1290 Build Thread

[Joe Malone]

Quickest & most compact way to build a 1290/1073 mic pre. Only need to solder 36 parts to motherboard PCB. BAX83NV & BAX83AM modules fully built and tested. BAX83AM trim pot preset for Neve LO1166 & JLM111DC output transformer.


1290 Build
The 1290micro or macro PCB has no variations on it so can be built from the PCB overlay in the general rule of lowest height part to the tallest.
The Full 1290 build PDF overlay below has most of the info you will need to build and connect all the PCBs together. Please have a good read of it before you start. But feel free to post any questions on this thread if you need help or more into.

Full 1290 build PDF overlay Ver2 here Latest version
Full 1290 build PDF overlay here Older version
1290 PCB Schematic here

1. Build TREX2 kit with 25turn 5k trim pot option if using our 48v SMPS power supply (24v zener NOT used) and fit both to back panel with insulation kits provided.
2. Check with ohmmeter that metal tab on the Tip122 transistors are not shorting to the metal back panel.
3. Wire power wiring from DC connector to fuse and power switch to TREX PCBs.
4. Turn on and adjust both TREX trim pots for 24v output before connecting them to the 1290 PCB.
5. Build and wire all other PCBs together for one channel at a time.
6. When load of 1290 is on the TREX the 24v trim may need to be fine adjusted to exactly 24v again.


JLM BAX83NV & BAX83AM PCBs are both 1.6" (32.7mm) wide x 1" (25.4mm) high. Modules come fully assembled and tested. With the BAX83AM module trim pot preset for Neve LO1166 & JLM111DC output transformers.

PCB Overlay of new MACRO 1290 PCB.


Some photo's of the new MACRO 1290 PCB to help.





Back panel layout and wiring. (Note heatsink is no longer used with TREX2 or 2 x older TREX.)


Notes and Errata
1. TREX2 replaces 2 x TREX kit (simple zener regulator kit).
2. Micro 1290 PCB has been replaced with New Macro 1290 PCB which uses our new smaller 2 x 12 position switch and a better layout. Also eliminates the 1N914 diode across the relay coil to save confusion be it and the 5v1 zener. Adds 0.1uF across relay coil instead.
3. Heatsink eliminated from kit. Back panel is enough heatsinking for the TREX2 or 2 x TREX kit.
4. Follow overlay on XLRIO PCB for 10 pin header positioning. Locate opening on header maybe in or out depending on version of the PCB.

FAQ
Q. Power switch kit is missing the 1N4007?
A. 1N4007 is not used when switching DC so is not supplied.

Q. Do I need to add the resistors shown on the XLRIO PCB?
A. No. They are not used or supplied in XLRIO kit.

[ciscan.81]

Hi Joe & Co.

I started building my 1290 Macro today...A few things I'm not sure about:

1. Which way round does the 180pF plastic cap in the top left corner next to the relay go? The cap has one long leg so I'm assuming it is polarized...? Long leg on the PCB edge or towards rotary switch?

2. Does the 5v reed relay need to go one way or the other? Text toward or away from board?

3. Does the 5v1 zener diode go with the black line to the right? (as indicated on the PCB, I think) ie black line towards ins and outs at the back of the board...?

Thanks again!

[Joe Malone]

Hi Joe & Co.

I started building my 1290 Macro today...A few things I'm not sure about:

ok

1. Which way round does the 180pF plastic cap in the top left corner next to the relay go? The cap has one long leg so I'm assuming it is polarized...? Long leg on the PCB edge or towards rotary switch?

180pF is NOT polarized can go in either way around.

2. Does the 5v reed relay need to go one way or the other? Text toward or away from board?

5v reed relay also is NOT polarized and can go in either way around. The PCB shows pin 1 as a square pad which is the end with the beveled edge.

3. Does the 5v1 zener diode go with the black line to the right? (as indicated on the PCB, I think) ie black line towards ins and outs at the back of the board...?

The 5v1 zener goes on the PCB with its stripe at the same end as the PCB overlay shows as a wider end (which is with the stripe closest to the back edge of the PCB).

PCB Overlay of new MACRO 1290 PCB.


Some photo's of the new MACRO 1290 PCB to help.




Let me know if you have any more questions

[ciscan.81]

Thanks for putting my mind at ease again Joe.

Just remembered, one other thing: There was no 820R (for the stepped gain switch) included in my kit, but I received one spare 470R, is this telling me something or should I pop down to Jaycar for the 820R...

Thanks again

-W

[Joe Malone]

Thanks for putting my mind at ease again Joe.

Just remembered, one other thing: There was no 820R (for the stepped gain switch) included in my kit, but I received one spare 470R, is this telling me something or should I pop down to Jaycar for the 820R...

Thanks again

-W

Feel free to grab a 820R metal film from jaycar if it is quicker or I can send you down one.

Thanks for the heads up I will check the other kits in that batch for the 820R as it may have been missed for the whole batch.

[ciscan.81]

No Worries Joe,

I'll grab one here.

Thanks again.

[ciscan.81]

Hi again Joe

I finally put my 1290 Macro together today having finished my custom rack cases...

The build is standard with FET DI and a VU meter running through a buffer kit.

The unit is working and sounds great when it does but is displaying some strange behaviour:

The signal cuts out whenever the PAD is engaged and also cuts out occasionally when switching the gain.

When this happens I can power the unit off, wait for about 10 seconds, switch it back on and the signal returns (provided the PAD has been switched off.)

Switching the stepped gain rotary switch is also quite noisy and also switching the pad in and out also gives a loud pop.

Any thoughts on where I should start my fault finding? I'm at a bit of a loss.

ps. I finished my first two BA channels yesterday, all working fine...they sound AMAZING!!! and look great in their custom case Couldn't be happier. I'll post some pics etc once I've got the 1290 sorted.

Thanks again

[ciscan.81]

Hi Joe

UPDATE: ALL FIXED!

I reluctantly pulled the go-between and 1290 out of the rack case this morning to look for faults...BINGO!

I had missed a solder pad on the input transformer, must have just been contacting intermittently. Fixed.

The next problem was the middle position on the stepped gain switch wasn't working. (ie signal in all other positions but this one)

I replaced the Resistor in this position and now all is working great.

VERY VERY happy with the sound, function and look of the pre, the 'pull switch' output attenuator pot is really handy!...and I'm actually quite pleased with myself having found and fixed the faults! All part of the learning process I suppose.

All that is left to do is replace the gain pot on my BA312 style build and all four pre's are done! (I embarrassingly connected the gain pot to +48v IN by accident and smoked it, oops ...you may have seen the replacement order in the system.

Sorry to have bothered you unnecessarily, just panicked a bit when things went haywire!

Many thanks again for all your help along the way.

I plan to post some pics to show off my new pres once the BA312 is done, hopefully early next week when the pot arrives!

[Joe Malone]

HI Wayne sorry had missed this post. Good to hear you got it all working

[weroflu]

what do you think the minimum case dimensions could be for two channels, carnhills in/out, no DI, smps external supply

i assume the the regulator board also needs to be in there?

using a scavenged smaller case like behringer or dmp2 or 3 , open to recommendations on this

is a tight layout not conducive to noise issues?

trying to make a stereo unit portable. not happy about having to even drill out the go between holes though. or maybe you guys have a confabulated smallish case in your laboratory?

[Joe Malone]

what do you think the minimum case dimensions could be for two channels, carnhills in/out, no DI, smps external supply

i assume the the regulator board also needs to be in there?

using a scavenged smaller case like behringer or dmp2 or 3 , open to recommendations on this

is a tight layout not conducive to noise issues?

trying to make a stereo unit portable. not happy about having to even drill out the go between holes though. or maybe you guys have a confabulated smallish case in your laboratory?

I have seen guys fit 2 channels in a 1 unit high half rack. We fit 4 in a 1 unit high full rack case easy.

Just have to be careful with the in and out wiring and transformers positioning so at high gain the unit doesn't oscillate.

[bsatriani]

Hi Joe,
I bought only one TREX kit for two 1290 modules - cause I saw in the trex description : "Using on of the 48v 380mA SMPS prebuilt supplies and a TREX or TREX2 kit is the easiest and cheapest way to power 2 x 1073 , 1290, 1272 neve modules."

However in the build thread I've noticed that there are 2xTREX for 2x1290modules.

Can work one TREX with 2x1290 modules, or should I buy one more TREX kit ? (SMPS is a 48V 520mA)

Thanks,
Regards, Bogdan

[Joe Malone]

Hi Joe,
I bought only one TREX kit for two 1290 modules - cause I saw in the trex description : "Using on of the 48v 380mA SMPS prebuilt supplies and a TREX or TREX2 kit is the easiest and cheapest way to power 2 x 1073 , 1290, 1272 neve modules."

However in the build thread I've noticed that there are 2xTREX for 2x1290modules.

Can work one TREX with 2x1290 modules, or should I buy one more TREX kit ? (SMPS is a 48V 520mA)

Thanks,
Regards, Bogdan

1 x TREX kit will run 2 x 1290 kit easy. We usually use 2 x TREX kit or a TREX2 to spread the heat into the case better thats all.

[weroflu]

what is the difference in sound between your kits and something like the seventh circle or others that claim to follow the 1272 or 1290 circuit exactly.

i'm sure yours sounds good, i'm just curious about the sonic differences.

[Joe Malone]

what is the difference in sound between your kits and something like the seventh circle or others that claim to follow the 1272 or 1290 circuit exactly.

i'm sure yours sounds good, i'm just curious about the sonic differences.

Electrically and sound wise our micro or macro 1290 kit is exactly the same as the Neve 1290 at ever gain step for the audio path. We have just changed the way the switching is done so a 2 bank 12 position switch and 1 reed relay replaces the 3 bank 12 position switch.

If you are including our full 1290 rack kit with in and out transformers the only difference is the output transformer stays flat frequency response under all output loads without changing anything. Where as the original LO1166 neve output transformer needs a 680ohm load on it to work with all modern 10k input gear and for the load to be removed when driving 600ohm vintage gear. Our output transformer definitely has a nicer low end compared to the original Neve. If you bounce several tracks together the original Neve turns into mud in the low end especially with the number of tracks used these days. This is why we have a lot of well know engineers use our version over the original as it has the warmth but not the mud