Says 3Wpc on 33ohm headphone, can this be for real?
Says 3Wpc on 33ohm headphone, can this be for real?
Looks too good to be true.
Search for "muse portable headphone amp" here on head fi, to get impressions of the build quality of their amps.
If anybody wants to mod it, it would be a ok start.
2011 MacBook Pro, into Muse TU-20, into Sony MDR-XD200 headphones
First off, the MacBook Pro already has some pretty good sound coming out of the headphone jack...
With regards to the TU-20
The noise floor is pretty substantial, I can hear the 60Hz hum just past the 3-4 volume level, and as I turn up the volume just past 5 I start hearing all sorts of buzzing.. Maybe a better 12V power supply would fix that.....
I analyzed the power supply and it had a nice noisy ripple at about 71kHz.. This is typical of most SMPS but it comes out in audio.. Maybe there's cleaner 12V supplies that this can work on.
And the 6V tube heater supply had a nice 1.2V ripple of around 20kHz, but that's also typical of those cheap little LM7806's... more filtering is in order in my opinion.
definitely does Not work with 12AX7 tubes :-( so much for Tube Rolling if you only have 12AX7's.
Does not sound all that much better, and sadly I don't have my tube ears all tuned up so it's hard for me to notice the subtleties but it does amplify and sort of sound beefy when it's not quiet.
Maybe on a different listening environment the subtleties can be noticed but in general I think it looks nicer than it sounds and I'd rather spend the $80 or so on a very clean solid state headphone amp.
So I checked out the power supply..... I'm here in the US of A and the power supply out of the box was a 240V european type SMPS with a little adapter for 120VAC.
The measured voltage of that supply was 11.88VDC; it's supposed to be 12V at 0.5A
So then I picked out a 12V 2.5A SMPS from my box of goodies and I measured it at 12.28VDC (With a FLUKE Multimeter!).
When I plugged it in, the noise floor reduced significantly but there was a hum every time I touched the volume pot???????
When I measured the current.... even with no input and no load (no headphones) it drew 0.545A!! So, the SMPS that was given with the unit is under powered and noisy as heck!
I'm gonna see what I can do to clean it up and hack it up to something decent... After all, it is in a nice metallic box!!
I just received mine from China. Muse TU-20 EH6922, but I will not touch it until the April 6th, for I am on the road. I have another 12 Volt supply for it too. A few decent 12AU7 tubes too, but before I do any tube rolling, I plan on cleaning up some of the circuits, maybe replace a few caps and other things. I will figure it out when I start measuring and playing with it.
Listening as I was burring the Muse TU-20, I changed the op amp again to a Dual Brown dog adapter with two LME49990. I adjusted the bios, by setting the volume to max, with a 32 ohm load. Played a 1khz -26dB sign wave. Then adjusted both channel outputs at the op amps to 6.30 Vdc. Sounds good, haven't done anything with rolling tubes, but I did add a case ground to the board, to kill the buzz.
It sounds good for an inexpensive amp. Will play more later. I only have 24 hours of burn in, should have at least 48hrs before playing.
The LME49990s are very fast and accurate, lack warmth but are very crisp when it comes to high end. I think I will attempt to soften them with the tube I select, after a good burn in. All my op amps and tubes I will roll have been burned in, they are parts from other rolling projects.
Received mine today. With original wall wart there was mains hum and a whistling tone (around 1 kHz or so). Tried a few other mains adapters and one simple, switched one got rid of hum and noise. The amp is powerful, drives my AKG K501 from a Sansa Clip well, but distorsion is noticable at loud levels. Need to listen some more to determine if this is critical (piano etc), or just flaws in the recordings revealed by the high resolution K501. Some harshness, but that may soften with time.
awesome work Bearington.... however for a $100 and all that work I don't think it's worth it...
I also purchased this little beast:
It's about $50 and I had to troubleshoot the transformer to make sure I got the right voltages, but at least it came assembled...... MAN this thing sounds AMAZING!!!! much better than "The Quickie" which was $100 and I had to assemble the whole thing and it didn't even come with a box!!!
Look forward to the photos with instructions on where to measure the bias. I've been listening to the amp a lot this weekend and it really shines with my AKG headphones, especially the K401 which I haven't listened to much since I bought it. It's dynamic, full-blooded and with an amazing sound stage. The upper mids are a little bit forward (quality of the headphone), but apart from that it sounds very realistic.
Also tried some orthos but I guess they craved too much current - started to clip with volume set at 12 (with a rockboxed Sansa Clip+ at 0 level). The AKG is 120 ohms and probably suits the amp better.
Is this the adapter you used, and does it fit in the box?