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Adding Neurochrome's GUARDIAN-86 to Purifi Build

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#1
Hi, first time posting but I've been following the forum for some time.

I recently purchased this 3ch 1ET400A based amplifier from Nord Acoustics. It works well in my setup and I'm very happy with it outside of a single niggle. Every so often it produces a relatively loud pop/crackle from one or more of the speakers on start up. Component power up order/delay or preamp volume doesn't impact the occurrence.

To address the issue I thought I might purchase 3 GUARDIAN-86 boards from Neurochrome. Would this be a workable solution? What would be the correct way to connect such a board to the SMPS1200A400?
 

tomchr

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#3
I'm surprised the Nord 1ET400A amp is producing pops on startup. I run my 1ET400A with the Neurochrome 1ET400A Input Buffer and the Hypex SMPS1200A400. It's dead quiet on startup.
I would ask Nord why your amp pops/crackles on startup. That sounds like a cold solder joint.

You can use the Guardian-86 I you wish. Assuming the auxiliary power supply shuts down when you turn your amp off, I would power the Guardian-86 from that supply. You'll have to change a zener diode to make the Guardian work with the lower voltage of the AUX supply, but that's the only change necessary.
You can also run the Guardian-86 from the main (±65 V) supply. Just change the zener diode (D4) to a 47 V, 1-1.3 W type. I'm happy to help you get going on this. Just toss me an email (via the Contact Us form on my website or by adding @neurochrome.com to my user ID here).

Tom
 
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Thread Starter #4
I'm surprised the Nord 1ET400A amp is producing pops on startup. I run my 1ET400A with the Neurochrome 1ET400A Input Buffer and the Hypex SMPS1200A400. It's dead quiet on startup.
I would ask Nord why your amp pops/crackles on startup. That sounds like a cold solder joint.
I wrote to Nord about it and received a response from Colin saying that he had noticed a few pops he couldn't account for on the standard amps using OPA1612. The amp in question has a separate power supply for each module and considering the "pop" does the rounds across speakers, I thought it unlikely to be down to a single defect - but I'm certainly no expert in this field.

You can use the Guardian-86 I you wish. Assuming the auxiliary power supply shuts down when you turn your amp off, I would power the Guardian-86 from that supply. You'll have to change a zener diode to make the Guardian work with the lower voltage of the AUX supply, but that's the only change necessary.
You can also run the Guardian-86 from the main (±65 V) supply. Just change the zener diode (D4) to a 47 V, 1-1.3 W type. I'm happy to help you get going on this. Just toss me an email (via the Contact Us form on my website or by adding @neurochrome.com to my user ID here).

Tom
Thank you, I'll definitely get in contact if I decide to go this route.
 

tomchr

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#5
I wrote to Nord about it and received a response from Colin saying that he had noticed a few pops he couldn't account for on the standard amps using OPA1612.
That's disappointing. I would have expected more of a commercially available product.

The amp in question has a separate power supply for each module and considering the "pop" does the rounds across speakers, I thought it unlikely to be down to a single defect - but I'm certainly no expert in this field.
At TI (and National Semiconductor) we'd call it a design oversight.

Tom
 
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Thread Starter #6
That's disappointing. I would have expected more of a commercially available product.

At TI (and National Semiconductor) we'd call it a design oversight.

Tom
Would a more elegant possible solution to my problem not be to swap out the input buffers?
 

Phorize

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#7
Hi, first time posting but I've been following the forum for some time.

I recently purchased this 3ch 1ET400A based amplifier from Nord Acoustics. It works well in my setup and I'm very happy with it outside of a single niggle. Every so often it produces a relatively loud pop/crackle from one or more of the speakers on start up. Component power up order/delay or preamp volume doesn't impact the occurrence.

To address the issue I thought I might purchase 3 GUARDIAN-86 boards from Neurochrome. Would this be a workable solution? What would be the correct way to connect such a board to the SMPS1200A400?
I have no axe to grind with Nord here but I’m not sure you should be having to add extra circuitry to a new £1600 amplifier to stop it harming your speakers. If there is a real prospect of speaker damage then it’s not fit for purpose IMO. It’s not great that the manufacturers response is ‘yes I noticed that my product is behaving badly, oh well’. My March p452 is silent on power up, in operation and on shutdown BTW.
 

tomchr

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#8
Would a more elegant possible solution to my problem not be to swap out the input buffers?
That's another option. I know a guy who makes some really good ones. Let me know if I should put a word in for you. :)

I have no axe to grind with Nord here but I’m not sure you should be having to add extra circuitry to a new £1600 amplifier to stop it harming your speakers.
I agree with that, but from Post #4 it sounds like the manufacturer is aware of the problem and has decided not to fix it. One possibility would be to see if they take returns.

Yet another option might be to hold the amps in mute/standby for long enough that the stock buffer can regain its senses following power-up.

Tom
 
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Thread Starter #9
That's another option. I know a guy who makes some really good ones. Let me know if I should put a word in for you. :)
I think that is what I'll do. Colin did offer to take a look at it, but I'm not too keen on the idea of couriering it back to the UK from Denmark. From what I can tell, the boards are reasonably "plug-n-play"?
 

tomchr

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#10
I've designed a couple of these buffers for OEMs. I have yet to hear of a complaint. So I tend to agree with your assessment that the buffers are "reasonably PnP".

At least the EU demands a fairly generous warranty term (two years). I'd push on that.

Tom
 
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Thread Starter #11
@tomchr, I've received my Neurochrome buffers and am currently in the process of installing them. Each unit is connected to an SMPS1200a400 (J4>J2) - to confirm, would I be correct in setting the J6 & J7 jumpers to Regulated?
 

tomchr

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#12
If you are not using the optional Neurochrome voltage regulators with the Buffers, you set J6 and J7 on the SMPS1200A400 to provide the regulated AUX voltage, yes. Leave the two jumpers on J4 of the Buffer in their default positions (1-2, 5-6).

Then connect J1 on the SMPS to J6 on the Buffer (6-pin power harness). If you need to create a Y to power multiple boards from the same supply, I do offer the SMPS Splitter.

Connect J4 of the SMPS to J2 of the Buffer using a 10-pin ribbon cable.

Connect the amp module to the 36-pin connector on the Buffer. That part is hopefully pretty obvious. :)

Connect input and output to the Buffer.

<tada.wav> You're done. :)

Tom
 
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Thread Starter #13
If you are not using the optional Neurochrome voltage regulators with the Buffers, you set J6 and J7 on the SMPS1200A400 to provide the regulated AUX voltage, yes. Leave the two jumpers on J4 of the Buffer in their default positions (1-2, 5-6).

Then connect J1 on the SMPS to J6 on the Buffer (6-pin power harness). If you need to create a Y to power multiple boards from the same supply, I do offer the SMPS Splitter.

Connect J4 of the SMPS to J2 of the Buffer using a 10-pin ribbon cable.

Connect the amp module to the 36-pin connector on the Buffer. That part is hopefully pretty obvious. :)

Connect input and output to the Buffer.

<tada.wav> You're done. :)

Tom
Thanks!
 

tomchr

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#14
No worries. Have fun building. I'd love it if you'd share some build pictures here once you get there.

Tom
 
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