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Old 16th November 2010, 06:56 PM   #11
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Quote:
Originally Posted by audiotux View Post
Hi Migkiller ,

for example , a simple Metalloxidschichtwiderstand from Mundorf
MR10 , 22R 2% 10 Watt ca. 1,60€ is okay .
You can see that Resistor on Schuro - Elektronik, Lautsprecherbau, High End-Audiotechnik .
So ask at a lokal Shop in your aera for a 10 Watt Resistor and the
job is done !

Jürgen

Thank for your Help Jurgen! I really appreciate it! I ended up getting a:

MRA-12 22R 1% MILLS
RESISTOR (12 watt.)


I have acouple of other ideas for this phono preamp. If anyone has suggestions, That would be wonderful. Below is what I plan to Mod if I can or if it makes a difference.

Click the image to open in full size.
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Old 19th November 2010, 05:46 PM   #12
toufu is offline toufu  United States
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Here is the schematic for the MS12B. I have one, but the sounds is a little bit too muddy and mushy for my taste (compared to a Pro-ject Tubebox I had and an Aikido phono amp I currently use), I didn't try to modify it, other than changing the stock tubes to NOS.
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Old 19th November 2010, 08:54 PM   #13
Cobra2 is offline Cobra2  Norway
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I had one too. And after checking the schematics, I sold it quickly ;-)

Arne K
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Old 19th November 2010, 10:14 PM   #14
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Quote:
Originally Posted by toufu View Post
Here is the schematic for the MS12B. I have one, but the sounds is a little bit too muddy and mushy for my taste (compared to a Pro-ject Tubebox I had and an Aikido phono amp I currently use), I didn't try to modify it, other than changing the stock tubes to NOS.

Thank you so much. Well for me its all about learning and venturing to the unknown. Great Hobby...I'm having great fun reading about mods with Capacitors, resistors etc..etc.. I used to be a generator Tech for the Army some 20 years ago and used to read schematics like nothing. I was great at it and Its all coming back slowing, very slowly..lol.. this is my first Phono preamp but I'm sure it won't be my last. I'm sure there are way better phono preamps out there for less.. Cheers and thank you again!!
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Old 19th November 2010, 10:59 PM   #15
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Hi Migkiller ,

as the other Forummembers said , there is only little advantage to mod the thingie .
For that money you better invest in a other Phono-Stage .
If Sand is no problem , the simple Salas N J-Fet RIAA is the simplest Phono i can
think of and recommend . I would like to see a PCB for newbees or starters at the
DiyAudio-Shop , maybe in the future the dream come true .

Greetings and enjoy your black disks
Juergen
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Old 12th December 2010, 01:34 AM   #16
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Hi Everyone,

Back again. This phono amp is sounding sweeter and sweeter. I guess it takes time for those Caps to break in. I'm amazed on how the sounds changes when using different tubes. Thanks to Audiotux for helping me with that risistor. I can listen to vinyl for hours and the chassis is nice and cool... I have pairs of 12ax7 and 12au7 tubes coming in next week. Which comes to my second question. GRID STOPPERS. I'm getting slight oscillation "only" in certain tubes on the output. Looking at the schematic that TOUFU kindly put up. Should I also add Grid stoppers to the 12ax7? if so, I figured that 1k carbon Comp Resistors should be soldered directly on pins 2 and 7. Pin 2 (L) Pins 7 (R) goes to the input and pin 7(L) Pin 2(R) goes after the 2M resistor? after would be closer to ground or at the 2m symbol? Do I need to cut the circuit on the pcb? Pin 2 and 7 on the output (12au7) is where I get totally lost. Usually pin 2 and 7 are soldered to a 470k type resistor?
Danke, Thanks
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Old 13th December 2010, 12:08 AM   #17
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Hi Migkiller ,

nice that you enjoy your vinyl !
i am not a tube guy , but as i understand the schematic ,
that 2 Megaohm is the Grid-Thingie .
So check the tubes or maybe a 2M carbon will help you out .
Hope this helps in your situation , good luck !

Greetings
Juergen
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Old 13th December 2010, 01:26 AM   #18
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sorry had forgotten one point ,
if the tolerance of that 2M is too high , than adding 1k or so
is evtl. needed and a good thing , depents on the tolerance .

Juergen
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Old 13th December 2010, 02:06 AM   #19
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To tell you the truth I'm not really worried about the 12ax7 (would Be nice) but I really need to put grid stoppers on the 12au7. I get slight oscillation when I used my Ribbed Telefunken 12au7 (which I love) but none with the Cheap Chinese, or the Jan phillips or the a pair of baldwins which I don't like. I have some NOS RCA Clear top coming in. Looking at the schematics, I think I have to cut the pcb track to the grid. I also know that these grid stoppers should be put after the grid-to-ground resistor.
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Old 13th December 2010, 02:57 PM   #20
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Hi Migkiller ,

sorry had misunderstood the last posting .
Maybe that oscilation is on the second half without that
grid stopper in the Schematic ?

Greetings
Jürgen
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