Building a DIY amp with NVA amplifier boards

A place for DIY project discussions.
Forum rules
1. No ad-hominem
2. No spamming or shilling
User avatar
karatestu
Posts: 1209
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Great Britain

Re: Building a DIY amp with NVA amplifier boards

Unread post by karatestu » Tue Mar 06, 2018 12:57 pm

_D_S_J_R_ wrote:
Tue Mar 06, 2018 12:36 pm
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...
Hi Dave,

These amps will be going on my up firing mids and tweeters initially so not such a bad load for them. However, the isobaric bass cubes are a 4 ohm load (the two 12 inchers are in parallel) and will be more demanding obviously.

I did not have you down as a techno fan Dave. Can imagine you throwing some shapes :grin:

Stu
Naim, Linn & Harbeth fanboy

User avatar
karatestu
Posts: 1209
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Great Britain

Re: Building a DIY amp with NVA amplifier boards

Unread post by karatestu » Tue Mar 06, 2018 3:04 pm

Some more progress with pictures.

I have bolted the boards down very loosely whilst waiting for thermal pads, stainless bolts, nuts and washers to arrive. Fitted speaker outlets to back panel. I have cut and bent all the wires so they go where they need to. Some still need to be soldered.

Image

The Avondale cap banks which I will be using initially have been turned up side down so the DC wiring does not have to cross. They use spade connectors :roll: but I will have to put up with that for the time being. I put some rubber feet like the ones in the foreground under the heat sink to give better air flow around it.

Image

Rather than go around the board with the 0V wire I decided to go over the top so that it was not near the DC wires. It is one continuous wire length from cap bank to phono connector. I have tried to keep distance between all wires to prevent crosstalk and capacitive coupling.

Image

Speaker return goes back to the "dirty" end of the cap bank where the transformer centre tap is also connected. This is how Les W at Avondale always does it with his amps and so not knowing any different I have done the same. It is a long way from the back panel to the dirty end of the cap bank and I did it with 2mm tinned wire. The wire is very stiff and does not sag. It is a couple of centimetres above the aluminium heat sink but I may put a plastic support in at either end and half way along it.

This is not exactly how I want it but good enough to get started with and leave room for extra transformers, rectifiers and caps for splitting the amp board power supply. Lots of things to play with once I get them going (pray to the magic smoke god to be kind to me :guiness; :grin: ) Going to test the power supply shortly after removing the wiring to the amp boards. Some time this week I should be able to insert the thermal pads and stainless steel fixings and solder up the last few joints. Then it is time to get the variac out :pray:

Stu
Naim, Linn & Harbeth fanboy

User avatar
karatestu
Posts: 1209
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Great Britain

Re: Building a DIY amp with NVA amplifier boards

Unread post by karatestu » Tue Mar 06, 2018 4:28 pm

Power supply now working and burning in. First time used for those rectifiers and caps. Left it to soak.

Mains is 239V ac - a bit lower than usual for here.
Transformers before rectifier - 27.8-0-27.8 V ac
After rectifier- 38.9-0-38.9 V dc

All good so far :grin:
Naim, Linn & Harbeth fanboy

User avatar
karatestu
Posts: 1209
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Great Britain

Re: Building a DIY amp with NVA amplifier boards

Unread post by karatestu » Wed Mar 07, 2018 5:54 pm

Just to reply to Doc's statement about not selling them on as NVA amps. Like Steve I will never be parting with these. I am thankful for the chance to do this.

Anyway, mine wont be going in cases - well not of the usual kind. Nobody would want to buy them anyway :lol: They will sound killer though I am sure :grin:

Stu
Naim, Linn & Harbeth fanboy

Chunk McDaniel
Posts: 232
Joined: Wed Mar 01, 2017 10:25 am
Great Britain

Re: Building a DIY amp with NVA amplifier boards

Unread post by Chunk McDaniel » Thu Mar 08, 2018 1:45 am

Why do I get the feeling this is some sort of test by the Doc.Before you know it you will be roped in and building NVA amps in the Docs bid for world domination and the destruction of all things flat earth. Power to NVA. :dance:

User avatar
Dr Bunsen Honeydew
Posts: 28510
Joined: Wed Jul 11, 2012 7:26 pm
Location: Muppet Labs
Great Britain

Re: Building a DIY amp with NVA amplifier boards

Unread post by Dr Bunsen Honeydew » Thu Mar 08, 2018 2:26 am

Damn and curses, spotted again.

User avatar
karatestu
Posts: 1209
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Great Britain

Re: Building a DIY amp with NVA amplifier boards

Unread post by karatestu » Thu Mar 08, 2018 11:35 am

They work :grin: :grin: :grin: :grin: :grin: :guiness; :guiness; :guiness; :guiness; :guiness; :dance: :dance: :dance: :dance: :dance: , so far anyway.

No load put on them yet but start up with the variac was incident free. :pray: :pray: :pray:

Checked DC offset and they are fractionaly below the figure the Doc said they would be.

Leaving them cooking while i go for a cup of tea. :guiness;
Naim, Linn & Harbeth fanboy

User avatar
SteveTheShadow
Posts: 944
Joined: Thu Sep 12, 2013 5:24 pm
Location: S Yorks
Great Britain

Re: Building a DIY amp with NVA amplifier boards

Unread post by SteveTheShadow » Thu Mar 08, 2018 12:13 pm

I don't have a variac.

Switch on and duck is my method.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Sealed cabs with Fane 12-250-TC 12" full range drivers. Also, Winslow Burhoe/Roy Allison/Richard Dunn influenced semi-omnidirectional.

User avatar
Dr Bunsen Honeydew
Posts: 28510
Joined: Wed Jul 11, 2012 7:26 pm
Location: Muppet Labs
Great Britain

Re: Building a DIY amp with NVA amplifier boards

Unread post by Dr Bunsen Honeydew » Thu Mar 08, 2018 12:16 pm

Use a broom handle :mrgreen: :mrgreen:

User avatar
SteveTheShadow
Posts: 944
Joined: Thu Sep 12, 2013 5:24 pm
Location: S Yorks
Great Britain

Re: Building a DIY amp with NVA amplifier boards

Unread post by SteveTheShadow » Thu Mar 08, 2018 12:31 pm

Dr Bunsen Honeydew wrote:
Thu Mar 08, 2018 12:16 pm
Use a broom handle :mrgreen: :mrgreen:
When I first got into building valve amps using 500V of DC, I used to clip all the meters in place and put the amp switch in the "on" position. I made up a 12ft long IEC lead, which I then plugged into a switched extension block outside the room. I then threw the switch on that to turn the thing on. If there was no bang or smell of burning, I would cautiously peek round the door and look at the meters, to check for correct operation, before going into the room.
I have had two bangs and both were from output transformerless valve amps. Scared me crapless and one of the bastards threw me onto my back, when I got my hand across a 2300uF cap, charged to 120V. I wouldn't build one of those again after my experiences. :lol:
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Sealed cabs with Fane 12-250-TC 12" full range drivers. Also, Winslow Burhoe/Roy Allison/Richard Dunn influenced semi-omnidirectional.

Post Reply