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Part Sourcing Assistance/Advice Thread


n_maher

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I bought a few aluminum chassises from VT4C before. The QC is non-exisitent. One of the chassis is impossible to put together due to serious misalignment. One of the chassis cover was not even rectangular. 

Don't have experience with their other products. 

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1 hour ago, johnwmclean said:

http://www.viljomarrandi.com/gallery/

Vilts will make any custom knob to your liking.

I am actually working on a better way to get all your knob needs met - www.knobsly.com. Prices are still tentative for the custom part and I have bunch of knobs that need to get photographed and put up there. But it's a start :)

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8 hours ago, vilts said:

I am actually working on a better way to get all your knob needs met - www.knobsly.com. Prices are still tentative for the custom part and I have bunch of knobs that need to get photographed and put up there. But it's a start :)

Your custom order form doesn't have a shaft diameter parameter, but other than that, that looks excellent! (Sending you a PM shortly.)

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  • 2 weeks later...

Ran into the same problem a while ago. and found two potential solutions:

1) There is an equivalent size (as far as I can see) with an M3-hole called the SK437 xx STS 2 from Fischer Elektronik (xx is length in mm.). However, note that only the STS 2 version has the right pin configuration for our use. Available from TME in the EU, but I haven't checked for other sources.

2) I mounted my parts with a (nylon) M3 screw, where I trimmed the head slightly with a Dremel-type tool so it would fit between the fins of the original Aavid HS, with an M3 nut on the device side. A bit of a faff to do, but seems to work OK.

//UFN

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  • 2 weeks later...
  • 4 weeks later...

I have a real simple question maybe someone can help me with. Given an opamp connected as a buffer, if instead shorting the output and inverting input, I place a resistor here, this should have the effect of bandwidth limiting the buffer effectively, correct? How can I calculate the effect of this value on the overall bandwidth? I can't seem to find this discussed in any detail in intro texts on opamp circuits.

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I've checked with all my usual suspects on the bookshelf, and the only thing that I can find relates to minimising DC offset - in a unity gain buffer fed by a source with output resistance R, you put R between output and inverting input - so the same bias current flows into both inputs and hence minimises output offset in a simple way.

Why would it act as a bandwidth limiter?

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Analog Devices (actually now TI) just announced the obsolescence of the lowest available noise biplolar parts - pnp matched doubles with a noise of <0.7nV/root Hz and 1/f corner of 3Hz - SSM2220 and MAT3 http://www.analog.com/media/en/PCN/ADI_PDN_16_0034_Rev_-_Form.pdf .  The MAT12 is still current, buy eye poppingly expensive in a metal can only.  These have a noise equivalent resistance of about 30 ohms.

The only thing I know of that used to have lower noise was the late lamented Rohm 2SB737 with <0.4nV/root Hz and <10 ohms equivalent resistance.  That was just too damned useful to survive without being discontinued.  Lots of fake Chinese stuff out there.

Also the On Semi 2N5087 low-ish noise PNP is now obsolete too.

What have manufacturers got against audio?

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2 hours ago, Craig Sawyers said:

Analog Devices (actually now TI) just announced the obsolescence of the lowest available noise biplolar parts - pnp matched doubles with a noise of <0.7nV/root Hz and 1/f corner of 3Hz - SSM2220 and MAT3 http://www.analog.com/media/en/PCN/ADI_PDN_16_0034_Rev_-_Form.pdf .  The MAT12 is still current, buy eye poppingly expensive in a metal can only.  These have a noise equivalent resistance of about 30 ohms.

The only thing I know of that used to have lower noise was the late lamented Rohm 2SB737 with <0.4nV/root Hz and <10 ohms equivalent resistance.  That was just too damned useful to survive without being discontinued.  Lots of fake Chinese stuff out there.

Also the On Semi 2N5087 low-ish noise PNP is now obsolete too.

What have manufacturers got against audio?

These are sad days indeed.  We should all be using opamps for everything...  ^_^

I'm sure somebody will make high performance parts for us but they won't be as cheap as the K389/J109 were back in the day. 

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I've been thinking about replacing Phoenix Contact terminal blocks on future builds with Molex connectors. The SPOX line with a 5.08mm pitch seems like it would be a drop-in replacement on all Mafia PCBs. I am worried about the voltage ratings, though: Molex datasheets say 250V, whereas Phoenix datasheets for the terminals I've been buying say 400V.

Judging by photos I saw posted, some people here use Molex. What's your take on this?

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