skunks

There were actually 2 big capacitors (2200uF and 1000uF) in front of it. Thank you for faster diodes idea.

I just remembered one thing to add to Shuriken's post. Especially if you are dealing with multiple separate MB CORE and SID modules (not MB-6582 where there are easy pre-built PSU Options). 1. Bypass bridge rectifiers if you are using DC as input (more about it in this ) in order to avoid shifted grounds 2. Avoid ground loops (grounds must not be connected more then once) I found a little improvement on my noise level when removed ground connection coming in ribbon cable between Core and SID module and put a separate thick wire.

Hawkeye, thank you for giving your complete view on "why 9VAC worked" from different perspectives. It's more clear now for me. Shuriken, I tried both, transformer and switching PSU (from dead printer). As you advised I set LM2596 output voltage to 8v. And it helped. Thanks :-) Now LM2596 presence is not audible. And it's input doesn't have to be regulated, at least why care about it's input if you have to regulate it's output anyway. Shuriken, you assembled so much useful info in one post! Is transformer voltage in that table AC? Where it's better to apply it? In powersupply box or after that long wires? According to my tests you may even choose cheap LM switcher but have to use 78xx afterwards in order to cut noise.

Hawkeye, I just looked at your calculations again and wondered, why 9V AC input for MB-6582 in PSU Option A is considered OK even with plain 7809 (non-LDO) ? I make an assumption that it worked in your case because your transformed was good enough (25VA) to sustain 9V AC under load.

OK, I'll try it. Hovever shouldn't it sound good even without 7805?

Thanks for reviews everyone! Hawkeye, that's how I measured it previously (I can do other tests if you have another ideas). I didn't connect extra capacitors except that was on board of LM2596 I've bought and Core8 board. I connected LM2596 from SID module's 7809's output to Core module 7805's output (bypassing 7805 and therefore 2200uF cap, but 10uF and 100nF were working). SID module was fed with 9.2V AC. LM2596 was set to output 5v. This was noisy. Then 7805 was inserted between LM2596 and Core, I mean I connected LM2596's output to 7805 input. LM2596 was set to output ~6.3v. This was a little better, but also noisy. Then I thew away LM2596 and connected 7809's output to 7805's input directly. It was MUCH, MUCH better. I can upload mp3's if you wish. BTW, this way of cascading 78xx is a little more noisy then using separate transformer's outputs. I can't guess why.

Hello Shuriken! Thank you for advice! I've already got LM2596 and found it's rater noisy. I see Altitude and other people here advice more expensive switchers: PT78ST105 - 600Hz ($33 is cheapest I could find on ebay), Traco DC/DC converter - 500Hz (~9 euro), R78C9-1.0 and a R78B5.0-1.5 - 300Hz ($10 each). I have not tested neither of these. It could be great if anyone could give a comparison.

In TK's PSU optimized scheme there are also 2 extra 2200uF caps (but on 14V line). I think 14V is intended not only for older SIDs, but also for good S/N ratio for newer SIDs - 5v drop on 7809 might give much less noise. Here http://www.ucapps.de/mbhp_sid.html TK says: 14-15V AC (!!!before!!! the regulation unit) are required for a good and noiseless sound. 14 * 1.4 - 2 ~= 17.6 DC - that's quite a lot...

That LC filter manual is straight and simple, thank you Hawkeye! I read carefully about fighting with noise in your report. You compared new and old PSUs. What powering option did you use for your MB-6582? Was it the same with old and new PSUs? There is no option if you have "PSU optimized" scheme already done. Here I found an invention of Option E for this case: http://www.subatomicglue.com/sidl0g/ (see the post dated "5.12.2008") I pressed "Query" button, so the message got updated. But OK, I won't touch it :-)

Wadesey, the first page seems to be archived, but without images, so it isn't very helpful: https://web.archive.org/web/20121114031919/http://www.danielprice.org.uk/synth-diy/sid_2.htm In my experiments I found that power connection topology really matters. Of course, ground loops must be avoided, but even without them optimal Vs and Vd connection scheme is not obvious for me. If you are building single core-SID pair, probably you supply both modules with say 9v AC and 12v AC. Then you connect Ground and +5v from core module to SID. That's the only point grounds are connected, so no ground loops. The second idea is to rectify, filter and regulate AC to DC inside PSU box. Grounds will be connected there as well (and not between modules). As far as I understood 1st idea is better then 2nd. But filtering capacitors in SID/Core modules should not be removed. Am I right?

Thank you Hawkeye for sharing your thoughts. It sound quite reasonable! While experimenting with different PSU's and different way to connect grounds I found an interesting bug (or feature) during ALL experiments. If I touch a big electrolytic condenser (or sometimes even regulator) with some metallic tool, core module hangs (no sound anymore, no notes sent to midi are playing, but MIOS Studio says: "Application is up & running!") and needs to be reset. Is it OK or I have to do smth about it? (I would certainly if I could) Can you give an exact advice on LC filter you are talking about? I'd like to experiment a little :-)

Partymode :-) He-he, I took it into consideration while following your calculations. So I decided to experiment a little with plain 78xx, if they doesn't work - will go and buy LDO :-) But then 9v AC line is converted to DC (in PSU optimized scheme) and regulated. Can that vreg go berserk? Today I made a couple of tests. 12v DC from cheap switcher was regulated to 9v (to power 6580 SID) and then to 5v (to power core & SID). Of course, all bridge rectifiers were bypassed. The noise was less audible then when getting 5v directly from switcher. But! It was much-much stronger then noise I got when using transformer (6.2v AC, 9.5v AC). I can attach sound examples if anyone is interested. Maybe it would be better if my cheap switcher would output 15v instead of 12v. Or if it would be expensive switcher :-) may be I've got to get one

Thank you, Hawkeye and Altitude! I really appreciate your help, guys! I measured my transformer under load: 9.5VAC turnes into 9.1VAC if current is 1.5A. But... Arrhh... I missed the big one. :pirate: Now it is 8.83VDC after 7809. It's output voltage doesn't change even if I feed it with 12VDC instead of 9.5VAC. So I make a conclusion 9.5VAC is enough to feed it. Only 7805 needs minimum 6.2V on input... In order to feed 7809 and 7812 , 9VAC and 12VAC (respectively) are enough, am I right? I still wondering why TK designed PSU optimized scheme that way - using 7809, adding 5v to get 14v, then using 7812/7809 on SID modules. I don't think it is to distribute heat between 78xx, but for extra smoothing / denoising. Do I think in right direction? What about Retro-Donald's PDF schem, why only 5V line needs protection? Altitude, it's encouraging news. I also wanted to make some tests to compare this approach with linear. But now I'm not sure if it is necessary if you compared it with 2 linear PSUs.

By the way, PSU optimized scheme http://www.ucapps.de/mbhp/mbhp_8xsid_c64_psu_optimized.pdf shows 9VAC going through bridge rectifier and 7809 regulator in order to get 9VDC (for adding to 5VDC) But I've tried to pass my 9.5VAC through bridge rectifier and 7809 and got 8.32V DC after bridge and 6.82VDC after 7809. What I am missing? May be Commodore PSU's 9VAC was not exactly 9VAC, but a little more?

Hello Hawkeye! Thank you for the solid reply ! Do your 9V stepper have high (>100kHz) "non-audible" switching frequency? And you still find a positive effect of lowering it via 5v linear regulator? I also thought about a crowbar design! Can you give a schematic? (Retro-Donald link is dead) I have a transformer that outputs 6.2VAC 1.15A (it can be split into 2 * 3.1VAC) 19.2VAC 0.8Ð (it can be split into 2 * 9.5VAC) 29.8VAC 0.4Ð (cannot be split) 17.2VAC 0.32A (cannot be split) I thought about doing something like PSU optimized by getting 5V from 6.2VAC and getting ~14VDC from... aaah.. Don't know yet... I'm wondering if I have to remove bridge rectifiers from SID modules, but leave regulators alone. It is not stated implicitly, however 14VDC has to be converted to 9v/12v somehow.

Hello guys! While digging dipper into MidiBox SID project I came across some new questions. Powering questions. Switching PSUs with high switching frequency are regulated, so we have to bypass regulator. But they have a switching noise/crackle. Is it a good idea to grab a switching PSU on e.g. 15v and pass it though a 7812 ? Will this remove the noise? Are computer PSUs good? TK mentioned 50Hz hum if core module is powered from USB. Maybe the same with computer PSUs, but why? Where does this hum come from? Question about protection. I guess both linear and switching PSUs need good protection. What is the reason the C64 PSU fries precious SIDs? I heard the reason is it’s regulators, but MB SID/ MB6582 has it’s own regulators. So I’m confused. The only possibility how it can happen that I can see is that 7805 is bypassed because C64 PSU gives 5v DC. Am I right? Are cheap PSUs also bad in terms of protection and what can one do about it?

I'm happy to help and very interested in seeing what it turns out to become :)

Thank you all guys, I'll probably proceed with hi-freq. switching Mean Well PSU. Unfortunately bulk order from NorthernLightX is finished.

Sorry if it is not too late. Your panel spells the following: myadyabox SYAD 6581 :) May be that's what you meant? I've attached russian logos in different fonts that spells exactly "Midi Box SID" if read in Russian. You should not be concerned that abbreviation SID is not translated, right? (if you'd like I can translate it :))

I have build several plastic buttons using silicon for molding. What about graphite contacts for emulating modern keyboards I've tried to mix graphite with several substances, however nothing works. But I think mixing it with Liquid Tape would: http://www.instructables.com/id/Make-Conductive-Glue-and-Glue-a-Circuit/ But I'm not sure about it's stickiness to silicone. Related link: http://arduino.cc/forum/index.php/topic,17510.0.html

Is it a good idea to use LM2596 Step Down (to get 5v from 12v) http://www.buyincoin...oduct-9004.html in conjunction with smth like this: (will 1A be enought?)

To Ukraine :) graantjes, was that exactly C64 PSU that didn't work? (I've found one guy here that can sell me C64C power supply (for $20: Commodores were not very popular here). Is this solution as good (in terms of noise) as 3-rd pary linear Power Supply ? Maybe that's a bad idea in terms of max. current) Could anybody post links to strong but not noisy PSU-s? (Liner or high-freq. switching)

Yes, that's true :) strophlex, what were your ideas? Some tricky PSU combinations? I'm going to use 5/12v 2A PSU for external HD's (like Pollin's recommened here by T.K., but Chinese analog found at eBay): http://www.ebay.com/itm/130770985328?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

I've received nice window! Thank you Freddy!

please add me one window for MB6582