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PostPosted: Sat Jul 08, 2017 1:49 pm 
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Location: Dawsonville, GA, US
Stevedlu wrote:
I believe it is the input cap going to the choke, I could be wrong. Good to hear you are enjoying your modded 301. Which size Mdorf's did you end up going with?


Based on other posts i did go with the .22's. Reason? I just have some bookshelf speakers. Not the best Sensitivity but about 3 years old. They sound pretty good for what they are. Others noted there might have been some closing of the sound stage, pushing of voices into the background a bit with the .33's so i figured i would swap the .22's for the .33 when i have better speakers. I would like to build a good set of high sensitivity speakers, i just need to find a kit.
Now i barely have to turn up my sub woofer. The range is much better, bass thumps cleaner. Lead guitar sounds in my face! I do have to turn up the volume alot more.
Now, singing does seem to be a bit more in the background. I wonder which cap changes did that? Then again i am used to how bright my system used to be.
The rest of the mods were what was recommended. I want to reread everything and learn more about what each part i swapped out does and how changing the values changes the sound.
See this is what happened when i started rolling tubes. Now i have a shelf full of tubes. :o


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PostPosted: Sat Jul 08, 2017 2:45 pm 
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Location: Layton, UT, US
the vocals will come back once your Mdorfs burn-in. It takes a bit, i switched to the silver oil .22 recently. you can look at my list of changes on pg. 15 to get a better idea of what each change does.


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PostPosted: Sat Jul 08, 2017 3:05 pm 
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Stevedlu wrote:
the vocals will come back once your Mdorfs burn-in. It takes a bit, i switched to the silver oil .22 recently. you can look at my list of changes on pg. 15 to get a better idea of what each change does.


Sweet!
I ran it part of the day yesterday with my FLAC player on repeat knowing caps break in as well. I havnt been able to get back on it since. All we have had is thunderstorms here and i unplug everything until its over.
Today we all went out and i was able to pick up some new LP's. Im dying to listen but mom and daughter for some reason decided to watch tv down in the basement where i lurk.

While i was doing my mods i kept it on your post on page 15. It was nicely detailed listing location of cap to replace and with what value.
Now that i have done the mods i understand it more.
I will probably stick with what i have for now, maybe roll my other tubes again.


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PostPosted: Sat Jul 08, 2017 3:20 pm 
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cap burn-in can be frustrating, it takes a series of constant playing and turn off for settling. Ive heard tubes literally transform right before my ears while burning them in but caps dont really work that way.


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PostPosted: Sun Jul 09, 2017 11:53 pm 
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Location: Chino Hills, CA, US
Hi Steve and/or Peter, I think at least one of you mentioned use isolation transformer. Do you mind sharing what you use?

I've been using a very simple (Cheap!) Furman M-8X2 conditioner with my MP301 connected via Pangea AC-14 power cable. I don't have any problem with it but I'm just wondering if isolation transformer is the way to go. Or perhaps combine them like :

(outlet)----->[Power conditioner]--->[Isolation Transformer]---->MP301.

Bad idea?


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PostPosted: Mon Jul 10, 2017 4:22 am 
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Stevedlu wrote:
cap burn-in can be frustrating, it takes a series of constant playing and turn off for settling. Ive heard tubes literally transform right before my ears while burning them in but caps dont really work that way.


I got a chance most of the day to let things burn in. Last night i spun Queen on the player.
Everything sounded good. It is different. Mercury's voice was a bit more subdued and i turned up the volume to hear him than the chorus came on and about blew me away.
Same with my CD.
6SJ7's have a metal ring around the base. When i touch it while the amp is on i get a loud buzzing sound even with the volume off. I did not before


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PostPosted: Wed Jul 12, 2017 5:10 am 
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Make sure you did the ground lead mod correctly. The resistor goes in series with the ground lead and use the capacitor across the series resistor and you should be golden. If not try soldering the ground lead back where it originated and see if that helps. You might have some strange ground loop issues that we might be able to help out with.

-- 12 Jul 2017 07:11 --

ferdzb wrote:
Hi Steve and/or Peter, I think at least one of you mentioned use isolation transformer. Do you mind sharing what you use?

I've been using a very simple (Cheap!) Furman M-8X2 conditioner with my MP301 connected via Pangea AC-14 power cable. I don't have any problem with it but I'm just wondering if isolation transformer is the way to go. Or perhaps combine them like :

(outlet)----->[Power conditioner]--->[Isolation Transformer]---->MP301.

Bad idea?


That was probably Steve, mine is wired direct to the wall and I don't use a PC or IT in this small system with the 301.

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PostPosted: Wed Jul 12, 2017 7:09 am 
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[quote="petersch"]Make sure you did the ground lead mod correctly. The resistor goes in series with the ground lead and use the capacitor across the series resistor and you should be golden. If not try soldering the ground lead back where it originated and see if that helps. You might have some strange ground loop issues that we might be able to help out with.

I did not see any black/ground wire going to the chassis so i did the mod using the green wire with the stripe coming off the terminal block in the back in front of the plug. I have the cap in parallel with the resistor and that in series with the wire.
I really dont have much noise at all so i might just remove it and see if it clears up the ground issue.


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PostPosted: Thu Jul 13, 2017 6:49 pm 
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Location: Layton, UT, US
ferdzb wrote:
Hi Steve and/or Peter, I think at least one of you mentioned use isolation transformer. Do you mind sharing what you use?

I've been using a very simple (Cheap!) Furman M-8X2 conditioner with my MP301 connected via Pangea AC-14 power cable. I don't have any problem with it but I'm just wondering if isolation transformer is the way to go. Or perhaps combine them like :

(outlet)----->[Power conditioner]--->[Isolation Transformer]---->MP301.

Bad idea?


I use a voltage regulating isolation transformer because I have power that flucuates in my apartment building. I do notice deeper blacks though with the transformer, its a big ball of power and your gear gets first dibs. I hook up my transformer from the wall to my Furman PF pro power conditioner. Id say the power conditioner is the biggest step up, the PF pro has a giant ac filter capacitor in it that makes a huge differancein in the weight and size of sound. If i had to pick one it would be the power factor conditioner over the transformer.


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PostPosted: Tue Jul 18, 2017 10:45 pm 
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Location: Chino Hills, CA, US
Thanks Steve and Peter for your replies. It looks like I don't need to worry too much in the power supply department. I will be on lookout though perhaps a more capable PC comes up in craigslist :mrgreen:


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PostPosted: Wed Jul 19, 2017 1:40 pm 
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WCarson wrote:
6SJ7's have a metal ring around the base. When i touch it while the amp is on i get a loud buzzing sound even with the volume off. I did not before


I did a test with another MP301 that was NOT modified and it did exactly the same thing, Buzzed when touching the metal base of the tube. I think it's safe to say this is normal operation as most of us don't listen to music touching the hot base of a Vacuum tube, LOL

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PostPosted: Wed Jul 19, 2017 2:29 pm 
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petersch wrote:
WCarson wrote:
6SJ7's have a metal ring around the base. When i touch it while the amp is on i get a loud buzzing sound even with the volume off. I did not before


I did a test with another MP301 that was NOT modified and it did exactly the same thing, Buzzed when touching the metal base of the tube. I think it's safe to say this is normal operation as most of us don't listen to music touching the hot base of a Vacuum tube, LOL


Odd. Mine didnt really do that before. I was tapping for microphonics on a new set of 6Sj7 tubes. Its the same thing i did with my last pair, the red can type and a different set with a ring around the bottom. Very slight buzz out of the right side before. Now it sings if i touch it lol. No harm, but im always asking "why?"
That ring shouldn't be connected to any ground at all. Its just clamped around the bottom of the tube.
I checked the pin holes in the socket, all are seated fine.
EM? No i had all the lights turned off. Sounds nice and quiet now too.
Static? Should have discharged with a pop IF the ring even went to ground.
I tried with cheater plug and grounded. No difference.
Next time i dig around in it i will check and see if i missed something but if you say the other ones do it than ok.

What i am really trying to figure out at the moment is just exactly what the 2 caps i replaced on top do. We went from 180 to 470uF. Ive been looking at the simple diagram posted earlier.
What would happen if i changed it to a 330? How would it sound?


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PostPosted: Wed Jul 19, 2017 3:59 pm 
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Location: london, ON, CA
Mine hums loudly if I touch the tube bases, and it always has. The metal canister Visseaux 6SJ7s buzz like crazy when I touch them. Don't all MP-301s do this?


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PostPosted: Wed Jul 19, 2017 6:07 pm 
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Those 2 caps up top are the main power supply filters. The bigger they are the less hum and more power supply reserve you will have for peaks and transients. Making them a lesser value is the same as installing a smaller battery in your car, less reserved power. Bigger power supply filter should net you a blacker background with harder hitting bass.

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PostPosted: Thu Jul 20, 2017 12:05 pm 
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Location: toronto, ON, CA
petersch wrote:
Those 2 caps up top are the main power supply filters. The bigger they are the less hum and more power supply reserve you will have for peaks and transients. Making them a lesser value is the same as installing a smaller battery in your car, less reserved power. Bigger power supply filter should net you a blacker background with harder hitting bass.


And the bigger they are the larger the power surge on start up is going to be -- hopefully within the capacity of the rectifier diodes.


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