Building a DIY amp with NVA amplifier boards

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karatestu
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Re: Building a DIY amp with NVA amplifier boards

Unread post by karatestu »

Jammy Dodger wrote: Thu Aug 29, 2019 2:46 pm Stu.......you never cease to amaze me bud.

Not a clue what your on about, but hats off to ya anyway.

Enjoy.👍
Cheers Jammy. :guiness;

All i have done is solder in the eight output transistors (two for each board). Just cleaned up a 6 mm sheet of aluminum to bolt the buggers to. Getting the heat sinked away from these darlington output transistors is very important. RD did stress this point on my first build.

I have enough transformers to make all 6 channels have separate psu's for input & output stages. I will be using EI frame transformers for the tweeter amps which are lower voltage and VA than my other Canterbury windings jobbies. Shouldn't matter so much having them on the tweeters. They give better isolation from mains crap than toroids and might be more suited to high frequency duty as that is where our ears are most critical apparently.
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Building a DIY amp with NVA amplifier boards

Unread post by Jammy Dodger »

I suppose an enclosure case is out of the question............😂

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Re: Building a DIY amp with NVA amplifier boards

Unread post by Jammy Dodger »

You just stapeling, gluing, tying components to a sheet of chip board again.

Respect......I think.🤔😁

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karatestu
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Re: Building a DIY amp with NVA amplifier boards

Unread post by karatestu »

Jammy Dodger wrote: Thu Aug 29, 2019 3:19 pm You just stapeling, gluing, tying components to a sheet of chip board again.

Respect......I think.🤔😁
It' s all still prototype work in progress jammy. I still have loads of things to try and experiment with. If i had them cased up then it would be a right pain getting access with the iron and in my diy world things change so much and the case design would be no good.

I see what you are saying though. Eventually when i have finished dicking about they will be cased up. To the delight of many here i should think (Tomasz especially) . :grin:
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Building a DIY amp with NVA amplifier boards

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Tonight i have got another two channels of nva amplifier boards wired up and tested. Used the trusty variac to ease them in to life. Only one psu per channel at first. DC offset is good so i am now draining the cap banks before wiring up the second PSU's which has already been tested and is in place.

Very excited to get my speakers on full nva style amplification. Had two monoblocs using nva boards on mid & tweeter duties and two using Avondale Voyagers on bass. Now i can sell all four of my Avondale boards (hopefully). I just swapped the amplifier boards over and so knew the psu's were good but just had to lower the voltage for the nva front ends a touch. I'm using 350VA, 35-0-35V Canterbury windings custom made transformers (over sized core, electrostatic shielding, Goss band) and Avondale Cap6 and Minicap boards. Excellent quality items which i will be keeping. May need to take the low value inductors out of the minicap boards which form a CLCLC configuration. Still using Avondale HCR200 regulators on the front end's.

Just two more monoblocs to make now with my last two remaining nva boards. That will make a six pack :dance: to drive my 3 way speakers. I haven't any more Canterbury windings transformers left or Avondale HCR200 regulators so the last two are going to be different. I do have four excellent quality 100VA Avondale EI transformers with two secondary windings of 25-0-25V that i could use. Or two 500VA Naim hicap transformers with two secondary windings of 28-0-28V. Choices choices.I think Doc will be spinning in his grave if i use the hicap transformers :hand: .

No regulators would be needed for the last two and with those transformers i dont think i can afford the dropout. Only way would be to use a LM317 /LM337 combo. Not sure i will bother. Anyway the last two monoblocs having lower voltage and VA transformers than the other four monoblocs will probably go on the tweeters.
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Building a DIY amp with NVA amplifier boards

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Second psu for front ends now up and running. Output stage running at 53V and front end running at 45V. DC offset is good to go :dance:

The heavens have opened here so i will get the chance to play some music :dance:
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Building a DIY amp with NVA amplifier boards

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I have music and lovely music at that. :dance: :dance: :dance:

I did not think that replacing the Avondale amp boards for NVA on the 12" isobaric bass drivers would make as much difference as it has. The NVA boards have higher gain and i have cleaned all the contacts throughout the system by unplugging and plugging back in. They might be contributing factors but there is more to it than that i am pretty sure. :think:
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Building a DIY amp with NVA amplifier boards

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Can't believe it's been four months since i updated this thread. Been all nva based amplification since September when i swapped out the avondale boards on bass duties.

I am listening to my speakers quite a lot at the moment with as much different music as i can throw at them so decided to do something whilst listening. I need to get my last two nva monblocs up and running to make up the six pack that i always promised myself :guiness; Two on bass drivers, two on mid bass and two on the tweeter family :grin: . I could go to eight (separate out the two bass drivers in the isobaric pair) but that would be just greedy and it would take up half the room :lol:

These last two amps are going to be on tweeter duties because i am running out of big transformers. What i do have are two 200VA 28-0-28 V ac single centre tapped secondary transformers that used to live in my Naim Nap140 amplifiers (long pulled to bits and abandoned :grin: ) I am going to use them for the output stages of these two amps.

For the input and driver stages i have four rather lovely audio grade 100VA EI transformers with twin centre tapped secondary windings of 26-0-26 V ac. I am going to use two of these for the input stages, the other two are going to be used elsewhere (phono stage). I have used these before on tweeter duties but with one winding on the output stage and one on the input stage. I do love what a good EI transformer does (not the stray field though :naughty: ).

The plan here is to use one of the secondary windings for the positive side of the psu and one for the negative side. Yes it can be done, i am using figure two.

Image

It helps make use of the whole of the transformer rather than just one winding. I have one powered up and it gives 39-0-39 V dc on the output of the kendeil smoothing capacitors. A slightly blurry photo.

Image

I am using Avondale Audio minicap boards for this(had them for ten years) which have rectifier diodes on and then six 6,800 uf caps (three in parallel per polarity) with very small value chokes (12 uH) in between. These chokes filter out some high frequency crap. Not to be used on output stages though as we need to keep the psu impedance as low as possible.

There was a small snag. I couldn't use the psu boards as they were because the diodes share a common AC input trace and i needed them to separate in order to run each polarity of the psu from a separate transformer winding. So i had to lift one of the legs of two of the rectifier diodes (the negative side of the psu) to isolate them. Then i could wire in the two sets of transformer secondary wires. The transformer centre tap wires go to a common 0V point on the rectifier side of the board. Look away if you are from the internet diy electrical safety police :shhh: :shhh: :shhh:

Image

Just one more of those to do and the two output stage psu's. Waiting for some pads to electrically isolate the output transistors from the heat sink so i will get all the psu's ready and tested .

I have regulators on the front ends of my other four nva based amps. I had excess voltage from the four transformers so it was a good way to burn a few off for the input stage. In my opinion it does bring many benefits sound wise. Sorry Doc :oops: I don't have any excess voltage to play with when using these transformers so no regulators on these last two.
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Building a DIY amp with NVA amplifier boards

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The images are not showing.
System DC Blocker, NVA BMU, Cisco 2960G, NA Eno, Sonore MicroRendu/MCRU PS, AQ JB, ifi iPurifier 3, Chord Mscaler, Chord Qutest/MCRU PS, NVA P90SA Mk2, NVA A80s Mk3, NVA Cube 1s, NVA TSCS, NVA TIS, DH Labs Mirage USB/Silver Sonic BNC, Cat 8 ethernet.
HP Grado SR 325e, Chord Mojo, AQ Carbon.
Analogue Rega Planar 3, Denon DL-110, NVA Phono 1.
Second System Topping E30, NVA P20, NVA A20, NVA Cubettes, NVA LS3, NVA, NVA SSP, SSC, AQ Carbon.
Out Beyerdynamic Avenha, AQ DF Red.

RIP Doc

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Re: Building a DIY amp with NVA amplifier boards

Unread post by karatestu »

Thanks for letting me know. I wonder if others are not seeing them either. I will have to look in to it later. They show for me :think:
DIY inspired by Richard "The Doc" Dunn RIP

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