[Terja]

Just recently got this amp and have read the woes and wows about it  -- from my view the wows far outweigh the woes. I have the version with the internal mini switch for selecting headphone impedance (yes it's in there, lol). Anyway, I'm using this mostly with headphones (Hifiman HE-500s - 38ohm). While experimenting I discovered one thing -- THE ELECTRONIC SOURCE OF THE MUSIC MAKES A DIFFERENCE IN WHETHER THE AMP HUMS OR NOT.
 
i) Playing lossless tracks from my iPod into the amp via headphones produces no hum or hiss from the amp. It is black as night and quiet - a zero hiss background.
 
ii) Playing tracks via computer usb/dac or spdif picks up background interference. It is definitely coming from the computer NOT the amplifier. I even tried different DACs with essentially the same result. Somehow or other the amplifier is very sensitive and picks up electronic interference - I don't know why. With the HE-500s it is barely noticeable, you can just hear it when there is no music playing. With Grados (SR80s - 32ohm) the hum is more distinct - but it's funny - the Grados sound just fantastic with the amp. The mini switch is initially set for low impedance cans and it does reduce the interference.
 
I do not think this hum/hiss is mostly to do with tubes but rather with the electronic source of the music. I wasn't that surprised when I came across BmWr75's post -- see highlight below. Granted there are other factors, eg 600ohm headphones, but I think it has something to do with the initial source.
 
Anyway, just my 0.02 -- it may be worth considering the initial source as contributory to distortion issues and not the amp itself.
 
All that aside this is a fantastic amp, looks great too. The fact that I can drive a Hifiman phone with it is a real bonus. It sounds very detailed and warm (oh dang! maybe I'm just feeling the heat from the tubes). I've rolled some Groove Tubes power tubes in there and they sound much better than stock. Oh yeah, another thing, that mini internal switch in there is like a mini EQ

(don't know whether it's worth cracking the base open for though!).
 
 
Quote:

I've never had a hum issue with this amp, but have been using it with 600 ohm Beyer cans.
 
Just for grins I decided to see if the amp hums with high sensitivity speakers. Bottom-line - this specific amp is not hum prone with speakers.

To summarize my tube comparisons:

Amp = Musical Paradise MKII
Source = iPod playing Apple Lossless files via an HRT iStreamer DAC
Speakers = Klispch KLF-20s (100 dB efficient) with Crites titanium tweeters and Crites crossovers

Note: the hum heard on two sets of tubes below is not dependent on volume setting. The barely audible hum is the same an min and max volume.

Sylvania 6SK7GT - most hum of any tubes tried, but would not be noticeable from >3' away from the speakers and acceptable to my ears.

Tung-Sol 6SK7GT - less hum than Sylvanias. Sounded good.

Red can 5693 - no hum, noticeably more gain that the other tubes tried, sound great driving the speakers.

JAN Phillips 6SJ7WGT - no hum. These are the best sounding tubes I've found when using 600 ohm headphones. Was not as impressed with them driving the speakers, but still sounded good.

 

[Terja]

80 - 90% of the problem solved!
 
I had a laptop cooler I was running via one of the USB ports - I unplugged it and now the HE-500s are dead quiet via the amplifier. I can't believe how much distortion that cooler was adding to my usb channel - shikes! I also tested the Grados and they still pick up some distortion but it is greatly reduced. Grados just don't seem to mesh well with the MP-301 but the irony lies in how great they sound out of it. Anyways, there is something to cleaning up the audio input you feed into this amp. It seems to need a very clean channel, or perhaps looked at another way, it is extremely revealing, unabashedly so. So there ... a few of my pebbles in a row!

 

[Terja]

last 20 - 10% of the problem eliminated!
 
The last bit had to do with the ground line I was feeding into the amp. Turns out it's not as clean as I thought it was.  Lol .. without it the amp is dead quiet while playing via usb/dac. My Grado SR80i's are finally quiet when matched with the amp and they sound really really good; not as good as the HE-500s but for a seventh of the cost they sound amazing.
 
This is a great amp, its unfortunate that out of the box it does present a challenge to get it to play nice with all kinds of set ups. For example if you were matching it with say an iPod or similar source you would not encounter problems at all. Also higher impedance cans seem an ideal match to the amp and not so much low impedance cans like mine. I'm just glad I've solved the set match-up and can finally sit back, enjoy and take it all in

! If you have the amp or are thinking of getting it (a fantastic medium powerful tube amp at an affordable price - what's not to like) don't give up on it. There are clues about solving problems if you come across them. Maybe tubes could be the issue for you but they were not for me.

 

[soundoff88]

I didn't see anyone mention about measuring the noise at the speaker terminals. Did I missed it?

 

[Terja]

There were some users complaining of hum/noise while using speakers. Do a search of the thread.
 
Just recently I tried replacing the stock driver tubes with NOS Philips 6SJ7. These tubes produced a faint hum at the speaker terminal via my headphones which is how I've been using the amp (with resistors). I do not think the hum would be as noticeable through regular speaker as opposed to headphones. I have since replaced them with the stock tubes which do not produce hum/noise. It seems tubes may also be part of the equation, depending on what you use. The stock driver tubes are well-matched to the amp, some users found this to be true too and recommended keeping them in.
 

 

[soundoff88]

numerous posts mentioned noise with speakers but no one measured it. it is an easy thing to do. I do own this gear thus the question.  

 

[Sniper1]

This amp was recently revised to MK3.
The hum noise problem seems to have been mostly corrected. However, you need to plug in with 24ohm or + phones.
http://www.musicalparadise.ca/store/index.php?route=product/product&product_id=54
BTW, pre-orders gets 10% off and we possibly have up to mid- or end-august 2012 to benefit the discount.
 
Here is the list of improvements:

• The power transformer is upgraded. The EI core is 30% larger to lower the working temperature. The potting material is upgraded to higher grade epoxy to improve the strength and heat resistance. More precise user configurable input voltages: 110V, 120V, 220V, 240V.
• Add KT88 and 6550 power tube support.
• The case construction is improved to be stronger and much easier to access when service or upgrade is needed. Since the steel is thicker, and the case is a bit wider, the background hum is much lower than the MK2 version when using low impedance headphones. It is hardly noticeable now.
• The circuit is improved to further lower distortion and increase the stability when using some lower quality power tubes.
• High quality screw-in connectors are used on the PCB boards, so the PCB can be removed much easier without soldering when service or upgrade is required.
• Output transformers are improved with better construction to improve low frequency response.
• Total power supply filtering capacitance is increased by 60uf to further lower background noise.

 
 
 

 

 

 

[popa]

Garry Huang who designs these amps, mentioned in a correspondence to me that Skylab will be reviewing this amp also.

I own three of his amps and I am looking forward to this review by Skylab.

 

[mrarroyo]

Darn, so tempted to buy. I have listened to some of the Musical Paradise units and they sound very nice at a good price point. Sure hope this further improves the sound quality.

 

[wotts]

I can totally understand that. My coworker bought my MK2 because he just loved the sound and I miss it. I'd love to give the new amp a listen.

 

[Rockyhill]

I'm looking forward to reviews of the MK3, especially in light of my poor experience with the MK2.

 

[Sniper1]

I should receive my MK3 (+EL34's) either today or next week. Will also get next week my 1st decent pair of closed headphones; ATH-M50s
However this will be my 1st tube amplifier. And the only other headphone amp i have to compare it to is the PA2V2. But i also have 18ohms earbuds; Klipsch image S4... That will make an interesting test to assesss background hum.

 

[Zerogravity1]

I have had this amp just about a year now! I measured the noise from the speaker with my SPL meter, pushed almost up against the drivers and got a reading of -6 db. When I press my ear up against the speaker, I can barely hear anything and this is when music is paused and the volume of the amp set at its highest level! The noise with Headphones, is just unacceptable and the volume needs to raised quite a bit just to drown it out! I certainly hope Gary's upgraded amp eliminates this issue, however, it shouldnt have been in this amp in the first place and certainly more R&D was needed before the MK2s release. 

 

[Raser]

Quote:

I should receive my MK3 (+EL34's) either today or next week. Will also get next week my 1st decent pair of closed headphones; ATH-M50s
However this will be my 1st tube amplifier. And the only other headphone amp i have to compare it to is the PA2V2. But i also have 18ohms earbuds; Klipsch image S4... That will make an interesting test to assesss background hum.

Please post your impressions. The headphone section is propably good (at least at the mk2 version it was good). And i think that this one could pair well with my full range speakers

 

[lbhajdu]

I do not believe I have this amp however I have an amp which looks remarkably close to it. I won this amp at a head-fi N.Y. meet a few years ago for about ~$100 and I think it was just about the best deal I ever got. It came with 6P13P power tubes in the power section which I have replaced with 6p13s (got some $3/each on e-bay). The 6P13P was red plating but the 6p13s does not.  And it uses 6J8P for the input tube though I replaced this with a Philips 6SJ7. The amp does look very close to the earlier models of this amp right down to having the same CLC filter inductor in the middle.  Pictures can be found here (not my own pictures):
 
http://195.84.101.101/~goranl/projects/nad_stereo/tubeamp/
 
However I do not in fact believe it to be the same amp. I know this because the [size=10.5pt]MP-301 states [/size]on its website that it has zero negative feedback and I know that my amp does have feedback, which is applied by taking signal from the output transformer via a 47K resistor and feeding it to the 2k cathode bias resistor of the 6sj7 / 6J8.
 
I use this mostly as a speaker amp for my Fostex 6” speakers (Tekton Design) of 93dB/w sensitivity.  The only way 60Hz hum can be heard is if you put your ear one foot away from the speaker. However I do, do this when I am sitting at my computer desk and turn the volume down really low. This is one of the few amps that still sound good when you turn down the volume.  I prefer this amp to my 6SJ7 -> 300B amp which sounds much darker. The 6SJ7 -> 300B amp is however dead quiet. This is most likely because even though it uses the same input tube (6SJ7) it has DC rectified filaments.  It seems a fool's errand to try and keep swapping tubes until you find one where the filament sits just perfectly to cancel the 60Hz buzz when you can just use DC. I am not sure which percentage of the buzz comes from the heater as compared to ripple on the high voltage lines. I am working on other things at the moment but one day I might build myself an external power supply for this amp, if correctly done I am confident it can be as quiet as the grave.  It would need a four pin plug carrying:
 
+330VDC@300mA (tube HV)
+3.15VDC@6A (fill +)
-3.15VDC@6A (fill -)
GND
 
This is at the moment a pipe dream given other projects on my plate.
 
An actual test I will be trying is to replace the input tube 6SJ7 with an EF86. I have seen adapters for this however they were pricy. So I have ordered a 9 pin socket and an 8 pin tube base on e-bay and I’ll make my own adapter. I got an e-mail from the socket vender saying it’s going to take 4 weeks for them to ship to me. It may have more buzz because my understanding is that the EF86 has more gain, but I guess I’ll see when it arrives.
 
Last summer I swapped this amp out for a class-d amp because of heat. I’ll most likely do that again this year and forget about it for a few months.
 
Sorry that this is getting a bit diy,
Leve