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Old 13th October 2012, 08:59 AM   #1641
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Default Z-foil SMD

Texas COmponents´Zfoil ASM / ASMP resistors are available from 0805 size to 2512 size. 0805 is possible to solder even with my eye sight
(OK, I use enlargement glasses)

I will stick with the 0805 ASM/ASMP resistors.



/S


Quote:
Originally Posted by RNMarsh View Post
If we are into fine tuning -- the discrete R's have lower THD. I have a problem with smd when I cant read/see the part number or its value, it is a b**ch. smd is great for small spaces and automation. For me, I'll stick to the best parts (lowest distortion). Even if I have to lay out my own pcb artwork. Thx - RNM
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Old 13th October 2012, 12:49 PM   #1642
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Originally Posted by RNMarsh View Post
Whats for dinner? - I'm having Pad Thai tonight- RNM

Shanghai ham, but DIY. I'm surprised you have not seen the LNL report on SMT resistors? There are several exellent choices. Texas Components is part of the Vishay group, their foil SMD resistors have excellent specs.
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Last edited by scott wurcer; 13th October 2012 at 01:03 PM.
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Old 13th October 2012, 01:10 PM   #1643
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Tsk, tsk ... everyone has their own approach and ideas on things, I enjoy playing with other people's ideas, to see where that can lead, since I'm coming from a completely different perspective.

Frank
Yes, keep this a group effort. Too cold to golf today, might start up a non-SMD breadboard.
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Old 13th October 2012, 01:49 PM   #1644
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Quote:
Originally Posted by scott wurcer View Post
Shanghai ham, but DIY. I'm surprised you have not seen the LNL report on SMT resistors? There are several exellent choices. Texas Components is part of the Vishay group, their foil SMD resistors have excellent specs.
yep part of vishay, so much cheaper though, I was really blown away when I went to buy some at digikey one time as I couldnt wait the 2 weeks for custom production. for an equivalent zfoil VPG part from digikey you pay about $40-50USD for standard values in 0.01%; for what you will get in exactly the custom value you want from Texas components in 0.02% for ~$10-12....

you can start to pay up around the $50 mark if you want them to do global value and relative matching in quads or something. global match at 0.02% is fine for me unless i'm going a bit silly, given what you get is usually better than that anyway.

as a bonus you get them with the clear conformal coating so you can see the foil
Attached Images
File Type: jpg Zfoil SMD ASMP identical lorez.jpg (135.9 KB, 303 views)
File Type: jpg TSMP naked smd Z foils on IV closeup.jpg (323.2 KB, 300 views)
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Old 13th October 2012, 02:02 PM   #1645
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Default I'M WITH YOU RM!

Quote:
Originally Posted by RNMarsh View Post
If we are into fine tuning -- the discrete R's have lower THD. I have a problem with smd when I cant read/see the part number or its value, it is a b**ch. smd is great for small spaces and automation. For me, I'll stick to the best parts (lowest distortion). Even if I have to lay out my own pcb artwork. Thx - RNM
I'm not buying a stereo 45X assembly microscope or wave soldering gear to build this using SOT23 devices and my eyesight is not the best. Maybe the complementary devices and the diff amp in SOT23 but I will attach copper leads to to them and use a thru hole board and mostly to92 devices elsewhere.
There are also NPD5566 dual 8pin dip devices still in inventory all over the globe which would make a nice diff amp and they are matched I think and in SOT23 also. They are also higher voltage. I really think the diff amp njfet ought to be a dual device, whatever that might be. I also think the power supply rails should be 24v. My board would be pin compatible with a JE990. Ray
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Old 13th October 2012, 02:02 PM   #1646
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you wouldnt happen to know of any matching quality SMD caps would you Scott? as you can see the RTE polystyrenes are somewhat disproportionate for this filter. theyre over on their side because this id for a portable headphone amp/IV i've been using.

I ended up changing to some copper foil/pps because they were smaller, but i'de love something in SMD

@grhughs: attaching copper leads to a sot23 would be much harder than just soldering it... I do all my soldering with either naked eye, or a 10x loupe and use a standard, 3mm chisel tip on a standard hakko 936

Last edited by qusp; 13th October 2012 at 02:06 PM.
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Old 13th October 2012, 02:21 PM   #1647
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if you are here Jan, I havent got that particular linear audio, late to buying the mag but very interested in this current edition. did you test any MELF types at all, or just thin film? I gather the results you got were thermally based, which are a complete non-issue with the vishay parts and as Scott pointed out, unlikely an issue here

apples to apples
Actually is was an article by Ed Simon who used to roam these corridors, but I haven't seen him lately.

Ed?

jan
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Old 13th October 2012, 02:46 PM   #1648
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Where can a sot23 socket be had for matching. I've never seen one. Also just applying pressure to the device on a sot foil platform is rather tedious is it not for checking Idss. What if your hand slips and static charge destroys the device??? Don't you have to wait for the device to stabalize a half minute or so?? Thanks, Ray
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Old 13th October 2012, 03:11 PM   #1649
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I found this on the web. Looks like a good rig for matching SOT23 devices or something like it. Maybe it would apply pressure without one's shakky fingers??? Ray PIC SOT23 test socket programming adapter PIC10F
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Old 13th October 2012, 03:11 PM   #1650
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matching anything is tedious, no way around that. I wouldnt think it would be that bad, i'll let you know =) no I wouldnt think you would need to keep it there long to stabilize, given the size of the device/die I couldnt see it taking long to get up to temp

@ Jan: thanks for the reply, might see if a friend has it to borrow, but I suspect given the reported results that it couldnt include foil types, the TCR is very good; there used to be a vid on the TC site that illustrated this by pointing a hot air tool at one in circuit and measuring the response of the amplifier, after first showing the effect on thick film and then thin film

Expect an order from me for the current issue though, looks really good! seems like the mag is going from strength to strength.
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