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
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
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.
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.
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.
What about the new M77 pre, any diagrams that would be nice
the new M77 pre, any diagrams, that would be nice
the new M77 pre, any diagrams, that would be nice
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
Hope this helps.
Ronald
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.😕
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.😕
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.php?f=46&t=18564&start=0
It seems that I was wrong with the 2.7K cathode resistor it actually is 2K.
http://www.vnav.vn/forum/viewtopic.php?f=46&t=18564&start=0
It seems that I was wrong with the 2.7K cathode resistor it actually is 2K.
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
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
Connect the 12.6 V to pin 4 and 5 and connect the bottom of the 100k (or the top of the 20k) of the voltage divider to pin 8. In this way your heater is 20/120 x B+ above ground (should be about 40 volts cause B+ is about 240V).
No, pin 8 is the heater centertap of a 5687, unlike most of the 12A?7 types that use pin 9 as heater centertap
thanks a lot for the answer...
but just to be sure that i understood right: is this right?
i mean: let's call A the upper node at the 12.6V, and B the lower node on the same line (A is the node between 2x10 ohm and + of the 2 2200 uF capacitors; B is the node at the - lead of the 3 2200uF capacitors )
A --> pin 4
B --> pin 5
B+ --> pin 8
??
thanks
but just to be sure that i understood right: is this right?
i mean: let's call A the upper node at the 12.6V, and B the lower node on the same line (A is the node between 2x10 ohm and + of the 2 2200 uF capacitors; B is the node at the - lead of the 3 2200uF capacitors )
A --> pin 4
B --> pin 5
B+ --> pin 8
??
thanks
Attachments
A is OK, B is OK but pin 8 should not be connect directly to B+ but to where the schematic says 'PIN 8 of the 5687', this is the output of a voltage divider, the input of this voltage divider is connected to the B+.
As i am about to build a new preamp i have been browsing old threads for interesting clues and ideas.
I was quite surprised by the circuit bee696 posted. Why run a 5687 at such a low current? Signature AN sound? Very strange.
I was quite surprised by the circuit bee696 posted. Why run a 5687 at such a low current? Signature AN sound? Very strange.
Indeed it is strange to run the 5687 at 230-240V (including Ra) with an Ia of about 2.75 mA. But I tried all kind of preamps last year 5687 with lineoutputtransformer Ia varying from 9-18mA, 417A with lopt, 26 and 27 with lopt, but I like this one very much. I use the single tube/channel version and not the two paralleled tubes version of the schematic you mention. The single tube version is from about 1994, the parallel version is younger. I also did built the M7 Tube with all 6072A tubes, this one also sounds very nice but has 6dB more gain. I am not the only one....an audio friend of mine also did built the M7 Line and he likes it very much. Be aware to choose high quality parts for best results.
kor952 thank you for sharing your experience. It is not what anyone would assume from looking at the characteristics and this is why experience is so valuable. I am ready to revisit resistor, transformer, choke and ccs loading and will certainly try the M7 bias point as well.