TRANTEC S4.04-B-EB-GD5 Belt Pack System

[Bazz339]

Does anyone have experience of using these? 

I purchased one  (without a mic) for installation in a church to replace a faulty TOA system, I have used many of the basic Trantec systems over the years starting with the S2000, S3600 and S4.04 from a couple of years ago and they have always performed well for the price for speech apart from an earlier variant of the S4.04 (I think) also sold as a Sennheiser Freeport which put a click onto the system when powered up with the mic channel open (As happens with small non operated 100V line speech systems) 

This unit seems to be a dog, I tried it first in my workshop and experienced a type of feedback like I had never heard before, I had never used the type of capsule that I was using with it before and tried others but the system still seemed unstable despite adjusting input gain, ouput gain, volume of loudpeaker etc.  My workshop is small, I took it to my local church and tried it there and then took it to site a few miles away. Whilst things were better in the intended church I still felt it was not stable and decided I could not leave it with them. It felt like there was an issue with some automatic gain, or compander circuitry. 

Has anyone else experienced this with these units? The ones I bought most recently (A couple of years ago) prior to this were fine, Is this is a revised version does anyone know? 

As there seems to be supply problems with the Trantec units a JTS system E-6+E-6TB+CM-501 CH70 was suggested as a replacement.  Has anyone used these?

Main requirements are reliability, reliability of reception, speech clarity and absence of click when switched on and off  with channel open, 50 M line of site range (Although in fact maximum distance TX to RX is cc 15m). 

Edited May 19, 2023 by Bazz339

[richardash1981]

As far as I know the Sennheiser Freeport was the S4.4 (no zero), with different channel frequencies. Ran on 9V batteries.

The S4.04 is the "successor" to the S4.4 and runs on a AA battery.

The S4.4 and S4.04 seem to use the same channel frequencies - I've certainly encountered others mixing the ranges - but that doesn't mean the companders match properly. Or you might have a dud compander at one end of the link, which would make a complete mess of the gain structure.

[Bazz339]

I am not trying to use tx's and RX's from different sets. This is newly purchased set that seems to be functioning other than I would expect. 

[sunray]

2 hours ago, richardash1981 said:

As far as I know the Sennheiser Freeport was the S4.4 (no zero), with different channel frequencies. Ran on 9V batteries.

The S4.04 is the "successor" to the S4.4 and runs on a AA battery.

The S4.4 and S4.04 seem to use the same channel frequencies - I've certainly encountered others mixing the ranges - but that doesn't mean the companders match properly. Or you might have a dud compander at one end of the link, which would make a complete mess of the gain structure.

It gets very confusing, I have done some work for a guy who had a number of Freeport systems in CH70 (yes correct they are similar to S4.4 but not the same) and not all had the same 4 frequencies (IIRC some had one or two frequencies compatible with S4.4) but they were close enough to work when the TX was adjacent to the RX up to maybe 3metres. He had used coloured stickers on them to identify but not told me.

I've successfully mixed 4.4 and 4.04 systems and not noticed any discrepancies. 

Someone else reckons some of the handheld 4.04's were released using 9V batteries, I've not come across that myself.

Edited May 19, 2023 by sunray
I will say I've never considered the 4.04 to be the same quality as the 4.4 in just about every respect, to the point I preferred to purchase second hand from Ebay.

[paulears]

If you open the box at home, connect the receiver to an amp of some kind and speak into the mic with the transmitter close to the receiver - do you get crystal clear audio that is stable and trouble free?

 

If you don't, it's faulty. It's possible the programming is wrong - maybe the supplier has put two different versions together (maybe one that has been reprogrammed for some reason). If you can get access to something like a radio scanner, other receiver or even an SDR into a computer you can determine if the problem is with the receiver, or the transmitter. If close to each other there is a problem, then distance and location changes won't make it better.

[Bazz339]

4 hours ago, paulears said:

If you open the box at home, connect the receiver to an amp of some kind and speak into the mic with the transmitter close to the receiver - do you get crystal clear audio that is stable and trouble free

I tested it before I took it to site and was a little concerned, however, site was only a couple of miles away and I decided to try it in situ.

I am used to testing radio mics in my (SmalI) workshop and accept that gain before feedback is low because of the proximity of mic to loudspeaker but the feedback experienced on this occasion was different to normal. 

I have arranged a return. I will do a bit more testing to make sure I am not missing anything. but at present don't have confidence in the unit. 

Edited May 21, 2023 by Bazz339

[paulears]

I've had Sennheiser and Trantec kit now for over 20 years and have no problems with their products, and they've been reliable and solid. When you say you were concerned? I assume you meant it did not give decent audio in the workshop? I wasn't talking about gain before feedback, just audio quality, end to end. If it is an audio feedback issue that's something different. Audio feedback could be the normal type, or some kind of fault that has a big peak in the response curve triggering audio feedback, or even something microphonic? The test is to stick earphones in, stuff audio through and see what it sounds like - if it sounds clean and natural, it's probably not the unit - if it sounds strange tonally, then that sounds like a real fault, or perhaps even a dodgy mic?

[richardash1981]

Not directly relevant, but in the same space.
I had two lapel mics in use today (on someone else's system), the actual mics were identical looking Trantec LP2s. The receivers were identical S4.4 receivers. The beltpacks were one original S4.4, and one newer S4.04 beltpack. As the packs moved around over the day, I ended up with both packs on the same speaker at different times.

I had hugely more issues with feedback from the S4.04 beltpack. The sound from this had a much less even frequency response, seemed to have a pronounced peak around 2kHz, and maybe some net compression - the gain seemed to go up in silences.

I didn't have a chance to play with swapping microphones etc., and I don't know the history of why one of the beltpacks was replaced, but it felt odd, and reminded me of this thread.

[sunray]

14 hours ago, richardash1981 said:

Not directly relevant, but in the same space.
I had two lapel mics in use today (on someone else's system), the actual mics were identical looking Trantec LP2s. The receivers were identical S4.4 receivers. The beltpacks were one original S4.4, and one newer S4.04 beltpack. As the packs moved around over the day, I ended up with both packs on the same speaker at different times.

I had hugely more issues with feedback from the S4.04 beltpack. The sound from this had a much less even frequency response, seemed to have a pronounced peak around 2kHz, and maybe some net compression - the gain seemed to go up in silences.

I didn't have a chance to play with swapping microphones etc., and I don't know the history of why one of the beltpacks was replaced, but it felt odd, and reminded me of this thread.

Yes I'll agree the AGC on some of the cheap end mics is a little hairy and I've often wondered if the S4.04 system falls into the rebadged black box environment. I have a VHF system here somewhere, I think unbadged, which if left in a quiet room the AGC will open to the point it's quite hissy then start feeding back in a series of gentle, slow "sssooo sssooo sssooo sssooowoomf" sounds then go silent and start again. In normal use the attack is a bit slow for gentle rises then very quick (the woomf sound) but for sudden loud parts the attack is far too quick. Delay is slow, for example a loud drum beat of 150 BPM will be more like a click at 50 BPM.

One thing to be aware of is the frequencies allocated to S4.04 is different to S4.4. Off the top of my head I think one is 25KHz away and it often works over short distances. Quite often I've done the ol' "1, 2, 1, 2." at the mixer then handed the mic to the speaker and as soon as it's 10 feet away it sounds carp or stops working. However not all S4.04's contain the same frequencies.

[richardash1981]

Thanks for the information on frequencies - the receivers were on Channels 1 and 3 (and I had brought some more S4.4 along, so had Channel 2 switched on but muted as well). No idea what the beltpack was doing as it doesn't have a display! Range the length of a 100 seat church was OK (it didn't seem any difference up close).

Thinking again about AGC, it there are of course trimmers on the beltpacks and on the receivers, and neither is calibrated, so I couldn't see what was set. I seem to remember doing some testing on other beltpacks years ago and finding that those beltpacks would compress (more than the receiver could expand) rather than clip when over-driven (too much gain set on the pack). Maybe the problem set here had ended up the same - beltpack gain high, compressing more than the receiver can expand, and then the receiver had been turned down to compensate?

I wonder if you can measure beltpack frequency deviation (and actual carrier centre frequency) with an SDR dongle?

[sandall]

1 hour ago, richardash1981 said:

wonder if you can measure beltpack frequency deviation (and actual carrier centre frequency) with an SDR dongle?

Don't see why not (though I've never tried to check deviation), at least to see whether 2 beltpacks on nomimally the same freq actually are. 

[DrV]

Have done that with a HackRF although not in any scientific way - just out of curiosity.

[Bazz339]

The later replies to this thread were interesting and in line with what I felt was possibly happening re AGC etc.