It probably just stated the conditions required, warm up, no audio and no load attached.
As long as the current is within range and does not go to high when the amp is hot then it should OK.
As long as the current is within range and does not go to high when the amp is hot then it should OK.
No, the loading of the DVM is far to high (about 10 megohms per volt) so it has no practical effect at all.
Not in the scheme of things 🙂 Look at any silicon transistor data sheet and the maximum junction temperature will be in the 150 to 200C range.
Providing your idle current is maintained at the correct value then the heat produced is what is normal for that amp and the heatsink capacity.
If the idle current is increasing with temperature (and this is always the big big problem) then the amp is running hotter than it should.
You could keep the 1 ohms in circuit and add a strand of wire across them. Play it loud so it gets really hot and then quickly turn the volume down, remove the speakers, snip the wire and measure the value.
Providing your idle current is maintained at the correct value then the heat produced is what is normal for that amp and the heatsink capacity.
If the idle current is increasing with temperature (and this is always the big big problem) then the amp is running hotter than it should.
You could keep the 1 ohms in circuit and add a strand of wire across them. Play it loud so it gets really hot and then quickly turn the volume down, remove the speakers, snip the wire and measure the value.
mmm got a problem with the neighbours in so i cant turn it up too much at the moment.
the heatsink is 57c, that seems high to me, but others may say this is ok?
the heatsink is 57c, that seems high to me, but others may say this is ok?
back in the old days, were speaker mopre generaly 4ohms rather than 8ohm? reason i ask is the impedence switch on the back says 8 ohms or
4 ohms(normal) most of the old amps say the same thing.
I'm not sure tbh. Lower impedance speakers all things being equal can be more efficient for a given level of signal voltage but at the expense of drawing more current. That is why car speakers tend to be low impedance because of the limited supply voltages available.
The switch on the NAD changes the voltage tapping's on the transformer secondary to give slightly lower supplies for 4 ohm speakers which gives the amp an easier time.
Its probably no bad thing to run it on 4 ohm anyway because I doubt you will ever come close to needing the full output voltage at the speaker terminals.
Also remember that speaker impedance isn't quite the same as 'resistance'. An 8 ohm resistor draws the same current no matter what the frequency of the signal. It is a constant 8 ohm load whether it is DC or whether it is 1Hz, 100Hz or 100kHz. A speaker has a different 'resistance' or impedance that depends on the frequency of the signal.
My B&W703's are nominally 8 ohm according to the manufacturer and yet the impedance dips as low as 2.7 ohms from memory. So that really classes those as 'tough' load although in practice it is not a problem.
The switch on the NAD changes the voltage tapping's on the transformer secondary to give slightly lower supplies for 4 ohm speakers which gives the amp an easier time.
Its probably no bad thing to run it on 4 ohm anyway because I doubt you will ever come close to needing the full output voltage at the speaker terminals.
Also remember that speaker impedance isn't quite the same as 'resistance'. An 8 ohm resistor draws the same current no matter what the frequency of the signal. It is a constant 8 ohm load whether it is DC or whether it is 1Hz, 100Hz or 100kHz. A speaker has a different 'resistance' or impedance that depends on the frequency of the signal.
My B&W703's are nominally 8 ohm according to the manufacturer and yet the impedance dips as low as 2.7 ohms from memory. So that really classes those as 'tough' load although in practice it is not a problem.
Do like I do when power testing amplifiers with music. Use dummy loads on both channels, and listen through 1k ohm resistors in series with the speakers (or use the headphone jack). You can then turn it up to distortion for as long as you need to while monitoring for misbehavior. With an amp this small 20 watt resistors are probably plenty. Average power would be around 5 watts per channel, maybe 10 if you’ve got it ‘blasted’. A 6.8 ohm resistor is about the right value, and whether it’s non-inductive or has steel end caps doesn’t matter. You should be able to get a pair anywhere you can buy 2N3055’s. If you intend to play with big amps, get a bunch - so you can series/parallel them. Up to about 70C would be fine when turned up to as “loud” as you would ever want to.
wow 703's they are a great loudpeaker
which version do you have 1's or 2's they are at least £2.5k a pair and are realy good speaker-need alot of room though.
i heard a pair of these years ago in a test studio and i was realy impressed, fantastic rock speaker.I listed to dark side of the moon in the studio, and it was amaizing with the room set up they had.
back in the 80's when i started getting the HIFI bug, B and W were a real leader and i always toyed with the idea of getting a pair, but never did.
I ended up being a kef man and had carina 11's,concords and eventualy a pair of kef 105/3 which i saved for a whole year to get, but i could never do them justice as my rooms were always too small, i had these paired with a marantz PM 500,eventualy sold them on.(my brother blew up the marantz and thats when i brought my first NAD 3130)
these days i use fyne audio F303,s and to be fair they are realy good too.They are a bunch of ex tannoy employees who started out on thier own.
if i ever get the money and a room big enough id like the the fyne audio F1-12, but i think that will just remain a dream(unless i win the lottery lol anyway thats prob enough of the PP HIFI history lesson)😀
The 703's are quite old now, I must have had them 17 years or so I guess. I'd imagine they are Mk1's in fact I didn't know there was a Mk2 tbh.
I'm not particularly well informed on speakers tbh, in fact I've not even heard of Fyne but I'm just looking at a review of them... they look good 🙂
I'm just trying something with LTspice which you might like, if it works that is... and the 703's feature in that.
I'm not particularly well informed on speakers tbh, in fact I've not even heard of Fyne but I'm just looking at a review of them... they look good 🙂
I'm just trying something with LTspice which you might like, if it works that is... and the 703's feature in that.
i had an idea after you talked about the MP3 bit and playing it back in spice
would a recording from say my turntable onto cd writen on my cd player play back in spice and show any distortion?
would a recording from say my turntable onto cd writen on my cd player play back in spice and show any distortion?
Only if you have a test record with a test tone on it.
Distortion figures can not be derived from music, it has to be a pure tone that is looked at and anything present other than the single tone is distortion. Even if you can hear bad distortion on music, you can't put a figure on unless you look at individual test tones.
Distortion figures can not be derived from music, it has to be a pure tone that is looked at and anything present other than the single tone is distortion. Even if you can hear bad distortion on music, you can't put a figure on unless you look at individual test tones.
Just to add to that, you could play a test tone from a CD player through your real amp and record the output of that. You could then look at the distortion present by looking at the recorded tone and analysing that.
Hmmm... you could try it. Its something I've never done from an analogue source (wow and flutter and so on) but it should be possible to see an FFT (plot of harmonics to see what distortion is there)
We only need a few seconds worth to analyse it.
We only need a few seconds worth to analyse it.
its a radio show broadcast of radio Luxemburg of the night elvis presley died and at the beginning is quite a long single test tone before the broadcast starts so this should do it.
I think I'm misunderstanding what you are trying to do actually. I thought you wanted to look at the turntable distortion.
Is it your amp you are wanting to test? If so we can easily do that. If it is the turntable then you have to work with the recording and record the output of the RIAA preamp to get a usable workable signal level.
Feeding time 🙂
Is it your amp you are wanting to test? If so we can easily do that. If it is the turntable then you have to work with the recording and record the output of the RIAA preamp to get a usable workable signal level.
Feeding time 🙂
That makes it easier. First thing to know is what hardware you have to play a file a test tone back on. You need something with an audio output on it such as a DAC or a laptop. No idea how good a mobile would be tbh. A cd player and a CDR or RW is a good option as well.
Then you need a test file. You can make your own in seconds in Audacity.
This is an old thread but it still covers installing it.
Installing and using Audacity. A get you started guide.
Audacity itself is now here:
Audacity (R) | Free, open source, cross-platform audio software for multi-track recording and editing.
You will also need a dummy load for the amp (just one channel) of a 4 or 8 ohm resistor. It doesn't need be massive wattage but should be at least 2 watt.
You also need to add a divider network across that resistor (so either a preset or a couple of resistors) to attenuate the speaker signal back to a lower level to feed into a PC or laptop to record it. It doesn't need to look pretty, just bits tagged together is fine.
It sounds complicated bit its not, it only takes a minute or two to rig up.
Then you need a test file. You can make your own in seconds in Audacity.
This is an old thread but it still covers installing it.
Installing and using Audacity. A get you started guide.
Audacity itself is now here:
Audacity (R) | Free, open source, cross-platform audio software for multi-track recording and editing.
You will also need a dummy load for the amp (just one channel) of a 4 or 8 ohm resistor. It doesn't need be massive wattage but should be at least 2 watt.
You also need to add a divider network across that resistor (so either a preset or a couple of resistors) to attenuate the speaker signal back to a lower level to feed into a PC or laptop to record it. It doesn't need to look pretty, just bits tagged together is fine.
It sounds complicated bit its not, it only takes a minute or two to rig up.