Reddish 500 EQ

materials to outlet said:

I greatly appreciate that you have used the much better "champing at the bit" than the clearly inferior "chomping at the bit" to describe mine and other's excitement.
Also, thanks for all the work on this!

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My mother, a former copy editor, would have my hide if I used "chomping at the bit."

Great news! Production order for boards has been submitted. That's kind of a scary moment, after agonizing over this final version for so long!

BOM is on its way, I probably need one more day for that.

Hate to be the bearer of bad news, but from the looks of it. This project needs two grayhill 71BDF30-02-1-AJS switches and according to octopart at the time of writing this there is only 13 available to purchase at the moment. https://octopart.com/search?q=71BDF30-02-1-AJS&currency=USD&specs=0
Someone will have to host a groupbuy. The current lead time is 9 weeks.

Looks like the 3 deck option is in stock though. https://octopart.com/search?q=71BDF30-03-1-AJS&currency=USD&specs=0

This guy on Ebay has them, at a discount for quantity:
The only difference I can see is they are non shorting contacts, noisier switching but they should work fine, no?
Anyone up for a running a group buy?
I got my hands full with theUTM & Link orders...

https://www.ebay.com/itm/1758941978...VD4GRSQTJuZ+Hk4QZ7+taGPnHtQu|tkp:BFBMoqa16uRj

The non shorting AJN will have pops if there is DC present in the circuit. It would defiantly work just not good for speakers while mixing. I would recommend the shorting AJS version.

There should not be any DC present at those switches, as far as I'm aware, although perhaps someone else knows better. If that's the case, though, you should be safe on that front using the non-shorting, although yes, you'd expect the switching to be a little less seamless.

As previously mentioned, the 3 deck version can also be used as a drop-in substitute if it is more readily available. This situation is precisely why I designed the pcbs to work with either one. Grayhills are such nice switches, but the availability is so fickle.

I am offering a group buy of the Grayhill Series 71 3 deck, 1 pole, 12 position, fixed, shorting PCB pin version that will fit these boards. They are meant for a bunch of preamps that I am building but I will use some for this for this project as well. You can change the fixed versions to whatever step you want but it requires minor surgery. I posted a link to it in the group buy thread in the black market. Or, you can just use them as is and don't select the twelfth position and/or solder pins 11 and 12 together. I'm not doing the adjustable version for these as when you buy a large quantity the stickers and pins are all separate from the switches and it's a pain to keep track of them.

Thanks!

Paul

There should be no dc flowing in the filter circuits. If there is, clicking is caused by switching from the dc level in one part of the circuit to a different dc level in the adjacent one. Shorting contacts will not prevent this. If you do have dc getting into the filter section then the only way to prevent clicks is to make sure that every position of the switch has exactly the same dc potential. Back in the day at Neve this was achieved by wiring 4M7 resistors across adjacent contacts on the switch - probably not an option in this case.

Cheers

Ian

Thanks for confirming, Ian! This was my understanding, but it's always good to hear it from someone more experienced.

The filter circuit is passive and as such is not drawing anything from the +/-16vdc rails -- in this unit, the DC rails are only used for relay switching and to power the OPA2134 in the make-up amplifier circuit. So here again, the non-shorting switches should be fine to use without producing the unwanted clicking, but be aware that I have not tested them myself.

Also, finishing touches were put on the BOM and schematic late last night. I'll do my best to get them posted later this evening when I get home from work.

Hi Everyone,

Board production seems to be coming along nicely.

In the meantime, I've attached a BOM and schematic to the first post in this thread. I've gone over it several times and it should be fully correct, but of course if we encounter any mistakes or omissions I'll update the docs as they are discovered. I've also added some build notes. I'm hoping I can find the time to create a proper build guide once I have a chance to put together another unit, but for now, those notes should be plenty to work from.

Lastly, I want to mention -- I have just one or two folks from outside the US who haven't sent payment yet. If I haven't received it by the time all non-US orders go to Kevin for distribution, you won't be able to take advantage of that significant cost savings on your shipping, so please bear that in mind!

Production update:

Boards should be ready soon and shipping to me. Once I have them in hand, I'll probably need two or three days to sort and pack all the orders. For US builders, I've already got the shipping boxes ready to go in an effort to minimize turnaround time. For builders outside the US, your pcbs will go to Kevin at Link Audio Design for subsequent distribution, and you should expect a small additional lead time.
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On another note, I'm seeing some muddying of the waters across the various threads that have a relation to this project (as well as in some PMs), so I think it bears a bit of clarification for anyone who might be feeling confused:

This thread is where questions about PCBs and the actual build process should go. For now, I am the only person who can provide any answers about the PCBs. Feel free to ask! I'm trying to keep this thread updated as things move along as well. If you haven't already, please see the first post for BOM, schematic, and some preliminary build notes.

For US builders only, nielsk's group buy thread (which I believe is closed at time of writing) is where questions about, well, that group buy should go. PCBs are not included in it, so nielsk should not be expected to answer questions about their production schedule, etc. It was created so that US builders could get the parts that need to come from Europe without paying exorbitant shipping.

And finally, Potato Cakes' group buy for the 3-deck Grayhill switches is a great solution for the two gain switches needed for this project. HOWEVER, please be sure to look carefully at posts #3 & 4 in that thread, as these are not plug-and-play for our purposes, and they require a small amount of extra tweaking to function correctly in this build. Anyone who has taken apart a Grayhill before will likely agree, it's not too bad if you work slowly and methodically, but you have to be willing to actually do that.

EDIT: Potato Cakes group buy is also now closed

I was impulsively looking around and I found a good source for in-stock gray and black 30mm Fairchild type knobs, but shipping is a killer!
Quantity should work out much better for those purchasing multiple sets.

My old friend Grace Chen at Yueqing Omter Electronic and Technology has them in stock on Alibaba. It’s “Trade Protected” so it’s not impossible to get your money back if something is wrong. They will clarify every detail before the order goes through, I’ve ordered from them before and you do get Chinese knobs.
$21 for six knobs!

Crazy , I was just doing the same! I found these phenolic ones at a reasonable price in the US.

https://www.tubesandmore.com/products/knob-phenolic-set-screw-fairchild-style-small-pointer-30mm

The Bakelite ones look cooler in my opinion though!

TimG said:

I was impulsively looking around and I found a good source for in-stock gray and black 30mm Fairchild type knobs, but shipping is a killer!
Quantity should work out much better for those purchasing multiple sets.

My old friend Grace Chen at Yueqing Omter Electronic and Technology has them in stock on Alibaba. It’s “Trade Protected” so it’s not impossible to get your money back if something is wrong. They will clarify every detail before the order goes through, I’ve ordered from them before and you do get Chinese knobs.
$21 for six knobs!
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How did you select the a color?

I would have ordered from Tubes and More had I seen them in stock!

Probably the same knobs!

But to order the gray ones from Omter, on Alibaba, you should open an order inquiry instead of trying to find the item to put it in the basket. When they confirm all your details, they will give you a checkout ticket to approve and click through.

Two sets Tubes and more is cheaper by 20 bucks to a US address! But if you need knobs for 6 units you will do better on Alibaba.

I bought the knobs on Alibaba, 4-Black and 2-Grey, for $65.78 shipped to Houston TX. Hopefully they’re the correct size!

Shipping was $38! I’ll be ordering a lot more to make it worthwhile, next time.