Hi,
Hmmm....I fail to see what that circuit has to do with the AN M7.
Other than that, the M7 used the, to my taste, much less dark sounding, 6072.
The cathode of the anode follower wasn't decoupled either.
All in all a classic topology of which all and sundry claimed that the CF sucked sonically....
Cheers,
Hmmm....I fail to see what that circuit has to do with the AN M7.
Other than that, the M7 used the, to my taste, much less dark sounding, 6072.
The cathode of the anode follower wasn't decoupled either.
All in all a classic topology of which all and sundry claimed that the CF sucked sonically....
Cheers,
Hi!
Fscarpa; I didn't understand very well what You have in mind- my English sucks. You have suggested to remove cathode bypass cap from the first stage if I get this right?
To my information (and I belive the source is good one) Mr. Kondo developed M7 prototype with 5687 anode follower (as in my first stage). Unfortunately this was shown only on few Hi-Fi shows and never came to life. What did came to life is 6072 that You are talking about. Many people think that 5687 anode foll. that was used as a prototype is the m7 preamp- so I have written AN7 prototype-variation.
Cathode follower (second stage) if not made well will sound awfull- so I have thought- why not have first stage as in prototype and second as cathode follower (since I hace 6 pieces of 5687).
I have tried 5687 in anode follower as in first stage and it works o.k. - if I put it as in datasheets than it becomes microphonic. So I thought why not put it as in my first post?!
I would like to drive my bipolar power amplifier (input resistance around 47k).
Fscarpa; I didn't understand very well what You have in mind- my English sucks. You have suggested to remove cathode bypass cap from the first stage if I get this right?
To my information (and I belive the source is good one) Mr. Kondo developed M7 prototype with 5687 anode follower (as in my first stage). Unfortunately this was shown only on few Hi-Fi shows and never came to life. What did came to life is 6072 that You are talking about. Many people think that 5687 anode foll. that was used as a prototype is the m7 preamp- so I have written AN7 prototype-variation.
Cathode follower (second stage) if not made well will sound awfull- so I have thought- why not have first stage as in prototype and second as cathode follower (since I hace 6 pieces of 5687).
I have tried 5687 in anode follower as in first stage and it works o.k. - if I put it as in datasheets than it becomes microphonic. So I thought why not put it as in my first post?!
I would like to drive my bipolar power amplifier (input resistance around 47k).
Hi sparkle,
I mean an arrangment like this.
The catode resistance of the 2nd tube
can be selected according to two
different targets.
One can chose to minimize
(to cancel,if possible ) AC voltage
signal at point A ( VA= const., thus making
useless the bypass cap.), or
to minimize AC current drawn from
PSU.
Usually the two conditions
are rather near.
Federico
I mean an arrangment like this.
The catode resistance of the 2nd tube
can be selected according to two
different targets.
One can chose to minimize
(to cancel,if possible ) AC voltage
signal at point A ( VA= const., thus making
useless the bypass cap.), or
to minimize AC current drawn from
PSU.
Usually the two conditions
are rather near.
Federico
Attachments
sparkle said:
I would increase the value the output capacitor for something like 0,47uF or more because you are driving a 47K Ohms load...and with your 0,1 uF you will loose bass and will increase the phase shift in the lowest octaves...
Another point is to have a very well smoothed suplly becase this circuit have very low PSRR...
But at the end of the day....i like the circuit...because i like simple circuits...
Good luck!
fdegrove said:Hi,
True, but that's not a problem per se. The value of the CF cathode resistor (PFB resistor is you prefer) is very critical to the final outcome.
Cheers,
Yes...if it was a capacitor ...we can call that a bootstrap circuit...
Of course is not a problem...i only have pointed the issue because of the promise
Cheers
But this is accomplished with positif feedback from the output...Yes...there is no negatif feedback in the input circuit (grid - cathode)...but there is positif feedback inside the loop (cathode of the first valve-output of the amp)...fscarpa58 said:
Think that way...if you connect the output with a resistor to the grid of the first valve...you have negatif feedback...if it is to the cathode...is positif feedback...
Cheers
Hi,
Another way of going about it is to stick a grounded grid triode in the tail of the CF and apply positive FB to the cathode of the first stage.
Keep in mind the very high B+ for the to triode so this heater will need to be biased.
An example from a Jean Hiraga preamp that I know to sound very good:
Cheers,
Another way of going about it is to stick a grounded grid triode in the tail of the CF and apply positive FB to the cathode of the first stage.
Keep in mind the very high B+ for the to triode so this heater will need to be biased.
An example from a Jean Hiraga preamp that I know to sound very good:
Cheers,
Attachments
My own:
E80CC with 100k load and 2.2k cathode, unbypassed.
6201 (ECC81) grid to E80CC without stopper and 22k cathode.
Coupling cap out 3.3uF and a 1Mohm to ground.
Volume control an Alps 100k.
B+ 250V.
In my case I have another CF before the volume control, it's a bootstrapped CF using 6201. Input impedance many Mohms
E80CC with 100k load and 2.2k cathode, unbypassed.
6201 (ECC81) grid to E80CC without stopper and 22k cathode.
Coupling cap out 3.3uF and a 1Mohm to ground.
Volume control an Alps 100k.
B+ 250V.
In my case I have another CF before the volume control, it's a bootstrapped CF using 6201. Input impedance many Mohms
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