1290 Build Thread

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Re: 1290 Build Thread

Postby Joe Malone » Tue Feb 21, 2017 10:04 am

jb2060 wrote:Hi Joe,

Everything seems to be working well now. I still need to do some more test tracking but the initial results are very pleasing (certainly heaps of gain). When I turn the 1290 off with the monitors still on, i get a small high pitched squeal (in the monitors) as it powers down. Is this normal behavior or do I need to check something.

Thanks, Jason


Cool great to hear it is working :-)

It can make a low level thump and squeal noise on shut down and power up due to the vintage single power rail design and the 48v smps.

Remember always standard engineer rule of monitors muted before turning anything on or off in the studio.
Joe :-)
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htm
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Re: 1290 Build Thread

Postby htm » Tue Apr 18, 2017 4:20 pm

Hi Joe

I just ordered my set of 1290 kits and I'm about to order Carnhill input TX. I'm guessing that the pinout doesn't allow me to stick the Mu-Metal can version ( http://www.audiomaintenance.com/acatalo ... _info.html ) straight into the pcb, so I need to fix the TX to the chassis (maybe the bigger blue version) and connect it with wires.

Also if I want to add faders. Propably after the output TX? 10k?

thanks, Hannu

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Re: 1290 Build Thread

Postby Joe Malone » Mon Apr 24, 2017 11:50 am

htm wrote:Hi Joe

I just ordered my set of 1290 kits and I'm about to order Carnhill input TX. I'm guessing that the pinout doesn't allow me to stick the Mu-Metal can version ( http://www.audiomaintenance.com/acatalo ... _info.html ) straight into the pcb, so I need to fix the TX to the chassis (maybe the bigger blue version) and connect it with wires.

Also if I want to add faders. Propably after the output TX? 10k?

thanks, Hannu


Yes pinout doesn't match the GO Between PLUS multi transformer layout. So you will have to mount it and wire it back to the PCB.

It is a bad idea to use a 10k fader after the output transformer. Best to wire the 10k log fader to the INSert in and out terminals on the 1290 PCB back edge like a real Neve 1290. See 1290 overlay for how to wire this.
Joe :-)

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Re: 1290 Build Thread

Postby PeterBregman » Tue Aug 29, 2017 4:14 am

Hey Joe,

I'm seeing some strange behavior with one of the DIs on my 1290. I figured I would run it by you so see if it sounds familiar before I pull it out of the rack and put it on the bench.

When I first plug something into the left channel's DI, it seems to behave properly for about 5-10 seconds, and then slowly loses about 12dB and gets thinner sounding. If I unplug from the DI and re-insert the jack, it does the same thing again (works, then fades out). Channel 2 seems to be behaving correctly. One other quirk - if I plug in a stereo instrument (like a synth), channel 2 works, but channel one is down 12dB and thinner immediately (no delay).

I'm not sure what exactly is going on. The delay has me confused. Something drawing current/getting over heated? Both channels seem to be behaving with microphones, so it's probably an issue with the DI on channel 1? Any ideas would be appreciated, thanks!

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Re: 1290 Build Thread

Postby Joe Malone » Tue Aug 29, 2017 9:49 am

PeterBregman wrote:Hey Joe,

I'm seeing some strange behavior with one of the DIs on my 1290. I figured I would run it by you so see if it sounds familiar before I pull it out of the rack and put it on the bench.

When I first plug something into the left channel's DI, it seems to behave properly for about 5-10 seconds, and then slowly loses about 12dB and gets thinner sounding. If I unplug from the DI and re-insert the jack, it does the same thing again (works, then fades out). Channel 2 seems to be behaving correctly. One other quirk - if I plug in a stereo instrument (like a synth), channel 2 works, but channel one is down 12dB and thinner immediately (no delay).

I'm not sure what exactly is going on. The delay has me confused. Something drawing current/getting over heated? Both channels seem to be behaving with microphones, so it's probably an issue with the DI on channel 1? Any ideas would be appreciated, thanks!


Need to know if these are FETDI or OPAMPDI kits. But if FETDI sounds like 1 of the fets is damaged. Usually this will discolour a couple of resistors as well. Replacing the 2 fets and any damaged resistors will usually return the DI to 100%. First test to do is to swap the DI's between the 2 x 1290 channels to see if the fault stays with the DI pcb or the 1290 channel.

Let me know what you find. Feel free to put some photos of the DI up here if you are not sure of the problem.
Joe :-)

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Re: 1290 Build Thread

Postby PeterBregman » Fri Sep 01, 2017 7:34 am

Joe Malone wrote:Need to know if these are FETDI or OPAMPDI kits. But if FETDI sounds like 1 of the fets is damaged. Usually this will discolour a couple of resistors as well. Replacing the 2 fets and any damaged resistors will usually return the DI to 100%. First test to do is to swap the DI's between the 2 x 1290 channels to see if the fault stays with the DI pcb or the 1290 channel.

Let me know what you find. Feel free to put some photos of the DI up here if you are not sure of the problem.


For a moment there I thought it might have been something else, but it is definitely the DI board. I have the FETDIs. There doesn't seem to be any discoloration though. Here are some photos:

Image
Image

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Re: 1290 Build Thread

Postby Joe Malone » Fri Sep 01, 2017 12:18 pm

PeterBregman wrote:
Joe Malone wrote:Need to know if these are FETDI or OPAMPDI kits. But if FETDI sounds like 1 of the fets is damaged. Usually this will discolour a couple of resistors as well. Replacing the 2 fets and any damaged resistors will usually return the DI to 100%. First test to do is to swap the DI's between the 2 x 1290 channels to see if the fault stays with the DI pcb or the 1290 channel.

Let me know what you find. Feel free to put some photos of the DI up here if you are not sure of the problem.


For a moment there I thought it might have been something else, but it is definitely the DI board. I have the FETDIs. There doesn't seem to be any discoloration though. Here are some photos:


OK if you have swapped DI's and the fault is on that DI. Then it will most likely be the input FET has been damaged so will need replacing.

But often just easier to replace both FETs to be sure it is 100% again.
Joe :-)

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Re: 1290 Build Thread

Postby PeterBregman » Fri Sep 01, 2017 12:43 pm

Sounds good. What's the part # (I can't quite make it out because they're mounted face to face)? Also, do they need to be matched? I might have some in my parts bins, otherwise I'm sure I can find some locally.

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Re: 1290 Build Thread

Postby Joe Malone » Fri Sep 01, 2017 1:22 pm

PeterBregman wrote:Sounds good. What's the part # (I can't quite make it out because they're mounted face to face)? Also, do they need to be matched? I might have some in my parts bins, otherwise I'm sure I can find some locally.


They have to be 2SK170-BL and no matching needed.

Available on our webshop at link below if you get stuck.
https://www.jlmaudio.com/shop/2sk170-fet.html
Joe :-)

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Re: 1290 Build Thread

Postby PeterBregman » Sun Sep 03, 2017 9:55 am

Joe Malone wrote:[They have to be 2SK170-BL and no matching needed.

Available on our webshop at link below if you get stuck.
https://www.jlmaudio.com/shop/2sk170-fet.html


Thanks, I managed to track some down locally, and replacing them did the trick. The two channels match and sound good now! Just for future reference, is it possible that I did something to damage the FETs (too much signal?), or was this probably just a fluke?

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Re: 1290 Build Thread

Postby Joe Malone » Mon Sep 04, 2017 12:12 pm

PeterBregman wrote:
Joe Malone wrote:[They have to be 2SK170-BL and no matching needed.

Available on our webshop at link below if you get stuck.
https://www.jlmaudio.com/shop/2sk170-fet.html


Thanks, I managed to track some down locally, and replacing them did the trick. The two channels match and sound good now! Just for future reference, is it possible that I did something to damage the FETs (too much signal?), or was this probably just a fluke?


Cool great to hear you go it going :-)

If you extremely overdrive the DI into the input transformer without the pad switched on there is a chance the fet can be damaged. But usually there will be burnt resistors. So not sure what happened to your fet.
Joe :-)

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Re: 1290 Build Thread

Postby PeterBregman » Sun Dec 30, 2018 1:58 am

Hi Joe,

A strange new problem has started happening. The right channel works fine normally (although there's more hum than I remember with the gain turned up high), but once I engage the PAD, there is a lot of crackling and distortion, and when I disengage the PAD, the signal is gone entirely. The only way to get that channel to work again is to power cycle the whole preamp. Any thoughts on this? I'm guessing it's a problem on the go-between board, but it seems strange that the signal would be gone after I disengage the PAD. Any help would be greatly appreciated. Thanks!

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Re: 1290 Build Thread

Postby Joe Malone » Mon Jan 07, 2019 9:42 pm

PeterBregman wrote:Hi Joe,

A strange new problem has started happening. The right channel works fine normally (although there's more hum than I remember with the gain turned up high), but once I engage the PAD, there is a lot of crackling and distortion, and when I disengage the PAD, the signal is gone entirely. The only way to get that channel to work again is to power cycle the whole preamp. Any thoughts on this? I'm guessing it's a problem on the go-between board, but it seems strange that the signal would be gone after I disengage the PAD. Any help would be greatly appreciated. Thanks!


Does the FetDI input on that channel have the same problems?
Joe :-)

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Re: 1290 Build Thread

Postby PeterBregman » Thu Jan 10, 2019 1:14 pm

Hey Joe,

Sorry for the delay. I was doing a bunch of tests. I think I have it figured out, but I want to run this by you. Here's what I observed:

-On the right channel, both the PAD and Phase switched caused issues. Sometimes one would cut the signal, sometimes the other, and sometimes in combination. The FET DI seemed to behave normally on this channel.

-The left channel had intermittent, crunchy "gremlin" noises. The FET DI on this channel was distorted and crackled.

-I bypassed the left FET DI, but the noises were still there. On a whim, I tapped the heatsink at the back of the left 1290 with a chopstick and the signal crackled. The right channel didn't do this.

-I disconnected and reconnected all the wires going to and from the left 1290, and the noise went away. It no longer crackled when I tapped the heatsink.

-I reconnected the left FET DI, and it was no longer noisy or distorted.

-I tested the PAD and Phase switches on the right channel, and they both seemed to work fine.

Everything *seems* to be working fine now, but it sure was a strange one. Is it possible that a loose ground or power connection to the left 1290 could cause issues with both channels and the FET DIs?

Thanks again!

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Re: 1290 Build Thread

Postby Joe Malone » Thu Jan 10, 2019 5:28 pm

PeterBregman wrote:Hey Joe,

Sorry for the delay. I was doing a bunch of tests. I think I have it figured out, but I want to run this by you. Here's what I observed:

-On the right channel, both the PAD and Phase switched caused issues. Sometimes one would cut the signal, sometimes the other, and sometimes in combination. The FET DI seemed to behave normally on this channel.

-The left channel had intermittent, crunchy "gremlin" noises. The FET DI on this channel was distorted and crackled.

-I bypassed the left FET DI, but the noises were still there. On a whim, I tapped the heatsink at the back of the left 1290 with a chopstick and the signal crackled. The right channel didn't do this.

-I disconnected and reconnected all the wires going to and from the left 1290, and the noise went away. It no longer crackled when I tapped the heatsink.

-I reconnected the left FET DI, and it was no longer noisy or distorted.

-I tested the PAD and Phase switches on the right channel, and they both seemed to work fine.

Everything *seems* to be working fine now, but it sure was a strange one. Is it possible that a loose ground or power connection to the left 1290 could cause issues with both channels and the FET DIs?

Thanks again!


HI Peter yes sounds like bad ground or power connection or solder joint. Good to hear it is working now.
Joe :-)

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