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Old 3rd March 2019, 09:37 AM   #61
maty tinman is offline maty tinman  Spain
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One of my tweaks/mods of my AV Marantz SR4500 was to increase the bias -> better sound too. More bass and clean sound. Music with more energy. 3-D? I think the same... 2-D , but usually I listen to in near field, unless the music excites me, now more frequently than a week before!

Well, Hugh must to know something
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Old 3rd March 2019, 10:07 AM   #62
maty tinman is offline maty tinman  Spain
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Quote:
Originally Posted by andyr View Post
Sorry, I have no idea, maty (but I don't think bias changes power output - this depends only on the +/- DC rails).

Make the change (to 60mV bias) and see how it sounds!

Andy
Higher bias: class AB amps work like class A few watts more, if I am not wrong. In my AV -> only more bass and cleanner sound. And more heat but until reasonable, even in the Mediterranean summer.

You are right, I should have asked better: how much the NAKSA 80 works as class A and how much with the new bias?
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Old 5th March 2019, 10:10 AM   #63
AKSA is offline AKSA  Australia
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Maty,

I have not experimented with the NAKSA, or the new SAKSA, under heavy bias. I have tried it at 150mA, and aside from producing quite a bit of heat, it does sound richer and more scale.

When you do this you increase the range of both outputs on. At 150mA quiescent, I make this range 6Vpp on LTSpice, which corresponds to 36/64=547mW, not a lot of power in Class A, but probably worthwhile for very quiet listening. Certainly the transitions are very smooth and well controlled.

Hugh
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Old 5th March 2019, 10:15 AM   #64
maty tinman is offline maty tinman  Spain
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Only one more question.

From NAKSA 80, brochure: "300VA toroid with two 30 Vac secondary windings"

How much higher could the voltage be? With (or not) the N80 heatsinks.
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Old 5th March 2019, 10:20 AM   #65
maty tinman is offline maty tinman  Spain
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I must be blind: "Do not exceed 45 volts (42 volts recommended)"
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Old 5th March 2019, 09:53 PM   #66
AKSA is offline AKSA  Australia
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Maty,

I don't like to go over 45V on these 280W mosfets. Reason: the heatsink needs more capacity at 50V, and I have some belief that stability and longevity is superior under 50V rails.

But they are very low Rdson, around 100 milliohms, so they really do drive rock and orchestral music very well.

Hugh
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Old 31st May 2020, 06:35 AM   #67
Rhythm Willie is offline Rhythm Willie  Australia
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Just looked at this thread again as I just had the lids off my Soraya's to replace a fuse (it was only 3amp, must of run out of 7.5amp ones the last time I changed it), anyway, decided to check the bias which I originally set at 65mv, both channels were at 60mv, just wondering again what I should try as the heatsinks never even get warmish running Vaf I93's at high levels
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Old 31st May 2020, 09:38 AM   #68
andyr is offline andyr  Australia
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Quote:
Originally Posted by Rhythm Willie View Post
Just looked at this thread again as I just had the lids off my Soraya's to replace a fuse (it was only 3amp, must of run out of 7.5amp ones the last time I changed it), anyway, decided to check the bias which I originally set at 65mv, both channels were at 60mv, just wondering again what I should try as the heatsinks never even get warmish running Vaf I93's at high levels
Just checked - I use 7a fuses on my Soraya monoblocs.

Yes, as you increase bias current - the heatsinks get warmer.

But if yours "never even get warmish " ... I would thoroughly suggest increasing the bias reading to 120mV.

Andy
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Old 31st May 2020, 10:25 AM   #69
AKSA is offline AKSA  Australia
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Yes, Dennis, Andy is correct, and his advice excellent. Increase the bias to increase the Class A output, up to 120mV.
You could increase the fuses to 10A each.

Cheers,

Hugh
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Old 1st June 2020, 01:32 AM   #70
Rhythm Willie is offline Rhythm Willie  Australia
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Thanks for the advice Andy and Hugh, I will head to the Aztronics to get new fuses, so does the increase in bias also increase current through the fuses?

I was also using some Holton based monos for bass, but I decided to tidy up my system and reduced wiring/clutter and have happily settled on the Aksas for full duties, I am tempted to maybe update the Holtons, they both have 400VA 45v toroids(which I would like to recycle), Hugh what would you suggest I purchase Aksa based these days that would suite?
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Increasing the bias current on my NAKSA80s & Sorayas ... seems to be a good thing!!Hide this!Advertise here!
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