DrBunsen Posted February 21, 2008 Report Share Posted February 21, 2008 I'm looking for suggestions for a small, cheap and simple DIY compressor design. I'd like to build 8 into a shallow 1U rack, hence the small, simple and cheap. More if I can fit them.These would be used on individual analogue drum voices, pre-mix. Something dead simple as far as user controls go too - like one knob per channel ;D or none ...Line level synth type signals, not guitar, but range would be an advantage. Running from DC power would be nice.One thought I've had is to mod the Oatley valve pre kit with gain and volume. The board might look big but 2/3 of that is the power supply, which will run 2 pres. It's a little pricier than I was hoping, and they've taken the schematic and PCB artwork down from the site >:(Did I mention it should sound nice? Quote Link to comment Share on other sites More sharing options...
moxi Posted February 21, 2008 Report Share Posted February 21, 2008 hi,you can see here:http://www.thatcorp.com/aneng.htmlthis chips are used in a lot of pro-gear, as DBX.. Quote Link to comment Share on other sites More sharing options...
DrBunsen Posted February 22, 2008 Author Report Share Posted February 22, 2008 That's not a bad suggestion. The 4301 is available in DIP. Profusion have them for ~5 UKP in small quantities. And there are two unassigned op-amps on board (hello filter?) combines in a single IC,all the active circuitry needed to construct a wide range of dynamic processors. / exponentially-controlled VCA, a log-responding RMS-level sensor and three general purpose op-amps./The combination of exponential VCA gain control and logarithmic detector response (‘decibel-linear’ response) simplifies the control path mathematics of the dynamics processors. This makes it easy to design audio compressors, limiters, gates, expanders, de-essers, duckers, noise reduction systems and the like./ Quote Link to comment Share on other sites More sharing options...
dj3nk Posted February 22, 2008 Report Share Posted February 22, 2008 sounds intresting, cant wait for the MB-FX gear ;) Quote Link to comment Share on other sites More sharing options...
ptitjes Posted February 22, 2008 Report Share Posted February 22, 2008 And there are two unassigned op-amps on boardSorry, but the two op-amps in the chip are available to transform the log RMS-level sensor signal in a compression level signal to feed to the internal VCA... IIRC you need one op-amp to compare to your compression threshold and one to adjust it according to your compression level. Just look at the typical application in the datasheet.However this makes a simple compression to build. This chip is so great! This is also on my todo list :) I would like to make a digitally-controlled compression. So if you go the That way please share your experience!Best regards, Didier. Quote Link to comment Share on other sites More sharing options...
stryd_one Posted February 22, 2008 Report Share Posted February 22, 2008 Yeh, interesting indeed. If you wan a local partner in crime just shout bud.Something worth noting: (Bolded by me)1. More information on this compressor design, along with suggestions for converting it to soft-knee operation,is given in AN100, Basic Compressor Limiter Design. The designs in AN100 are based on THAT Corporation’s2150-Series VCAs and 2252 RMS Detector, but are readily adaptable to the 4301 with only minor modifications. Infact, the circuit presented here is functionally identical to the hard-knee circuit published in AN100.That's a must, IMO. Quote Link to comment Share on other sites More sharing options...
ptitjes Posted February 22, 2008 Report Share Posted February 22, 2008 Yeah I do agree :) But that is a pity there is no adjustable attack and release time in their typical design...Hehehe! I'm weak! :) Quote Link to comment Share on other sites More sharing options...
stryd_one Posted February 22, 2008 Report Share Posted February 22, 2008 mmm, even just a fast/slow switch would be nice.... Quote Link to comment Share on other sites More sharing options...
cimo Posted February 22, 2008 Report Share Posted February 22, 2008 .. what about the tonepad compressors?http://www.tonepad.com/they are designed for guitars but you can just adapt them easilysimone Quote Link to comment Share on other sites More sharing options...
DrBunsen Posted February 23, 2008 Author Report Share Posted February 23, 2008 stryd: you're on buddy.Let's say I wanted the ultra-ultra-cheapest comp possible: a light bulb and an LDR? optocoupler design?/edit/ The DOD 280 optical comp from tonepad fits the bill. And it's pretty darn small.Yeah I do agree :) But that is a pity there is no adjustable attack and release time in their typical designCheck out their "full featured compressor" PDFthey are designed for guitars but you can just adapt them easilyWhat's the difference, and what's involved in making the change? The word "impedance" springs to mind...Now I'm picturing a 1U case with in/out jacks on the back panel, soldered to an edge connector ... small FX boards plug in to the edge connectors. Another edge connector on the front end of the card connects to unlabelled pots on the front panel, with a scribble strip above them for labelling.I also founf some more compressor ICs at Smallbear Quote Link to comment Share on other sites More sharing options...
cimo Posted February 23, 2008 Report Share Posted February 23, 2008 What's the difference, and what's involved in making the change? The word "impedance" springs to mind...yep!I also founf some more compressor ICs at Smallbearsmallbear is the natural spouse for tonepad projectssimone Quote Link to comment Share on other sites More sharing options...
stryd_one Posted February 23, 2008 Report Share Posted February 23, 2008 yep!Hahaha very informative ;) Quote Link to comment Share on other sites More sharing options...
cimo Posted February 23, 2008 Report Share Posted February 23, 2008 Quote from: cimo on Today at 12:37QuoteWhat's the difference, and what's involved in making the change? The word "impedance" springs to mind...yep!Hahaha very informative Winkthat s the answer when you have a 85 cm human being around asking for winnie the pooh, hold on she ll tell ya..yu dvbhhhhhhhhggggggggggdsee? ;) Quote Link to comment Share on other sites More sharing options...
DrBunsen Posted February 28, 2008 Author Report Share Posted February 28, 2008 After discussions in chat (thanks bugfight and stryd_one) it looks like a combination of the DOD 280 and Ken Stone's Stomp Box adapter is a reasonable build Quote Link to comment Share on other sites More sharing options...
stryd_one Posted February 29, 2008 Report Share Posted February 29, 2008 Ken Stone's Stomp Box adapter YAY!! (Finally a straight answer :D )the DOD 280Yucky. What about the what comp? that looked much nicer. Quote Link to comment Share on other sites More sharing options...
Sasha Posted February 29, 2008 Report Share Posted February 29, 2008 I am interested in building Ken Stone Adapter myself but seams all the links from the page are broken. Are these PCBs artworks freely available as that DOD 280 compressor? Somebody tried DOD 280? Is there any other tonepad FX that some of you liked using with synths?EDIT: Are there any disadvantages using LED and LDR instead of optoelement? Quote Link to comment Share on other sites More sharing options...
Sasha Posted February 29, 2008 Report Share Posted February 29, 2008 As this Stomp Box Adapter PCB is pretty simple I redraw it in Corel and EPS file is attached in this post. I don`t know is it legal as I didn`t find PCB artwork published, but as the schematic is free I hope this could be too. Hope You`ll find it useful.adapter.zipadapter.zip Quote Link to comment Share on other sites More sharing options...
cimo Posted February 29, 2008 Report Share Posted February 29, 2008 hiIs there any other tonepad FX that some of you liked using with synths?nothing is crunchier than a http://www.tonepad.com/project.asp?id=23 tube preamp circuit with a quality tube stuffed in it.I plan to make a stereo one as soon as i ll get some free time! Quote Link to comment Share on other sites More sharing options...
DrBunsen Posted March 4, 2008 Author Report Share Posted March 4, 2008 Yucky. What about the what comp? that looked much nicer.Sure. But unless I can get this under $30 a channel, it's not worth the bother. I might as well pick up a few Borrowerhingers. I might stretch the budget a bit to go tubular Quote Link to comment Share on other sites More sharing options...
TheAncientOne Posted March 5, 2008 Report Share Posted March 5, 2008 Take a look PicoCompressor.I've just built the stereo for final mixes and live work - a really good piece of design, (though contains a few mad resistor values). Pro quality kit, boards have good part spacing, proper ground planes, and go together well. Quote Link to comment Share on other sites More sharing options...
stryd_one Posted March 5, 2008 Report Share Posted March 5, 2008 Wow! Thanks Mike... I came across the Pico when I was buying a LED-meter for my GSSL (they use the same board) and I even looked it up the other day when Bunsen first posted here... I should have scrolled down, cause I didn't realise how bloody cheap they are!DrBunsen, I know this is ever-so-slightly over the $30 /channel target, but these things are darn nice and totally worth the little extra - not to mention they're designed for balanced IO so no need for additional stompbox conversion stuff ;)(oh and the PCB's are really nicely done)See you in the chat (hint) Quote Link to comment Share on other sites More sharing options...
TheAncientOne Posted March 5, 2008 Report Share Posted March 5, 2008 @ strydWhen you're building your meter, take a look at their build instructions: there is a totally cool way of forming the LED leads so that they come out nicely aligned.I think we're doing a mutual stalk here: I'm doing a pair of MNats 1176 compressor boards, (finally get to use the pair of SEW cream faced VU meters I bought just after leaving school!). I've just finished the internals for a G9 preamp, (and I've got real 'long box' Mullard ECC82's from my collection of old parts). I've also, perhaps rather ambitiously, started doing a Neve 1084 channel clone, (I nearly cried at the bill for the Carnhill ironware). Last 'character' mic preamp for now will hopefully be a Jensen double servo, using MNats and PTownKids 990 kits, (that was a soldering test!). I take it you've already had a serious letch over the kits from JLM Audio. Quote Link to comment Share on other sites More sharing options...
DrBunsen Posted March 6, 2008 Author Report Share Posted March 6, 2008 ever-so-slightly over the $30 /channel targetMono Pico Compressor basic kit with circuit board and THAT ICs. with 10 segment meter: $39.95 USpower supply $13.95 USPrice does not include shippingThis is a bare PC board and does not include any components. Add all other board components, and shipping, convert from US pesos dollars to $AU. Multiply by number of drum channels.Then compare I'm not raggin on your suggestion (well maybe a little :-P). I'm also considering a box-otrix or two, or the PAiA tube pres. Also, a THAT based design on perfboard.At the moment I'm running each drum machine (707, SDS) in to a separate stereo compressor patch, pre-mix. I'd *like* to run each voice separately, but maybe that's not realistic. Note though that I'm not talking about final mixdown stereo studio grade niceness - just a bit of tailored chunk and thunk to each drum voice pre-mix, with the option of overdriven nasty. Hence the cheap as possible drive - the cheaper, the more drum voices I can abuse treat this way. Balanced I/O is way overkillAnyone have any thoughts on the Oatley valve pre from way back in the thread? Quote Link to comment Share on other sites More sharing options...
DrBunsen Posted March 6, 2008 Author Report Share Posted March 6, 2008 Also, I'm happy for people to throw any other DIY comps they find into this thread for future reference. Quote Link to comment Share on other sites More sharing options...
TheAncientOne Posted March 6, 2008 Report Share Posted March 6, 2008 Another minor reference. Cheap but complex."Joe Cheep" Quote Link to comment Share on other sites More sharing options...
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