73 replies to this topic

[Hawkeye]

Regarding a linear psu, you can also build them yourself (but be careful with the high voltages) for low credits.
http://sound.westhos...er-supplies.htm for an overview
Coils are available at Reichelt "Flachtransformatoren" for 5-8€ a piece.
Linear PSUs are difficult to get (or expensive, 80€+), because they are considered special nowadays, switching PSUs normally do the job more efficiently (albeit for a few audio audio people who hear ´em :-)).

[kristal=]

@imp: We sure have, but I'm too lazy to visit one. Why leave the house if the mailman can bring me one ^_^

@Hawkeye: You have a great DIY-attitude :-) But with my experience, I will likely blow the sFM into pieces instead of powering her. Therefore I will stick with my switch-mode PSU first and see if induced noise will occur. If so, I'll try the Pollin PSU and report on the forum.

Edited by kristal=, 26 May 2011 - 08:17.

[talon]

Try looking at the Boss guitar pedal range of PSU's, no doubt you'll find one to match.

[Wilba]

I recently discovered a 9V DC 300mA plugpack worked perfectly.

[m00dawg]

Regarding a linear psu, you can also build them yourself (but be careful with the high voltages) for low credits.
http://sound.westhos...er-supplies.htm for an overview
Coils are available at Reichelt "Flachtransformatoren" for 5-8€ a piece.
Linear PSUs are difficult to get (or expensive, 80€+), because they are considered special nowadays, switching PSUs normally do the job more efficiently (albeit for a few audio audio people who hear ´em :-)).

That's usually my favorite option, though for the Sammich I didn't want a huge power brick as I can't build my own PSUs smaller than a commercial solution. Plus, there's that epic thread about adding circuit protection stuff and all that so I figured the Sammich might be best served via a $20 regulated power brick someone else built.

[toneburst]

I haz Sammich! Just arrived this morning. Haven't checked contents, but I'm sure it's all here.

a|x

[pulsn]

I haz sammichFM too! I just picked it up today from the german "Zoll". Seems everything to be there. Now please...another batch of sammichSIDs...my 8580s are freezing alone in the box... ;)
Maybe some kaffeSEQ too?

Edited by pulsn, 03 June 2011 - 16:08.

[Elop]

I can not edit in the wiki!

here a link for a PSU that works fine with both sammichSID and FM (Europe/Germany)

VOLTCRAFT® USPS-600

[ilmenator]

I can not edit in the wiki!

You'll have to log in with your forum's username and password first. Go and try !

[kristal=]

The PSU from Pollin turned out as a switch-mode PSU from goobay. But I do not notice any noise. At least when no sound is generated. In contrary to my sammichSID, where I always noticed a slight hum even when no sound was generated. So my question is: how do I have to understand the sentence "They generate far too much noise in the audio." from the building guide? Only noise within the sound generation or a general noise on the audio outputs?

[m00dawg]

I would describe it as transient noise that comes from the high frequency noise in the DC power output itself. The noise is caused by the high frequency circuity that is acting like an on/off switch flipping the source input on and off rapidly to end up with the output. It's a very efficient process - much more so than linear PSUs. They can also handle a wider range of input voltages because the switching circuits just switch at different rates depending on the input to produce the stable output.

The trade-off is that what you really end up with is a bunch of pulses on the DC signal that look like a certain voltage overall (say 12V). Think of it as a somewhat ugly high frequency square-wave of sorts. The problem here is that the high frequency noise this creates cannot be totally filtered out without using capacitors that are built to dampen HF noise (such as tantalum). These can be both expensive, some say dangerous (I tend to disagree), and a bit of a black art. From what I have read, ceramics can reduce HF noise but this comes at a price. So you have to end up using various different types of caps. In the end, capacitors are not perfect and you may need to use quite a few to remove the noise, or may not be able to remove all of it regardless.

Linear PSUs do not have this problem as the noise they generate is typically easier to filter out and it's usually HF (though I think if you have HF noise coming from the AC side, you may see some of that on the DC - not entirely sure though).

All that said, if you're not hearing the noise, it could be too high pitched for your ears - either because you went to too many concerts without earplugs Or because the switching frequency of your DC supply is above the audio range (say 1MHz). In those cases, the noise is likely there but you and your audio equipment can't really pick it up. Some might call that a non-issue but I prefer linear PSUs just because I don't want HF noise of any kind in my audio signal, regardless of whether or not I can hear it. Plus I find them more interesting.

TL;DR If you can't hear it, it's probably ok.

[kristal=]

Did read all So I plugged in my goobay PSU and listened closly to it. Indeed, it produces some kind of high-pitched, squeeky noise. I consider myself having a good hearing, I never go to concerts without earplugs. But this squeeky noise doesn't appear on the headphones. They are Sony MDR-V500 ones, not the best, but also not the worst. I'm not sure, if the not hearing is due to the headphones. Will check the signal of the audio output with my soundcard. Maybe I can see it, instead of hearing it. Will report later on.

[m00dawg]

Yeah a spectrum analyzer may help there. I find myself using the one in Live a lot more, particularly when mastering, so it may show you what's going on. Thinking about it, you could always filter it out with EQ if you don't mind losses in treble but it's generally nice to know that isn't required as a default option, particularly if the high pitched noise is in the audio band enough to affect things (such as noise drums and such).

If you do some searching on the forums, you'll likely find a few flamewars over whether or not switch-mode is really that bad or if it's Satan himself being resurrected through audio. The best advice I can give is do some research (including the audio tests like you are doing) and form your own opinion I will say that for the Sammich kits, since the power supply requirements are simple, linear is still probably your best bet.

Switchmode tends to be discussed more in a practical sense for the larger projects that need a series of voltages, such as the MB-6582 or when using SSM filters and other fun things. In those cases, switchmode tends to offer multiple voltages in smaller packages than a linear supply and with a lot less heat. Sort of an aside but I thought I'd mention it anyway.

[kristal=]

Lol'd at the Satan thing. Oh no, flamewars... let the numbers speak. Did some testings with my Terratec Phase USB 26 (24bit/48khz) and the Spectrum Analyzer in Live. First spectrum shows the signals of the shut off click and the signal of the sammich being turned on without ever being played or being shut off via the power switch. Second spectrum shows the signal of the Rhodes Piano played and then the signal of the sammich being stopped playing tunes. There is a slight difference (the -24db peak at 500hz) between the signal being on but stopped playing and being turned on anew. You can see it, but you can't hear it. Has someone an opinion on why this happens? Noticed the same thing with the sammichSID back then.

Attached Files

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[toneburst]

Just completed (bar painting the panel labels) my sammichFM. NIce work Wilba and Nils!

a|x

[toneburst]

All done!



a|x

[m00dawg]

Damn that looks nice! I, too, opted to use green (though I have a black case) although it didn't work out as well this time as when I painted my sammichSID. Looks like you have much better luck than I. It looks fantastic!

[toneburst]

Thanks m00dawg. It does look nice in the photo. Up close, it's not so great though. It's a bit uneven, and the paint isn't thick enough to smooth over the bumps at the bottom of the engraving, so it looks quite messy, unfortunately. I used acrylic paint, rather than an oil-based gloss enamel, as recommended, which in retrospect maybe wasn't the best choice. Having said that, I'm generally pleased with it overall. The sound is good, too, once you get over how terrible the presets are, and start creating your own sounds. The patching randomising functions are both inspiring and addictive, I've been finding!

Incidentally, I had no problem at all finding a power-supply that worked. I've tried two different cheapo 9v DC wall-warts, and both have worked fine. I'll probable settle on the £7 one I got from Farnell, as I bought a matching set of 4, to power this box, and my 3x Shruthi-1 synths.


a|x

Edited by toneburst, 28 July 2011 - 23:36.

[m00dawg]

I used acrylic for my sammichSID and while it looks grainy up close, at normal distances my blind ass can't tell

[oootini]

any update on the latest batch of kits?