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Audio Note M7 Line Preamp??
Audio Note M7 Line Preamp??
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Old 31st October 2012, 11:26 AM   #61
john65b is offline john65b  United States
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Do you have a good single star ground?
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Old 31st October 2012, 01:48 PM   #62
valvesound is offline valvesound  South Africa
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Quote:
Originally Posted by thomasfw View Post
Dear all,
I'm so confused !
Which one is the most update schemtic for M7/M77 ?
What is the "Tube" using now ?
What is the year of the attached one ?
Many Thanks !
I hope this will ease your pain look here Kondo - Audio Note M7 Tube Pre-amp Clone | D.M.S
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Old 31st October 2012, 03:15 PM   #63
thomasfw is offline thomasfw  Hong Kong
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Quote:
Originally Posted by valvesound View Post
I hope this will ease your pain look here Kondo - Audio Note M7 Tube Pre-amp Clone | D.M.S
Thank You For Your Information !
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Old 31st October 2012, 03:21 PM   #64
smbrown is offline smbrown  United States
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It's interesting how many variations there are on this design. The original (I think!) used a choke input, tube rectified PS. The one linked above is a SS voltage doubler - couldn't get much different.
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Old 31st October 2012, 08:51 PM   #65
themystical is offline themystical  United Kingdom
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Quote:
Originally Posted by john65b View Post
Do you have a good single star ground?
Thanks for the hint. On further investigation, I seem to have some ground loop issues involving some of the other gear connected to it. I will complete the investigations and report.
Many thanks again.
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Old 1st November 2012, 08:18 AM   #66
valvesound is offline valvesound  South Africa
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Quote:
Originally Posted by smbrown View Post
It's interesting how many variations there are on this design. The original (I think!) used a choke input, tube rectified PS. The one linked above is a SS voltage doubler - couldn't get much different.
yes, as mentioned on the site, the power supply comes from another 12B4 tube project. But the question was regarding the amplifier itself and the correct values. That is a working and tested design and the author is very happy with the results. if you want a paint by numbers approach (monkey see monkey do) ignore the link I posted.
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Old 15th April 2013, 04:47 PM   #67
McGyver is offline McGyver  Poland
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I built line preamp after inspiration of Kondo KSL-M7 (remote volume control added as i am slightly lazy ). Been confused about so many versions, and original 6072 tubes was unavailable at the time, so I go for E88CC tubes wchich I had plenty in my drawer. I used regulated power supply very similar to that used in Klimo Merlin pre. It sounds fantastic even using standard metallized resistors and fairly unexceptional components. Only the output capacitors must be highest possible quality because it has huge impact on sound. Tried many of them.
- vintage Sprague metal can oil caps sounded quite well, warm and saturated, but slightly lacking fine details and dynamic.
- SCR FEP teflon/tinfoil great disappointment. Synthetic, artificial sound, like instant coffee vs italian aromatic espresso. Lack of accoustic, lack of finest details, lack of emotion. The sound was not dry, but clinical sterile, deprived of liveness
- obbligato gold premium sounded fair, but lacking in bass depth and volume
- Audio Note Copper foil mylar in oil rich, full sound with lot of space. Very pleasant to listen, but slightly lacking in top end and overall dynamic
- Mundorf Supreme Silver Oil is a great capacitor, very precise, spatial and silk at the same time. It's little on the bright side, but without any harshness. In my system it overperforms Audio Note.
- Audyn Cap True Copper - this capacitor outperformed anything I tried so far. It is as full, reach sounding as Audio Note, but without lacking in top and dynamics. It's as spatial and precise as Mundorf, but with better tonal balance. I'm nicely surprised. Very recommended. My personal favourite.

The tubes have also big impact on sound. I'm only using NOS and I prefer Telefunken and Amperex Bugle Boy.
There are some pictures, regulated power supply not implemented yet:

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

It easily outperformed Sonic Frontiers SFL2, Audio Innovations L-2 and Tube Technology Prophet. Audio Research L-1 was literally mopped the floor. I'm very satisfied with this design. Rest of my system is here: Mój system
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Old 16th April 2013, 10:31 AM   #68
valvesound is offline valvesound  South Africa
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@McGyver....what circuit did you use, mind posting the complete circuit with power supply?
I'm always interested to hear reviews on caps in certain projects / designs. Where can I buy the Audyn caps, I would like to try them? (BTW the caps in your picture do not look like the Audyn true coppers)

Thanks

Last edited by valvesound; 16th April 2013 at 10:33 AM.
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Old 16th April 2013, 03:59 PM   #69
McGyver is offline McGyver  Poland
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Yes, I'll post the schematics, only must find the drawing. Or draw it again
You can buy Audyn True Copper caps at Inter Technik Germany.

The caps on my picture are made in Poland vintage military MBM type paper capacitors, that picture was taken when I tested them. They're quite good capacitors, far better than almost every metallized polypropylene and costs about nothing.
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Old 16th April 2013, 10:29 PM   #70
McGyver is offline McGyver  Poland
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Schematics here:

Click the image to open in full size.

P-100k black Alps
R1 - 820k
R2 - 1k
R3 - 8k2/2W
R4 - 150R
R5 - 15k/2W
R6 - 220k
C2 - 0,47uF Audyn True Copper
C5 - 47uF/250V
The diode function requires a commentary. This circuit suffers from the problem that on start up, the grid of second halve will immediately rise to HT potential while the cathode is still cold and tubes conducts no any current. It causes arcing between the electrodes, and rapid destruction of the valve. This problem can be easily resolved by connecting an ordinary rectifier diode (such as a 1N4007) between grid and cathode. At start up, this will keep the cathode within a few tens of volts of the grid. Once hot, the valve will bias with the cathode at a higher potential than the grid and the diode will be reverse biased, off. It will be present only as junction capacitance (few PF) between cathode and grid, wchich is negligible.

Simple mosfet regulated anode power supply:

Click the image to open in full size.

(in my preamp zener diode is 180V, not 350V)
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