That's exactly what I'd expect. Most DMMs aren't good enough to resolve the 50-100 uV of typical output offset on the Modulus-series amps.
If you have money burning holes in your pocket, I'd look at a HP/Agilent/Keysight/Whatever-Their-Name-is-This-Week 34401A. It's a 6.5 digit bench top multimeter. It'll set you back about $1200. Nice meter. I have two of them that I picked up calibrated for dimes on the dollar during the recession. The HP 3478A isn't bad either, though for measuring on tube circuits its 300 V limit can be annoying. That one is more like $150. Get a calibrated one if you go that route.
Seriously, though. You're trying to invent problems where there are none. Everything you've reported so far indicates that your amp works as designed.
That's within the measurement tolerances of your meter.
If you don't have a scope you can't look at the clipping behaviour. However, as I pointed to earlier you're creating problems where there are none. Plug the amp in and enjoy the music.
...unless you're trying to learn how to test an amp, in which case you should get a scope and learn how to use it.
You can kinda/sorta test clipping my measuring the gain. You did that earlier. Input voltage: 0.102 V; output voltage: 2.08 V. Calculate the gain (Vout/Vin). Crank the input up to 0.2 V. Measure again. Draw gain vs input voltage. Or Vout vs Vin. You'll find that once you reach about 900 mV on the input, the output no longer tracks the input. I.e. as the input voltage is increased, the output voltage no longer increases. That's hard clipping. To look at the clipping behaviour, look at the output on a scope.
I'll drop off for a couple of weeks. I hope you've plugged the amp in and taken a listen by the time I come back.
Tom
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Hi,
I use Fusion 360, it's free for hobbyists / non-professionals although that's not obvious from the landing page - if you download the demo version and read through the license info you can apply for a license annually. It's fantastic, I've used it to model the whole amp chassis, the top and bottom panels are being laser cut and the front panel and volume knob are being cnc'd - I just sent the manufacturers STP files from fusion.
Finally Done!!
Hi,
Just a quick update... I finally finished the amp today and gave it a good listening to. Very happy with the results, without further measurement I can't say for sure how good it is but in comparison with my UCD180 set-up it certainly stands it's ground sounding smooth, controlled and open. I wan't sure whether it'd have enough power but it's loud enough through my Seas A26 speakers (88dB sensitivity).
Starting on a phono stage next, thinking of using the LME49710... I'm storing up all my dumb questions to start another thread on that.
Here are a few pics...
Hi,
Just a quick update... I finally finished the amp today and gave it a good listening to. Very happy with the results, without further measurement I can't say for sure how good it is but in comparison with my UCD180 set-up it certainly stands it's ground sounding smooth, controlled and open. I wan't sure whether it'd have enough power but it's loud enough through my Seas A26 speakers (88dB sensitivity).
Starting on a phono stage next, thinking of using the LME49710... I'm storing up all my dumb questions to start another thread on that.
Here are a few pics...
Attachments
I would recommend to use inline fuse holder with solder lugs instead of screw type to prevent accidentally pulling live wire out of the fuseholder.
Trickiest bit with the heatsinks was tapping the M3 holes in the top and bottom - I ended up buying a pillar drill to do the job, was fairly straight forward after that.
Chassis top and bottom covers were laser cut by lasermaster.co.uk, not as expensive as you might think; the front panel and volume control were cnc'd, they were a lot more expensive but I managed to get a decent price from starrapid.com, brilliant quality.
Chassis top and bottom covers were laser cut by lasermaster.co.uk, not as expensive as you might think; the front panel and volume control were cnc'd, they were a lot more expensive but I managed to get a decent price from starrapid.com, brilliant quality.
Thanks, that would probably be better; I'll carry on looking for something suitable. Think I might buy these ones anyway and see how much strain they gan take.
I wholeheartedly agree. I use my pillar drill (aka drill press on this side of the pond) all the time.
Tom
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