Group order of non-inverted LM3875 pc boards? Anyone interested? - diyAudio
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Old 22nd February 2004, 08:37 PM   #1
BrianGT is offline BrianGT  United States
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Default Group order of non-inverted LM3875 pc boards? Anyone interested?

I made this board for the gainclone this weekend, based on the components used in Peter Daniel's unit. It is in non-inverting configuration.

Any one interested in a group order of non-inverted LM3875 pc boards?

For resistors, Caddock MK132V resistors were used for the input, shunt and feedback resistors. A Riken 680 ohm resistor was used for the resistor setting the gain with the NFB resistor. The board is designed with these components in mind, so the group order could also include these components.

As far as power supply capacitors, the board has room and component pads for using the BlackGate 1000uF 50v caps, Panasonic FC 50v 1000uF caps and Panasonic FK SMD 1000uF capacitors (new product).

I am also looking at making a power supply board to go with this.

Is anyone interested in a group order of these boards, and possibly also interested in a group order of the components used on the boards if we can get a substantial discount over single unit quantities?

More info & to get on the list:

http://www.diyaudio.com/wiki/index.p...CB+Group+Order

Order Form

-- Brian
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Old 22nd February 2004, 08:40 PM   #2
BrianGT is offline BrianGT  United States
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Schematic used for layout:

(NFB resistor is to be soldered directly to the LM3875 pins.)

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Old 22nd February 2004, 09:11 PM   #3
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Default Yes I am

I am in on the boards and the other components as well. The PS board too if you design it. I guess that we can source our own caps as I am sure everyone will not want the same ones. I will probably be in for 20 or so channels worth. It looks like that would be 5 boards.

Thanks for taking the initiative. If you need any assistance along the way, let me know.


Jeff
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Old 22nd February 2004, 09:15 PM   #4
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Hello,

I would be in for a couple boards.

KevinLee
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Old 22nd February 2004, 09:29 PM   #5
elizard is offline elizard  Canada
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Count me in for a board or two. Quite possibly for the resistor pack too if its available.
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Old 22nd February 2004, 09:40 PM   #6
hifi is offline hifi  Sweden
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ill take a couple of boards and resistor kits

/ Micke
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Old 22nd February 2004, 09:51 PM   #7
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Hi Brian,

You know me, if there are boards for sale, I'm in. I guess I would be interested in a couple.

BTW, to those thinking about getting boards, if you need parts, read on.

If you're a Cardas fan, the 2nd annual Cardas bulk purchase is well under way. If you're interested see this thread in the trading Post Forum and the WIKI Page for details.

I have already started to send order confirmation emails to those that already placed their orders.

I will be accepting requests for the price list up until Wednesday, the 25th at 12 midnight EST.

PS: I will delete this post after Wednesday.
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Old 22nd February 2004, 09:53 PM   #8
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Default alltough

I prefer Peer peer connection and have made quite a few gc sets I would be interested in 2 boards provided all the right components can come with it.

Power supply pcb is not really essentials but, again, if they can come with the good stuff components, write me down for 4 of them !


Jean-Pierre
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Old 22nd February 2004, 09:56 PM   #9
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Count me in for a couple of boards. Also possibly interested in component kits depending on what those look like finally.
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Old 22nd February 2004, 10:17 PM   #10
tiroth is offline tiroth  United States
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I'm in for a couple (8 amps); more if the price happens to go down as people pile in.

I think it is great to stock up as these make great little surround or multi-amp setups, and they are much faster than doing P2Ps. Instant amps when you want to try out a new project.
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Old 22nd February 2004, 10:52 PM   #11
hifi is offline hifi  Sweden
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"Instant amp just add solder"




/ Micke
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Old 22nd February 2004, 11:56 PM   #12
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i would be in for a couple of boards.

a resistor pack would be great!

actually a resistor/capacitor pack would be better!

PSU boards too.
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Old 23rd February 2004, 12:03 AM   #13
elizard is offline elizard  Canada
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Pansonic FC caps can be had for $1.11 each from digikey in quantities of 100, or $0.65 for 1000!
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Old 23rd February 2004, 12:03 AM   #14
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I interest to buy and count me with 6pcs.
Packed with resister is great for me.
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Old 23rd February 2004, 12:29 AM   #15
elizard is offline elizard  Canada
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Well, I just did a quick calculation based on www.partsconnexion.com, and here's what I came up with:

Caddock 220R, CADDOCK- 62279, $3.55
Caddock 22K, CADDOCK- 51206, $3.55
Riken 680R, RIKEN- 62147, $3.20

Are these the right resistors btw?

That's $10.30 per channel for the 3 resistors (pricey little things, aren't they?), but there may be a discount. Also, if anyone else knows of a cheaper place to get resistors from, they should suggest it. (I'm sure there is).

If partsconnexion is in fact the cheapest, I would be more than willing to do the order from them, and re-ship it to everyone, as this would save a bit of money when it comes to customs (if someone from the statest orders it they'll for customs b/c of canadian origin), as well, it'll cut down on shipping (cheaper to ship it within canada originally, then separately to everywhere else.
The shipping then within canada would be around $2.50 for a standard bubble envelope, and like $3-$4 for US shipping.

Anyway, just something I came up with at work. If someone else knows of a cheaper place, please do recommend it. I would definitely be interested in a resistor + capacitor pack, and wouldn't mind organizing something.
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Old 23rd February 2004, 12:39 AM   #16
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check percyaudio.com
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Old 23rd February 2004, 12:40 AM   #17
hifi is offline hifi  Sweden
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I think you took the wrong riken this is the 0,5W variaty:

RIKEN- 62079 680R $2.40

But where there not also some Vishay resistors in PD:s schematic?

But then again PD might have specified a 1W Riken but it will not fit the PCB (lead spacing ~10mm)


/ Micke
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Old 23rd February 2004, 12:41 AM   #18
BrianGT is offline BrianGT  United States
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I made a Wiki for expressing interest in this order. It should be pretty self explantory
http://www.diyaudio.com/wiki/index.p...CB+Group+Order

Let me know if you have any questions.

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Old 23rd February 2004, 12:50 AM   #19
elizard is offline elizard  Canada
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percyaudio doesn't stock riken, as well partsconnexion is slightly cheaper.
partsconnexion is $0.05 cheaper than percy

also, with that other riken resistor, the total is $9.50 without any further discounts
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Old 23rd February 2004, 12:54 AM   #20
BrianGT is offline BrianGT  United States
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Well, if a bulk order is made of a significant amount, ordering from individual vendors for the resistors shouldn't matter too much.

Peter, can 20k MK132 resistors be used? It will lower the gain a bit, but it already seems high enough.

from Mouser.com
1 $ 3.400
10 $ 2.720
25 $ 2.520
50 $ 2.380
100 $ 2.240

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Old 23rd February 2004, 12:57 AM   #21
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I think it can be used, there shouldn't be any major difference here.
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Old 23rd February 2004, 12:57 AM   #22
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One question - if you use a pot, you just connect the output from the pot to the "in" on the board without omitting any resistors?
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Old 23rd February 2004, 12:59 AM   #23
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Quote:
Originally posted by hifi
I think you took the wrong riken this is the 0,5W variaty:

RIKEN- 62079 680R $2.40

But where there not also some Vishay resistors in PD:s schematic?

But then again PD might have specified a 1W Riken but it will not fit the PCB (lead spacing ~10mm)

I'm using 0.5W Riken. Also, for series 220R resistor, you might not need it, depending on your system. I'm using it only to prevent any excessive DC offset jump.

Vishay S102 is good in this position, and it seems to be more neutral than Caddock, but some people may prefer some extra touch and Caddock seem to add that extra bit of speed and dimentionality, but it could also be interpreted as edginess. The choice is yours.
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Old 23rd February 2004, 01:01 AM   #24
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Quote:
Originally posted by elizard
One question - if you use a pot, you just connect the output from the pot to the "in" on the board without omitting any resistors?
Yes, and because I'm using 50K pot, I need 22k shunt resistor to lower input impedance (from + to ground). But if your pot is around 20k in value, you don't need 22k shunt resistor.
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Old 23rd February 2004, 01:01 AM   #25
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Hi,BrianGT.you do a good pcb work,the style of your PCB overall arrangement is very nice!!
Did you use Protel for that?
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Old 23rd February 2004, 01:02 AM   #26
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Quote:
Originally posted by Peter Daniel


Yes, and because I'm using 50K pot, I need 22k shunt resistor to lower input impedance (from + to ground). But if your pot is around 20k in value, you don't need 22k shunt resistor.
no, it would be the 50k i got from you .. thank you
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Old 23rd February 2004, 01:07 AM   #27
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by digi01
Hi,BrianGT.you do a good pcb work,the style of your PCB overall arrangement is very nice!!
Did you use Protel for that?
Yes. I used Protel for it.

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Old 23rd February 2004, 01:17 AM   #28
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by elizard
One question - if you use a pot, you just connect the output from the pot to the "in" on the board without omitting any resistors?

Quote:
Originally posted by Peter Daniel


Yes, and because I'm using 50K pot, I need 22k shunt resistor to lower input impedance (from + to ground). But if your pot is around 20k in value, you don't need 22k shunt resistor.
As Peter stated, if you are using a 20k pot, you do not need the shunt resistor to ground [R2]. You also might not need the 220 ohm series resistor on the input pin. I made the second pad on the R1 pad (series resistor) larger, so that the input wire can be wired directly into this pad if the 220 resistor is omitted.

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Old 23rd February 2004, 02:40 AM   #29
elizard is offline elizard  Canada
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Well, a little research done
www.alliedelec.com has cheap resistors!

$2.20 for the 20k in 100+ quantities (model#: 524-5575)
$1.58 for the 220R in 1+ quantity!!! (model#: 524-9996)

so that's $3.78 for these 2, plus the $2.40 for the riken .. not too bad, $6.18 for the 3 resistors ..

am i missing a resistor here?
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Old 23rd February 2004, 03:05 AM   #30
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by elizard
Well, a little research done
www.alliedelec.com has cheap resistors!

$2.20 for the 20k in 100+ quantities (model#: 524-5575)
$1.58 for the 220R in 1+ quantity!!! (model#: 524-9996)

so that's $3.78 for these 2, plus the $2.40 for the riken .. not too bad, $6.18 for the 3 resistors ..

am i missing a resistor here?
Don't forget that you need a 20k for the negative feedback resistor, which mounts directly to the chip.

We are probably talking about $12 per board for resistors and Panasonic FC power caps, including the shipping of the components to me.

I have a prototype of the power supply board done, which is 2.5" x 1.5". 2 boards and the power supply board would make a single board that is 3.5" x 2.5".

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Old 23rd February 2004, 03:23 AM   #31
elizard is offline elizard  Canada
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i knew i was forgetting a resistor ..
but at $12/board, that's still a damn good price!
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Old 23rd February 2004, 03:41 AM   #32
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by elizard
i knew i was forgetting a resistor ..
but at $12/board, that's still a damn good price!
I am estimating $50 or less for all the parts, pcbs for 2 channels and the power supply (8 x MUR860 and 2 x 4.7uF caps), including packing and shipping. (this is for panasonic caps, not BG. I am considering omitting the BG caps from this order, since I can't seem to find good quantity discounts anyway. In addition, most of the interest for this order seems to be for the Panasonic FC caps.)

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Old 23rd February 2004, 05:51 AM   #33
BrianGT is offline BrianGT  United States
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The newer Panasonic FK capacitors get cheaper if bought in discount: $102.25 for 125 of them, $0.82 each

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Old 23rd February 2004, 05:54 AM   #34
elizard is offline elizard  Canada
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Quote:
Originally posted by BrianGT
The newer Panasonic FK capacitors get cheaper if bought in discount: $102.25 for 125 of them, $0.82 each

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You said they're surface mount types, right?
I do not like those
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Old 23rd February 2004, 06:26 AM   #35
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by elizard

You said they're surface mount types, right?
I do not like those
Well, the regular FC caps will work fine, and have proven to work fine, though the many gainclones built with them. I allowed for the option for trying the FK caps if anyone is interested.

Has anyone compared the different sized FC 1000uF 50v caps? They make 2 different sizes, 16mm x 25mm x 7.5mm or 12.5mm x 40mm x 5mm [ diameter x length x spacing ]. I have only used the 12.5mm x 40mm caps, which cost a bit more, and have a slightly lower ESR. Both will work on the PCB.

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Old 23rd February 2004, 06:46 AM   #36
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I am interested in 4 boards ( or more ) but I would like to have 3 mm mounting holes at both sides to support the board in the case.

The following comment is meant as positive input:

It seems the amp will be "hanging" at only one screw this way. The weight of the caps will cause mechanical stress at the solder joints possibly causing premature failure. Also the risk of short circuits with "loose" PCB's is higher than with well mounted boards.
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Old 23rd February 2004, 06:54 AM   #37
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Default I see

you did not put me in the wiki list ?

that's ok, i'll keep making them the way I am used to, however, too bad for me, I would have thought the thing would have gotten cheaper when as expressed in my earlier message I would have been on the list for 4 ....

J-P
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Old 23rd February 2004, 06:56 AM   #38
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I'd be interested in a few boards, caps and resistors. What is the final price looking like?

Cheers,
Zach
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Old 23rd February 2004, 06:58 AM   #39
Variac is offline Variac  United States
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Should't there be an option to actually also get the 3875s also, or is everyone going to use sampling?

UVODEE: I think you are supposed to put yourself on the wiki list.
That way your future is in your own hands!!!
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Old 23rd February 2004, 07:01 AM   #40
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by jean-paul
I am interested in 4 boards ( or more ) but I would like to have 3 mm mounting holes at both sides to support the board in the case. It seems the amp will be "hanging" at only one screw this way. The weight of the caps will cause mechanical stress at the solder joints possibly causing premature failure.
What about a single hole in the middle of the board, to relieve stress on the solder joints? With the current positioning of the capacitors, and board dimensions, there is no easy way to put holes on the sides of the boards.

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