28 - Mic Preamp with Audio Compression (PLEASE SEE VIDEO DESCRIPTION)

Nick M0NTV discusses and demonstrates a homebrew microphone preamplifier with compression for extra audio punch!
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IMPORTANT NOTICE
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Since the release of this video I have learnt more about these SSM2167 boards and I regret that some of the information presented here is not correct. So in November 2023 I rebuilt and tested this design afresh and created a new video which shares these results. The new version works much better!
PLEASE WATCH THE NEW UPDATED VIDEO HERE: • 46 - Mic Amp & Compressor
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John VK2ETA has done some excellent work on using the SSM2167 breakout board with the uBitx:
ubitx.net/2018/09/02/ssm2167-...
The Analogue Devices SSM2167 Datasheet can be found here:
www.analog.com/media/en/techn...

[@acestudioscouk-Ace-G0ACE]

Another really useful video, thanks Nick. Microphones is a subject that often gets missed, so this introduction to the SSM2167 breakout board was good to see.

[@M0NTVHomebrewing]

Thanks very much for watching. Glad it was of some interest!

[@BobMellor1954]

A very useful, yet relatively straightforward build Nick, I will certainly look into this chip; thank you for sharing

[@M0NTVHomebrewing]

Thanks very much Bob. Glad it was of interest. 73 Nick

[@istingingjellysquid]

Hi, I purchased .My board doesn't have 6 holes like yours .( max4466/ssm2167 ) Connected to baofeng external hand held mic.Works as intended could not be happier. The reason for comment is all I did was disconnect electrect mic wires on hand held mic and hook up to preamp board.The output on preamp board connected to were electrect mic originally was connected to in handheld.Added the 3volts separately. This gave me over modulation, all I did was hook a 10k pot to output of preamp board. Easy / Simple just the 3 volts and 10k pot

[@M0NTVHomebrewing]

Hi there! Pleased it worked for you. Did you test it was actually giving you the right compression level and not just acting as a limiter? Please check out my video number 46 which is a major update to No. 28. It sounds like it is a different board entirely so hopefully they soldered in the resistors into the right places on yours! 73, Nick

[@istingingjellysquid]

Hi Nick, the only testing i did was on ham radio asking my contacts if i sound better with or without external mic.Every contact said I sounded much better with board. The board I used was a updated one preamp / compression

[@istingingjellysquid]

Sorry , dont know if it's an updated one , but mine is a combination of max4466 and the one you have ssm2167

[@petemillis4666]

Great video Nick. I bought 10 of the SSM2167 chips years ago with the intention of building a preamp/compressor for my FT817, and passing the spares along. Then realised after adjusting USB and LSB carrier insertion points and mic gain to suit my voice that I really didn't need any preamp and compression. So I never got any further. I then went nearly 100% CW. I think may I was just putting off trying to solder the little SMD chip and wouldn have got further had the breakout board been available. I've still got those 10 chips in my components box somewhere! 73 de M3KXZ

[@M0NTVHomebrewing]

Thanks Pete. Yeah, I know what you mean. I've got packets of components lying around for projects that one day I might get around to building! Some I forget what they are and why I bought them!!! 73 Nick

[@TheTemporalAnomaly]

Great video! I bought two of those units and when tested they just performed like limiter amplifiers. I was short on patience and just thought they were Chineasium fakes and didn`t investigate further. I will pull them out of the piling system and have another go. Just a point about noise, (in any pre amp circuit using electrets), I filter the phantom power to the mic - +v supply through 1k res, 1000uf to gnd, then 4.7k to the mic. This helps a lot getting rid of noise on the supply getting into the mic line. Many thanks, Chris & the lads of 1977khz

[@M0NTVHomebrewing]

Cheers Chris.

[@itrema]

hello and thanks for the video. i bought the same board, remove resistors and soldered trimpots to test, board as labelled 17:07 R1 stands for noise gate & R2 stands for compression. Maybe mine or yours was inverted.

[@M0NTVHomebrewing]

Have you watched the updated video yet? All of my boards so far have come with the resistors swapped over i.e. soldered in the wrong place. The advantage with trimpots is that you can play with the gate and thresholds. 73, Nick

[@tdumnxy]

Another useful & interesting video, thank you. Please don't apologise for your hand-drawn circuit diagram/schematic. It was really well done I thought and it reminded me of those old Radio Shack Learn Electronics books done in the same style. Very good, very clear and self explanatory. Great stuff. 73 2E0FXZ

[@M0NTVHomebrewing]

Thanks very much Stephen - that’s very kind of you. Glad it was of some interest 👍

[@Steve-GM0HUU]

Think I have an SSM2165 IC which was a predecessor to the SSM2167. It's on my list of projects to make an inline compressor for my FT-817 or homebrew rigs.

[@M0NTVHomebrewing]

That should work pretty well I should think Steve. I got the idea from the guys that were retro-fitting them to their BitX rigs. I have to say that it definitely helps with making the audio a bit punchier - especially when you're not running much power. A little can go a long way! 73

[@_MisterG]

Newbie here: If I were to use the preamp condenser with a fist mic would I still need the dc bias via the 4.7k resistor? Or would I just leave it out altogether? Thank you

[@M0NTVHomebrewing]

Hi! Thanks for watching. It depends upon your fist mic. If it is a condenser mic with an electret capsule then it will need bias. Only if its a dynamic mic would you need no bias. I would imagine most fist mics will be condensers and hence require some power. 73 Nick

[@SeAfasia]

nice and clever useful schematic...73

[@M0NTVHomebrewing]

Thanks very much.

[@barrygeary1890]

Thats like BBC radio 4 they use compressior it give you radio sound and well done for building it ❤

[@M0NTVHomebrewing]

Thanks. Stay tuned for another updated video coming soon about this same module! I've now got it working correctly! 73, Nick

[@bearweethus8066]

Can we make a fethead or dynamic mic booster DIY? I have been searching for that video but could not find so far.

[@M0NTVHomebrewing]

Someone has probably made one! Perhaps try some of the (non ham-related) audio channels out there? 73 Nick

[@Alan-bn6ii]

i i have a cobra power mic but the dam thing wont work on my anytone at-5555n

[@pitranaa1954]

I'm confused with the r comp and r gate value,on the data sheet it shows r comp are 15K(2:1) and r gate 1K(-48dBV)...but on the chinese board it was different? The board shows r comp(R1) 1K and r gate(R2)15K?

[@M0NTVHomebrewing]

Thanks for asking that question. Someone else contacted me to say they had done some investigating and found that on the Chinese board R1 and R2 are the wrong way around i.e. R1 is actually connected to pin 7 (gate) and R2 to pin 8 (compression). He desoldered the resistors and swapped them over. This would mean that the board acts as a kind of limiter but not a compressor. I'd not heard this before but I've just checked on a spare board I have and it seems he is right! So I think I'll have a go at removing R1 and R2 and doing some testing with the values swapped over. There are some spare holes on the pcb for each resistor so I can probably use through hole resistors or maybe even trimpots. It's interesting stuff this! Thanks again. 73 Nick

[@pitranaa1954]

@@M0NTVHomebrewing I've swap the bias resistor and now its work! The compression is great but the noise gate release time feels a little bit long so if i get to close to my monitor speaker it always gives a feedback,maybe i'll try to replace it with a variable resistor and give it a try. Thanks nick 73,regards from Indonesia

[@garycook5125]

Video suggestion: Build a box that allows a 150 Ohm dynamic microphone (EV RE20), to replace stock 600 Ohm microphone for two-way radio, using a Hammond 148A 150-600 Ohm transformer.

[@M0NTVHomebrewing]

Thanks Gary - I'll bear it in mind. Microphones are an interesting subject in themselves. My current favourite is a cheap podcasting mic that performs really well. It does need some external PTT switching but it is not difficult to do. Incidentally I'm going to revisit this video very soon with some updated information for better results. Thanks for watching. 73, Nick

[@mahlonkarpaiya252]

good day. Th 6 holes on the red board near the end ,do you know what they are for. Is it to put pots to control the compression?

[@M0NTVHomebrewing]

Hi! They are connected to R1 and R2. So you can desolder those resistors and connect through-hole replacements. I've actually done it - so you can play around with the different gate and compression values. I will probably do another video on this at some point. On my board (perhaps all of them?) it seems that they have mixed up the surface mount resistors and R1 is where R2 should be and vice versa. This clearly affects the performance of the module. It is worth playing with! Thanks Mahlon.

[@mahlonkarpaiya252]

@@M0NTVHomebrewing Thaanks Alot for the help and the fast reply. I have added a 200k and 5 k pot to the extra holes and i have removed the resistors r1 and r2. Now it works somewhat. If i hold the mic close to my mouth it worrks but if im a few 3cm away from the mic it does not pic up my voice. Im just learning and i think my mistake is this is for a cb type radio and not my Dynamic PA mic. I was trying to make a compessor for small pa system.

[@M0NTVHomebrewing]

Hi Mahlon, yes it sounds like a mic mismatch. If your mic is a condenser type (e.g. uses an electret insert) then it will need bias. If you wire the module up the way I show in the video then it will certainly get some bias. If you are using a dynamic mic then you won't need any bias. I use a cheap podcasting condenser mic but it works very well with the module I built. All the best. 73 Nick

[@mahlonkarpaiya252]

@@M0NTVHomebrewing You have been a great help. I have the compressor working on a Dynamic mic. im using a 200k on the comp and a 50k on the other one. All i find is that i need a less senitive pot instead of the 200k. If i turn it any more than say 1/8 of the way its way too loud. Not sure if i should go to 100k or to say 500k. Thanks alot for your help and assistance

[@grupomontanadezacan6062]

Buenos días, me interesaría saber si el módulo pudiera funcionar con un micrófono de diadema??

[@M0NTVHomebrewing]

¡Hola! El esquema es para una cápsula de electreto que requiere cierta polarización de CC. Por lo tanto, depende del diseño particular del micrófono de sus auriculares. Necesitarías ver un esquema de tus auriculares y luego continuar desde allí. La mejor de las suertes para ti. Muchas gracias. 73, Nick

[@grupomontanadezacan6062]

@@M0NTVHomebrewing ok, Muchas gracias por su respuesta, saludos desde michoacan

[@M0NTVHomebrewing]

No hay problema! Mis mejores deseos, Nick

[@HamRadioPogaduchyPA1RAF]

Do I need change something if I would like use the pre amp with a original mh31 yaesu dynamic microphone 🎤?

[@M0NTVHomebrewing]

Hi there! Thanks for watching. There are 2 things here: (1) You need to watch video 46 which is a remake of 28 and includes some vital changes to this circuit to get it to work right. (2) The circuit is designed for a condenser mic that requires a DC bias - specifically an electret capsule. I've never tried to adapt it for a dynamic mic but I imagine it can be done. You'd have to strip out the biasing on the audio signal input. I can't really advise you further on this as I've never tried it. Others may have though. Hope this helps. 73, Nick

[@rudinei_do_conto]

Olá. Essa placa tem qualidade para usar de forma profissional? Qual a porcentagem que ela atua amplificando sons baixos, e comprimindo sons altos? obrigado.

[@M0NTVHomebrewing]

Olá! Supõe-se que comprima o áudio em uma proporção específica, dependendo de um dos resistores da placa. No entanto, vou fazer outro vídeo sobre isso porque já tive várias dessas placas com os resistores soldados nos lugares errados, ou seja, R1 onde deveria estar R2 etc. Eu não poderia dizer se é bom o suficiente para uso profissional. Obrigado. 73 Nick

[@rudinei_do_conto]

​@@M0NTVHomebrewingok, tank you. I Like video, and subscribe in your channel.