Another DIY SS Amplifier with NVA Boards

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow »

Hi Nick,
The orange and yellow are connected together as the two secondaries are in series, so the orange and yellow form a centre tap, to produce the pos and neg rails off a single rectifier bridge.

The whole thing needs tidying up, so I'll move the black and red as you suggest and reroute a couple of other wires that are bothering me.
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu »

Glad i inspired you Steve. The bug is easily caught :grin:
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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

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karatestu wrote: Sat Oct 13, 2018 6:15 pm Glad i inspired you Steve. The bug is easily caught :grin:
Aye,
Have just built an OTL for one of Ant's clients Nigel, so I've got my eye in with the soldering iron again.

Have tidied up the insides of the NVA clone and moved the wires as Nick suggested. None of the take-offs to the boards are in the path of the charging current now.
Image

The amp is pumping out the beats to Strictly Come Dancing at the mo and sounding mighty fine.
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Lurcher300b
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Lurcher300b »

The orange and yellow are connected together as the two secondaries are in series, so the orange and yellow form a centre tap
Yep, I get that, but the normal transformer secondaries are as shown in this doc

Image

But yours are clearly different.

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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu »

Avondale cap banks have 3 caps per polarity. The centre tap is connected to 0V at the end where the first pair are (there is a "T" off) together with the speaker return. At the third pair of caps there is another "T" off and the 0V from the amp boards are connected here. Signal 0V from the preamp goes to the amplifier board where it is starred with input stage filter caps etc.

Nothing like an nva amp but there you go. There are all sorts of different ways that it gets done.
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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

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Lurcher300b wrote: Sat Oct 13, 2018 7:05 pm
The orange and yellow are connected together as the two secondaries are in series, so the orange and yellow form a centre tap
Yep, I get that, but the normal transformer secondaries are as shown in this doc

Image

But yours are clearly different.
I'll have to check now :shock:
But here is a pic of the early stages of the build with the two voltmeters one on each rail to earth.
Image
I can't see how I would get the two polarities if it was wrongly wired.
Last edited by SteveTheShadow on Sat Oct 13, 2018 7:40 pm, edited 1 time in total.
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu »

I got the polarities wrong with an EI transformer i was using with my nva amps. And it still worked. I only noticed when messing about weeks later.
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Lurcher300b »

Not saying its wrong, but just that expecting what I normally see on transformers caused me to do a double take.

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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Dr Bunsen Honeydew »

Normal colour code is centre taps of the secondary are orange and red they go to the earth on the caps. Yellow and black go to the input pins of the bridge (either way around).

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow »

Lurcher300b wrote: Sat Oct 13, 2018 7:34 pm Not saying its wrong, but just that expecting what I normally see on transformers caused me to do a double take.
Yep, just checked

Secondary 1 : Red Orange
Secondary 2 : Yellow Black.

Panic over. :)
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