[Greeni]

 
Quote:

Thanks for everyone's input - this thread should get interesting as these units start shipping.
 
For those who have rolled their tubes has it addressed some of the hum that several initially mentioned?
 
Also,  who is a good source for the Tung-Sol 6SD7GT  - I also am new at this tube rolling thing and can't seem to find them online [maybe I am not searching for it properly????]
 
Greeni/Raul - what headphones are you using? 
 
 
Thanks all.

Hi Monday
 
I am using mainly the Sony MDR 7506 with the amp which I found hum least and sound tightest. The other phones I have on hand are more expensive than 7506 but they are all very efficient and they hum with the amp, plus they do not sound as tight.
 
I found that the hum seem to have been reduced after some use. It is taking a longer time for run-in because the amp runs hot and I am weary of letting it run-in un-attended. You certainly cannot file a claim in China with such hazards. Also my Freudian superego is taking a toll on me and making me feel guilty of being not environmentally friendly in generating those fleeting watts.

 
 

 

[Skylab]

6SJ7 tubes can hum like beasts at first, if they are true NOS. Sometimes takes 20+ hours to quiet down completely, and during the first 10 hours the hum/buzz can be so bad it's basically unlistenable. Strange behavior - it's the only tube I know that behaves this way. But it was pretty consistent for me in using a lot of different 6SJ7's in the Darkvoice 337.

 

[Rockyhill]

 
Quote:

 

Hi Monday
 
I am using mainly the Sony MDR 7506 with the amp which I found hum least and sound tightest. The other phones I have on hand are more expensive than 7506 but they are all very efficient and they hum with the amp, plus they do not sound as tight.
 
I found that the hum seem to have been reduced after some use. It is taking a longer time for run-in because the amp runs hot and I am weary of letting it run-in un-attended. You certainly cannot file a claim in China with such hazards. Also my Freudian superego is taking a toll on me and making me feel guilty of being not environmentally friendly in generating those fleeting watts.

 
 

Greeni - what tubes are you using?
 
I rationalize keeping the amp on (while I'm at home) by treating it as a heat source!
 
Any comments on my prior post about the RCA 6SD7GT with significant hum? Only been running a few hours so I'm hoping that will diminish with use. Also, these RCA are very microphonic. If I tap the amp, I can hear that through the speakers. Too bad because they sound the best out of what I've used (stock and Tung-Sol).
 
 

 

[Raul]

 
Quote:

6SJ7 tubes can hum like beasts at first, if they are true NOS. Sometimes takes 20+ hours to quiet down completely, and during the first 10 hours the hum/buzz can be so bad it's basically unlistenable. Strange behavior - it's the only tube I know that behaves this way. But it was pretty consistent for me in using a lot of different 6SJ7's in the Darkvoice 337.

As my RCA 6SJ7 aren't NOS, but used, maybe this is the reason I don't hear any hum in mine.

 

[Rockyhill]

Mine are definitely NOS. The tube paper sleeve says something like "This package used for wartime purposes"

 

[Monday]

"can hum like beasts"
 
don't know why that line conjures such visual imagery?  - maybe too much Maurice Sendak as a child.  But it is nice to know that is normal and tones down after burn-in.  Thanks Skylab - and others for sharing.
 
I think I'm going to go ahead and try this little guy - the first one seemed to be well received and the mkii sounds like it can only be better [at least on paper - which I know is a risk].  But hey at 250 it seems worth the experiment.
 
Keep on burnin' in those tubes!!

 

[Greeni]

 
Quote:

 

Greeni - what tubes are you using?
 
I rationalize keeping the amp on (while I'm at home) by treating it as a heat source!
 
Any comments on my prior post about the RCA 6SD7GT with significant hum? Only been running a few hours so I'm hoping that will diminish with use. Also, these RCA are very microphonic. If I tap the amp, I can hear that through the speakers. Too bad because they sound the best out of what I've used (stock and Tung-Sol).
 
 

Rockyhill
 
Am still using the stock tubes.  Have a very closely matched pair of Tung Sol 6SJ7 coming, brought for $40 over ebay. Your comment makes me wonder if I should have gotten the RCA instead. What exactly did you found the RCA  better than Tung-Sol ?
 
Yeah I guess it would be nice to lay your hands over the transformer in Winter times and listening to Christmas songs.
 
If microphonic is the issue, drop a note to Herbie audio and see if their ultrasonic tuble dampers could help.
 
http://herbiesaudiolab.net/tube.htm
 
This discussion is fast turning into a tube rolling thread.
 
It always happen like that. Just when you are telling your wife how good you are at buying a China amp for $250 and not the other expensive amp, there comes the inevitable Tung-Sol, then RCA, tube dampers, and may be power cords...and before long you realised that the spending is much more than you budgeted.

 

[Rockyhill]

 
Quote:

 

Rockyhill
 
Am still using the stock tubes.  Have a very closely matched pair of Tung Sol 6SJ7 coming, brought for $40 over ebay. Your comment makes me wonder if I should have gotten the RCA instead. What exactly did you found the RCA  better than Tung-Sol ?
 
Yeah I guess it would be nice to lay your hands over the transformer in Winter times and listening to Christmas songs.
 
If microphonic is the issue, drop a note to Herbie audio and see if their ultrasonic tuble dampers could help.
 
http://herbiesaudiolab.net/tube.htm
 
This discussion is fast turning into a tube rolling thread.
 
It always happen like that. Just when you are telling your wife how good you are at buying a China amp for $250 and not the other expensive amp, there comes the inevitable Tung-Sol, then RCA, tube dampers, and may be power cords...and before long you realised that the spending is much more than you budgeted.

The Tung-Sol are a little lacking in low end, but that's only after a couple days of listening. YMMV. The RCA have more low and high end. Overall very nice response (hum not withstanding). I may try some dampers. I'm also interested in the re-issue 5881 output tubes. However, I should probably wait for more reviews. Also, my WAF may start to wane as I buy more stuff!
 
 

 

[popa]

 

Thought I would bring up that I tried the 6SJ7GT. I do not think they were NOS because they were very quite. They looked really old and the paper box fell apart in my hand. I have tried quite a few different power tubes and I tried one that was quite different. It was by REFLECTOR, a Russian tube of coarse. Any it was a 6P3S-E by Cryoset. It actually sounded okay the longer it burned in.The one thing that really surprised me was the amp cooled down. This amp runs awfully hot and with this pair it did not run hot. I have also put in my first MP-301 and sounds even better there. But it also runs cooler. Not sure why. >  Had to up date on Reflector tube. I would not recommend in original MP-301. It did sound pretty smooth and lows and highs were solid. But amp still got awful hot just seem to take longer. My worries came with the driver tubes seem to get hotter and brighter. Maybe nothing, but wanting everyone  to be aware.

 

 

[aajohan]

Probably a noob question (but hey, I am a noob 

):
Can the MP-301 MK2 really drive any speakers properly with only 6.5 W from each channel? I can kinda see from this thread that it can, but how? And how loud could I expect it to drive a pair of smaller, moderately sensitive speakers? (not at all specific, I know - bear with me)

 

[Skylab]

It cannot drive ALL speakers properly.  It can drive MANY speakers to reasonable levels, yes.
 
Speaker sensitivity ratings are generally given as a certain loudness level at 1 watt of power at 1 meter distance.  The latter part is important, as if you are farther than 1 M, you need more power - at 2M, you need DOUBLE the power to get the same volume level.
 
So if a speaker will play at 90dB with 1 W at 1M, and you sit 3M from the speakers, you would need 4W for the same 90dB.  That already is not leaving the MP301 much headroom.
 
So - drive sensitive speakers and don't listen too far away from them, and all will be well.  But don't expect the MP301 to crank out rock concert levels from across a large room.
 
 
 
BTW: my review loaner is here, and I plan to listen to it this weekend.

 

[Rockyhill]

It drives my Realistic Nova 8's (of unknown sensitivity) just fine at low to medium sound levels. (my wife would say it's loud) Room is 16x18-ish.
 
I am still struggling with the burn-in hum of my RCA 6SD7GT. Seems slightly better after ~6 hours... Will run amp all weekend too.
 
I look forward to your review, Skylab.

 

[Canuck57]

I'm anxious to hook the amp up to my vintage 1977 Klipsch Cornwalls, their sensitivity is 101dB @ 1watt/1meter
 
http://www.klipsch.com/na-en/products/cornwall-ii-1-specifications/
 
 
 

 

[maverickronin]

Horns give your pretty crazy efficiency.  Some La Scalas or Klipschorns will probably rock the whole house from one of these.

 

[Canuck57]

Quote:

Horns give your pretty crazy efficiency.  Some La Scalas or Klipschorns will probably rock the whole house from one of these.

For sure, when I had La Scalas, I tired them with a low powered T-amp & the combination was magical!