Ive been trying to fix mufollower with 6sn7 always some sort of hum and little hf noise.
Fedup with it thinking to move to cathode follower for preamp application. Is it right to move to cathode follower?
Fedup with it thinking to move to cathode follower for preamp application. Is it right to move to cathode follower?
Yes, but did you elevate the filament on the mu follower?
You should do that for the cathode follower as well.
You can read anything on the internet.
Since your chokes (no caps??) didn't help, I would think layout issues.
But go ahead and try different topologies.
Think the cathode follower schem would have less gain than the mu-follower. But you can easily correct with setting higher gain in the first stage.
Properly loaded CF gain is about 0.9. The Mu follower gain will approach Mu of the lower tube.🙂
Yes it is for linestage.
My major concern was hum in the prestage for which once I tried keeping everything out of metal chassis ( made of mild steel ) and then later when moved to mild steel im getting constant hum.
Now im using CLC setup like 220uF/450V , 2H ( iguess ), 220uF/450V but now im thinking to move to as LCC combination that first the peak voltage be suppressed by the choke and then to use caps after that.
I have been said that using Mu follower its very sensitive to the power supply ripple so thinking to move to Cathode follower. Any input that anyone can provide will be very helpful.
Mu follower and cathode follower are not the same thing. The former has about µ times voltage gain while the former about µ / (µ + 1) or about 1.
Try a tube that has been designed to operate in series, like 6BQ7 6BK7, ECC84/88, or this kind of double triodes intended for Cascode circuits.
Try a tube that has been designed to operate in series, like 6BQ7 6BK7, ECC84/88, or this kind of double triodes intended for Cascode circuits.
A mu follower should have good PSRR, so should not be too sensitive to ripple.
You keep talking about switching between mu follower and cathode follower, as though these two quite different circuits are comparable in some way. They are not. If one of these seems to satisfy your needs, then it is almost certain that the other one will not.
The mu follower is not a follower, so it is an unfortunate name but too late to change it now. It is essentially a mu gain stage closely coupled to a modified cathode follower.
You keep talking about switching between mu follower and cathode follower, as though these two quite different circuits are comparable in some way. They are not. If one of these seems to satisfy your needs, then it is almost certain that the other one will not.
The mu follower is not a follower, so it is an unfortunate name but too late to change it now. It is essentially a mu gain stage closely coupled to a modified cathode follower.
Can you upload à picture of your amplifier? While your mild steel enclosure is transporting the magnetic field originating from the power transformer and choke, there is no part amplifying this field. Or, possibly the anode when iT is near.
How about this? Im about to start PCB design for this. Any suggestions are purely welcome.
Attachments
Have you tried a different 6SN7? The sample you are trying may be defective, H-K leakage. And check for ground loops in your wiring, both inside the chassis & the external wiring to the cct input.
Is there hum & noise with the input shorted?😱
Is there hum & noise with the input shorted?😱
Folks, the OP is comparing a mu-follower to a two-stage common-cathode DC-coupled to cathode-follower. Gain would be in the ballpark/similar (mu-follower somewhat higher gain).
Theoretically, the mu follower should have better PSRR than the common-cathode+CF.
Why not wire it up point-to-point to troubleshoot the hum issue, then lay out the PCB after you've solved the problem?
Also, grid stopper resistors might be helpful.
Theoretically, the mu follower should have better PSRR than the common-cathode+CF.
Why not wire it up point-to-point to troubleshoot the hum issue, then lay out the PCB after you've solved the problem?
Also, grid stopper resistors might be helpful.