You could also change the cathode resistor from 6K to 500R, and use a 33K anode resistor to B+290.
That would put you at 9mA biased around -5.5V and should be more linear still. and closer to the recommended operating point.
There is a lot of room to work with once you reference the anode resistor to the B+290 supply.
That would put you at 9mA biased around -5.5V and should be more linear still. and closer to the recommended operating point.
There is a lot of room to work with once you reference the anode resistor to the B+290 supply.
You could also change the cathode resistor from 6K to 500R, and use a 33K anode resistor to B+290.
That would put you at 9mA biased around -5.5V and should be more linear still. and closer to the recommended operating point.
There is a lot of room to work with once you reference the anode resistor to the B+290 supply.
I think i'll go with the 500 ohm cathode resistor and the 33k anode resistor from a divider on the 290v supply. You just solved a mystery for me on the original LW where the anode resistor is tapped above the cathode of the second tube on the resistive divider from b+ to ground. -Fred
Hi Jeff,
Ever tried the 6AN4. High mu, and with current drive to spare ?
No, But I will look it up and see its curves for linearity.
High current is NOT particularly needed and wanted in a L-W to a 2A3.
Asano used 0.43 mA., Shishido 1.0 mA. with two sections ( NG-skews) , Fraker 0.6 mA. I THINK the term is grid admittance, where the input signal has to overcome a wall of current.
Jeff
I think i'll go with the 500 ohm cathode resistor and the 33k anode resistor from a divider on the 290v supply. You just solved a mystery for me on the original LW where the anode resistor is tapped above the cathode of the second tube on the resistive divider from b+ to ground. -Fred
Gimp gave you some very good advice.
The first thing to do is to study exising L-W circuits, ( Lipman, Asano, Shushido ) and email me privately for a write up I did on designing such a circuit.
Your minor mistake was to stack supplies, a SINGLE 490 VDC supply actually sounds better to me !!!
Your major mistake was to use a mu of 20 tube in a two stage amp. It will only sound good when PUSHED HARD. Try a 6SL7WGT, mu of 70. Use 225 Ea, -1.85 VDC bias, and about .00215 A. current.
The grid stoppers are useless, a sonic degrade. Eliminate them.
Use HIGH QUALITY wire to the grid of the Driver and to the grid of the Finals. Eg: (1) Siltech is best, (2) two Kimber TCSS, or (3) One Kimber AGSS, one TCSS.
Use only ONE tube in the Finals, no skewing or choir effect. Try a 6AQ5/6005 in place of the 6V6. Use about 210 VDC P-K, .028 A Ia, and ABOUT -12.5 or -13 VDC ( guessing ) bias.
Write to me. drlowmu@gmail.com
Jeff
Hi. I appreciate all the help I can get. I'll try thegimp's suggestion first. I'm interested to read your write-up. -Fred
Edit: I am, however, very interested in retaining the stacked power supplies and is a huge part of my inspiration for building any of it. I respect your perspective on this though.
Edit: I am, however, very interested in retaining the stacked power supplies and is a huge part of my inspiration for building any of it. I respect your perspective on this though.
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The grid stoppers are useless, a sonic degrade. Eliminate them.
Use HIGH QUALITY wire to the grid of the Driver and to the grid of the Finals. Eg: (1) Siltech is best, (2) two Kimber TCSS, or (3) One Kimber AGSS, one TCSS.
Use only ONE tube in the Finals, no skewing or choir effect. Try a 6AQ5/6005 in place of the 6V6.
Hi Jeff. I removed the grid stoppers and adjusted the layout a bit and I like it better for sure. Thank you. I'll have to look and see if I have a 6AQ5 in my stash. I acquired several hundred tubes recently and I still don't know what I have. I just recently found the 6V6's and I like them a lot.
I like the idea of one power tube and I'll be trying that. I started a new thread on it here since I realize it's not a LW. Thanks for your help and ideas. I'll give you an email. -Fred
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