[kosi]

couldn't resist

[qmp audio]

Hello everyone.  I'm building a nv73 with eq add-on.  Im just getting to the wiring portion of the nv73.  It appears i will need to test and calibrate the preamp unit before i wire in the eq add-on.   For someone who has built this,  is that correct?  Will i need to wire up the nv73 first to calibrate.  Then remove the wires and wire in the eq?  Thanks.  looking forward to getting these in action.

[Unit7]

Hello everyone.  I'm building a nv73 with eq add-on.  Im just getting to the wiring portion of the nv73.  It appears i will need to test and calibrate the preamp unit before i wire in the eq add-on.   For someone who has built this,  is that correct?  Will i need to wire up the nv73 first to calibrate.  Then remove the wires and wire in the eq?  Thanks.  looking forward to getting these in action.

The answer is yes

I've built a few of these and did it like this to save some time disassembling/re assembling the pre completely after it's tested and calibrated (copied this from one of my posts at RGO btw):
- Solder the shielded wire (from P to P) on the top side of the main PCB
- Before test/calibration don't use the nuts for the heatsink, just squeeze it in place on top of the 2N3055, works as long as the 2N3055 chassis shorts to the screws. Or you could probably just skip the heatsink for the calib
- After calibration, to be able to reach the screws on the 16->24V PCB, remove the heatsink and then unscrew/remove the 16->24V PCB
- If you have an iron with a pointy tip you should be able to unsolder both wires at P (close to the trim resistor) from the top side of PCB, and then re wire the ends to the eq boards
- Prepare/solder the 24V wire for the eq boards. I chose to squeeze it in the +24V terminal on the green 4 way terminal on the 16->24V board
- Re assemble 16->24V board and heatsink secured with nuts this time
- Proceed with the Don Classics manual

For this to work here are the wire lengths that have worked for me (including stripped ends of approx 3-4mm):
- Shielded cable: 11cm (after calibration could be cut to proper length for rewiring to the eq boards)
- Output pot wires: 6cm minimum for the K wire to reach the eq board after it has been desoldered from P at main board. Not important but the 0V wire could be 0.5-1cm shorter because it's pad is closer to the output pot
- 48V switch wires: 8cm has worked for me

[Blondino]

Hi there, I have a couple of questions about this build. I still trying to get the parts and didn't start yet.
I'm trying to get the grayhill switches from somewhere else then AML since they are out of stock and they have no idea when they will receive them.
I'm located in US and I need the preamp 12 way and the 3 EQ. Do somebody have the right code for the switches or the alternative one? on AML there is not code and seems impossible to find them thru pics or description.
Example I have 2 different DIY compressor 500 series. One use 71ADF30-02-2-AJS (1/8" SHAFT), and the other 71ADF30-01-2-AJS, there is just one number difference but both of them are 2x6 and they do and look exactly the same

the preamp switch is a 3 gang... is this code correct for this one: 71BDF30-03-1-AJN I can't find it anywhere

on the CAPI web site I saw they have 1x12 and 2x6... those one can fit this build or I need something else?

Thanks for the help in advance

[mesajoe]

Hey Blondino,

I have built quite a few of these add ons and the preamp itself of course. It is a really nice version of the EQ section as you can use a wide variety of capacitor makes, including vintage mustard caps, if you have them.

If you get stuck for advice, try David at [email protected], he is a jolly nice chap..

Trouble is, finding these in stock, you can get you can get 71BDF30-01-1-AJN from US Farnell, 71BDF30-01-2-AJN from US Digikey but nowhere seems to have 71BDF30-03-1-AJN (unless you backorder 25!) -  finding a 71BDF30-03-1-AJN won't matter if you are only building the add-on EQ and you have the preamp already, and my usual go-to place,  AML, is quoting back in stock by Nov this year. I don't know why this is, whether it is Covid-19 related or manufacturing problems..

I think Blore-Edwards are prototyping an equivalent switch designed by themselves (or at least this is the hint on their Facebook page), but this is only a guess and who knows when it will be available and how much it will cost... I tried messaging them, but didn't get a reply..

You want:

- 1 x 71BDF30-03-1-AJN - for the preamp gain switch (1 pole, 12 position, 3 gang) - you don't need this if you already have the preamp
- 1 x 71BDF30-01-1-AJN - for one of the eq freq selectors (1 pole, 12 position, 1 gang)
- 2 x 71BDF30-01-2-AJN - for two of the eq freq selectors (2 pole, 6 position, 1 gang)

Unfortunately you have to get the right switches (71BDF for through hole, not 71BD wired, AJN non-shorting, not AJS shorting, the AJS CAPI ones won't do).

Good luck hunting..

Thx, Mark

[Blondino]

Hey Blondino,

I have built quite a few of these add ons and the preamp itself of course. It is a really nice version of the EQ section as you can use a wide variety of capacitor makes, including vintage mustard caps, if you have them.

If you get stuck for advice, try David at [email protected], he is a jolly nice chap..

Trouble is, finding these in stock, you can get you can get 71BDF30-01-1-AJN from US Farnell, 71BDF30-01-2-AJN from US Digikey but nowhere seems to have 71BDF30-03-1-AJN (unless you backorder 25!) -  finding a 71BDF30-03-1-AJN won't matter if you are only building the add-on EQ and you have the preamp already, and my usual go-to place,  AML, is quoting back in stock by Nov this year. I don't know why this is, whether it is Covid-19 related or manufacturing problems..

I think Blore-Edwards are prototyping an equivalent switch designed by themselves (or at least this is the hint on their Facebook page), but this is only a guess and who knows when it will be available and how much it will cost... I tried messaging them, but didn't get a reply..

You want:

- 1 x 71BDF30-03-1-AJN - for the preamp gain switch (1 pole, 12 position, 3 gang) - you don't need this if you already have the preamp
- 1 x 71BDF30-01-1-AJN - for one of the eq freq selectors (1 pole, 12 position, 1 gang)
- 2 x 71BDF30-01-2-AJN - for two of the eq freq selectors (2 pole, 6 position, 1 gang)

Unfortunately you have to get the right switches (71BDF for through hole, not 71BD wired, AJN non-shorting, not AJS shorting, the AJS CAPI ones won't do).

Good luck hunting..

Thx, Mark

Thanks Mark,
you have no idea how helpful you have been right now. Yea I already contacted David several times, but I don't wanna bother to much, especially for those shopping situation. I already checked all the stores you mentioned and i also emailed Grayhill factory about the 3 gang preamp switch. They reply to me that the same model is in stock at "Brevan Electronics Inc" and "Master Electronics", but the part number is #71BDF30‍‐03PAJS.
So I look up the web sites and I found this part number on Brevan website. The picture doesn't match the switch but I emailed them on monday I guess with no reply yet.   
I was hoping that the CAPI one would work . I need to make a purchase there, fortunally I didn't get them, but I also asked Jeff about it.

I will certainly check Blore Edwards out. As far as the switch has same functionality and especially  quality, I don't really care about the brand

I still haven't start the kit yet since I'm waiting on mauser components, and also them have a lot of stuff out of stock. I will be patience.

Thanks again Mark, now at least I have the right codes and I won't make mistakes

[mesajoe]

Hey Blondino,

Glad my ramblings were of help, that's the power of this forum..

Let us know how you get on..

Thx,
Mark 

[Blondino.82]

Hey Blondino,

Glad my ramblings were of help, that's the power of this forum..

Let us know how you get on..

Thx,
Mark 

Hey Mark,
Even if I have 3 backorder on the way for components (and no grayhill yet  ) I started the build, since the guide need more attention that I thought. Anyway, since you made a few already, do you have any advice for rookies .

I'm not sure what good cable I can use to extends the pots. The inside of an audio cable or the remains of an output transformer can work as a 20AWG/24AWG like in the description manual? or should I get the right ones?

I'll keep you post it how it goes