Hello people,
I do have 3 stage stereo phono preamp, 2nd 3rd stages are halves of the ecc88/6922 tube. Wanna try battery bias, should i split for each channel or channel and stage (for total 16 batteries OMG!) or i could use one only supply for a whole device?
I do have 3 stage stereo phono preamp, 2nd 3rd stages are halves of the ecc88/6922 tube. Wanna try battery bias, should i split for each channel or channel and stage (for total 16 batteries OMG!) or i could use one only supply for a whole device?
Did you mean 6 batteries?
One battery for everything would probably be OK, since batteries have low internal resistance and crosstalk isn't really an issue in a phono stage since it's so much worse on the vinyl anyway. Or one battery per channel if you want to keep the grounds separate.
It also depends on where you're planning on using the batteries. In the cathode or the grid?
Personally, I bias using the battery in series with the grid - that's why you need one for each tube IMHO. Doing this means the batteries won't discharge and depending on chemistry will last for decades. I had a VTVM with a 50 year old Eveready carbon cell as bias cell, and it still measured 1.5V before I replaced it with an LM317 based voltage source.
Personally, I bias using the battery in series with the grid - that's why you need one for each tube IMHO. Doing this means the batteries won't discharge and depending on chemistry will last for decades. I had a VTVM with a 50 year old Eveready carbon cell as bias cell, and it still measured 1.5V before I replaced it with an LM317 based voltage source.
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I mean 4*1.2v for each half of ecc88 both channels its 16! So one for both is to degrade crosstalk?
3x1.5V = 12 total if you bias like in the picture above. Or 6V using these: https://www.amazon.ca/Collar-Batteries-GutAlkaLi-Alkaline-Battery/dp/B07TNH9QV7
If you use method C, you need an input capacitor, or B, the battery will discharge over time. If you use method A, the battery will charge while in use, and if you use method D, the battery will basically last forever.
If you use method C, you need an input capacitor, or B, the battery will discharge over time. If you use method A, the battery will charge while in use, and if you use method D, the battery will basically last forever.
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Using method C, yes. Battery lasts forever but you need a blocking cap on each stage, and crosstalk is possible but likely negligible.
Using D, the battery will never discharge (except while in use slightly, but when the tube is cold it's disconnected) and no cap is needed.
Blocking cap is already there, interstage one. So no additional penalties. D is maybe to consider, but for me put signal through the battery is unlikely in terms of SQ. (And cant be shared too)
The internal resistance of a battery is so low that it may as well be a wire. I feel the coupling cap would effect SQ more than a battery but that's just my opinion, I could be wrong.
RE 2032: Lithium batteries don't like getting hot. I would avoid using lithium cells inside a hot tube amp. Carbon-Zinc is cheap.
RE 2032: Lithium batteries don't like getting hot. I would avoid using lithium cells inside a hot tube amp. Carbon-Zinc is cheap.
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Re sesebe: I want 4.0-4.8v for 6n6p or ecc88.
Re sjs: i do plan grid bias. Battery between grid and ground.
Re sjs: i do plan grid bias. Battery between grid and ground.
I have used grid bias at 1.5 V with an AA battery and really like it, and meant to try 3 V with button battery but never got around to it
Best of luck
Best of luck
I agree with kodabmx.
A series battery from the signal source to the grid.
Typical circuit is RCA phono jack input; then either a resistor, rg, to ground, or a potentiometer to ground, then the battery + to rg or the pot wiper, battery - to the grid.
Worked well for many of my amplifiers. I used lithium and alkaline, depending on the voltage needed, and the space that was needed.
If you need a grid stopper, then battery -, to the grid stopper, to the grid.
Always measure the installed battery capacitance to ground, so you know what high frequency effects it might, or might not have, in your circuit.
A series battery from the signal source to the grid.
Typical circuit is RCA phono jack input; then either a resistor, rg, to ground, or a potentiometer to ground, then the battery + to rg or the pot wiper, battery - to the grid.
Worked well for many of my amplifiers. I used lithium and alkaline, depending on the voltage needed, and the space that was needed.
If you need a grid stopper, then battery -, to the grid stopper, to the grid.
Always measure the installed battery capacitance to ground, so you know what high frequency effects it might, or might not have, in your circuit.
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There's also a special case for the first stage of a phono equalizer. A bias battery can sit between signal ground and the bottom of the phono input and its loading resistor, which then floats up from ground by the amount of bias. No coupling cap needed. First cathode is bolted to signal ground. Turntable chassis ground wire must be separate, and should be anyway.
All good fortune,
Chris
ps: I mount the battery on the outside of the chassis, and sometimes forget to check it. This means I have to replace the corroded battery holder too. The battery lasts its shelf life, but that's not forever. Lazy people (like me) work the hardest.
All good fortune,
Chris
ps: I mount the battery on the outside of the chassis, and sometimes forget to check it. This means I have to replace the corroded battery holder too. The battery lasts its shelf life, but that's not forever. Lazy people (like me) work the hardest.
A. Doing it the following way, has a problem . . .
Connect a phono cartridge coil through the shielded wire, and connect it across the RCA phono input jack.
Then connect the center lead of the RCA jack to the top of a 47k ohm resistor, and the bottom of the resistor to the negative of a battery, and the positive of the battery to ground.
Connect the top of the 47k Ohm resistor to the tube grid, and the cathode to ground.
That will bias the tube, but . . .
The battery sees 47k Ohms, going to the cartridge coil DCR. There will always be DC current there, 24/7, until the battery is discharged.
Not a good idea.
B. Instead, connect the 47k Ohm resistor across the RCA phono jack, connect the center lead of the RCA phono jack to the positive battery lead, and the negative lead to the grid.
Then connect the shield lead of the RCA phono jack to the cathode.
This works, and does not discharge the battery, like the above circuit in #1 above does.
C. Post # 18 works, unless anybody shorts the RCA connection to ground, either at the turntable/tone arm, or at a grounded signal source selector switch (that has common ground connections to multiple turntables/tone arms, with one of them that grounds the shields).
But if nothing grounds out (across the battery) that is an elegant solution.
I never thought of that.
That is a good one.
Connect a phono cartridge coil through the shielded wire, and connect it across the RCA phono input jack.
Then connect the center lead of the RCA jack to the top of a 47k ohm resistor, and the bottom of the resistor to the negative of a battery, and the positive of the battery to ground.
Connect the top of the 47k Ohm resistor to the tube grid, and the cathode to ground.
That will bias the tube, but . . .
The battery sees 47k Ohms, going to the cartridge coil DCR. There will always be DC current there, 24/7, until the battery is discharged.
Not a good idea.
B. Instead, connect the 47k Ohm resistor across the RCA phono jack, connect the center lead of the RCA phono jack to the positive battery lead, and the negative lead to the grid.
Then connect the shield lead of the RCA phono jack to the cathode.
This works, and does not discharge the battery, like the above circuit in #1 above does.
C. Post # 18 works, unless anybody shorts the RCA connection to ground, either at the turntable/tone arm, or at a grounded signal source selector switch (that has common ground connections to multiple turntables/tone arms, with one of them that grounds the shields).
But if nothing grounds out (across the battery) that is an elegant solution.
I never thought of that.
That is a good one.
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Sorry, I thought I was clearer than it turned out to be. I connect the bias battery between the turntable's signal grounds (usually also the shields, not ideal, but usual) and phono first stage signal ground(s). So the whole phono cartridge and its wiring and loading Z sits up (down?) from electronics signal ground by a Volt and a half.
Batteries have a very low impedance so don't cause any noise issues. Been doing it for decades without issue.
Not all topologies will let you clamp the first stage cathode to signal ground, but total loss eq or my favorite, second stage anode follower, benefit.
All good fortune,
Chris
Batteries have a very low impedance so don't cause any noise issues. Been doing it for decades without issue.
Not all topologies will let you clamp the first stage cathode to signal ground, but total loss eq or my favorite, second stage anode follower, benefit.
All good fortune,
Chris