Building a DIY amp with NVA amplifier boards

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Lurcher300b
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Re: Building a DIY amp with NVA amplifier boards

Unread post by Lurcher300b »

valvesRus wrote: Sat Mar 03, 2018 1:50 pm
karatestu wrote: Sat Mar 03, 2018 1:45 pm
I always use a very small amount of heat transfer paste (snot) It is only to fill and tiny voids between the two surfaces. I am of the opinion that too much snot would be a bad thing.

Stu
Correct you are. :)
Yes, you only need enough to fill the voids between the transistor, insulator and heatsink. But unless they are unusual you dont need (want) that with sil pads. Read the docs that refer to the parts you are using, this is all known stuff, so read the literature. The danger of overtighting is not so much damaging the transistors, as reducing coupling by causing them to bow and lift up at the edges. Also you may cut through the pads with too much torque.

I use a torque screwdriver to prevent too much torque, not too little.

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Dr Bunsen Honeydew
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Re: Building a DIY amp with NVA amplifier boards

Unread post by Dr Bunsen Honeydew »

I use thermal glue and very pleased I do :mrgreen: :geek:

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Re: Building a DIY amp with NVA amplifier boards

Unread post by _D_S_J_R_ »

karatestu wrote: Sat Mar 03, 2018 1:45 pm
Linn tight is just fricking ridiculous.

I always use a very small amount of heat transfer paste (snot) It is only to fill and tiny voids between the two surfaces. I am of the opinion that too much snot would be a bad thing.

Stu
'Linn tight' was the 80's and it cost Linn in many warranty return Akito mk1's which were made of metallic plasticene it seemed and crushed the pillars all too easily. Current stuff doesn't need it done like that in my experience.

Regarding amounts of stuff. There's a vid somewhere on YouTube I think regarding cpu paste where a chap used a tiny pea shaped dob in the centre of the cpu plate and found that it spread evenly around the top plate of the processor when the cooler was plonked on top. Using too much offered no more coupling and the overspill looked awful and might have damaged the components around the plate from memory. An output transistor should be self limiting in this, but being sensible is the method I reckon if an almighty overspill is to be avoided. The adhesive I use needs to have slightly too much so when pressure is applied to fix the paste to the liquid 'primer' the coverage inside is even right out to the edge - I learned to my cost what using too little can do in this case, so the comments here come from the heart...
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Dr Bunsen Honeydew
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Re: Building a DIY amp with NVA amplifier boards

Unread post by Dr Bunsen Honeydew »

_D_S_J_R_ wrote: Sat Mar 03, 2018 4:24 pm
I learned to my cost what using too little can do in this case, so the comments here come from the heart...
Magic smoke :naughty:

:whistle:

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Re: Building a DIY amp with NVA amplifier boards

Unread post by karatestu »

Lurcher300b wrote: Sat Mar 03, 2018 3:16 pm
valvesRus wrote: Sat Mar 03, 2018 1:50 pm
karatestu wrote: Sat Mar 03, 2018 1:45 pm
I always use a very small amount of heat transfer paste (snot) It is only to fill and tiny voids between the two surfaces. I am of the opinion that too much snot would be a bad thing.

Stu
Correct you are. :)
Yes, you only need enough to fill the voids between the transistor, insulator and heatsink. But unless they are unusual you dont need (want) that with sil pads. Read the docs that refer to the parts you are using, this is all known stuff, so read the literature. The danger of overtighting is not so much damaging the transistors, as reducing coupling by causing them to bow and lift up at the edges. Also you may cut through the pads with too much torque.

I use a torque screwdriver to prevent too much torque, not too little.
Thanks Nick. Reading the instructions would be a good idea.

So, not all sil pads need thermal paste ? I obviously really do need to read the technical docs on the output transistors and the sil pads.

I took an old cambridge audio amp apart recently (electrolyte leaked out of caps all over the board :roll: ) and was going to reuse the sil pads from that but i may need a rethink. Probably better to buy new ones. The Cambridge amp used paste between the pads and the heat sink.

Stu
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Lurcher300b
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Re: Building a DIY amp with NVA amplifier boards

Unread post by Lurcher300b »

Could be wrong but I have never seen sil pads needing grease. Normally its used with mica insulators. I would certainly not suggest reusing them. This (IMHO) is a example of insanity, worrying about the torque and using nylon bolts, then considering reusing insulators. I like these

https://www.rapidonline.com/bergquist-b ... 3p-38-0402

When first used at temperature, the surface coating melts and runs to fill all voids.

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Re: Building a DIY amp with NVA amplifier boards

Unread post by karatestu »

Lurcher300b wrote: Sat Mar 03, 2018 6:31 pm Could be wrong but I have never seen sil pads needing grease. Normally its used with mica insulators. I would certainly not suggest reusing them. This (IMHO) is a example of insanity, worrying about the torque and using nylon pads, then considering reusing insulators. I like these

https://www.rapidonline.com/bergquist-b ... 3p-38-0402

When first used at temperature, the surface melts and runs to fill all voids.
Insanity - no room for that with this !

Thanks for the link. I did not know that the surface melts and runs to fill the voids. Very neat.

Another Rapid order is in order i think. :lol:

Stu
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karatestu
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Re: Building a DIY amp with NVA amplifier boards

Unread post by karatestu »

Another Rapid order should be with me tomorrow.

I decided to buy the thermal pads that Nick recommended :guiness; They are really neat, above 65 deg C they turn to a liquid state and fill all the voids. Thought I would get some TO220 as well but minimum order is 200 packs of 10 :o I don't have that many LM317's :roll:

Got some stainless steel bolts, non slip washers and nuts coming as well. I thought the transistors would take a M4 bolt but they wont - M3 at the most.

Managed to put a temporary back panel on the chipboard sheet to attach the phono sockets and speaker outlets. The finest 3mm hardboard :lol: . You guessed it, it was from ikea originally. It was easy to cut and make holes in for a temporary solution, in my usual Heath Robinson style. Also got some rubber feet to put under each corner of the heat sink for better air flow.

Stu
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Re: Building a DIY amp with NVA amplifier boards

Unread post by _D_S_J_R_ »

Probably irrelevant here, but NVA amps don't run hot unless you're absolutely thrashing them and even then, they're never so hot you can't put your hand on a heat-sink. Mine never get beyond faintly warm, even if I'm playing techno or similar... I have neighbours you see and despite the thick party wall, some sound at moderate level filters through...
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Re: Building a DIY amp with NVA amplifier boards

Unread post by CN211276 »

My NVA amps never get hot and I live in a detached house and play a lot of hard rock and metal.
Main System
NVA BMU, P90SA/A80s (latest spec), Cube 1s, TIS, TISC(LS7)
Sonore OpticalRendu, Chord Mscaler & Qutest, Sbooster PSs
Network Acoustics Eno, ifi iPurifier3, AQ JB FMJ, Cisco 2940 & 2960
DH Labs ethernet, BNC & USB cables, Farnells cat 8 ethernet cable

Second System
NVA P20/ A20, Cubettes, LS3, SSP, SC
Sonore MicroRendu, Chord Mojo 2 MCRU PSs, AQ Carbon USB cable & JB FMJ

Headphones
Grado SR325e/Chord Mojo, Beyerdynamic Avetho/AQ DF Colbat

RIP Doc

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