Hi,

I am looking to get a limiter/compressor hooked up to my audio source before the audio
goes into my transmitter, as currently now and again some of the output audio distorts from
it being too loud. At the moment I am having to dial back the volume on the transmitter
to help it from distorting too much, but this then affects the overall loudness of the broadcast.

I currently have stereo audio leaving my audio source via a 3.5mm stereo plug and at the other
end entering my transmitter via left (white) and right (red) audio plugs.

Does anyone know where I can find a Limiter/Compressor that would work with the set-up above?
If I had the soldering skills I would attempt to make one myself but as my soldering skills are
very limited I would rather buy one pre made.

Cheers

Yes its definitely good to have a limiter as you don't wont to overmodulate the carrier. I have been building a few this week on the breadboard.

You can get the pira limiter (ready built) on ebay from the turkish guy...

http://www.ebay.co.uk/itm/pira-compress ... SwoudW4zkZ

Believe it is the mono version so you would need two for stereo. Not sure how good it is, I am about to build it on breadboard when I get more free time.

They work well, i built a couple of the pira limiters to use in stereo mode, they take a bit of setting up adjusting the trimmers until you think you've got it sounding right.

Hi both, thanks for the info and link.

Just went there and he has sold out of them, so will have to keep a lookout
and see if he makes up some more.

Btw.
How would I connect the Audio plugs to the board, would I need to buy sockets
and solder them on? Also would I need to power the board if so what with?

I am not sure what the connectors are on the board as it a bit difficult to see
for the Audio Input, Audio Output and Power.

Those connectors used on that Limiter are just 2.54mm header pins, and he has a tendency to use them on everything he sells including a 15W Amplifier and PLL driver board that I bought off him a while ago.

As I was dealing with RF, I desoldered the header pins on my Amp and Driver and replaced them with proper connectors designed for RF (BNC and SO239). At AF (Audio) those 2.54mm headers are fine, but apart from "header sockets" the only way to connect audio to them would be to directly solder to them, unless I'm mistaken.

The Turkish limiter boards use 9 - 16 VDC at a low current, so I'd use 12V as you'll no doubt have various things running at that Voltage.

By the way - with Polestar, the Turkish guy, I found it best to put him under "followed searches" on eBay on my phone and that way I got an instant notification as soon as something is listed.

It's been discussed before; he sells things so cheap that they tend to sell quickly as buyers think they're worth a punt and no loss even if it's not upto much.

Those limiter boards seem pretty good though as others have said.

Hi MiXiN,

Thanks for the info. I will do as you say and put him under "followed searches",
so will wait until they are listed again and buy a couple.

Cheers

If Turkish guy as copied the pira limiter part for part with the same pcb layout it should work perfectly, theres another seller on ebay from Greece selling the same pira limiter but with what looks to be an homemade board for around 22 quid.

This is the greek one

http://www.ebay.co.uk/itm/COMPRESSOR-LI ... pCbolzGYGA

Probably better to wait for the guy in Turkey to relist, then get two for what you would pay for one plus postage from Greece.

You can get header pins from here:

http://www.ebay.co.uk/itm/10-x-2PIN-2-5 ... Sw6aVUpAbZ

There is a good video on how to use them.

https://www.youtube.com/watch?v=c-pTsccCizA

By the way I use them all the time but don't even have a crimping tool, usually I fold the metal over onto the cable with long nose pliers and then solder a little bit. Seems to work ok

Shorty;
Thanks for heads up. I will probably wait for the Turkish guy to list again though.

s2000:
Thanks for the video post. I will have a go when I get the limiters and see how it
turns out.

Hello Mr Wave
Pira also do a very simple limiter which works great and could easily be built on prototype board
Compression ratio, attack and release are preset but can be modified for personal preference!
Ive built many of them!
I would recommend shielded coax style for audio connections and as short as possible!

Halfwave,

Per chance you're unaware, the Turkish guy has just listed more Pira limiters.

Hi sinus trouble, thanks for the info.

MiXiN:
Thanks for the heads up on the re listing. My phone battery is about to die so I will have to have a look later and hope they are still there.

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I suppose it depends if your are a hardware or software type of guy, but why not a multi-band software audio processor/limiter? Someone will probably contradict me, but I think most people would agree a multi-band audio processor always sounds better than single band or simple limiters. If you have some spare old PC hardware then for free you could use Sonos 4 - what's more it would do the stereo encoding too (if the soundcard can run 192kHz - my old Celeron Dell laptop does it perfectly). Apparently there are Linux equivalents too for free. Or if you have money to spend you could buy Stereo Tool (which also has a free version and does RDS as well) or Breakaway Broadcast, and if you set it up right be louder or as loud and nicer sounding that many commercial stations.....

I'm an analogue sort of guy - for me digits and audio don't mix too well (most CDs sound really horrible these days because they're all deliberately clipped). You're right - frequency selective compression can sound better than single band, but usually doesn't because of the clueless morons setting them up! Even my most loathed of all processors - the Orban Optimod - can sound pretty good if sensibly set up.

Given the choice, I prefer "lookahead" processing - introducing a small delay (around 1ms) into the audio path to eliminate the overshoot, pumping and low frequency distortion inherent with basic limiters. My most recent design includes 1ms delay (using a charge-coupled BBD device per channel) and split-band processing. Properly set up, it sounds superb, with none of the artefacts associated with basic audio limiting.

The delay is the same as being (roughly) 1ft from the speaker, so it's insignificant. The only expensive parts are the BBDs which are no longer made by Panasonic, but are still available if you shop around. For the gain controls I use dual operational transconductance amplifiers (LM13700) to change the negative feedback around op-amps - using the OTA to pass audio is a way to add noise and distortion. However, if the OTA is in the negative feedback loop of an op-amp, the more gain the OTA has, the more the level through the op-amp is reduced. The noise floor and the distortion specification are mostly governed by the BBDs, but these are being clocked so fast, that their noise is very low, and their bandwidth is much more than we need for stereo FM.

The filtering - for the split-band function - is quite critical. I use -18dB/oct Sallen and Key filters dimensioned to overlap at 240Hz. This means that the bass end can have a different time constant to the high end, and it's possible to include a "de-essing" function with little extra hardware.

Most crucially of all - I do not need to use a clipper! There is one at the output of the board to prevent really gross overloads getting through, but the distortion will be so nasty that even the most deaf DJ will back off the levels!

Sounds interesting Mr H - I'd like to hear one. We'll have to agree to disagree on Optimods. Especially the old analogue 8100's! But at least we can all agree that Kiss, Crapital etc don't have the good sense to use processors properly!

For any of you guys thinking of getting anything from Polestar be aware that after the 6th of June he won't be able to accept paypal. It may be worth getting your orders in ASAP. http://en.webrazzi.com/2016/05/30/paypa ... in-turkey/

He won't be able to use eBay, then.

DBX or Behringer are okish and at reasonable prices. If not, get a PC and run software processors, if you're not too bothered about latency.


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