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Old 22nd January 2009, 08:48 PM   #21
smbrown is offline smbrown  United States
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Here's the schematic I used: http://www.drtube.com/schematics/an/m7.gif
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Old 24th January 2009, 11:40 AM   #22
LENB is offline LENB  United Kingdom
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To Smbrown
Thanks for your reply,so what preamplifier would you sugest that l could build that would be a great valve preamp to tackle.
Regards LenB
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Old 24th January 2009, 01:33 PM   #23
smbrown is offline smbrown  United States
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Toward the top of this thread is a schematic posted by Bee696 using a 5687. That's a great design, and very easy to implement. You might start there. Some depends on what you'll be driving w/the preamp. If it is a low Z in SS amp, a lower Z out preamp is likely needed. If you're driving most tube amps, output impedance of the pre isn't as critical. If you're driving a 100k input amp, and reasonable length interconnects, I'd suggest the 5687 without paralleling the two sections, as was shown in the bee696 schematic.
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Old 18th March 2009, 12:39 AM   #24
kor952 is offline kor952  Netherlands
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Default M7-Line

I actualy am listning to a M7-line clone right now, it sounds very nice, just like Thorsten already did write in 2006 in this thread. It is the oldest version with a single 5687 per channel, anode resistor 47k cathode resistor 2k bypased by a 100uF 6.3V, output cap at the moment is a 0.15uF Mundorf silver/oil, I also tried a Jensen copper PIO, both sound OK.
Is there anyone who knows the current M7 line stage setup? I am pretty shure that in the M7-IIK linestage 6072As in SRPP (2k cathode resistors) where used, but now they use 2 x 5687 again but in what configuration? Because I presumed there is a good chance that they also are in SRPP I have at the moment a test setup with 5687s in SRPP (2K cathode resistors, Ub=225V). I can't tell wich one sounds better. Yes they differ but both have their goods and bads, but also, the caps and PSUs of both lineamps are not identical

Ronald.
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Old 18th March 2009, 03:17 PM   #25
LENB is offline LENB  United Kingdom
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Default What about the new M77 pre, any diagrams that would be nice

the new M77 pre, any diagrams, that would be nice
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Old 18th March 2009, 03:38 PM   #26
kor952 is offline kor952  Netherlands
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Find a Schematic of the M7-tube (can be found all over the net), double (parallel) the tubes (not the resistor values, instead of the 5.1k//6.2k as in the 6072A cathode use a single 2.7k 2W resistor) in the line stage and you got the M77. Enough pictures can be found to see how the PSU is setup. The last stage of the phono is exactly like the line stage of the m7-tube linestage so common cathode direct coupled to a cathode follower here also use a 2.7k 2W cathode resistor instead of the 5.1k//6.2k.
Hope this helps.

Ronald
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Old 25th March 2009, 10:21 AM   #27
LENB is offline LENB  United Kingdom
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To Kor 952
Do you think a M77 would be a better preamp to build, over the M7
LenB
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Old 25th March 2009, 10:47 AM   #28
kor952 is offline kor952  Netherlands
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Personally I don't think a M77 will sound better as a M7, because whenever you parallel tubes or components the sound becomes a bit out of focus (difused), but I never heard the original M7 neither the M77 so maybe I am totally wrong. But the fact they still use the same (principle) schematic as in early '90s (also for the M1000) tells something about it.
At the moment my M7-line with the 5687 in SRPP (2 x 2K cathode resistor, Ub 225-230V) beats my M7-line with single SE 5687 (2k cathode bypassed with 100uF, 47k anoderesistor, Ub 230V). I would have expected otherwise, but I did not use the same output cap, so I replaced the cap of the SE version with the same cap as in the SRPP. We'll wait and see.
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Old 4th May 2009, 10:58 PM   #29
kor952 is offline kor952  Netherlands
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I just found a Vietnamees forum with photos and a schematic (line part) of the M77 here is the URL...

http://www.vnav.vn/forum/viewtopic.p...=18564&start=0

It seems that I was wrong with the 2.7K cathode resistor it actually is 2K.
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Old 6th May 2009, 02:03 PM   #30
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hi, i'm thinking about to build a pre according to the schematics posted here by Bee696.
Just one question to the tube gurus here: it's not very clear where to connect the rectified 12.6 V for the heater. Do i have to wire 1 end to pin 4 and the other to pin 5 of the tube? if i wire like it like this, i get on the heater vith the center tap at about 1/6 of V(B+) volts and
6.3 V + 1/6 V(B+) on pin 4 and 6.3 V + 1/6 V(B+) on pin 5???
thanks a lot

dimitrij
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