Too Many NADs...

[sessylU]

... so to speak.

I've been using a NAD 3130 for the last couple of years. Lovely amp, very fond of it.

Recently, it's developed an issue with the left channel on the phono channel where it will work for a little while, then cuts out. Having cleaned and exercised every switch, pot, selector and socket (a lot!) and checked all the fuses, I'm left with the conclusion that the issue is cause by heat buildup. I've run out of skill and knowledge in fixing it (for now).

My wonderful wife, having seen me struggle with this (and having put up with me taking the living room apart umpteen times trying to fix the issue) has surprised me with a replacement 3130 unit. Brilliant. Works well, sounds great!

Now though, the sillier part of my brain has started to wonder...

I have one unit with a good phono preamp, and two units with good power amps. There are pre-outs and main-ins on each unit...

Can I take the pre out of the good one, get a couple of Y cables, route two L signals to both main-ins of one unit, two R signals to the main-ins on the other, then use the mono switches to sum each power amp into mono blocks.

It's also possible (likely) that I've completely misunderstood how pre-amps, power-amps, pre-outs, main-ins and mono buttons all work.

[Barry]

Yes, that should work. I assume each unit has 'pre out' to 'power amp in' links. Obviously these will have to be removed.

[Pigmy Pony]

This is what he'll have Barry.

https://inverted-audio.store/cdn/shop/files/NAD3130IntegratedStereoAmplifier3.jpg?v=1702125319&width=1680

I'll admit when I first saw the thread title I thought it might be a comment on how many blokes there are on hifi forums and how few women :doh:

[sessylU]

Yeah, I'm assuming that main in is power amp in.

Then I assume that on the back of each amp, it's both positive terminals to a single positive terminal on the corresponding speaker (and vice-versa for negative)?

[sessylU]

Thinking/reading around this, I think I might be confusing the function of the mono switch. It's not the same thing as bridging, is it?

[Barry]

I too made the erroneous assumption that you could parallel the two outputs of the 3130 amplifier. Having had a read of the operating manual, this cannot be done.

To make matters worse, even if you could you would not double the available power, since the power drawn by the speaker depends on the speaker impedance and this is unchanged.

Furthermore since the two channels are not identical, due to component tolerance, if connected in parallel one channel will try to drive current into the other channel with disasterous results. To get around this, two low value (~ 1Ohm) resistors have to be put in series with the output from each channel. Power dissipated in these resistors will reduce the available power to the speaker.

Sorry to have raised your hopes only to dash them later.

[Pigmy Pony]

I too made the erroneous assumption that you could parallel the two outputs of the 3130 amplifier. Having had a read of the operating manual, this cannot be done.

To make matters worse, even if you could you would not double the available power, since the power drawn by the speaker depends on the speaker impedance and this is unchanged.

Furthermore since the two channels are not identical, due to component tolerance, if connected in parallel one channel will try to drive current into the other channel with disasterous results. To get around this, two low value (~ 1Ohm) resistors have to be put in series with the output from each channel. Power dissipated in these resistors will reduce the available power to the speaker.

Sorry to have raised your hopes only to dash them later.

At the risk of looking like a right dummy, I'm wondering if this impedance switch would help his cause?

https://inverted-audio.store/cdn/shop/files/NAD3130IntegratedStereoAmplifier4.jpg?v=1702125319&width=1680

[Barry]

At the risk of looking like a right dummy, I'm wondering if this impedance switch would help his cause?

https://inverted-audio.store/cdn/shop/files/NAD3130IntegratedStereoAmplifier4.jpg?v=1702125319&width=1680

No, I think it optimises the power output per channel into 4 Ohm speakers. It will not help in connecting the two channels in parallel.

[Lawrence001]

Can I take the pre out of the good one, get a couple of Y cables, route two L signals to both main-ins of one unit, two R signals to the main-ins on the other, then use the mono switches to sum each power amp into mono blocks.

It's also possible (likely) that I've completely misunderstood how pre-amps, power-amps, pre-outs, main-ins and mono buttons all work.

No but if your speakers have biwire inputs you can biamp them with one amp driving the woofers and the other amp driving the tweeters.

[Barry]

No but if your speakers have biwire inputs you can biamp them with one amp driving the woofers and the other amp driving the tweeters.

Agreed - if the speakers are bi-wireable. Since the two sections of the crossover networks are completely separate, each will present a higher load impedance to the respective amplifiers.

[sessylU]

Speakers are not biwireable. An old set of Mordaunt Short Pageant II's. They get on well with the 3130, and in truth, this setup is better than my room and ears can facilitate.

Suppose it's time to stop being greedy and wallow in the awesome sounds already available.

[Pigmy Pony]

When you have a set up that works for you, having a spare amp of the same make/model can only be a good thing. And buying a phono stage would have your old NAD up and running, wouldn't have to be too expensive :)

[Barry]

Speakers are not biwireable. An old set of Mordaunt Short Pageant II's. They get on well with the 3130, and in truth, this setup is better than my room and ears can facilitate.

Suppose it's time to stop being greedy and wallow in the awesome sounds already available.

Good speakers the MS Pageant II.

You have the right attitude: when you have a system with which you are comfortable, then stop worrying about upgrading. Just sit back and enjoy the music. :)