Garage system

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Nobeone
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Re: Garage system

Post by Nobeone »

The difficult thing is knowing quite how to set 7.2mV when you can only read to 1mV resolution and are accurate to 2mV :D
That 10mV cold reading could be a just a touch under 8mV which would be close to spot on. Warm readings are a whole new thing.
hifiaf
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Re: Garage system

Post by hifiaf »

Right -- wait for a decent multimeter before taking the next step in biasing! Well, I'll need to get one anyway, to check the bias on the Paradise. Any recommendations for models?

The buzzing has indeed decreased. Not gone, but I think closer to Nait 2 normal.

Thinking back on this, there has always been a channel imbalance issue with this Nait. (It's been a few years since I've used it regularly. I didn't bring it with me when I lived in San Diego, and since moving back here I've barely used it.) I used to use the balance knob to get the two channels equal in volume. So I bet I've had this bias issue the whole time I've owned it (assuming bias affects channel balance, that is!). Those pots are very, very sensitive -- I wonder where along the line this one got its quarter-turn counterclockwise...

Just listening through the Missions for now... Will get it back attached to the Yammies for listening tonight...
Last edited by hifiaf on Thu Jun 18, 2020 6:00 pm, edited 3 times in total.
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YNWaN
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Re: Garage system

Post by YNWaN »

I think Fluke are the most renowned brand but other than that I don’t know.
Mark
Nobeone
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Re: Garage system

Post by Nobeone »

The balance pots are poor on Naim gear :D (used another word but thought Andrew would dislike my blunt term ... I'm trying to be good Andrew, I promise) It is not unusual to have the balance pot over at say 30 degrees to get the balance OK.

The bias is another matter, I don't think it would effect balance particularly, but too low and you get increased distortion, too high and you get increased distortion, and way too high like that was, well, dunno, and could end in thermal runaway and destruction.

There are all sorts of noises that are normal, but it should not have audible buzzing coming from the speakers while playing music:

The transformers hum at 50/60Hz, with dc on the mains the really hum. Torroidal, and large ones, are all susceptible to some extent, some worse than others, mechanical mounting can help, a dc blocker can stop the really nasty stuff.

Unterminated inputs will hum at 50/60 Hz, but the CD input should not be as bad, and if you short the unused input then it should not be as bad, that is just pick up on the long tracks inside the PCB running right next to the main PSU, not a great piece of design, but in budget integrated amplifiers, they all seem to do it so some extent or other!

Yes I think a meter with a mV range so you can set it accurately would be a good thing. Next step I would suggest, if all seems OK, is not push it and go for high listening levels until that bias is set to 7.2mV from cold on both channels! If it is a bit high, which it seems to be even at 10mV from cold, then going for loud for a long time might overheat the poor thing. You could play safe, get it cold, set it to 7mV both channels with your current multimeter, wait until you get a new better meter and then check it again, from cold.
hifiaf
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Re: Garage system

Post by hifiaf »

Okay, good advice -- I'll get it cold and back down to around 7mV with the current gear and order myself something decent.

The cheaper Flukes are about $100 CDN, not so bad. They go way up from there. I seems like the question is whether one needs "True RMS" for non-linear loads. Si will know!
Nobeone
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Re: Garage system

Post by Nobeone »

Yes ask Si for a recommendation, on my part I would just suggest some test probes so slips are less likely and less likely to cause damage, we have all been there, anybody that hasn't, hasn't done any work ;)
hifiaf
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Re: Garage system

Post by hifiaf »

Okay, 0.007V on my meter from both channels on a cold start. I can't imagine how fine an adjustment would be needed on those pots to get to 0.1mV increments -- even a tiny, tiny turn could move things my 2-3 mV. But consistently even now. I'll let the Nait warm up in its case for a bit (shouldn't take long -- 30C here today) and do some listening later...
hifiaf
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Re: Garage system

Post by hifiaf »

Are these the kinds of clips you use, Will?

https://www.amazon.ca/Uxcell-a11031200u ... 43&sr=8-18
Nobeone
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Re: Garage system

Post by Nobeone »

That sort of thing can help, yes, power off, clip them on, connect up leads to meter, power on!

You can also get shrouded probes, they just have a little contact area in a shroud so you make contact on a leg but if you slip, the shroud protects you. I'll try an find an example.

A new meter may come with some or all of these ...

... hmm can't find any quickly, the insulation goes right down to cover the tip, except there is a "v" shaped cut back up to the tip, this allows you to put it on a leg and get a good connection but if you slip, the insulated side hits the next component along.
MTPapaDan
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Re: Garage system

Post by MTPapaDan »

YNWaN wrote: Thu Jun 18, 2020 5:57 pm I think Fluke are the most renowned brand but other than that I don’t know.
I was a Test, Measurement, and Diagnostic technician in USAF back in the day and we used Fluke meters to calibrate and repair lots of other electronic equipment. IMHO you can't get better though they may not be the cheapest. Remember to use a fresh battery and zero the meter. All our readings were taken with all the equipment warmed up fully. However, ALL digital multimeters have a tolerance, generally plus or minus 1 on lowest digit plus a low percentage of reading. Generally, less than .5% on the best meters. This is an extremely low value when you talking about 22mv. Less than the lowest digit. It does no good to use a nanovoltmeter if the potentiometer is very sensitive. You can't physically turn it .01 volts (actually .00 to .02 tolerance). You want better than that buy a 20 turn pot of same value. I'd say it isn't that important or the engineers would have used a better pot.
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