Yamaha NS1000M - Tweaks

[Qwin]

Yes, LM3886 is a chip amp, one of a group of four chips who's circuits are loosely referred to as Gainclones, 68w/4R, 38w/8R for this one, but output is voltage dependant so these figures vary as does distortion levels. The harder you push it the more heat is generated and the bigger the heat sink you require.
Rod Elliot, who's opinion I have a lot of respect for, built a circuit to try these chips and described the sound as "very good, audiophile sound with a caveat" that being you shouldn't push the chip too close to its limits, where the "SPiKe" clipping protection kicks in, it gets noisy around this point.

Link to spec comparison of the four chips: http://home.pacific.net.au/~gnb/audio/lmcomp.html

The Connexeltronic link I gave a few posts back is for a stereo amp module using two of these LM3886 chips and a switch mode power supply all built on to a 100mm square PCB. This is what I am going to try out. You simply mount it on a heat sink, connect an AC supply and give it an input from your pre amp, some speaker leads to the output and your in business. the voltage from the smps gives an output of 40w/8R. These modules have DC detection/shut down for speaker protection, soft start to avoid switch on thumps, and over/under voltage protection.

It can be used for woofers, though it probably isn't going to get the best out of the 12" Yammies, which by reputation, are hard to drive. Rod said they were ideal for Mid/tweeter use in an active set up.

KMTech, who make my crossover boards (same circuit as Rods), are developing a board with 3 way crossovers, trimmer pots for driver matching and 6 channels of amplification using these chips as we speak. These are designed to go inside the speaker cabinet, or can be used external. They have a few substandard boards, suitable for DIYers for sale in their ebay shop.

[Mika K]

Old salt makes you thirsty, so inspired by this topic just had to try how these stock NS-1000M's without any other tweaks than modern binding posts would sound nowadays after living few years with the JBLs. Well, not bad at all being pretty transparent and accurate despite being little harsh and lacking some of sheer power I'm used to..

[sq225917]

A little harsh, funny how things are perceived,

[Mika K]

Indeed. I think it is a subjective matter and more about what the adjective means to different people and compared to what.

This is my fourth pair of NS-1000M's during my journey and all together have spent years and years with them using different amps etc. Some also had updated xo, so I think I'm pretty familiar with the sound they are able to produce in passive configuration

[Qwin]

That's a fair description of how mine sounded in stock form, the recap helped clean up the mids/high frequencies and going active took it further.

Brass instruments were a bit harsh and slightly piercing, plenty of detail, and very transparent, just a bit too forward and grainy.

Being very picky with these comments, still sounded pretty good.

[Mika K]

Yes the compared to the cost of these speakers the sound quality you get is still astonishing. Despite of the development of the prices during the past years..

[drSM]

KMTech, who make my crossover boards (same circuit as Rods), are developing a board with 3 way crossovers, trimmer pots for driver matching and 6 channels of amplification using these chips as we speak. These are designed to go inside the speaker cabinet, or can be used external. They have a few substandard boards, suitable for DIYers for sale in their ebay shop.[/QUOTE]

Thats interesting.
Altho the Yammy woofers would need more grunt, yes?

[Qwin]

Yes, a bit more needed, that's my feeling and others said the same earlier.

I have been in conversation with Connexelectronic about using one of their class D amp/smps for bass duties and they recommended the IRS400SMPS.
With an input of 1.5v this would give 200w into 8ohm, it has gain of 26.67. Its a single channel unit so two will be required. I would team these up with a pair of their LM3886SMPS two channel units and that would give me my six channels. Either of these SMPS auxiliary outputs is suitable, via a regulator board, for powering the crossover boards as well. A plan is forming.

[drSM]

Excellent
Fingers crossed. Looking forwards to good news

[YNWaN]

How does this balance the outputs for bass mid and tweeter drivers that have vastly different requirements?

Am I missing something here?
As I understand things, Gain is just the multiplying factor of the amp, if all channels are multiplied by the same figure for a given input voltage the high and midrange content will be way too much and you wont reach a very high level of bass before the tweeters blow, all other things being equal. Attenuating the mid range and tweeters is necessary with amps of roughly equal sensitivity and gain to balance the output for each drivers needs. If amps of different sensitivity and or gain are used the criterion changes as to where the attenuation is needed. Sensitivity being the min voltage required for the amp to achieve its maximum gain.

Give me a clue if I'm wrong.

I'm sorry but I'm not sure what you are missing here, it may well be a communication/Internet issue. The active crossover sets the relative balance, the power amp input gain sets the relative level amplified - this has nothing to do with the maximum output available. This is well known system architecture and beyond this I don't understand what is being confused (sorry). The maximum output of the amps is not relevant though (or at least it shouldn't be in terms of frequency response).