Part Sourcing Assistance/Advice Thread

[mwl168]

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. 

[vilts]

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

[gepardcv]

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.)

[nopants]

I placed an order, how can you resist work like that

[luvdunhill]

Looks like these Toshiba MOSFETs won't fit a #6-32 screw (I had to drill them out slightly). Is there an equivalent part to these Aavid heatsinks that accepts a metric screw? Any other ideas or similarly sized heatsinks?

[UFN]

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

[luvdunhill]

Very nice. The dimensions are "close". I will try and order some and then if needed incorporate them into my board respin. Thanks!

Edit: and bought them all

[Flyingsparks]

Can anyone help with a source for the HE90 Fischer panel sockets? I am trying to decide if I bother with one or just go with more Stax sockets.

[spritzer]

http://www.moon-audio.com/sennheiser-headphone-chassis-mount-connector-he90.html

 

[Flyingsparks]

Ouch - Thanks Spritzer. I was hoping for another source other than moon-audio, but this helped make up my mind. All Stax jacks it is  

[nopants]

I placed an order, how can you resist work like that

I got my order, how can you resist work like that

sandblasted titanium finish, opted for the tritium tube so I can see things in the dark

[vilts]

I made a little gif to see and show how the tritium tube looks like under different lighting conditions.

http://imgur.com/V0dpYMR

[Fitz]

The image in the previous link:

[gepardcv]

Just received a titanium knob from @vilts for an RK50. Looks and feels pretty fantastic!

[luvdunhill]

Am I doing it wrong?

I hope I don't have to start over!

[Pars]

You sure that B&K will measure that low? My Fluke 89 will only go into nF. Like about 10...

[luvdunhill]

Oh yeah, it does much lower. The caps are mislabeled.

[luvdunhill]

Here is a PTFE trimmer measuring 1pF

[luvdunhill]

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.

[Craig Sawyers]

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?

[Craig Sawyers]

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?

[cetoole]

16 hours ago, Craig Sawyers said:

 

Why would it act as a bandwidth limiter?

Series resistance forming a pole with the input capacitance/Miller capacitance of the inverting input?

Edited April 28, 2016 by cetoole

[spritzer]

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. 

[gepardcv]

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?

[luvdunhill]

Once you go connectors, you don't go back