Part Sourcing Assistance/Advice Thread

[spritzer]

No need to use a regulator for that.  You know the current draw and the voltage drop needed.  Simple Ohm's law for the resistor whether it is fixed or not. 

[luvdunhill]

It's funny, Nelson Pass has several products that do exactly that - use LM317 as a programmable current source for just a LED.

[Tinkerer]

Made the regular adjustable voltage divider since I had all the parts. Turned out great. Thanks again.

[cspirou]

I found a site that has some surprisingly affordable stainless steel CNC. I know that most enclosures use aluminum, but is there any particular reason why I shouldn't use stainless steel?

[mypasswordis]

Had an interesting convo with a luthier who is friends with Sam Zygmuntowicz (the most famous still living luthier in the US and the creator of the strad3d project). He asked if it was possible to design a piezoelectric setup to monitor pressure from the sound post to top plate and I said I don't see why not. I think I can implement a version of what I've been developing in my take on Krell autobias to forward to Sam for his measurements, so he can monitor in real time from anywhere. Anyone have any suggestions on a nice piezo resistor strain gauge for this purpose?

[Kerry]

1 hour ago, cspirou said:

I found a site that has some surprisingly affordable stainless steel CNC. I know that most enclosures use aluminum, but is there any particular reason why I shouldn't use stainless steel?

SS should be a bit more ridged but it's much more about the design of the mill than just the materials

[cspirou]

15 minutes ago, Kerry said:

SS should be a bit more ridged but it's much more about the design of the mill than just the materials

It's actually not milled but laser cut. I want to try to do something using T-slots

It's at lasergist.com and they have 3 mm stainless steel available. 3 mm is also a common thickness for lasercutting wood so I could do wood first for prototyping before doing steel.

[Tinkerer]

I have looked high and low for a servo clamp big enough to mount my big old helipot potentiometer and I've struck out. Anybody got a source for one with a 3" clamp? Otherwise, could I just use a rubber-lined munsen ring?

Edited October 26, 2016 by Tinkerer

[muskyhuntr]

I'm not sure what you are asking for, but you might check out ServoCity, they have many parts you might find useful.

https://www.servocity.com/

Me

 

[Tinkerer]

I've already checked there and several other places. The problem is their biggest clamping mounts are 1.5" center bore or less, and I need a 3", over twice that size.

[Pars]

On 9/18/2016 at 8:25 AM, DefQon said:

Here's what it costs from my source:

2SJ74-BL @ $0.90 each 
2SJ74-V @ $0.90 each 
2SK170-BL @ $0.90 each 

GR grades are a bit harder to get in bulk at an appropriate price but I'm trying to haggle another supplier for roughly the same as the above.

Anything going on with this? I would take 20 2SJ74BLs...

[Craig Sawyers]

Haven't heard anything since that post; but yes like you I'd be up for a bunch (provided they are genuine new old stock).

[DefQon]

9 hours ago, Craig Sawyers said:

Haven't heard anything since that post; but yes like you I'd be up for a bunch (provided they are genuine new old stock).

They are genuine, I've linked Justin, Kevin Gilmore to the seller but not sure if Justin ordered any lot from him. Two other hc'ers and 5 people from diyaudio have ordered from him and confirmed testing and working fine, excluding myself.

PM me for details because I don't want shit bag unregistered lurkers or somebody from China buying the entire lot if I post the link here.

Edited October 28, 2016 by DefQon

[wokstarr26]

30 minutes ago, DefQon said:

Haven't heard anything since that post; but yes like you I'd be up for a bunch (provided they are genuine new old stock).

Confirm genuine. I have purchased  2SJ74BL/2SK170BL pairs recently from DefQon pm.

[DefQon]

So I got in touch with said seller offering BL J74's turns out his stock is gone (*looks at Justin's direction*).

I will keep those who got in contact with me and this thread updated when I get more genuine sources for various popular jfets.

Cheers

[Pars]

He replied to me and does have V grade of both available. That fucking Justin

And not really smiling happily either

[Pars]

BTW, I was curious as to why the BL grade of FETs seems to be more popular than the V grade, which has a higher Idss range? People seem to prefer BJTs with higher Hfe...


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Not sure what happened to the other post I wrote (on Tapatalk).
Why is the BL grade favored over the V grade (higher Idss). In BJTs it seems as though the higher the Hfe the better...


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[luvdunhill]

The reason is power dissipation. Folks run the devices at full Idss and when you do that and look at the range of rails required to stay under SOAR curve, the V devices aren't preferred.

You can use V devices, but need to add degeneration resistors (which reduce voltage swing), which your design / layout might not have locations for.

[Pars]

Yes, I obviously hadn't considered that aspect.

My main use would be in front-end stages (Dynalo Mk2 mainly, maybe Dynahi as well). Those seem to have enough emitter/collector resistors / current sources that it shouldn't be a problem, particularly if the V devices were in the BL/V overlap range (high end of BL Idss). I'll look at things some more before I decide whether to get some or not.

[luvdunhill]

In that case, you are loosing a ton of transconductance with that configuration in order to gain Vds. The question is whether the resulting Vds puts the device in is linear range (I assume so with KG's designs).

TL;DR A super high Idss puts Vds around 5V to stay within power dissipation limits which isn't a all that linear operating point for these devices. Adding degeneration resistors adds noise and reduces voltage swing.

[luvdunhill]

I am a big fan of Panasonic snap-in capacitors, such as TS-UP and TS-HA. Sadly these are no longer being sold. As it turns out, OnlineComponents has a number of popular values in stock, including the 22mF 25V and 15mF 35V. So I bought some. You should too.

[Pars]

Yes, those were my target cap for the GRLV... and they have some in either 50V or 63V that will be perfect. Thanks!

EDIT: Noticed they have a $50 min order. I was only going  order up to 6 caps, ~$22. Hopefully I can come up with enough that they stock to fill out the balance.

Edited November 8, 2016 by Pars

[Pars]

Placed an order with online components today.
Also noticed they have the MeanWell IRM-15-24 PSUs for the mini Dynalo2 for ~$8.50@, or $7.06@ in qty of 10-24. Considerably cheaper than Mouser, if someone wanted to do a group buy.


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[luvdunhill]

Generally - OnlineComponents is nice for more expensive items.

[Pars]

Yep, as long as you don't mind meeting their minimum. Thanks again for the heads up on the Pana TS series, always liked them. A shame Pana is getting out of anything bigger can/higher voltage like those. Great caps!