TKD 4CP-601 & 4CP-2500 4-gang volume pot and PCB GB

[Pars]

Keeping it the same would mean supporting both pots, wouldn't it?

Oh wait, I hadn't seen the mention of the CP2500 series. Those might be a problem as far as the pins go, as I thought they were solder lug (at least the ones I have are), and not really designed for PCB mount? I'll dig up the datasheet.

[GeorgeP]

That's right, not technically board mount:

 

[luvdunhill]

You can remove the lugs and replace them with right angle pins.

[Pars]

From experience, you really want to limit soldering on these. The pins are 2.5mm x 0.4mm. I should be able to create a pad with a slot to fit those. Caveat: I've never tried doing that

Here is the board so far with just the 4CP-601 on it, no labeling or anything. Inputs on R, Outputs on L:

 

 

[luvdunhill]

The only issue there is many board fans won't do plated slots. I would verify you have at least one reasonably priced fab that can, before moving forward.

[Pars]

Good point Marc.

[MLA]

So, I received a quotation from TKD this morning, and it seems the pricing of 3200 JPY per piece (what I've paid before) still stands.

In addition there will be shipping and customs fees for entry to Sweden, so in total, this makes a GB price about 42-43 USD per piece + shipping to wherever you live.

Price breaks can be had for orders of 500+ units, so not an option here

An important factor is that production lead time is quite long: 45-60 days after payment. In other words, don't plan to use these in any immediate builds...

[spritzer]

One word of warning, test all 601 pots as soon as you get them.  My most recent batch was horrible and I had to throw away roughly half of the pots due to imbalance issues.  So test before soldering them in. 

[MLA]

Thanks for the heads-up!

My previous ones were all good, but if we go this route, I'll definitely test all of them before shipping them onwards.

Seems you've gotten bad product a couple of times now (Toroidy, TKD). Is this just random bad luck, or are quality checks not in place at these companies?

 

[gepardcv]

I have no problem with the lead time and like the price. Still in for 3 units.

How much imbalance would be considered out of spec?

[sorenb]

1 hour ago, gepardcv said:

I have no problem with the lead time and like the price. Still in for 3 units.

How much imbalance would be considered out of spec?

Due to reported hail rate you need to:
1. If the current number is even, divide it by two; else if it is odd, multiply it by three and add one. 
2. Rinse and repeat.

..., and you'll find how many useful ones you end up having.

[mwl168]

17 hours ago, luvdunhill said:

The only issue there is many board fans won't do plated slots. I would verify you have at least one reasonably priced fab that can, before moving forward.

If Pars doesn't mind doing the heavy-lifting creating Gerbers with slots, I am happy to work with fab houses to get quotes  

Personally, I like the option of using the TKD CP2500 series. they seem to have a good reputation for sound quality and the cost is not outrageous.

[Pars]

I could use pads with 2.5mm holes in them, but a lot of solder fill and not great mechanical integrity. Looks like getting Eagle to do pads with slots could be somewhat "fun". Might look at diptrace, though I've never done a full board with it, nor created new parts.

[Laowei]

In case anyone missed this, TKD uses internal parallel load resistors shunting a linear center section to give a faked Log output.

One gets squirrelly resistance measurements on a DUT out of circuit. Especially if you were expecting a true Log Law potientometer, like an Alps or Noble. 

 

 

[sorenb]

13 hours ago, Laowei said:

In case anyone missed this, TKD uses internal parallel load resistors shunting a linear center section to give a faked Log output.

One gets squirrelly resistance measurements on a DUT out of circuit. Especially if you were expecting a true Log Law potientometer, like an Alps or Noble. 

to my knowledge the way most manufactors makes those log scales is by having two or three linears they combine, so I guess there are several ways of making the fit.

[Laowei]

Just a warning to folks that using an ohmmeter measuring a TKD log potientometer as a simple voltage divider can give false interpreted results. 

http://www.diyaudio.com/forums/parts/140241-faulty-tkd-potentiometers-video-link.html

 

 

[Pars]

Yes, but I've always liked these pots, particularly compared to the RK27.

Not sure this is going to work. Due to the slots, the pads have to be oblong. I initially can't get clearance on the middle two rows of pads vs. the 601. The center pin on the 2500 on these rows overlaps the outer pins on the 601. I'll keep playing with it, but I don't see any alternatives if you want the pots to be coincidental (close).

[Pars]

I might be able to make it work. I decreased the pad size a bit on the 2500. Slots are defined in milling layer 46. I will need to switch the sections of the 4CP601 to the 4CP2500 since the 2500 overlaps or touches sections 2 and 3 of the 601. I haven't generated a gerber yet and taken a look at it to see if the slots are showing up or not. EDIT: board is about 46x47 mm currently.

 

Edited August 20, 2016 by Pars

[Pars]

Re routed, still need to add labels, etc. Gerber looked OK (I think), but need to verify with board house how they want the slots indicated. They are on layer 46, which is milling in Eagle. Pins are 2.5 x 0.4mm, so made the slots 2.6 x 0.5 mm.

 

 

Edited August 20, 2016 by Pars

[sorenb]

9 hours ago, Pars said:

Re routed, still need to add labels, etc. Gerber looked OK (I think), but need to verify with board house how they want the slots indicated. They are on layer 46, which is milling in Eagle. Pins are 2.5 x 0.4mm, so made the slots 2.6 x 0.5 mm.

 

 

Can it be done as '1-layer' rather, using top layer as two separate ground planes (one each channel)?

[Pars]

I doubt it. If you notice, the section mapping between the 601 and the 2500 is:

            601        2500

              2              1

              3              2

              1              3

              4              4

The two top layer traces (section 3 on the 2500 to section 1 on the 601) could be routed on the bottom layer but they would have to go on the outside of the connectors and would be fairly long traces. The grounded pins on the pot sections for the 601 would also not correspond to a "channel".

Tell me more about your desire to have the separate ground planes, and what you feel constitutes a "channel".

My thoughts had been, as was done on Birgir's boards, to have the inputs on the right labeled as I1-I4 from bottom to top on the right side, and the outputs similarly on the left. I1/I2 would be a channel (+/-) and I3-I4 would be the other channel. As you can see above, if using the 601 pot, section 1 of the pot would be grounded on the L channel, but carrying the R+ signal (I3).

Edited August 21, 2016 by Pars

[Pars]

Split ground planes, all traces on bottom. Labeled. Let me know what else...

 

[nopants]

is the group buy including 2500s now as well? any price break?

[MLA]

Yes, depending on final interest (they don't do smaller qtys than 5 of any item for this type of direct purchase).

I haven't received the quotation foe those yet, but don't expect a price break unless the GB reaches 500+ units...

Edited August 22, 2016 by MLA

[MLA]

So, quotations for the 4CP-2511 10K are in, and the cost will be 105 USD per piece plus shipping from Sweden to wherever you live. No price break below 500+ units, sorry

TKD can of course do 50K or 100K versions of both the 601 and 25XX, but min qty is 5 pieces for any particular configuration.

I've cloned a "wants it" spreadsheet from sorenb's masterful original and populated it with interests already expressed in this thread (see link in next post). I will leave it open for a few days for people to add/change things before asking for payment and placing the order.

I've also put in a column with interest for pot boards. There is no quotation for these yet, but I figured it makes sense to have the interest check for those in the same place.

Edited August 23, 2016 by MLA
credit given where credit is due :)