They can be a bit fiddly to wire up though.
any premade ones. They can be a bit fiddly to wire up though.
@Zeta4, Those are nice! I will definitely be taking a closer look. I see the chassis mount requires a fair amount of depth but the overall footprint looks really good.
@billshurv, I'm finding that copper centers are a little tricky to come by; 140$ is the cheapest cable I have found so far. OTOH there seem to be several flavors of the steel with differing levels of fancy coatings like copper clad silver coated for about 20 bucks. But at low frequency that maybe doesn't mean a whole lot.
@billshurv, I'm finding that copper centers are a little tricky to come by; 140$ is the cheapest cable I have found so far. OTOH there seem to be several flavors of the steel with differing levels of fancy coatings like copper clad silver coated for about 20 bucks. But at low frequency that maybe doesn't mean a whole lot.
@Zeta4 did you mean 'tiny xlr'? I too am a fan of those.
Yes finding copper conductors is hard. Due to skin effect at the sort of frequencies these were designed for you it's not a problem. Realistically I don't personally think it's a problem for audio either but someone will claim they can hear the IMD. Oh and forgot to say with SMA you do need to leave space to screw them on and get a spanner in which does limit how close you can put them.
I won't tempt you with Fischer or Lemo...
Yes finding copper conductors is hard. Due to skin effect at the sort of frequencies these were designed for you it's not a problem. Realistically I don't personally think it's a problem for audio either but someone will claim they can hear the IMD. Oh and forgot to say with SMA you do need to leave space to screw them on and get a spanner in which does limit how close you can put them.
I won't tempt you with Fischer or Lemo...
Will be interesting to play around with and see if I can hear any difference with steel. Oh, and trust me, I've had my eye on LEMOs for a while now 😉
Hi,
You might want to take a look at ODU connectors, the bavarian equivalent of Fisher and Lemo ... at least of same quality but considerably lower cost ;-)
Regarding MCX and smaller connections ... Iirc the specced number of mating cycles for these connectors could be rather low.
jauu
Calvin
You might want to take a look at ODU connectors, the bavarian equivalent of Fisher and Lemo ... at least of same quality but considerably lower cost ;-)
Regarding MCX and smaller connections ... Iirc the specced number of mating cycles for these connectors could be rather low.
jauu
Calvin
Very nice! It's a battle between the REANs and ODU 🙂 Good point about limited connections on the super tiny connectors; that's the second strike against them. It's looking like REAN or ODU for the luxury option and standard SMA for the smallest and most affordable option. Great suggestions everyone!
Here's the ODUs and REANs for anyone curious:
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"RCA" is a compact CHEAP for-RF connector. OK, it started as the phonograph input on a radio, but it came to fame(?) as the 45MHz(?) IF output of TV tuners.
Historically BNC SMA and friends were expensive. Like "RCA" once they were everywhere the price fell.
One pitfall: your friend comes over with his new groovy Lissa ESX-47 line-amp to try in your system. Ah, the plugs won't fit? Make-up a pile of adapters? Of course you may not have, or want, friends like that. Here, my dog won't let them in the door. (She's been growling and barking at a ZOOM meeting all afternoon.)
Personally, I use SMB connectors for most of my instruments/audio gear: basically because they are compact, have a snap-in mechanism and are available in all sorts of shapes/finishes.
They aren't hugely expensive either, even the top-end ones. Many types of pre-made cords and cables are available at a reasonable price. One drawback is that they are RF-oriented, and the cable is often made from steel plated with silver.
This could (in theory) be problematic, since steel is magnetic, but in practice the most noticeable issue is the resistivity: for significant lengths, the center conductor has a non-negligible resistance
They aren't hugely expensive either, even the top-end ones. Many types of pre-made cords and cables are available at a reasonable price. One drawback is that they are RF-oriented, and the cable is often made from steel plated with silver.
This could (in theory) be problematic, since steel is magnetic, but in practice the most noticeable issue is the resistivity: for significant lengths, the center conductor has a non-negligible resistance
Not sure how I missed those, that is way more convenient than threaded. It was mentioned that the similar but smaller MCX have a poor cycle life and are delicate but I see the SMBs (at 2x the size) are rated for 500 cycles, which is plenty. Regarding the steel cores, billshurv also brought this to my attention and I noticed quite the sticker shock when I did find the copper variety. I can see why making custom cables has it's benefits as I assume there are deals to be had on Ebay for the occasional copper-core cable.
@PRR as far as the pitfalls, unfortunately I don't have friends that lug around their latest score 🙂 In all seriousness, the amp project started out being small and it has shrunk considerably since posting this thread a day or so back. Now even the REAN and ODU are just too bulky compared to the chassis. Current footprint is 2"x2"
I'm out of my my lane here, but how about rj45? that would give you 4 twisted pairs. and it's available in many different formulations, just look at belden website. Even smaller would be old telephone types rj11/12,but I don't think thise are twisted pairs.
and if I remember hdmi cables are actually a combination of twisted pairs and Coaxial in a very tidy package.
and if I remember hdmi cables are actually a combination of twisted pairs and Coaxial in a very tidy package.
That's a pretty interesting idea and I happen to have all the gear to do that thanks to a college lab course I took. It would probably work pretty well and the ability to fit multiple pairs would shrink the required space a good amount. The detractor is they don't have that metal "experience" going on. Regarding HDMI, I also have a few of those but they look pretty nasty to work with, plus the big size.
I have enough info about SMA/B and which coax to look for that I decided to go that route for single connections. If I want to do multi conductors in a single plug it will be LEMO/ODU/REAN just depending on what deal I can score on ebay. ATM I'm looking for deals on the crimp tool for 26AWG copper core to SMB. Having watched a few tutorials, custom builds are actual much easier than I anticipated. Looking forward to trying this strategy out-
🍻 Cheers for chiming in, everyone! 🍻