Kerry
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Posts posted by Kerry
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PLEASE SEE POST FOR THE LATEST COUNTS.
Here's the updated list:
EDIT:
I've modified this so if people want both assembled and bare boards they can.
Name - Assembled - Bare Boards
grawk - 4 - 0
Driftwood - 4 - 2
luvdunhill - 0 - 2
ujamerstand - 4 - 0
deepak - 2 - 0
cetoole - 0 - 10
manaox2 - 2 - 0
el_doug - 2 - 0
DouglasQuaid - 2 - 2
jgazal - 2 - 0
Lil Knight - 4 - 0
nattonrice - 0 - 4
kevin gilmore - 4 - 0
looser101 - 4 - 0
chinsettawong - 2 - 0
Kerry - 2 - 4
Fing - 4 - 0
blubliss - 4 - 0
n3rdling - 4 - 0
guzziguy - 2 - 0
Pars - 0 - 2
Nebby - 4 - 0
Flyingsparks - 0 - 4
morphsci - 4 - 0
dwhat - 4 - 0
minivan - 2 - 0
Craig Sawyers - 2 - 4
MASantos - 2 - 0
Vortex - 0 - 10
TOTAL - 70 - 44
Again, if anyone is interested please PM me and I'll add you to the list.
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Yes. We will effectively order a certain number of boards and have a percentage of them assembled.
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OK. I got the quote back from PCBNet (Imagineering) and I think the pricing looks pretty good.
The boards (4 layer) with electrical testing will be $9/board or a bit less depending on qty (based on 80).
The Assembly will be $22/board or a bit less depending on qty (based on 70).
The cost of parts will likely be between $50 and $70 per board depending on where we end up with part selection. I think we can lock the BOM up by early next week.
The thing to consider here since we are getting assembled boards is that they have a fallout rate (defects) of about 1% - 3% on the finished boards, so we may want to order a few extra. I think it is easy to include that in the overall price and it will only move the total per board by about $4 (for three extra boards).
If more are defective, then it is a bigger issue. I'll need to see what the warranty is from PCBNet, but it will minimally cost more in parts. If they all work we will end up with some extras. I might suggest to send them off to Kevin for all of his hard work.
This is my best guess on how to handle possible defects.
Turnaround time will be around a month, but only because we will run a test board first and will have it assembled it to make sure the board / assembly works before the final board run. This will add about $3/board.
This will put the assembled boards roughly between $88 and $108 for quantities of approximately 70 assembled. There will of course be shipping on top of this.
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So I think this baby deserves a name. Any thoughts?
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Did someone have suggestions for the resistors (2512 or 1206)? They should be thick film.
Edited.
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Link to the BOM:
It's hard to find all the resistor values from the same manufacturer. I also couldn't find 2 values in the appropriate package or in small quantities. Manufacturers are mixed and matched right now, but all of them are ±100ppm/°C, 1% 1W thick film resistors. Also need the value for the compensation caps. If anyone wants to edit or have it in a excel file let me know.
Thanks. I made a couple of small changes added the caps and sent this out for a quote. I think the PCF8574 and the ULN2803 should either both be the A version or not.
There aren't any compensation caps. You want the bypass caps to be .1uF ceramic, probably np0/c0g.
The original boards showed the .1uF caps but not the SMD version.
Kevin - did you want to add these back in.
Also, if it is difficult to get the right resistor values in the 2512 package, we might want to consider using a different sized package, like 1206.
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Not sure about the resistors, but they look like thick film SMD with 2512 size similar to this CRCW251210R0FKEG. Will likely want higher precision. The relay is g6sk-2f-dc12 (digikey has these in stock).
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PLEASE SEE POST FOR THE LATEST COUNTS.
Here the new board counts:
Name - Count - Preference
grawk - 4 - A
Driftwood - 6 - EA
luvdunhill - 2 - B
ujamerstand - 4 - E
deepak - 2 - A
cetoole - 4 - E
manaox2 - 2 - A
el_doug - 2 - E
DouglasQuaid - 2 - EA
jgazal - 2 - A
Lil Knight - 4 - A
nattonrice - 4 - E
kevin gilmore - 4 - EA
looser101 - 6 - E
chinsettawong - 2 - E
Kerry - 6 - B
Fing - 4 - A
blubliss - 4 - EA
n3rdling - 4 - EA
guzziguy - 2 - E
Pars - 2 - B
Nebby - 4 - EA
TOTAL 76
Preferences: A = Assembled; B = Board Only; E = Either; EA = Either-Assembled Preferred
Please let me know if I've made any mistakes.
Also, can anyone pull a BOM together real quick. It doesn't have to be perfect, but I need one to send over to the manufacturer to get a quote on the assembly. I would do it, but I'm not going to have time tonight.
Thanks
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PLEASE SEE POST FOR THE LATEST COUNTS.
Here's where we currently are:
Name - Count - Preference
grawk - 4 - A
Driftwood - 6 - EA
luvdunhill - 2 - B
ujamerstand - 4 - B
deepak - 3 - A
cetoole - 4 - E
manaox2 - 2 - A
el_doug - 2 - E
DouglasQuaid - 2 - EA
jgazal - 2 - A
Lil Knight - 4 - A
nattonrice - 4 - E
kevin gilmore - 4 - EA
looser101 - 6 - E
chinsettawong - 2 - E
Kerry - 6 - B
Fing - 4 - A
Preferences: A = Assembled; B = Board Only; E = Either; EA = Either-Assembled Preferred
If I have it wrong here or you would like to change something please PM me.
Just a reminder. Please PM me all requests so we can keep the thread clean. I'll post an update at the end of the day (will be on vacation soon so I hope I can keep up).
Also, depending on the pricing for assembly we may or may not end up doing this. I will reach out tomorrow for pricing based on a few different quantities.
Also, sounds like a group buy for relays might be a good idea as well.
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Seems like we could use different voltage relays (other that 12V) provided the coil current is under 500mA. Just wanted to double check this.
EDIT: Also the digital voltage could support 5V as well.
EDIT2: Nevermind. I see the address ID jumper.
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Sorry. This didn't include assebmly / parts / etc.
If enough people are interested in assembed boards, we can look into that as well. Please let me know if you are interested in "Assembled", "Boards Only" or "Either" (include preference).
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I don't mind doing this. Please PM me if you want in on the SMD version of the attenuator with how many boards you would like and I'll post the totals in this thread. Per Kevin, they will be approximately $15.28 + shipping depending on the final count.
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Now that is beautiful!
Thank you.
It would be nice if you could use some sort of ribbon cable on the digital side to connect it.
You can either mount them one on top of the other or two boards vertially depending on the spacing requirements. It seems that we can figure out a way to have this fit a T2, etc.
Do you see any value in trying to mount inside some aluminum channel?
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I'm basing it on the total cost. If Kevin can put half the relays on the other side of the board, it would put the board somewhere around 10 sq. inches. I'm guessing you could do that for about $20 per board (so $40 balanced). The rest of the parts will cost much more by comparison.
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Sounds really good. Four layer boards wouldn't add much to the cost.
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Thanks for looking at this. I know this is getting crazy now, but what if you flipped every other relay to the opposite side of the board and pull it in by .25". The resistors would then be spaced evenly. I agree that less people would be able to do this by hand.
EDIT: You can keep the signal path same as now if you also switched the pins on the flipped relays.
EDIT2: It might not be doable, but would be nice if it could be mounted inside 2" x 1" channel. Could probably do 2 1/2" x 1", but not sure about the control end.
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I found these (TX2SA-LT-5V-TH) SMD relays on Mouser. They are au+ag plated, dual coil latching relays and consume about 140mW, but only when switching. Not sure if you are interested, but could possibly do something using both sides of the board.
I know what you mean about too many projects
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Also, if you use SMD parts, you'll have more space because you loose a lot of through holes and can better use both sides of the board. If you did this it might fit better. Also, you can stack a couple of boards (one for left and and one for right), thought this is not as optimal.
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It would be nice to have a board that would would fit into the standard balanced POTs used for the T2, etc using some sort of pins and would mount above the amp board. A simple plug in. The board would also have a ribbon cable for the I2C control stuff. Not sure if the size would workout, but it would be nice.
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Beautiful job Birgir
I like the idea of using an SMD resistor for the PS fix, though I'll stick with the standard one for this build since it's already cut this way.
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Here's my progress on the power supply. I'm waiting on a couple of caps, but I've got most of the other components in. I'm going to mount this onto the rails and start populating the sand tomorrow. I've left this full size so you can see the fixes (reverse diode on on the neg 12V supply) and the 30V zeners instead of the 1N4007's.
http://img864.imageshack.us/img864/9232/t2ps001.jpg
I've also left out the 2SC3675's so that I can use the emmitter lead to apply the patch to the bottom of the board.
Here's a shot of the cut trace and I've also removed the solder mask (I used a 1/8" end mill on my drill press for this) on the traces so that I can use it to mount the resistor and one end of the .1uF by-pass cap:
EDIT: I also replaced the rectifer diodes because they were no longer available with these: DSEP12-12B
also a number of caps were no longer available:
220uF 250V caps with these: ECO-S2EP221BX from digikey
100uF 450V caps with these: ECO-S2WP101BA
680uF 450V caps with these: EET-UQ2W681EA
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As far as kerry's amp...
Turn up the bias current to 2 amps per leg.
Replace the output fets with the SiC fets that nelson is using.
BIGGER HEATSINKS. And my test bench thing works absolutely great
with +/-24 volt power supplys, and does about 30 pure class A watts
into 8 ohms. Currently using switchers for the power, and each
amplifier puts out about 200 watts of heat. Sounds really nice
into vintage VOTT's. REALLY NICE.
OK, so VOTT's are really more like 12 to 16 ohms...
Very cool
I was thinking of adding some local feedback on the output stage to keep the gain to about 10x (on the output stage). This will help keep the gain on the drains of the input stage closer to 1x amplification. Right now with all the negative feedback it is really low (hard to measure even on the scope).
What do you think?
Did I mention this is very cool!
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Likewise, sorry to hear that. Let us know when you track down the issue what cause it.
I should have the boards populated next week and I will be putting in the transformer order tomorrow, so I should be able to start testing the supply pretty soon (baring any forgotten components).
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Here's a new amp I just did based loosely on the T2 topology. I was trying to meet a $69 challeng. Close, but fun just the same. I built it for the NYC head-fi meet have a picture of it here:
Here's the schematic for it. Sounds pretty good, but there's a bit of tweeking I need to do. I think I'm going to raise the power up a bit (currently 250mA per balanced leg). The heat sinks will take it, but I need to modify the power supply a bit.
Thanks to Kevin for his pointers
digital attenuator
in Do It Yourself
Posted
Glad you're here Max!
I'm currently looking at thin film resistors in a 1206 package (similar to GoldPoint). The boards will support both 2512 and 1206 sizes. I'm not against metal film either.
I'm actually on vacation now, but will sneak in some geek time and see if I can find the required values
I know this is opening up a can of worms, but it might be possible to have a 10K version and one other like a 50K or 100K. Could possibly impact price a bit, but I just wanted to float this out there to get some feedback.